Abstrict A desiccant-assisted air conditioning system utilizes a compressor
(10), a condenser coil (11), an evaporator coil (13), supplemental
desiccant coils (19 20) connected therewith, and damper (18A, 19B)
and valve arrangements that direct air and refrigerant through the
system coils in several different thermodynamic operating paths.
The system combines, transfers and reverses thermodynamic energies
between the desiccant, the refrigerant and the crossing air, and
simultaneously maximizes the refrigerant vapor compression closed
cycle and desiccant vapor compression open cycle. The desiccant
coils (19 20) not only provide an effective gas phase change in
their crossing air streams, but also simultaneously provide endothermic
and exothermic energy exchanges between the air streams and the
passing refrigerant that maximize the operating efficiency of the
compressor, condenser coil, and evaporator coil, conserves energy,
and produces quality conditioned air output.
Claims 1. A desiccant-assisted air conditioning and dehumidification/humidificati-
on system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser coil connected in
series in a refrigerant flow path, a condenser fan that draws outdoor
air through the condenser coil and exhausts it back to the outdoors,
and a process fan that draws process air through the evaporator
coil and discharges it as supply air into a space to be conditioned;
a supplemental dehumidification/humidification system including
a first desiccant coil and a second desiccant coil in said refrigerant
flow path, each having desiccant material thereon, first valve means
disposed in the refrigerant flow path for controlling flow of refrigerant
between said desiccant coils and said compressor and said condenser
coil, second valve means disposed in the refrigerant flow path for
controlling flow of refrigerant between said desiccant coils and
said evaporator coil, and refrigerant metering means disposed in
the refrigerant flow path between said second valve means and said
evaporator coil for reducing the temperature and pressure of refrigerant
flowing therethrough; and air conveyance means for directing a regeneration
air stream through said first desiccant coil and exhausting it,
and directing a portion of the supply air discharged by said process
fan in a desiccant process air stream through said second desiccant
coil and exhausting it back into the supply air which is discharged
into the space to be conditioned; wherein in a first mode of operation,
said first desiccant coil receives condensed refrigerant from said
condenser coil and the regeneration air stream passing therethrough
further cools and condenses the refrigerant with the rejected heat
of said condensation concurrently drying the desiccant material
on the first desiccant coil and the thus cooled and condensed refrigerant
passes through said refrigerant metering means which further reduces
the temperature and pressure of refrigerant flowing therethrough
and the evaporator coil receives the lower temperature and pressure
refrigerant which absorbs heat from the process air stream passing
therethrough and the heated refrigerant passing therethrough; and
said second desiccant coil receives heated refrigerant from said
evaporator coil and the desiccant material on the second desiccant
coil concurrently absorbs moisture from the desiccant process air
stream passing therethrough and further heats the refrigerant passing
therethrough with the thus dryer desiccant process air stream discharged
back into the supply air and the further heated refrigerant is suctioned
to said compressor and discharged into the condenser coil; in a
second mode of operation, said first and second valve means and
said air conveyance means are positioned such that said regeneration
air stream is directed through said second desiccant coil and exhausted,
and said desiccant process air stream is directed through said first
desiccant coil and exhausted it back into the supply air; said previously
moistened second desiccant coil receives condensed refrigerant from
said condenser coil and the regeneration air stream passing therethrough
further cools and condenses the refrigerant with the rejected heat
of said condensation concurrently drying said desiccant material
and the thus cooled and condensed refrigerant passes through said
refrigerant metering means which further reduces the temperature
and pressure of refrigerant flowing therethrough and the evaporator
coil receives the lower temperature and pressure refrigerant which
absorbs heat from the process air stream passing therethrough and
the heated refrigerant; and said previously dried first desiccant
coil receives heated refrigerant from said evaporator coil and the
desiccant material on the first coil concurrently absorbs moisture
from the desiccant process air stream passing therethrough and further
heats the refrigerant passing therethrough with the thus dryer desiccant
process air stream discharged back into the supply air and the further
heated refrigerant is suctioned to said compressor and discharged
into the condenser coil.
2. The desiccant-assisted air conditioning and dehumidification/humidifica-
tion system according to claim 1 further comprising: a condenser
reheat coil in said refrigerant flow path connected in series between
said condenser coil and said first valve means and disposed downstream
from said process fan and through which said supply air stream passes
prior to being discharged into the space to be conditioned; and
in said first mode of operation, condensed refrigerant from said
condenser coil first passes through said condenser reheat coil and
is cooled and condensed by the supply air and concurrent therewith
the supply air is heated with the rejected heat of condensation,
then the cooled and condensed refrigerant is received by said first
desiccant coil, and thereafter continues in the refrigerant flow
path as recited in claim 1.
3. The desiccant-assisted air conditioning and dehumidification/humidifica-
tion system according to claim 1 further comprising: an alternate
refrigerant bypass flow path extending between said refrigerant
metering means and said second valve means, first pressure regulator
means in said refrigerant flow path downstream from said evaporator
coil, and second pressure regulator means in said refrigerant flow
path downstream from said second desiccant coil; and in said first
mode, depending upon the refrigerant pressure and pressure setting
of said first and second pressure regulator means, the refrigerant
after passing through said refrigerant metering means flows either
through said evaporator coil then passes through the first pressure
regulator means and back to said compressor as recited in claim
1 or through said bypass flow path and through said second desiccant
coil then passes through said second pressure regulator means and
back to said compressor as recited in claim 1 or passes proportionally
through both said evaporator coil and said second desiccant coil
then through said first and second pressure regulator means, respectively,
to said compressor; thereby concentrating refrigeration absorption
energy to either said evaporator coil or said second desiccant coil
or to both to provide desired supply air and process air output
conditions.
4. A desiccant-assisted air conditioning and dehumidification/humidificati-
on system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser coil connected in
a refrigerant flow path, a condenser fan that draws outdoor air
through the condenser coil and exhausts it back to the outdoors,
and a process fan that draws process air through the evaporator
coil and discharges it as supply air into a space to be conditioned;
a supplemental dehumidification/humidification system including
a first desiccant coil and a second desiccant coil in said refrigerant
flow path, each having desiccant material thereon, said first desiccant
coil connected in series between said compressor and said condenser
coil, first valve means disposed in the refrigerant flow path for
controlling flow of refrigerant between said desiccant coils and
said compressor and said evaporator coil, second valve means for
controlling flow of refrigerant between said desiccant coils and
said condenser coil, and refrigerant metering means disposed in
the refrigerant flow path between said second valve means and said
condenser coil for reducing the temperature and pressure of refrigerant
flowing therethrough; and air conveyance means for directing a regeneration
air stream through said first desiccant coil and exhausting it,
and directing a portion of the supply air discharged by said process
fan in a desiccant process air stream through said second desiccant
coil and exhausting it back into the supply air which passes into
the space to be conditioned; wherein in a first mode of operation,
said first desiccant coil receives hot refrigerant discharged from
said compressor and the regeneration air stream passing therethrough
cools and condenses the refrigerant with the rejected heat of said
condensation concurrently drying the desiccant material on the first
desiccant coil and the thus cooled and condensed refrigerant passes
through said condenser coil which further cools and condenses the
refrigerant and the thus cooled and condensed refrigerant from the
condenser coil passes through said refrigerant metering means which
further reduces the temperature and pressure of refrigerant flowing
therethrough; and the lower temperature and pressure refrigerant
passes through said second desiccant coil and the desiccant material
on the second desiccant coil concurrently absorbs moisture from
the desiccant process air stream passing therethrough and heats
the refrigerant passing therethrough with the thus dryer desiccant
process air stream discharged back into the supply air and said
evaporator coil receives the heated refrigerant which absorbs heat
from the process air stream passing therethrough and the further
heated refrigerant is suctioned to said compressor.
5. A desiccant-assisted air conditioning and dehumidification/humidificati-
on system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser coil connected in
a refrigerant flow path, a condenser fan that draws outdoor air
through the condenser coil and exhausts it back to the outdoors,
and a process fan that draws process air through the evaporator
coil and discharges it as supply air into a space to be conditioned;
a supplemental dehumidification/humidification system including
a first desiccant coil and a second desiccant coil in said refrigerant
flow path, each having desiccant material thereon, first valve means
disposed in the refrigerant flow path for controlling flow of refrigerant
between said desiccant coils and said compressor and said condenser
coil, second valve means disposed in the refrigerant flow path for
controlling flow of refrigerant between said desiccant coils and
said evaporator coil, first refrigerant metering means disposed
in the refrigerant flow path between said second valve means and
said evaporator coil, an alternate refrigerant bypass flow path
extending between said second valve means and said first refrigerant
metering means and said second valve means, and a second refrigerant
metering means in said bypass flow path, a first pressure regulator
in said refrigerant flow path downstream from said evaporator coil,
and a second pressure regulator in said refrigerant flow path downstream
from said second desiccant coil; and air conveyance means for directing
a regeneration air stream through said first desiccant coil and
exhausting it, and directing process air drawn by said process fan
through said second desiccant coil and through said evaporator coil
prior to being discharged as supply air into the space to be conditioned;
wherein in a first mode of operation, said first desiccant coil
receives condensed refrigerant from said condenser coil and the
regeneration air stream passing therethrough further cools and condenses
the refrigerant with the rejected heat of said condensation concurrently
drying the desiccant material on the first desiccant coil, and then;
depending upon the control settings of said first and second pressure
regulators and said first and second refrigerant metering means,
the thus cooled and condensed refrigerant flows either through the
first refrigerant metering means, which further reduces the temperature
and pressure of the refrigerant flowing therethrough, and then passes
through said evaporator coil where the lower temperature and pressure
refrigerant absorbs heat from the process air stream passing therethrough
and the heated refrigerant passes through said first pressure regular
and to the suction side of said compressor; or the cooled and condensed
refrigerant from said first desiccant coil flows through said second
pressure regular, which further reduces the temperature and pressure
of the refrigerant flowing therethrough, and then passes through
said second desiccant coil and the desiccant material on the second
desiccant coil concurrently absorbs moisture from the process air
stream passing therethrough and heats the refrigerant passing therethrough,
the heated refrigerant then being suctioned to said compressor and
the dryer process air stream then discharged through said evaporator
coil as supply air into the space to be conditioned.
6. A desiccant-assisted heat pump air conditioning and dehumidification/humidification
system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser coil connected in
a refrigerant flow path, a condenser fan that draws outdoor air
through the condenser coil and exhausts it back to the outdoors,
and a process fan that draws process air through the evaporator
coil and discharges it as supply air into a space to be conditioned;
a supplemental dehumidification/humidification system including
a first desiccant coil and a second desiccant coil in said refrigerant
flow path, each having desiccant material thereon, first valve means
disposed in the refrigerant flow path for controlling flow of refrigerant
between said desiccant coils and said compressor and said condenser
coil, second valve means disposed in the refrigerant flow path for
controlling flow of refrigerant between said desiccant coils and
said evaporator coil, refrigerant metering means disposed in the
refrigerant flow path connected with said second valve means; air
conveyance means for directing a regeneration air stream through
said first desiccant coil and exhausting it, and directing a portion
of the supply air discharged by said process fan in a desiccant
process air stream through said second desiccant coil and exhausting
it back into the supply air which passes through the evaporator
coil and into the space to be conditioned; and third valve means
in said refrigerant flow path and connected with said compressor
for selectively controlling the direction of the flow of refrigerant
to and from said compressor; wherein in a cooling mode of operation,
said first desiccant coil receives condensed refrigerant from said
condenser coil and the regeneration air stream passing therethrough
further cools and condenses the refrigerant with the rejected heat
of said condensation concurrently drying the desiccant material
on said first desiccant coil, and the thus cooled and condensed
refrigerant flows through said refrigerant metering means, which
further reduces the temperature and pressure of the refrigerant
flowing therethrough, passes through said second desiccant coil
and the desiccant material on the second desiccant coil concurrently
absorbs moisture from the desiccant process air stream passing therethrough
and heats the refrigerant passing therethrough, and the heated refrigerant
passes through said evaporator coil where it absorbs heat from the
desiccant process air stream passing therethrough, the heated refrigerant
then being suctioned to said compressor and discharged back to the
condenser coil and the dryer desiccant process air stream is mixed
with the supply air and discharged through said evaporator coil
into the space to be conditioned; and in a heating mode of operation,
refrigerant is drawn from said condenser by said compressor which
increases the temperature and pressure of the refrigerant and it
is discharged through said evaporator coil where the refrigerant
heat is dissipated into the process air stream passing therethrough
and the refrigerant is cooled and condensed, the cooled and condensed
refrigerant then passes through said second desiccant coil and the
desiccant material of the second desiccant coil in a desorption
process concurrently humidifies the desiccant process air stream
passing therethrough and cools the refrigerant passing therethrough,
the cooled refrigerant then flows through said refrigerant metering
means, which reduces the temperature and pressure of the refrigerant
flowing therethrough, and passes through said first desiccant coil
where the desiccant material of said first desiccant coil in a sorption
process concurrently adsorbs heat from the regeneration air stream
passing therethrough and heats the refrigerant passing therethrough,
the heated refrigerant then flows back into the condenser coil,
and the moist desiccant process air stream exiting the second desiccant
coil is mixed back into the supply air stream and passes through
the evaporator coil and into the space to be conditioned.
7. The desiccant-assisted heat pump air conditioning and dehumidification/humidification
system according to claim 6 further comprising: a regulating means
is disposed in said refrigerant flow path parallel with said condenser
for regulating refrigerant flow in response to the refrigerant pressure
and temperature conditions; and in said heating mode, depending
upon the refrigerant pressure and temperature conditions, the refrigerant
passing through said first desiccant coil is directed back into
said condenser, or is returned by said compressor and said third
valve means back through said evaporator coil, thereby bypassing
entry into said condenser until predetermined refrigerant pressure
and temperature conditions are achieved.
8. The desiccant-assisted heat pump air conditioning and dehumidification/humidification
system according to claim 6 wherein said second valve means comprises
a first and a second refrigerant metering means disposed in series
in the refrigerant flow path and connected in parallel with said
first and said desiccant coils, and said first and second refrigerant
metering means each having a bypass line containing a first and
second check valve connected in parallel therewith, respectively,
and each of said check valves operating in opposed relation to control
the direction of refrigerant flow, said first and second refrigerant
metering means being calibrated to only allow flow of refrigerant
of respective different temperature and pressure conditions therethrough;
such that in said cooling mode, the cooled and condensed refrigerant
after passing through said first desiccant coil bypasses said first
refrigerant metering means, passes through said first check valve
and then passes through said second refrigerant metering means and
into said second desiccant coil and thereafter continues in the
refrigerant flow path as recited in the cooling mode of claim 6;
and in said heating mode, the heated refrigerant after passing through
said second desiccant coil bypasses said second refrigerant metering
means, passes through said second check valve and then passes through
said first refrigerant metering means and into said first desiccant
coil and thereafter continues in the refrigerant flow path as recited
in the heating mode of claim 6.
9. A desiccant-assisted air conditioning and dehumidification/humidificati-
on system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser coil connected in
a refrigerant flow path, a condenser fan that draws outdoor air
through the condenser coil and exhausts it back to the outdoors,
and a process fan that draws process air through the evaporator
coil and discharges it as supply air into a space to be conditioned;
a supplemental dehumidification/humidification system including
a first desiccant coil and a second desiccant coil in said refrigerant
flow path, each having desiccant material thereon, first valve means
disposed in the refrigerant flow path for controlling flow of refrigerant
between said desiccant coils and said compressor and said condenser
coil, second valve means disposed in the refrigerant flow path for
controlling flow of refrigerant between said desiccant coils and
said evaporator coil, and a condenser reheat coil in said refrigerant
flow path disposed downstream from said process fan; a first refrigerant
bypass flow line connecting said reheat coil with said evaporator
coil, and a first refrigerant metering means disposed in said first
refrigerant bypass flow line, a second refrigerant bypass flow line
adjoined to said first refrigerant bypass flow line between said
first refrigerant metering means and extending to said second valve
means, and a second refrigerant metering means in said second refrigerant
bypass flow line, a first pressure regulator means in said refrigerant
flow path downstream from said evaporator coil, and a second pressure
regulator means in said refrigerant flow path downstream from said
second desiccant coil; air conveyance means for directing a regeneration
air stream through said first desiccant coil and exhausting it,
and directing process air drawn by said process fan through said
evaporator coil, said second desiccant coil, and then through said
condenser reheat coil prior to being discharged as supply air into
the space to be conditioned; wherein in a first mode of operation
(straight flow), refrigerant from said condenser coil first passes
through said first desiccant coil and the regeneration air stream
passing therethrough cools and condenses the refrigerant with the
rejected heat of said condensation concurrently drying the desiccant
material of the first desiccant coil, and then the condensed refrigerant
passes through said condenser reheat coil and is further cooled
and condensed by the process air stream passing therethrough and
concurrent therewith the process air is heated with the rejected
heat of condensation; then, depending upon the control settings
of said first and second pressure regulator means and said first
and second refrigerant metering means, the thus cooled and condensed
refrigerant flows either through said first refrigerant metering
means, which further reduces the temperature and pressure of the
refrigerant flowing therethrough, and then passes through said evaporator
coil where the lower temperature and pressure refrigerant absorbs
heat from the process air stream passing therethrough and the heated
refrigerant passes through said first pressure regular to the suction
side of said compressor; or the cooled and condensed refrigerant
from said reheat coil flows through said second refrigerant metering
means, which further reduces the temperature and pressure of the
refrigerant flowing therethrough, and then passes through said second
desiccant coil and the desiccant material of the second desiccant
coil concurrently absorbs moisture from the process air stream passing
therethrough and heats the refrigerant passing therethrough, and
the heated refrigerant passes through said second pressure regulator
means to the suction side of said compressor.
10. A desiccant-assisted air conditioning and dehumidification/humidificat-
ion system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser coil connected in
a refrigerant flow path, a condenser fan that draws outdoor air
through the condenser coil and exhausts it back to the outdoors,
and a process fan that draws process air through the evaporator
coil and discharges it as supply air into a space to be conditioned;
a supplemental dehumidification/humidification system including
a first desiccant coil and a second desiccant coil in said refrigerant
flow path, each having desiccant material thereon, said first desiccant
coil connected in series between said compressor and said condenser
coil, first valve means disposed in the refrigerant flow path for
controlling flow of refrigerant between said desiccant coils and
said compressor and said evaporator coil, first pressure regulator
means in said refrigerant flow path between said first valve means
and the suction side of said compressor, second valve means for
controlling flow of refrigerant between said desiccant coils and
said condenser coil, a first solenoid valve and a first refrigerant
metering means connected in series between said condenser coil and
said second valve means, a regeneration condenser coil in said refrigerant
flow path disposed between said second valve means and said condenser
coil, a first bypass line adjoined between said condenser coil and
said first solenoid valve and extending to said evaporator coil,
a second solenoid valve and a second refrigerant metering means
in said first bypass line, a second pressure regulator means disposed
between said evaporator coil and the suction side of said compressor,
a second bypass line between said condenser coil and the suction
side of said compressor, a fourth solenoid valve, a third refrigerant
metering means, a regeneration evaporator coil, and a third pressure
regulator means disposed in series in said second bypass line, said
regeneration evaporator coil disposed in said regeneration air stream
upstream from said regeneration condenser coil; air conveyance means
for directing a regeneration air stream through said regeneration
evaporator coil, said regeneration condenser coil, said first desiccant
coil and then exhausting it, and directing a portion of the supply
air discharged by said process fan in a desiccant process air stream
through said second desiccant coil and exhausting it back into the
supply air which passes into the space to be conditioned; wherein
in a cooling mode of operation, depending upon the demand and/or
settings of said solenoid valves, the refrigerant is selectively
directed back to said compressor, to said evaporator coil, or to
said regeneration evaporator coil, or to all simultaneously, or
to selected combinations thereof.
11. The desiccant-assisted air conditioning and dehumidification/humidific-
ation system according to claim 10 wherein: in a first flow path,
said first desiccant coil receives superheated refrigerant discharged
from said compressor and the regeneration air stream passes through
said regeneration evaporator coil, through said regeneration condenser
coil, through said first desiccant coil, and is exhausted, said
first desiccant coil cools and condenses the refrigerant with the
rejected heat of said condensation concurrently drying the desiccant
material of said first desiccant coil and the thus cooled and condensed
refrigerant passes through said regeneration condenser coil, and
through said condenser coil which further cools and condenses the
refrigerant and the thus cooled and condensed refrigerant from the
condenser coil passes through said first solenoid valve and said
first refrigerant metering means which further reduces the temperature
and pressure of refrigerant flowing therethrough; and the lower
temperature and pressure refrigerant passes through said second
desiccant coil and the desiccant material on the second desiccant
coil concurrently absorbs moisture from the desiccant process air
stream passing therethrough and heats the refrigerant passing therethrough
with the thus dryer desiccant process air stream discharged back
into the supply air and the heated refrigerant passes through said
first pressure regulator means and back to the suction side of the
compressor; in a second flow path, refrigerant from said condenser
coil passes through said second solenoid valve and said second refrigerant
metering means which reduces the temperature and pressure of refrigerant
flowing therethrough, and through said evaporator coil where the
lower temperature and pressure refrigerant absorbs heat from the
process air stream passing therethrough and the heated refrigerant
passes through said second pressure regulator means to the suction
side of said compressor; and in a third flow path, refrigerant from
said condenser coil passes through said third solenoid valve and
said third refrigerant metering means which reduces the temperature
and pressure of refrigerant flowing therethrough, and through said
regeneration evaporator coil where the lower temperature and pressure
refrigerant absorbs heat from the desiccant process air stream passing
therethrough and the heated refrigerant passes through said third
pressure regulator means to the suction side of said compressor;
and in a combined flow path, refrigerant flows selectively through
any or all of said flow paths, depending upon the demand.
12. The desiccant-assisted air conditioning and dehumidification/humidific-
ation system according to claim 10 wherein: said exhausted regeneration
air stream after passing through said first desiccant coil is directed
back through said regeneration evaporator coil, through said regeneration
condenser coil, and through said first desiccant coil, in an endless
loop.
13. A desiccant-assisted air conditioning and dehumidification/humidificat-
ion system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser reheat coil connected
in a refrigerant flow path, a process fan, and a regeneration fan;
a first desiccant coil and a second desiccant coil in said refrigerant
flow path, each having desiccant material thereon, first valve means
disposed in the refrigerant flow path for controlling flow of refrigerant
between said desiccant coils and said compressor and second valve
means disposed in the refrigerant flow path for controlling flow
of refrigerant between said desiccant coils and said evaporator
coil and said condenser reheat coil, a refrigerant flow line connecting
said reheat coil with said evaporator coil, and a refrigerant metering
means disposed in said refrigerant flow line; said evaporator coil
disposed upstream from said first desiccant coil, and said condenser
reheat coil disposed downstream from said second desiccant coil;
air conveyance means for directing a regeneration air stream drawn
by said regeneration fan through said first desiccant coil and exhausting
it as desiccant process air, and directing desiccant process air
drawn by said process fan through said evaporator coil, said second
desiccant coil, and then through said condenser reheat coil prior
to being discharged as supply air into the space to be conditioned;
wherein in a cooling mode of operation, refrigerant is discharged
from said compressor and passes through first desiccant coil and
the regeneration air stream passing therethrough cools and condenses
the refrigerant with the rejected heat of said condensation concurrently
drying the desiccant material of said first desiccant coil, and
the condensed refrigerant passes through said condenser reheat coil
and is further cooled and condensed by the desiccant process air
stream passing therethrough, then the thus cooled and condensed
refrigerant flows through said refrigerant metering means, which
further reduces the temperature and pressure of the refrigerant
flowing therethrough, and passes through said evaporator coil where
the lower temperature and pressure refrigerant absorbs heat from
the desiccant process air stream passing therethrough, then the
cooled and condensed refrigerant passes through said second desiccant
coil and the desiccant material of the second desiccant coil concurrently
absorbs moisture from and dehumidifies the desiccant process air
stream passing therethrough and heats the refrigerant passing therethrough,
and the heated refrigerant passes to the suction side of said compressor.
14. A desiccant-assisted air conditioning and dehumidification/humidificat-
ion system, comprising: a refrigeration circuit including a refrigerant
compressor, an evaporator coil, and a condenser coil connected in
a refrigerant flow path, a condenser fan that draws outdoor air
through the condenser coil and exhausts it back to the outdoors,
a process fan, and a regeneration fan; a first desiccant coil and
a second desiccant coil in said refrigerant flow path, each having
desiccant material thereon, first valve means disposed in the refrigerant
flow path for controlling flow of refrigerant between said desiccant
coils, said compressor, and said condenser coil, and second valve
means disposed in the refrigerant flow path for controlling flow
of refrigerant between said desiccant coils and said evaporator
coil, and a refrigerant metering means disposed in said refrigerant
flow line between said second valve means and said evaporator coil;
said evaporator coil disposed upstream from said first desiccant
coil; air conveyance means for directing a regeneration air stream
drawn by said regeneration fan through said first desiccant coil
and exhausting it as desiccant process air, and directing desiccant
process air drawn by said process fan through said evaporator coil,
said second desiccant coil, and discharging it as supply air into
the space to be conditioned; wherein in a cooling mode of operation,
said first desiccant coil receives condensed refrigerant from said
condenser coil and the regeneration air stream passing therethrough
further cools and condenses the refrigerant with the rejected heat
of said condensation concurrently drying the desiccant material
on said first desiccant coil, and the thus cooled and condensed
in a cooling mode of operation, hot refrigerant is discharged from
said compressor and passes through said condenser coil and the outdoor
air passing therethrough cools and condenses it and it passes through
said first desiccant coil and the regeneration air stream passing
therethrough further cools and condenses the refrigerant with the
rejected heat of said condensation concurrently drying the desiccant
material of said first desiccant coil, then the thus cooled and
condensed refrigerant flows through said refrigerant metering means,
which further reduces the temperature and pressure of the refrigerant
flowing therethrough, and passes through said evaporator coil where
the lower temperature and pressure refrigerant absorbs heat from
the desiccant process air stream passing therethrough, then the
cooled and condensed refrigerant passes through said second desiccant
coil and the desiccant material of the second desiccant coil concurrently
absorbs moisture from and dehumidifies the desiccant process air
stream passing therethrough and heats the refrigerant passing therethrough,
and the heated refrigerant passes to the suction side of said compressor;
and said process fan also draws process air through said evaporator
coil in a bypass process air stream isolated from said desiccant
process air stream and it is mixed with the desiccant process air
stream downstream from said second desiccant coil and the combined
air is then exhausted to the space to be conditioned.
15. A heat exchange desiccant coil for use in an air conditioning
and dehumidification/humidification system, comprising: a plurality
of rows of metallic refrigerant tubes through which refrigerant
is conducted connected with at least one refrigerant header pipe
for introducing refrigerant into said refrigerant tubes and at least
one return header pipe for returning refrigerant; a plurality of
adjacent metallic fins each having front and back surfaces secured
to said refrigerant tubes to form a generally rectangular configuration
with a plurality of adjacent air flow pathways transverse to said
refrigerant tubes through which air is conducted; and desiccant
material disposed between opposed facing surfaces of said adjacent
fins.
16. The heat exchange desiccant coil according to claim 15 wherein
said desiccant material is on said front and back surfaces of said
adjacent fins.
17. The heat exchange desiccant coil according to claim 15 wherein
said fins comprise a plurality of generally rectangular metallic
plates having a corrugated shape assembled to form a honeycomb pattern
of adjacent air flow pathways extending transverse to said refrigerant
tubes.
18. The heat exchange desiccant coil according to claim 15 wherein
said desiccant material is selected from the group consisting of
activated alumna, aluminas, silicas, titaniums, lithium chloride,
zeolites, polymers and clay or combinations thereof.
19. The heat exchange desiccant coil according to claim 15 wherein
said desiccant material contains additives to improve sorbant effectiveness
for unwanted gases or contaminant gases.
20. The heat exchange desiccant coil according to claim 15 wherein
said desiccant material is combined with a substrate material.
21. A desiccant-assisted air conditioning process for conditioning
a space, comprising the steps of: providing a compressor, and a
condenser coil connected in a refrigerant flow path; providing first
and second heat exchanging desiccant coils connected in heat exchange
relation with a selected refrigerant flow path, each having desiccant
material thereon disposed for thermal contact with a selected air
flow stream; providing an evaporator coil in the refrigerant flow
path connected with said first and second desiccant coils, and routing
a process air stream through the evaporator coil and discharging
it as supply air into the space to be conditioned; and in a first
mode of operation; routing condensed refrigerant from said condenser
through said first desiccant coil, and routing a regeneration air
flow stream through said first desiccant coil to further condense
and cool the refrigerant passing therethrough with the rejected
heat resulting from said condensation and simultaneously regenerating
(drying) the desiccant material of said first desiccant coil; routing
the cooled and condensed refrigerant from said first desiccant coil
through refrigerant metering means to further reduce the temperature
and pressure of the refrigerant flowing therethrough and then passing
the lower temperature and pressure through the evaporator coil where
the lower temperature and pressure refrigerant absorbs heat from
the process air stream passing therethrough and the heated refrigerant
passing therethrough; routing the thus condensed and cooled refrigerant
from said evaporator coil through said second desiccant coil, and
routing a portion of the discharged supply air in a desiccant process
air stream through said second desiccant coil to heat the refrigerant
passing therethrough with the desiccant material of said second
desiccant coil concurrently absorbing moisture from the desiccant
process air stream passing therethrough thereby dehumidifying and
cooling the desiccant process air stream which is then exhausted
back into the supply air which is discharged into the space to be
conditioned; and routing heated refrigerant from said second desiccant
coil to said compressor which discharges it into said condenser
coil; and in a second mode of operation; routing said regeneration
air stream through said second desiccant coil and exhausting it;
routing said desiccant process air stream through said first desiccant
coil and exhausting it back into said supply air; routing condensed
refrigerant from said condenser through said previously moistened
second desiccant coil and routing the regeneration air stream passing
therethrough to cool and condense the refrigerant with the rejected
heat of said condensation concurrently drying said desiccant material
of said second desiccant coil and routing the thus cooled and condensed
refrigerant through refrigerant metering means to further reduces
the temperature and pressure of refrigerant flowing therethrough
and routing lower temperature and pressure refrigerant to said evaporator
coil where it absorbs heat from the process air stream passing therethrough
and the heated refrigerant passing therethrough; and routing heated
refrigerant from said evaporator coil to said previously dried first
desiccant coil where the desiccant material of the first desiccant
coil concurrently absorbs moisture from the desiccant process air
stream passing therethrough thereby dehumidifying the desiccant
process air stream and further heating the refrigerant passing therethrough
with the thus dryer desiccant process air stream discharged back
into the supply air and the further heated refrigerant is returned
to said compressor which discharges it into the condenser coil.
Description CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority of U.S. Provisional Application
Ser. No. 60/573086 filed May 22 2004 U.S. Provisional Application
Ser. No. 60/588409 filed Jul. 16 2004 and U.S. Provisional Application
Ser. No. 60/592879 filed Jul. 30 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to desiccant-assisted air
conditioning systems and processes, and more particularly to an
air conditioning system utilizing a compressor, a condenser coil,
an evaporator coil, supplemental desiccant coils, and damper and
valve arrangements that direct air and refrigerant through the system
in several different thermodynamic operating paths and cycles for
significantly improved efficiency and energy conservation.
[0004] 2. Background Art
[0005] The control of humidity in indoor environments plays a very
important role in providing indoor air quality. Reducing the volume
of moisture indoors can reduce the growth of microbiological organisms
such as mold, mildew and bacteria, which require moisture to thrive.
Airborne contaminants are also often carried with the moisture in
the supplied air streams. Most conventional air conditioning processes
and systems do not effectively control humidity, nor provide adequate
delivery air conditions, in anticipation of the various changes
and demands of the indoor or outdoor environments. Although conventional
systems provide dehumidification, it is an uncontrolled byproduct
of its evaporator coil cooling process, and results in the inadequate
control of humidity, and excessive energy consumption, and can also
result in building and or space content damage.
[0006] In the refrigerant compression closed cycle of the conventional
air conditioning system, a compressor compresses refrigerant gas
to increases its pressure and temperature, in an isentropic adiabatic
process. The refrigerant is then passed through a condenser coil
where the superheated compressed refrigerant dissipates its heat
to the crossing air stream condensing the refrigerant into a high-pressure
liquid, which then flows through a metering device or expansion
valve that restricts the high-pressure liquid and creates a reverse
refrigerant adiabatic effect, after which, the refrigerant is discharged
or suctioned to an evaporator coil at lower refrigerant temperature
and pressure conditions, which enable the evaporator coil to absorb
heat from the crossing air that is forced through the coil by the
evaporator fan. The air exiting the evaporator coil is discharged
as cool air and the refrigerant absorption process changes the refrigerant
from liquid-gas to gas, which is then suctioned back to the compressor
to complete the closed cycle. Increasing the refrigerant conditions
of the evaporator, or lowering the condensing refrigerant temperature
and pressure improves the compressor and system performance and
energy consumption.
[0007] In the air cooling process, the conventional finned evaporator
coil provides dehumidification only if the saturated vapor conditions
are achieved in its crossing air, and additional cooling is typically
necessary to augment moisture removal. This accomplished by lowering
the refrigerant pressure and temperature by increasing the compressor
capacity or lowering the crossing air stream volume in the evaporator.
Efficient heat transfer of a coil is dependent upon the temperature
differential between the refrigerant temperature relative to the
temperature of the crossing air. The accumulation of water on the
evaporator fins serves as an excellent conductor for transferring
heat energy to its crossing air stream. The temperature of the water
on the fins tends to become lower quickly, because of its direct
conductive energy exchange, and at lower temperatures it consequently
crystallizes and freezes; it becomes an insulator and diminishes
energy transfer capabilities and effectiveness. The ice build can
also restrict the air path and further diminish the conductive thermal
energy transfer capabilities and efficiencies of the refrigerant.
[0008] Thus, if frost becomes a problem, the system requires sequencing
to a defrost mode, which stops the refrigeration cooling effects.
Added heat energy is often required to accelerate the ice melting
effect, or depending upon the temperature of the crossing air, the
air itself may be utilized to defrost the accumulated ice. Defrosting
or non-continuous cooling can adversely affect the air quality and/or
comfort level in the conditioned space. Additional cooling is needed
to compensate for any added heat provided by the defrost process
and circumstances.
[0009] A conventional heat pump also utilizes finned coils and
operates on the same principle as an air conditioning system, except
that it provides a reversing valve and other controls that reverse
the refrigerant flow between the evaporator and condenser coil so
that outdoor heat exchanger coil becomes the evaporator and the
indoor coil becomes the condenser. This enables the suctioned refrigerant
to absorb the remaining heat from the outdoor air and the compressed
refrigerant to dissipate its heat at the indoor coil which then
heats the conditioned space through its crossing air stream. In
the heating mode, the refrigerant cooling cycle takes place through
the outdoor coil. At low outdoor temperatures, frost tends to build
on the finned coil and lessens the system efficiencies, as previously
described; a defrosting mode to remove the frost build up becomes
necessary, which is accomplished by re-reversing the refrigerant
flow.
[0010] Desiccant assisted air conditioning systems are also known
in the art, which typically incorporate a rotating desiccant wheel
that rotates between two air streams to provide dehumidification
or humidification by alternating the energy in a gas phase change
process. In such systems, the air (process air) delivered to the
interior of a space to be conditioned space crosses the desiccant
material, which attracts and holds moisture. As the desiccant wheel
rotates, the moist desiccant material enters the regeneration air
stream where it is heated to release moisture, which is then vented
away. Because humidity is a function of vapor pressure, desiccant
materials have the ability to remove or add moisture adiabatically;
a reversible thermodynamic process in which the energy exchanges
result in substantially constant enthalpy equilibrium. The total
desiccant open cycle is somewhat similar to a refrigerant vapor-compression
cycle. In a desiccant and air system the heated regeneration air
adds energy to the moistened desiccant in a de-sorption process
and releases moisture in the regenerating crossing air stream in
an adiabatic cooling process. When the desiccant rotates to the
process air stream the pre-conditioned desiccant enables the sorption
of water and dehumidifies the crossing process air. Adiabatic re-heat
then is released in the air stream and completes the desiccant vapor-compression
open cycle.
[0011] Mathiprakasam, U.S. Pat. No. 4430864 discloses a hybrid
vapor compression and desiccant air conditioning system utilizing
an air thermodynamic cycle for simultaneous removal of the sensible
and latent heats from the room return air. The system employs a
pair of heat exchangers having a desiccant material thereon, which
replace the conventional condenser and evaporator. The refrigerant,
room and outside ambient air flows are selectively routed to the
heat exchangers to allow one heat exchanger to operate as an evaporator
to effect cooling and drying of the room return air while the other
heat exchanger acts as a condenser of the refrigerant and regenerates
the desiccant material thereon. The heat exchangers are switchable
between evaporator and condenser modes allowing for continuous conditioning
of the room return air.
[0012] The desiccant coils in U.S. Pat. No. 4430864 provide
a somewhat effective conductive energy transfer to occur, but the
desiccant serves primarily to accumulate water. The process re-uses
the condensing energy to regenerate its desiccant, which slightly
benefits the refrigeration cycle and performance by allowing refrigeration
absorption to accelerate and augment some dehumidification in the
crossing process air of the desiccant coil. However, the transferable
energy provided by the desiccant upon switching is far from being
maximized. The pre-wetted desiccant coil upon switching provides
a total cooling effect, but most of its interchangeable energy merely
replaces what a conventional condenser can already do effectively.
Very little refrigerant adiabatic cooling effect is added to augment
the compressor performance. The same is true in the process air
stream. The pre-dried desiccant merely replaces what a conventional
evaporator coil can already do effectively, and is still dependent
upon high refrigerant temperature and pressure conditions for the
removal of sensible and latent energy in its air stream. The amount
of absorbed refrigerant energy from the pre-dried desiccant and
crossing air is the direct result of the total average coil temperature
and vapor-pressure conditions of its desiccant and crossing air.
The total coil average temperature and the average regeneration
refrigerant energy transferred to the desiccant is definitely not
maximized and the pre-dried desiccant condition elevates very little
in proportion to the total average refrigerant conditions and results
in a less effective refrigerant adiabatic cooling effect in the
refrigeration cycle to augment the compressor efficiency. In the
coil switching process, the inefficient total coil average temperature
can produce a situation where the regenerated desiccant has insufficient
dryness and acts as a heat sink in the process air stream, which
results in re-heating the crossing process air and wasted heat energy.
A system with only two desiccant coils that replace the conventional
evaporator and condenser is also disadvantageous in that it does
not provide steady constant air delivery conditions when switching
the coils.
[0013] Dinnage et al, U.S. Pat. Nos. 6557365 6622508 6711907
Published Patent Application 2004/0060315 and Published Patent
Application 2005/0050906 disclose systems utilizing rotary desiccant
wheels, and utilizing rejected condenser heat as energy to regenerate
the desiccant. In general, the basic refrigeration system incorporates
part of the condenser coil in the regeneration air stream prior
to the desiccant wheel and the evaporator coil prior to the desiccant
wheel, in the process air stream. The refrigerant energy is re-used
to regenerate the desiccant and the evaporator provides refrigeration
capacity and conditions the process air prior contacting the wheel.
As with most desiccant wheel systems, this process has limitations
in effective cooling. The regeneration entering air is low in temperature,
and the vapor-pressure conditions are provided to the desiccant
externally in a gas phase change process, rather than heating it
directly by the internal refrigerant. Energy is also consumed by
continuously rotating the desiccant wheel.
[0014] Forkosh et al, U.S. Pat. Nos. 6487872 6494053 6546746
Published Patent Application 2004/0112077 and Published Patent
Application 2005/0211207 disclose dehumidification and air conditioning
systems utilizing liquid desiccants. Dehumidifying systems based
on liquid desiccants dehumidify air by passing the air through a
tank filled with desiccant. The moist air enters the tank via a
moist air inlet and dried air exits the tank via a dried air outlet.
In most liquid desiccant systems, a shower of desiccant from a reservoir
is sprayed into the tank and, as the desiccant droplets descend
through the moist air, they absorb water from it. The desiccant
is then returned to the reservoir for reuse. This causes an increase
in the water content of the desiccant. Water saturated desiccant
accumulates in the reservoir and is pumped therefrom to a regenerator
unit where it is heated to drive off its absorbed water as vapor.
Regenerated desiccant, which heats up in this process, is pumped
back into the reservoir, for reuse. Since the water absorption process
leads to heating of the air and the regeneration process heats the
desiccant, substantial heating of the air takes place during the
water absorption process.
SUMMARY OF THE INVENTION
[0015] The present invention overcomes the aforementioned problems
and is distinguished over the prior art in general, and these patents
in particular, by a desiccant-assisted air conditioning system and
process which utilizes a compressor, a condenser coil, an evaporator
coil, supplemental desiccant coils, and damper and valve arrangements
that direct air and refrigerant through the system coils in several
different thermodynamic operating paths and cycles for significantly
improved operating efficiency, energy conservation, and conditioned
air output. The system effectively combines, transfers and reverses
thermodynamic energies between the desiccant, the refrigerant and
the crossing air, and maximizes the refrigerant vapor compression
closed cycle and desiccant vapor compression open cycle.
[0016] The present invention utilizes the conventional condenser
and evaporator coils in combination with a pair of desiccant coils
to increase total coil average temperature and refrigerant energy
transfer capacity to the desiccant in regeneration. The system not
only utilizes the desiccant coils to exchange energy externally
in the crossing air gas phase, but also utilizes the desiccant coil
properties to augment the refrigerant absorption and rejection energies,
and utilizes the properties of the refrigerant to exchange internal
heat energy with the desiccant coils to condition the desiccant
more efficiently.
[0017] The normally rejected refrigerant energy is transferred
from the conventional condenser coil to the first desiccant coil,
thereby increasing its refrigeration pressure and temperature capacity.
The concentrated refrigerant energy and increased capacity dissipates
the concentrated heat through the desiccant material, thereby increasing
the vapor-pressure differential of the desiccant in relation to
its crossing air stream and vapor pressure conditions. The increased
refrigerant energy regenerates the desiccant material to a dryer
condition prior to the switching to a cross flow mode of operation.
In this process, the adiabatic cooling effect of the second desiccant
coil provided by the evaporation of the water content in its desiccant
material to the passing air stream is not adversely affected because
of the transferred increased concentrated refrigerant energy and
capacity, which is transferred gradually. The sorption process and
adiabatic heating effect of the second desiccant coil provides normally
rejected work energy which is used in series with the refrigerant
compressor to serve as a co-generator in the refrigeration cycle,
and also provides simultaneous rapid cooling of the desiccant, accelerates
dehumidification of its air stream with no appreciable sensible
heat added to the air stream, and allows the accumulation of moisture
prior to switching from a straight airflow mode to a cross airflow
mode.
[0018] In a combined refrigerant closed cycle and desiccant open
cycle, the refrigerant compression process occurs during the desiccant
sorption process; the refrigerant condensing process occurs during
the desiccant regeneration process; the refrigerant expansion process
occurs during the desiccant de-sorption process; and the refrigeration
evaporative process occurs during the desiccant expansion process.
In a refrigerant closed cycle and desiccant switching cycle, the
air and refrigerant paths are switched between the first and second
desiccant coils so that two sets of processes occur at the same
time. The desiccant de-sorption and regeneration process occurs
at the same time as the refrigerant expansion and condensing process,
and while the desiccant sorption and expansion process are also
occurring at the same time as the refrigeration compression and
evaporation process.
[0019] In the cross flow mode and desiccant switching cycle, when
the second coil has a diminished capacity to attract moisture and
after the first has sufficiently dried, the air and refrigerant
paths are switched between the desiccant coils and the previously
moistened second coil becomes the desiccant regeneration coil and
the dried first coil becomes the process desiccant coil. Thus, their
roles are reversed, and the states of their previous moisture conditions
facilitates the desiccant sorption and de-sorption process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In the drawing figures of the present invention, described
in detail hereinafter, the heavy line arrows represent the airflow
path of air and the thinner lines represent the flow path of refrigerant.
[0021] FIG. 1 is a diagrammatic view illustrating the components
of the air conditioning system showing the airflow and refrigerant
paths for routing the air and refrigerant through the coils in a
straight flow cooling mode of operation.
[0022] FIG. 2 is a diagrammatic view illustrating the components
of the air conditioning system showing the airflow and refrigerant
paths for routing the air and refrigerant through the coils in a
cross flow cooling mode of operation.
[0023] FIG. 3 illustrates schematically the air conditioning system
with the components incorporated in a conventional building air
conditioning system and showing the airflow and refrigerant paths
for routing the air and refrigerant through the outdoor condensing
unit and through the coils in the cross flow cooling mode of operation,
similar to FIG. 2.
[0024] FIG. 4A is a schematic perspective view of a desiccant coil
suitable for use in the present system.
[0025] FIG. 4B is a diagrammatic view illustrating an alternate
evaporator and desiccant coil parallel/series arrangement for the
present air conditioning system.
[0026] FIG. 5 is a diagrammatic view illustrating the components
of the air conditioning system showing the airflow and refrigerant
paths for routing the air and refrigerant through the coils in an
augmented straight flow dehumidification mode of operation.
[0027] FIG. 6A is a partial diagrammatic view illustrating the
components of the air conditioning system having an alternate coil
arrangement and showing the airflow and refrigeration path for routing
the air and refrigerant through the coils in straight flow condenser
reheating mode of operation
[0028] FIG. 6B is a partial diagrammatic view illustrating an alternate
evaporator and parallel/series desiccant coil arrangement.
[0029] FIG. 7 is a diagrammatic view illustrating the components
of the air conditioning system in an alternate heat pump/dehumidification/humidi-
fication air conditioning arrangement and showing the airflow and
refrigeration path for routing the air and refrigerant through the
coils in a straight flow cooling mode of operation.
[0030] FIG. 8 is a diagrammatic view, similar to FIG. 7 showing
the airflow and refrigeration path for routing the air and refrigerant
through the coils in a straight flow heat pump heating mode of operation.
[0031] FIGS. 9A and 9B are partial diagrammatic views illustrating
the components and refrigerant flow path of the air conditioning
system in an alternate heat pump condenser and desiccant coil switching
arrangement, respectively.
[0032] FIG. 9C is a diagrammatic view illustrating the components
of the air conditioning system and flow paths in an alternate arrangement
for augmenting dehumidification capacity, refrigerant temperature
diversity, and coil reheating.
[0033] FIG. 10 is a diagrammatic view, somewhat similar to FIG.
1 illustrating an alternate embodiment of the system having an
additional condenser and evaporator and showing the airflow and
refrigeration path for routing the air and refrigerant through the
coils in a straight flow mode of operation
[0034] FIG. 11A is a diagrammatic view, somewhat similar to FIG.
9C, illustrating the components of the system showing an alternate
path for routing the air and refrigerant through the coils in a
straight flow mode of operation to enhance dehumidification.
[0035] FIG. 11B is a diagrammatic view, somewhat similar to FIG.
11A, illustrating the components of the system showing an alternate
path for routing the air and refrigerant through the coils in a
straight flow mode of operation to enhance dehumidification and
cooling.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] As used herein, the term "air conditioning" is
a general term and includes dehumidified air, humidified air, and
cool or warm air, or a combination thereof. The term "process
air" means any air that is to be processed by the present system.
The term "regeneration air" means any air that is used
to regenerate the desiccant material. The term "supply air"
means the air that is supplied to a spaced to be provided with conditioned
air. The term "return air" means the air either returning
from the conditioned space or newly introduced air. The term "refrigerant"
means a substance used as an agent for cooling or heating, and includes
such substances in a liquid, gas, or vapor form. The term "desiccant"
means a drying substance or agent and may include materials such
as silicas, aluminas, titanium, lithium chloride, zeolites, polymers
and clay. The term "compressor" means a machine for reducing
the volume and increasing the pressure of gases in order to condense
and expand the gases. The term "condenser" means a device
for reducing gases or vapors to liquid form and includes air-cooled
and water-cooled heat exchangers.
[0037] In the drawing figures of the present invention, described
in detail hereinafter, the heavy line arrows represent the airflow
path of air and the thinner lines represent the flow path of refrigerant.
The outdoor portion of the system is shown at the top of the figure,
the indoor portion is show at the center, and the refrigerant flow
and valving arrangement for the desiccant coils is shown at the
bottom.
[0038] Referring now to the drawings, there is shown diagrammatically
in FIG. 1 the components of the present air conditioning system
showing the airflow and refrigerant paths for routing the air and
refrigerant through the coils in a straight flow cooling mode of
operation.
[0039] The present apparatus includes a conventional compressor
10 connected by a refrigerant discharge line 24 to the intake of
a condenser coil 11 having a condenser fan 12 that draws outdoor
air 7 through the condenser coil and exhausts it back to the outdoors
8. A conventional evaporator coil 13 is connected with the compressor
10 and the condenser coil 11 through a piping and valving arrangement,
as described in detail hereinafter. Process air 1 is drawn across
the evaporator coil 13 by a process air blower or fan 14 and is
discharged as supply air 9 either into the space to be conditioned
2 or a portion may be selectively conducted through a damper assembly
18A, 18B and across either of a pair of desiccant coils 19 20
as described hereinafter.
[0040] In the present system, a first desiccant coil 19 and a second
desiccant coil 20 are disposed between a first damper assembly 18A
and a second damper assembly 18B. Desiccant regeneration air 5 is
drawn by a regeneration air fan 16 through the damper assemblies
18A and 18B and exhausted as regeneration air exhaust 6 to the outdoors
or other suitable area. A desiccant process air fan 15 draws a portion
of the discharged supply air 9 from the evaporator coil 13 as desiccant
process air 3 through the damper assemblies 18A and 18B and discharges
it as desiccant process discharge air 4 back into the supply air
9 which is conducted into the space to be conditioned 2. The first
and second damper assemblies 18A and 18B have movable dampers 17A,
17B, 17C, and 17D for selectively directing the passage of desiccant
regeneration air 5 and desiccant process air 3 across either of
the first or second desiccant coils 19 or 20.
[0041] As shown at the bottom of FIG. 1 the first desiccant coil
19 is connected in series with a first port of a first reversing
valve 21 and a first port of a second reversing valve 22 by refrigerant
lines 40A and 40 B. The second desiccant coil 20 is connected in
series with a second port of the first reversing valve 21 and a
second port of the second reversing valve 22 by refrigerant lines
40C and 40 D. The suction side of the compressor 10 is connected
by a refrigerant line 26 to a third port of the first reversing
valve 21 and the outlet of the condenser coil 11 is connected by
a refrigerant line 25 to a fourth port of the first reversing valve
21.
[0042] The evaporator coil 13 is connected in series between a
third port of the second reversing valve 22 by a refrigerant line
28 and a fourth port of the second reversing valve through refrigerant
line 27 a metering device or expansion valve 23 and refrigerant
line 39. The reversing valves 21 22 can selectively redirect the
refrigerant path, as described hereinafter.
Straight Flow Cooling Mode
[0043] FIG. 1 shows the components of the present air conditioning
system and the airflow and refrigerant paths for routing the air
and refrigerant through the coils in a straight flow cooling mode
of operation.
[0044] The compressor 10 discharges high pressure superheated refrigerant
via line 24 through the condenser coil 11. The condenser fan 12
draws outdoor air 7 across the condenser coil 11 the refrigerant
dissipates heat at the coil and condenses into a high-pressure liquid,
and the heated air is exhausted back to the outdoors.
[0045] The cooled refrigerant from the condenser coil 11 flows
through line 25 to the first reversing valve 21 which is positioned
to direct the refrigerant via line 40A through the first desiccant
coil 19 through line 40B to the second reversing valve 22 which
is positioned to direct the refrigerant via line 39 through the
metering device or expansion valve 23. It is important to note that,
since the coils 11 and 19 are in series, the superheated refrigerant
is first cooled by the condenser coil 111 before entering the desiccant
coil 19. After passing through the metering device or expansion
valve 23 the refrigerant flows via line 27 into the evaporator
coil 13.
[0046] When the high-pressure cooled refrigerant passes through
the metering device or expansion valve 23 it is restricted and
it enters the evaporator coil 13 at a lower temperature and pressure.
The refrigerant passing through the evaporator coil 13 absorbs heat
from the process intake air 1 drawn across the coil by the process
air fan 14 and air exiting the evaporator coil is discharged as
cool air, at lower temperature and increased saturated vapor conditions.
After passing through the evaporator coil 13 the refrigerant passes
through refrigerant line 28 back through the second reversing valve
22 through line 40D, through the second desiccant coil 20 through
line 40C to the first reversing valve 21 which is positioned to
permit the refrigerant to continue through line 26 to the suction
side of the compressor 10. It is important to note that, since the
coils 13 and 20 are in series, the coldest refrigerant first enters
the evaporator coil 13 before entering the desiccant coil 20.
[0047] In the straight flow mode, as shown in FIG. 1 the dampers
17A and 17B of the damper assemblies 18A and 18B are positioned
to permit the air flow to cross straight across the desiccant coil
19 and the first desiccant coil 19 serves as the regeneration desiccant
coil. The regeneration air fan 16 draws desiccant regeneration air
5 straight through the first damper assembly 18A, across the first
desiccant coil 19 through the second damper assembly 18B and exhausts
it to the outdoors as regeneration air exhaust 6.
[0048] The dampers 17C and 17D of damper assemblies 18A, 18B are
positioned to allow air to flow straight across the second desiccant
coil 20 and the second desiccant coil 20 serves as the process desiccant
coil. A portion of the discharged supply air 9 from the evaporator
coil 13 is drawn by the desiccant process air fan 15 through the
first damper assembly 18A as process air 3 across the second desiccant
coil 20 through the damper assembly 18B and discharged as process
air exhaust 4 back into the supply air 9 which is conducted into
the space to be conditioned 2.
[0049] In the refrigeration condensing cycle, the refrigerant pressure
is substantially constant throughout the condenser coil 11 and the
regeneration desiccant coil 19 and the refrigerant temperature
decreases gradually through the series connected coil configurations.
The constant condensing pressure is substantially representative
of the refrigerant conditions at the saturation dew point, which
usually occurs in series, nearer to the end of this condensing cycle.
[0050] The desiccant coil 19 as explained hereinafter with reference
to FIG. 4A, may be pre-wetted to provide an additional cooling effect
to the average refrigerant condensing pressure, temperature, and
sub-cooling of the combined condenser adiabatic cooling coil 111
and desiccant regeneration coil 19. The cooling effect of the desiccant
coil 19 can be simulated by having the desiccant coil 19 replaced
by a typical coil whereby the air crossing the second coil 19 would
be entering at a lower temperature than the temperature of the air
entering the condenser coil 11. This would result in refrigerant
condensing pressure and temperature conditions similar to the effect
caused by the second air stream and coil. The evaporative cooling
effect from the desiccant coil 19 simulates the lower temperature
air stream.
[0051] Thus, the regeneration desiccant coil 19 desiccant content
provides a de-sorption process, a evaporative cooling effect, a
more direct and efficient energy transfer, and enables the refrigerant
to augment its energy dissipation, thereby resulting in lower refrigerant
pressure and temperature condenser conditions.
[0052] This arrangement enables a maximization of both coils 11
19 which are in series, and allows the hottest superheated refrigerant
to be distributed to the condenser coil 11 first to allow a highly
efficient energy transfer to occur caused by the temperature differential
between the refrigerant and its crossing air stream. Once the refrigerant
dissipates its heat at the condenser coil 11 to the crossing air
stream, the second desiccant coil 19 serves as the regeneration
desiccant coil and provides a supplemental desiccant adiabatic cooling
effect that enhances the refrigerant cycle performance and simultaneously
provides the refrigerant re-usable energy to regenerate its desiccant
content.
[0053] In the refrigerant suction or evaporation cycle, the refrigerant
pressure is substantially constant throughout the evaporator coil
13 and the process desiccant coil 20 and the refrigerant temperature
increases gradually through the series connected coil configurations.
The constant evaporating pressure is substantially representative
of the refrigerant conditions at the saturation point, which usually
occurs in series, nearer to the end of this cycle.
[0054] The desiccant coil 20 as explained hereinafter with reference
to FIG. 4A, is pre-dried to provide an additional sorption and heating
effect to the average refrigerant evaporative pressure, temperature,
and superheat conditions of the combined evaporator coil 13 and
process desiccant coil 20.
[0055] The series connected coil configuration 13 20 provides
an adiabatic heating effect wherein the air crossing the process
desiccant coil 20 enters at a higher temperature than the temperature
of the air entering the evaporator coil 13. This results in augmenting
higher refrigerant pressure and temperature conditions.
[0056] The desiccant coil 20 provides an adiabatic heating effect.
This heating effect can be simulated by having the desiccant coil
20 replaced by a typical coil whereby the air crossing the second
coil 20 would be entering at a higher temperature than the temperature
of the air entering the evaporator coil 13. This would result in
refrigerant evaporative pressure and temperature conditions similar
to the effect caused by the second air stream and coil. The sorption
adiabatic heating effect from the desiccant coil 20 simulates the
higher temperature air stream.
[0057] Thus, the process desiccant coil 20 provides a desiccant
sorption process, dehumidification and adiabatic heating effect
that augments the refrigerant conditions downstream of the evaporator
coil 13 and simultaneously decreases the desiccant vapor-pressure
conditions to increase the crossing air dehumidification.
[0058] The double effect of dehumidification and augmented refrigerant
conditions results in refrigerant pressure and temperature conditions
similar to the effect of having a co-generation compressor.
[0059] The air path sequence provides the second desiccant coil
20 with preconditioned air from the evaporator coil 13. The evaporator
coil 13 provides effective sensible energy cooling increasing the
air stream vapor ratio condition nearer to vapor saturation. The
entering air and temperature and vapor conditions entering the desiccant
coil 20 facilitate maximum desiccant evaporator coil energy transfer
and sorption for removal of water content in its air stream. Dehumidification
occurs with little air temperature increase. The re-heating effect
of the desiccant material is substantially absorbed by the passing
refrigerant and dissipated little in the air stream leaving the
coil 20. Thus the desiccant coil exhaust 4 is dehumidified and slightly
re-heated and the desiccant coil 20 more efficiently concentrates
its adiabatic energy exchange towards refrigerant suction, super-heat,
and temperature and pressure conditions, thereby increasing compressor
performance.
[0060] The combination of refrigerant and desiccant cycles results
in maximizing energy transfer during refrigerant vapor-compression
and desiccant vapor-compression, improves system performance and
reduces the energy consumption significantly.
[0061] The metering device or expansion valve 23 provides a reverse
adiabatic refrigerant process and plays an important role in the
thermodynamic effects of the desiccant coils on the refrigeration
suction cycle and reduces the likelihood of compressor overheating
or damage. A preferred metering device is a thermostatic expansion
valve having a heat-monitoring bulb that monitors and reacts not
only to the superheat but also to the inlet liquid pressure to enable
extra capacity fluctuation. Thus, if the inlet refrigerant pressure
decreases, it opens its port and allows a greater volume of refrigerant
to flow through, and also adjusts the port opening relative to the
superheat conditions of the refrigerant to provide an efficient
and safe compressor operating condition. The heat-monitoring bulb
of the metering device or expansion valve 23 is preferably strategically
located to enable maximization of the total refrigeration and desiccant
processes.
[0062] To further maximize and control the sorption process and
effect of the desiccant coil 20 the desiccant process air fan 15
may be modulated, and employed to control the percentage or quantity
of process air 3 (portion of the of the discharged supply air 9
from the evaporator coil 13) drawn across the second desiccant coil
20 to provide a steady and controlled process air delivery and conditions
anticipating the changing demands of the indoor and outdoor environments.
This modulation can either provide low relative humidity delivery
air or an added control to deliver steady conditioned air depending
on the energy stage of the desiccant coils.
[0063] The normally rejected refrigerant energy provided in the
refrigeration condensing cycle is used in the present system to
provide free work energy to regenerate and compress the vapor content
in the desiccant material of the desiccant coils. The desiccant
adiabatic cooling effect simultaneously augments the refrigeration
cycle and efficiencies. The final desiccant drying stage described
below provides an augmented energy transfer from the leaving refrigerant
to the desiccant which concurrently maximizes the desiccant conditions
prior to switching from the straight airflow mode, depicted in FIG.
1 to the cross airflow mode, depicted in FIG. 2.
[0064] When the process desiccant coil 20 has a diminished capacity
to attract moisture and after the regeneration desiccant coil 19
is sufficiently dried, the refrigerant path and the direction of
the air stream may be switched between the straight airflow, as
depicted in FIG. 1 and a cross airflow, depicted in FIG. 2 and
described hereinafter, to accommodate the existing conditions of
the desiccant coils.
[0065] To further maximize the regenerated conditioned of the desiccant
coil 19 the condenser fan 12 may be modulated, or conventional
refrigerant bypass means may be employed, to increase the pressure
and temperature conditions. The condenser fan modulation can be
applied for a short duration as the final desiccant drying stage
prior to switching the flow of any coils.
[0066] The present system results in transferring the normally
rejected refrigerant energy from the conventional condenser coil
11 to the desiccant coil 19 thereby increasing its refrigeration
pressure and temperature capacity. The concentrated refrigerant
energy and increased capacity dissipates the concentrated heat through
the desiccant material, thereby increasing the vapor-pressure differential
of the desiccant in relation to its crossing air stream and vapor
pressure conditions.
[0067] As result, the increased refrigerant energy regenerates
the desiccant material to a dryer condition prior to the switching
to the cross flow mode. In this process, the adiabatic cooling effect
of the second desiccant coil 20 provided by the evaporation of the
water content in its desiccant material to the passing air stream
is not adversely affected because of the transferred increased concentrated
refrigerant energy and capacity, which is transferred gradually
by modulating the condenser fan of the condenser 11.
[0068] The sorption process and adiabatic heating effect of the
desiccant coil 20 provides normally rejected work energy which is
used in the present system in series with the refrigerant compressor
10 to serve as a co-generator in the refrigeration cycle, allows
simultaneous rapid cooling of the desiccant, accelerates dehumidification
of its air stream with no appreciable sensible heat added to the
air stream, and allows the accumulation of moisture prior to switching
from the straight airflow mode, depicted in FIG. 1 to the cross
airflow mode, depicted in FIG. 2 and prepares itself for the switching
to be regenerated. The metering device or expansion valve 23 functions
to prevent overheating of the compressor 10 controls the co-generator
energy effect provided by the process desiccant coil conditions,
and shifts the absorbed energy for use in the refrigerant suction
cycle to augment the cooling process instead of co-generation.
[0069] In a combined refrigerant closed cycle and desiccant open
cycle, the refrigerant path is continuous and the desiccant cycle
lags the refrigeration cycle by one process. In other words, the
refrigerant compression process occurs during the desiccant sorption
process; the refrigerant condensing process occurs during the desiccant
regeneration process; the refrigerant expansion process occurs during
the desiccant de-sorption process; and the refrigeration evaporative
process occurs during the desiccant expansion process.
[0070] In a refrigerant closed cycle and desiccant switching cycle
(described below), the air and refrigerant paths are switched between
the desiccant coils 19 and 20 so that two sets of processes occur
at the same time. In other words, the desiccant de-sorption and
regeneration process occurs at the same time as the refrigerant
expansion and condensing process, and while the desiccant sorption
and expansion process are also occurring at the same time as the
refrigeration compression and evaporation process. Both the desiccant
open cycle and switching cycle result in the same effect and enables
the maximum transferable, reversible, interchangeable energies to
occur between its agents to improve effective cooling in the process
air stream. Each occurring refrigeration process simultaneously
improves each occurring desiccant processes and vice versa.
[0071] Alternatively, the compressor 10 may also be sequenced to
stop and consequently stop the refrigeration effect provided to
the desiccant coil 20. As result of dehumidification re-heating
of the air stream occurs to balance the desiccant enthalpy and no
energy is absorbed by the refrigeration process. The discharged
desiccant process air 4 delivers less dehumidification but provides
a sensible re-heat effect until the desiccant and air stream vapor-pressure
difference reaches equilibrium. This alternate mode also accommodates
the water residue usually remaining on the evaporator coil 13 which
re-evaporates into its air stream after the compressor has stopped.
[0072] If at anytime during normal operation, prior to the final
desiccant drying process, the desiccant moisture becomes insufficient
to provide adequate adiabatic cooling, additional water may be added
to augment and enable the refrigerant cooling effects to occur.
Adding water can damage the pores of the desiccant, so preferably
the water is added into the air stream before crossing the coil.
The desiccant then would interchange its moisture and energy content
with the air stream resulting a favorable cooling effect of the
refrigerant.
[0073] It should be understood that both dampers 17A, 17B of the
damper assemblies 18A, 18B may be positioned to permit a portion
of the outdoor air intake 5 to mix with the desiccant process air
3 to provide adequate fresh air and also permit the process intake
air 3 to be exhausted to the outdoor exhaust 6. This control could
be considered as a pressure-building device and/or air exchanger
and has the benefit of re-using the conditioned space air 2 to facilitate
the cooling effect of the regeneration desiccant coil.
Cross Flow Cooling Mode
[0074] Referring now to FIG. 2 the components of the system are
shown in the cross flow mode of operation. The same components are
assigned the same numerals of reference but will not be described
again in detail to avoid repetition. However, as described below,
in this mode the pre-moistened process desiccant coil 20 (second
coil 20) becomes the desiccant regeneration coil and the dried regeneration
coil 19 (first coil 19) becomes the process desiccant coil. The
switching occurs when the process desiccant coil 20 has a diminished
capacity to attract moisture and after the regeneration desiccant
coil 19 has sufficiently dried. Thus, their roles are reversed,
and the state of their previous moisture conditions initiate a fresh
new cycle and effects.
[0075] In this mode the first and second reversing valves are positioned
such that cooled refrigerant from the condenser coil 11 flows through
line 25 to the first reversing valve 21 which directs the refrigerant
via line 40C through the second desiccant coil 20 through line
40D to the second reversing valve 22 which directs the refrigerant
via line 39 through the metering device or expansion valve 23 and
through line 27 into the evaporator coil 13. When the high-pressure
cooled refrigerant passes through the metering device or expansion
valve 23 it is restricted and it enters the evaporator coil 13
at a lower temperature and pressure. The refrigerant passing through
the evaporator coil 13 absorbs heat from the process air 1 drawn
across the coil by the process air fan 14 and air exiting the evaporator
coil is discharged as cool air, at a lower temperature and higher
vapor-pressure. After passing through the evaporator coil 13 the
refrigerant passes through line 28 back through the second reversing
valve 22 through line 40B, through the first desiccant coil 19
and through line 26 to the suction side of the compressor 10.
[0076] Also, in this mode, the dampers 17A, 17B, 17C and 17D of
the first and second damper assemblies are positioned such that
a portion of the discharged supply air 9 from the evaporator coil
13 is drawn by the desiccant process air fan 15 through the first
damper assembly 18A as process air 3 across the first desiccant
coil 19 (now becoming the process desiccant coil), through the damper
assembly 18B and discharged as process air exhaust 4 back into the
supply air 9 which may be conducted into the space to be conditioned
2; and desiccant regeneration air 5 is drawn by the regeneration
air fan 16 through the first damper assembly 18A, across the second
desiccant coil 20 (now becoming the wetted desiccant regeneration
coil), through the second damper assembly 18B and is exhausted to
the outdoors as regeneration air exhaust 6.
[0077] As described previously, when the process desiccant coil
reaches the state of having a diminished capacity to attract moisture,
and after the regeneration desiccant coil is sufficiently dried,
the refrigerant path and the direction of the air stream may be
switched repetitively between the cross airflow and the straight
airflow and vice versa, as depicted in FIG. 1 and FIG. 2. Also,
as stated previously, at any time prior to switching, the condenser
fan can be modulated to augment the regeneration coil desiccant
dryness condition. Switching the coils facilitates the desiccant
sorption and de-sorption process, and it transfers the water content
from the process air into the regeneration air stream.
[0078] FIG. 3 illustrates schematically the air conditioning system
with the components incorporated in a conventional building air
conditioning system and showing the airflow and refrigerant paths
for routing the air and refrigerant through the outdoor condensing
unit and through the coils in the cross flow cooling mode of operation,
similar to FIG. 2.
[0079] The Desiccant Coils
[0080] The desiccant coils 19 20 are similar to a conventional
heat exchanging finned refrigerant coil having refrigerant conducting
conduit or tubing with a plurality of metal fins that provide a
large heat exchange surface area to a passing air stream and shaped
to enhance both the capture and release of moisture.
[0081] FIG. 4A illustrates somewhat schematically, an example of
a finned desiccant coil suitable for use in the present system.
It should be understood that desiccant coils of various other designs
may be used in the present system, and the present invention is
not limited to the illustrated example. The coils 19 20 each have
a number of rows of metallic conduit or tubing 50 connected with
metallic header pipes 51 52 for conducting refrigerant therethrough
in a serpentine path, as is conventional in the art. A plurality
of metallic fins 53 are secured to the refrigerant tubes to form
a generally rectangular configuration having a plurality of transverse
air pathways 54. In the example shown, the adjacent fins 53 have
a corrugated shape and form a honeycombed pattern air pathway 54
to increase the surface area and enhance the capture of moisture
from the crossing air. Both surfaces of the metallic fins 53 are
coated with a desiccant material 55 as described below. It should
be understood that desiccant material may be interspersed between
the fins, and that a substrate material may be combined with the
desiccant material to provide adequate bonding and thickness.
[0082] A preferred desiccant material for use with the present
desiccant coils is an activated alumna desiccant material that has
significant adsorption capacity for water at a relative high humidity,
which typically occurs in the process air stream downstream from
the evaporator coil 13. The activated alumna can be regenerated
under air and refrigerant operating conditions during the air conditioning
or refrigeration process.
[0083] In constructing such a coil, the coil surface is coated
with the desiccant using a sol-gel process wherein a stable boehmite
sol is used as the precursor for coating the alumna on a fin assembly.
The boehmite is commercially available in powder form and is mixed
into water to form the stable boehmite sol and is stabilized with
an acid solution to charge the surface of boehmite particles. The
boehmite sol solution is then sheared to a predetermined thickness.
The desiccant coil is washed in diluted acid for cleaning. The coil
is dipped into the boehmite sol solution and then heat treated for
a period of time sufficient to convert the boehmite sol thin liquid
film into boehmite gel when the solvent is removed during a drying
process, and the boehmlte gel is then converted into gamma-alumina
during calcinations.
[0084] Even though the activated alumna provides an effective moisture
adsorbent, it does not provide adsorption for a full range of contaminant
or unwanted gases such as carbon dioxide, carbon monoxide, ozone,
sulfur dioxide, nitrogen dioxide, formaldehyde and combinations
thereof. It should be understood that the desiccant may also be
impregnated with additional substances to improve the sorbant effectiveness
for these unwanted gases. Filtration of these unwanted gases can
also result in lowering the carbon dioxide levels in the outdoor
or fresh air intake, which can reduce energy consumption.
[0085] In the regeneration desiccant coil 19 the internal condenser
refrigerant energy provides free work energy which directly increases
the temperature of the coil fins and desiccant coating vapor-pressure
relative to its crossing air stream. As result, of the vapor-pressure
differential between the desiccant and the air stream the moisture
is evaporated to the air stream. This evaporation process provides
an adiabatic cooling effect that can either cool the refrigerant
or the air stream. Since sensible energy travels by temperature
differential, the refrigerant being more elevated than the crossing
air stream dissipates its energy into the desiccant and results
in an added cooling process in the refrigerant condensing cycle.
[0086] The increased evaporation rate also causes a sensible energy
decrease or cooling effect of the conductive fin material of the
desiccant coil. This effect is similar to a sling psychrometer having
a thermometer bulb wrapped in a moist cloth and swung in an air
stream. In this comparison, the fin acts as the surrounded thermometer
bulb and its temperature is lowered by the evaporation of water
contained in the desiccant. At a constant enthalpy, the vapor-pressure
between the cloth (desiccant) and its passing air stream attempts
equilibrium and results in the sensible cooling effect caused by
vaporization and decreases the temperature of the thermometer (metal
fin).
[0087] The desiccant de-sorption process simultaneously provides
an adiabatic cooling effect in the refrigeration cycle from the
existing stored moisture content, which is released and evaporated
in the passing air stream. In the condenser cycle, the energy relationship
and capacity between the entering air stream conditions, the refrigerant
entering conditions, and the moisture content conditions of the
desiccant coil provides a favorable combination to enable most of
the energy transfer to occur in the refrigerant. However, energy
is also transferred in its passing air stream as sensible re-heat
in relation to its wet bulb temperature condition.
[0088] In a typical evaporator coil at low temperature suction,
ice can build up on the coil and due to the insulation effect of
the ice; the thermal energy transfer efficiency is reduced. Depending
on the wetted condition of the desiccant in the regeneration desiccant
coil and its capacity, the water content in the desiccant is evaporated
and it also gradually acts as an insulator, thereby diminishing
its ability to efficiently transfer heat to the air stream and consequently
affect the refrigeration cycle. As result, the condition of the
refrigerant then also increases and accelerates the drying level
of the desiccant. This feature enables the energy to be applied
to the moisture content on the fins. Although activated alumina
is capable of withstanding frost build up, it should be understood
that the desiccant thickness may be decreased in some low temperature
applications to prevent damage to its desiccant pores.
[0089] In the present system, the water content is supplied by
the switching of the pre-conditioned process desiccant coil 20.
Adding water can also benefit the evaporative cooling effect generated
to the refrigerant process. A preferable adiabatic humidifying device
disposed upstream of the regeneration desiccant coil will enable
the moisture between the air stream and the desiccant to interchange
and provide adiabatic cooling to the refrigerant process air stream.
[0090] The cooling effect of the metallic fins and conduit piping
cools the refrigerant directly and provides additional cooling to
the refrigeration cycle, which augments its energy performance and
compressor energy ratio, and facilitates efficient desiccant coil
regeneration.
[0091] As described previously with reference to FIGS. 1 and 2
the desiccant coil needs to be dried and regenerated just before
the switching of the coils, wherein the desiccant regeneration coil
becomes the process desiccant coil and vice versa. The dried desiccant
condition of the process desiccant coil provides work energy to
either the internal refrigerant or external air. The vapor-pressure
differential between the desiccant content and the crossing air
dehumidifies the air and dehumidification results in an adiabatic
heating effect. Sensible energy travels by temperature differential,
and since the refrigerant temperature is lower than the crossing
air stream, the desiccant dissipates most of its energy into the
refrigerant. The refrigerant absorbs the desiccant energy and results
in acceleration of the dehumidification process.
[0092] The regenerated desiccant coil has lower desiccant temperature
and vapor-pressure conditions, which enable the attraction of water
through its energy exchange. The desiccant sorption process simultaneously
provides an adiabatic heating effect to the refrigeration evaporator
cycle and dehumidification of its passing air stream. As a result,
the refrigerant evaporation or suction increases and the desiccant
temperature and vapor-pressure differential are lowered relative
to its air stream, thereby accelerating its rate of sorption in
an attempt to balance the enthalpy equilibrium.
[0093] In the evaporator cycle, the direction of energy transfer
of the pre-dried desiccant coil to either the refrigerant or the
air stream is dependent upon the relationship between the entering
air stream conditions and the temperature of the entering refrigerant.
Also as described above, the pre-dried desiccant can also become
an insulator. It restricts the sensible energy thermal conduction
exchange between the refrigerant and passing air, yet allows vapor
pressure to travel efficiently.
[0094] It is also important to note that the pre-cooling of the
entering air of the process desiccant coil provides a saturated
vapor-pressure condition that produces a very favorable air-vapor
condition that enables the most efficient desiccant energy output
to provide dehumidification. The desiccant refrigerant absorption
through the fins and conduit of the coil also directly cools the
desiccant, results in dehumidification in its air stream and provides
additional adiabatic heating to the refrigeration cycle increasing
its ability to moisten the desiccant coil.
[0095] The present desiccant coil arrangement incorporates both
refrigerant vapor-compression technology and desiccant vapor-compression
technology and combines the internal and external exchange of energy
of both systems.
[0096] FIG. 4B is a diagrammatic view illustrating an alternate
evaporator and desiccant coil parallel/series arrangement for the
present air conditioning system. In this arrangement, the condensed
refrigerant from the condenser 11 (shown in FIG. 1) flows through
the liquid line 25 to the first reversing valve 21 which directs
it via line 40A through the first desiccant coil 19 and then via
line 40B to the second reversing valve 22 which directs it via line
39 to the metering device or expansion valve 23. The air path is
the straight flow path previously shown and described with reference
to FIG. 1.
[0097] The refrigerant path differs from FIG. 1 in that, after
passing through the metering device or expansion valve 23 the refrigerant
flows in parallel to either the evaporator coil 13 through line
27 or through line 66 back to the second reversing valve 22. If
it is directed through the evaporator coil 13 the refrigerant from
the evaporator coil flows through evaporator suction line 67 and
an evaporator pressure regulator 76 and then through line 78 to
the compressor or a rack system. If the refrigerant is directed
back to the second reversing valve 22 it flows via line 40D through
the second desiccant coil 20 then via line 40C to the first reversing
valve 21 which directs it via line 26 through an evaporator pressure
regulator 77 then though line 79 to the suction side of the compressor
or rack system.
[0098] The refrigerant energy transfer capabilities in this arrangement
also differ from FIG. 1 in that both evaporator pressure regulator
valves 76 77 enable dual refrigerant temperatures that concentrate
refrigeration absorption energy to either the evaporator coil 13
or the second desiccant coil 20 which are in parallel and provide
different air delivery output exhaust conditions. The parallel coil
arrangement allows refrigerant intake conditions to be the same
at the evaporator coil 13 and the desiccant coil 20 provides control
of various process air delivery outputs, and allows concentrated
refrigeration absorption energy to be provided proportionally to
either coil.
[0099] Increasing the absorption capacity in the desiccant coil
20 augments dehumidification and decreases any re-heat and can also
contribute to the sensible cooling effect in its air stream. Lowering
the absorption capacity reverses the process; it diminishes any
sensible cooling effect then adds to re-heat and lower dehumidification
ability.
[0100] In the refrigeration cycle, either in the suction or liquid
side, the refrigerant pressure is constant and its temperature changes
gradually in the series in coil configurations and results in an
average total output depending upon the coil conditions. In this
process, compared to the arrangement of FIG. 1 the results may
decrease the energy consumption but still provide adequate delivery
air for the purpose intended. The evaporator constant pressure is
substantially a direct representation of the refrigerant conditions
at the saturation point, and compared to FIG. 1 can result in a
less effective refrigeration cycle. The adiabatic heating effect
can be almost non-beneficial to the refrigerant suction cycle.
[0101] Alternatively, augmented compressor capacity may be provided
to compensate for the less efficient refrigeration cycle and provide
adequate process air delivery for the purpose intended. Increasing
the absorption capacity in either the evaporator coil or process
desiccant coil enables lower air conditions to occur and vice versa.
[0102] It should be understood that, in the arrangement of FIG.
4B, the refrigerant path and the direction of the air stream across
the desiccant coils may be switched between the cross airflow and
the straight airflow and vice versa, as depicted in FIGS. 1 and
2.
[0103] FIG. 5 is a diagrammatic view, somewhat similar to FIG.
1 illustrating an arrangement for providing an augmented straight
flow dehumidification mode of operation. The refrigerant |