Abstrict A desiccant assisted air conditioning system for delivering dehumidified
refrigerated supply air into a conditioned space and with return
therefrom divided between recirculation air and exhaust-relief air
employed to remove heat resulting from dehumification and employing
waste heat from refrigeration for desiccant regeneration.
Claims I claim:
1. A desiccant assisted air conditioning system for delivering
dehumidified refrigerated supply air into a conditioned space and
with return therefrom divided between recirculation air and exhaust
- relief air employed to remove heat resulting from dehumification
and employing waste heat from refrigeration for desiccant regeneration,
and including;
a first outside air inlet duct inducting minimum outside air through
a dehumidifying section of a desiccant dehumidifying means,
a second outside air inlet duct inducting maximum outside air and
connected into said first duct for mixing with the air conducted
through the dehumidifier means and delivering mixed air through
a cooling coil of a refrigeration means,
a blower means for circulating the mixed air through the cooling
coil and through a third supply air duct opening into the conditioned
space,
the refrigeration means being comprised of a compressor means delivering
liquid refrigerant through a condenser coil for discharge of waste
heat and through means for expansion in said cooling coil and return
to the compressor means as a gas,
a fourth return air duct from the conditioned space and connected
into said second outside air inlet duct downstream from a damper
and control means therein to regulate volume inlet of maximum outside
air and volume recirculation of return air,
a fifth relief air duct from the conditioned space and conducting
conditioned space air through an evaporative air cooling means and
discharging to exhaust through a heat exchanger means passing and
cooling heated air from the dehumidifying section of the dehumidifying
means upstream of said mixing with air delivery through the cooling
coil,
a sixth outside air duct and blower means delivering air through
the condenser coil of the refrigeration means for the absorption
of waste heat and conducting the same through a desiccant regenerating
section of the dehumidifying means and to exhaust,
and control means coordinating the damper and control means and
operation of the dehumidifying means and refrigeration means.
2. The desiccant assisted air conditioning system as set forth
in claim 1 wherein the fifth relief air duct is connected to the
fourth return air duct from the conditioned space.
3. The desiccant assisted air conditioning system as set forth
in claim 1 wherein damper and control means in the fourth return
air duct regulates the exhaust through the fifth relief air duct
substantially equal to the inducting of minimumn outside air through
the first outside air duct.
4. The desiccant assisted air conditioning system as set forth
in claim 1 wherein damper and control means in the fifth relief
air duct opens into an exhaust and regulates exhaust of relief air
not required in the exhaust of cooled relief air through the heat
exhanger means removing dehumidifier heat from the inlet duct of
minimum outside air.
5. The desiccant assisted air conditioning system as set forth
in claim 1 wherein a seventh transfer duct transfers the exhaust
of the fifth relief air duct through the heat exchanger means and
to the sixth outside air duct and blower means to mix with an to
add heat to the delivery of air through the condenser coil.
6. The desiccant assisted air conditioning system as set forth
in claim 1 wherein the desiccant dehumidifying means is a wheel
type desiccant dehumidifier means continuously rotated by motor
means with a first portion thereof progressively exposed to the
first outside air inlet duct as the dehumidifying section and with
a second portion thereof progressively exposed to the sixth outside
air duct and blower means as the regenerating section.
7. The desiccant assisted air conditioning system as set forth
in claim 1 wherein the desiccant dehumidiifying means is a wheel
type desiccant dehumidifying means continuously rotated by variable
speed motor and control means and with a first portion thereof exposed
to the first outside air inlet duct as the dehumidifying section
and with a second portion thereof progressively exposed to the sixth
outside air duct and blower means as the regenerating section.
8. The desiccant assisted air conditioning system as set forth
in claim 1 wherein a seventh trandfer duct transfers the exhaust
of the fifth relief air duct through the heat exhanger means and
to the sixth outside air duct and blower means to mix with and to
add heat to the delivery of air through the condenser coil, and
wherein the desiccant dehumidifying means is a wheel type desiccant
dehumnidifying means continuously rotated by motor means with a
first portion thereof progressively opened to the first outside
air inlet duct as the dehumidifying section and with a second portion
thereof progressively exposed to the sixth outside air duct and
blower means as the regenerating section.
9. The desiccant assisted air conditioning system as set forth
in claim 1 wherein a seventh transfer duct transfers the exhaust
of the fifth relief air duct through the heat exhanger means and
to the sixth outside air duct and blower means to mix with an to
add heat to the delivery of air through the condenser coil, and
wherein the desiccant dehumidifying means is a wheel type desicant
dehumidifying means continuously rotated by variable speed motor
and control means and with a first portion thereof exposed to the
first outside air inlet duct as the dehumidifying section and with
a second thereof progressively exposed to the sixth outside air
duct and blower means as the regenerating section.
10. The desiccant assisted air conditioning system as set forth
in claim 1 wherein the desiccant dehumidifying means is a packed
type dessiccant dehumidifying means with stationary dehumidifying
and regenerating sections in the first and second outside air inlet
ducts respectively.
11. The desiccant assisted air conditioning system as set forth
in claim 10 wherein a desuperheater means passes refrigeration
gas to the compressor of the refrigeration means and cools desiccant
liquid sequentially discharged over the regenerating section and
dehumidifying section, by pump means.
12. The desicant assisted air conditioning system as set forth
in claim 1 wherein a seventh transfer duct transfers the exhaust
of the fifth relief air duct through the heat exchanger means and
to the sixth outside air duct and blower means to mix with and to
add heat to the delivery of air through the condenser coil, and
wherein the desiccant dehumidifying means is a packed type desiccant
dehumidifying means with stationary dehumidifying and regenerating
sections in the first and second outside air inlet ducts respectively.
13. The desiccant assisted air conditioning system as set forth
in claim 1 wherein a seventh transfer duct transfers the exhaust
of the fifth relief air duct through the heat exchanger means and
to the sixth oustside air duct and blower means to mix with and
to add heat to the delivery of air thnrough the condenser coil,
wherein the desiccant dehumidifying means is a packed type desiccant
dehumidifying means with stationary dehumidifying and regenerating
sections in the first and second outside air inlet ducts respectively,
and wherein a desuperheater means passes refrigeration gas to the
compressor of the refrigeration means and cools desiccant liquid
sequentially discharged over the regenerating section and dehumidified
by pump means.
14. The desiccant assisted air conditioning system as set forth
in claim 11 wherein the desiccant liquid discharged over the regenerating
section is collected in a sump discharging over the dehumidifying
section, the pump means recirculating the desiccant liquid through
a cooling coil immersed in the sump.
15. The desiccant assisted air conditioning system as set forth
in claim 1 wherein liquid injection into the compressor of the
refrigeration means is from the condenser coil and ahead of the
means for expansion of refrigerant into the cooling coil.
16. The desiccant assisted air conditioning system as set forth
in claim 1 wherein liquid injection into the compressor of the
refrigeration means is from the desuperheater means and into the
shell of a compressor.
17. The desiccant assisted air conditioning system as set forth
in claim 1 wherein the heat exchanger means is comprised of at
least one heat pipe with a "heat out" cold end exposed
to exhaust air flow through the fifth relief air duct and a "heat
in" hot end exposed to and cooling the heated air from the
dehumidfying section of the dehumnidfying means.
18. A constant volume variable temperature desiccant assisted air
conditioning system for delivering dehumidified refrigerated supply
air into a conditioned space and with return therefrom divided between
recirculation air and exhaust-relief air employed to remove heat
resulting from dehumidification and employing waste heat from refrigeration
for desiccant regeneration, and including;
a first outside air inlet duct inducting minimum outside air through
a dehumidifying section of a variable capacity desiccant dehumidifying
means having inverter means control,
a second outside air inlet duct inducting maximum outside air and
connected into said first duct and with damper and control means
having actuator means control for mixing maximum outside inlet air
with minimum outside inlet air conducted through the dehumidifying
means and delivering mixed air through a cooling coil of a refrigeration
means,
a blower and motor means for circulating a constant volume of mixed
air through the cooling coil and through a third supply air duct
opening into the conditioned space,
the refrigeration means being comprised of a variable speed compressor
and motor means having inverter means control and delivering liquid
refrigerant through a condenser coil for discharge of waste heat
and through means for expansion in said cooling coil and return
to the compressor means as a gas,
a fourth return air duct from the conditioned space and connected
into said second outside air inlet duct downstream from the damper
and control means therein for recirculation of return air,
a fifth relief air duct from the conditioned space and with damper
and control means having actuator means regulating flow of said
relief air and with a variable speed blower and motor means having
inverter means control and delivering the regulated flow of conditioned
space air through an evaporative air cooling means for discharge
to exhaust through a heat exchanger means passing and cooling heated
air from the dehumidifying section of the dehumidifying means upstream
of said mixing with air delivery through the cooling coil,
a sixth outside air duct and variable speed blower and motor means
having inverter means control and delivering air through the condenser
coil of the refrigeration means for the absorption of waste heat
and conducting the same through a desiccant regenerating section
of the dehumidifying means and to exhaust,
and control means coordinating the actuator means controls and
the inverter means controls.
19. A variable volume constant temperature desiccant assisted air
conditioning system for delivering dehumidified refrigerated supply
air into a conditioned space and with return therefrom divided between
recirculation air and exhaust-relief air employed to remove heat
resulting from dehumidification and employing waste heat from refrigeration
for desiccant regeneration, and including;
a first outside air inlet duct and variable speed blower and motor
means having inverter means control and inducting minimum outside
air through a dehumidifying section of a variable capacity desiccant
dehumidifying means having inverter means control,
a second outside air inlet duct inducting maximum outside air and
connected into said first duct with damper and control means having
an actuator means control for mixing maximum outside inlet air with
minimum outside inlet air conducted through the dehumidifying means
and delivering mixed air through a cooling coil of a refrigeration
means,
a variable speed blower and motor means for circulating a variable
volume of mixed air through the cooling coil and through a third
supply air duct opening into the conditioned space,
the refrigeration means being comprised of a variable speed compressor
and motor means having inverter means control and delivering liquid
refrigerant through a condenser coil for discharge of waste heat
and through means for expansion in said cooling coil and return
to the compressor means as a gas,
a fourth return air duct from the conditioned space and connected
into said second outside air inlet duct downstream from the damper
and control means therein for recirculation of return air,
a fifth relief air duct from the conditioned space and with damper
and control means having actuator means regulating flow of said
relief air and with a variable speed blower and motor means having
inverter means control and delivering the regulated flow of conditioned
space air through an evaporative air cooling means for discharge
to exhaust through a heat exchanger means passing and cooling heated
air from the dehumidifying section of the dehumidifying means upstream
of said mixing with air delivery through the cooling coil.
a sixth outside air duct and variable blower and motor means having
inverter means control and delivering air through the condenser
coil of the refrigeration means for the absorption of waste heat
and conducting the same through a desiccant regenerating section
of the dehumidifying measn and to exhaust,
and control means coordinating the actuator means controls and
the inverter means controls.
Description BACKGROUND OF THE INVENTION
This invention relates to an electrically operated system that
conditions air to be used in occupied building space so that it
is both cooled and dehumidified. The optimum temperature range for
human comfort is well established while the humidity range is recognized
but not universally applied. For example, heretofore a range of
20% to 80% was thought to be permissive, while a more optimum range
of 40% to 60% is now shown to be required in order to minimize and/or
eliminate bacterial, viral and fungal growth. Humidity has its affect
upon air cleanliness, as it reduces the presence of dust particles,
and the deterioration of building structure and contents, otherwise
subjected to excess moisture. Accordingly, humidity control becomes
an important factor as related to both human comfort and health,
and to structural longevity as well.
Electrically powered mechanical refrigeration is employed here
for sensible cooling, and desiccant dehumidification is combined
therewith. Supply air (SA) to the building space is from both outside
air (OSA) and return air (RA), the proportion thereof being a greater
amount of return air and a minimized amount of outside air, for
example 75% RA to 25% OSA. The minimum outside air is dehumidified
and mixed with return air and controlled by a damper prior to cooling
by means of direct expansion in evaporator coils of the refrigeration
system, the air cooled or chilled thereby being discharged into
the building space as supply air (SA).
A feature of this invention is the desiccant dehumidifier that
is regenerated by a column of heated air tempered by waste heat
of the refrigeration system, a mechanical system with a condenser
coil thereof in the heated air column at the regeneration side of
the dehumidifier. It is to be understood that a solid desiccant
or liquid desiccant dehumidifier can be employed as desired. In
practice, a solid desiccant system is prefered, of the dynamic type
and of rotary bed configuration, wherein the bed is a wheel comprised
of a screen of tubes or plates of solid desiccant to which air can
be continuously exposed, progressively exposed to a dehumidifying
air duct and then to a regeneration air duct. The dehumidifying
is from minumum outside air (OSA) to be mixed with return air (RA)
and then cooled and discharged as supply air (SA). The regeneration
air duct is also from outside air (OSA) to be discharged to ambient
as exhaust (EXH). The greater portion, approximately 2/3 of the
rotary bed of desiccant is exposed to the dehumidifying duct, while
the lesser portion, approximately 1/3 is exposed to the regenerating
air duct. The heated air regeneration duct is supplied with outside
air (OSA) by means of a blower, and the air heated by a condenser
coil, and then discharged to atmosphere (EXH) after regeneration
of the desiccant. The air ducts are sealed with the rotary bed of
desiccant which is rotated slowly by a variable speed motor.
By using a solid desiccant to precondition the minimum outside
air (OSA) it is possible to operate the evaporator coil at a substantially
elevated temperature as compared with the conventional mechanical
refrigeration systems, thereby reducing net energy requirements
for the same net cooling load. When air is dried with desiccants,
it's temperature rises because the latent heat and heat from the
regenerated desiccant and its carrier are transferred to the dried
air. Therefore, it is an object of this invention to compensate
for this heat rise effect by providing an after cooling means associated
with the exhaust of excess return air (RA) to atmosphere, utilizing
a cooling effect therefrom to remove heat leaving the dehumidifying
desiccant. thereby reducing load on the downstream refrigerant evaporation
coil. The relative cooling requirements of the different available
desiccants relate directly to the amount of regenerating energy
employed, because of the carryover of heat by the desiccant and
associated structure. This heat, plus the heat of condensation,
must be removed by cooling. As a result, relative cooling requirements
for the different types of commercially available dehumidifiers
represent a significant portion of the regeneration energy requirement.
In accordance with this invention, the after cooling means is embodied
in several forms. The excess discharge of return air (RA) is at
a relatively low temperature and of relatively low humidity, coming
from the conditioned air space, and is subject to being evaporatively
cooled. Accordingly, it is this exhaust air flow which is advantageously
utilized to absorb heat from heated air leaving the desiccant dehumidifier;
in one embodiment by means of evaporatively cooled air flowing through
a heat exchanger; and in one embodiment by means of heat pipes extending
between cold side and hot side heat exchangers in the return air
exhaust duct and in the desiccant dehumidifier delivery duct. As
will be described, the evaporative cooler and/or heat pipes transfer
heat energy between the outgoing and incoming air.
Desuperheating is used to supply liquid desiccant in the liquid
desiccant embodiment herein disclosed, to spray cooler desiccant
liquid into the humidifying section thereof. The dehumidifying fluid
circuit is associated with the refrigeration compressor as will
be described.
SUMMARY OF THE INVENTION
This invention involves dehumidification and refrigeration of air,
utilizing a desiccant, and preferably a solid desiccant rotary wheel
in an electrically operated package air-conditioning or heat pump
unit. By reducing the operating cost of regenerating the desiccant
using a novel recovery system, net savings are realized so as to
recover any additional investment costs. The combined components
of a vapor-compression system with a desiccant system, a hybrid
system, efficiently removes the sensible and latent cooling loads,
a general object of this invention. The vapor-compression machine
operates with higher evaporator temperatures resulting in a higher
thermal (COP) or coefficient of performance than conventional vapor-compression
units wherein both latent and sensible loads are removed by a common
evaporator coil. A feature is that this hybrid system requires no
reheat for regeneration, while the dehumidifier need only remove
sufficient moisture to meet the latent load as the sensible load
is met by the vapor-compression machine, and consequently no overdrying
is required. This system thereby reduces the size of the dehumidifier
wheel and also the amount of energy required to regenerate the dehumidifier,
as compared with a separate desiccant system. A primary advantage
of this hybrid system is that it reduces the required energy input,
due to an increased overall coefficient of performance, heat rejected
by the refrigeration condenser air coil being used to regenerate
the desiccant, eliminating the need for external regenerative heat.
The performance of a desiccant dehumidifier is a direct function
of the type of desiccant material used, the internal geometry of
the dehumidifier (i.e., manner/arrangement by which the desiccant
is deployed within the dehumidifier matrix), and the equipment operating
parameters. The material type affects size, range of operation (temperature,
humidity), efficiency, cost, and service life. The desiccant choice
also affects the thermal COP and cooling capacity of the system.
The geometry of a dehumidifier affects it's pressure drop, size,
and cost, and thus the thermal and electrical COP'S and cost of
the cooling system. Control strategies also affect the overall performance.
Silica gel has a high moisture recycling capacity, whereas lithium
chloride, a hygroscopic salt used in currently available commercial
dehumidifiers, is preferred and considered the state of the art
desiccant for wheel type dehumidifiers, in particular. Parallel
passage geometries have high rates of heat and mass transfer and
low pressure drop. Savings in refrigeration capacity can be achieved
by using a solid desiccant wheel in lieu of a conventional cooling
coil to remove the latent load associated with minimum outdoor ventilation
air flow. Accordingly, minimum outdoor air requirements necessary
for maintaining satisfactory indoor air quality increase significantly
due to use of tighter building envelopes, and greater indoor air
quality (IAQ) concerns for outdoor/indoor contaminants. Therefore,
this all electric solid desiccant unit requires less refrigeration
capacity per net cooling ton, and the comparative performance of
the installed refrigeration also improves significantly since the
cooling coil suction temperature is raised and dehumidificaiton
provided upstream of the cooling coil.
Desiccant dehumidification significantly reduces the latent cooling
load burden on the refrigeration equipment, and overall effect is
a net increase in efficiency. Therefore, if the refrigeration equipment
performs only sensible cooling, then the ventilation and air conditioning
equipment will be using far less energy for the same thermal load
requirement, due to operation at a higher suction temperature. Use
of a solid desiccant dehumidifier wheel essentially allows operating
at a higher apparatus dew point so as to provide the same supply
air condition compared to the non-use of desiccant dehumidification.
As an approximation example, the horsepower per ton for a compressor
alone increases between 15 to 20 percent when the required evaporator
temperature drops from 40.degree. to 30.degree. F., the effect on
the sensible heat ratio. There is a need of reheating for refrigeration
dehumidification in those situations where coil temperatures approach
freezing, so that coil condensation is always maintained above freezing
on the air supply side.
The major operating cost of a desiccant dehumidifier wheel is the
reactivating cost, since moisture absorbed by the desiccant must
be removed in order to reactivate the desiccant for subsequent re-use.
Heretofore, air has been preheated using heaters and then applied
to dry the desiccant. With the present invention, efficiency at
design conditions is improved by using the waste heat from the refrigeration
condenser to heat the reactivation air. For units operating year-round
reactivation heat recovery is particularly effective during winter
when reactivation inlet air temperatures are relatively low. In
practice, it is possible to provide heated regenerator air temperature
up to 210.degree. F. using refrigerant-22. The moisture removal
capacity of the reactivation air depends upon the prevailing outdoor
weather conditions. However, for the required temperature of the
reactivation for silica gel or lithium chloride liquid desiccants,
air is not likely to exceed 210.degree. F. for most comfort applications.
Generally and for example, only 50% of the energy recovered will
be required to completely reactivate the desiccant using preheated
air at 190.degree. F.
One of the recognized problems in using a desiccant wheel exposed
to both incoming untreated air and heated regeneration air is the
associated thermal dumpback by conduction from the desiccant wheel
to the treated air which must then be removed by the downstream
cooling coil. It is an object of this invention to reduce this substantial
parasitic load by reducing the condenser coil discharge air temperature
automatically as latent loading is decreased by means of injecting
liquid refrigerant directly into the compressor while not affecting
its overall cooling capacity. Liquid injection is used herein to
increase the pressure ratio in a positive displacement type compressor.
Liquid injection also serves as a means to reduce its discharge
gas temperature and thereby reduce motor temperature, since its
associated hermetically sealed compressor motor is cooled by discharge
gas. For general purpose air conditioning, the pressure ratio does
not normally require special cooling if the motor is cooled by suction
gas. However, where higher discharge tmeperatures are required for
the regeneration of desiccant wheels, use of liquid injection reduces
excessive temperatures otherwise resulting from an increase in resulting
pressure ratios. This liquid injection is by means of metering a
small amount of liquid from the condenser to the compressor compression
chamber. And, since this injection occurs essentially after the
chamber is closed, the capacity is about the same, while the discharge
temperature is lower at any corresponding increased pressure ratio.
This injected liquid is an effective means that reduces discharge
temperature.
The foregoing and various objects and features of this invention
will be apparent and fully understood from the following detailed
description of the typical preferred forms and applications thereof,
throughout which description reference is made to the accompanying
drawings.
THE DRAWINGS
FIG. 1 is a schematic diagram of the desiccant assisted air conditioning
system of the present invention, characterized by after cooling
means, a cooled return air embodiment, that absorbs heat energy
resulting in the heat rise from the dehumidifying desiccant and
the discharge therefrom that employs waste heat from refrigeration
and used for regeneration of the desiccant.
FIG. 2 is a perspective diagram of the rotary desicant wheel of
FIG. 1 and its relationship to waste refrigeration heat and to return
air and exhaust associated with the after cooling means.
FIG. 3 is a schematic diagram, similar to a portion of FIG. 1
showing an embodiment of the invention characterized by the after
cooling means applied to a packed type desiccaant dehumidifier.
FIG. 4 is a perspective diagram of the packed type dehumidifier,
illustrating its relationship to the waste refrigeration heat and
to cooled return air associated with the after cooling means.
FIG. 5 is a schematic diagram similar to FIG. 1 showing an embodiment
of the invention characterized by the after cooling means employing
heat pipes that absorb heat energy resulting in the heat rise from
the dehumidifying desiccant.
FIG. 6 is a perspective fragmentary section of a heat pipe configuration
employed in the embodiment of FIG. 5 and
FIG. 6a is a sectional view showing an improved form of heat pipe,
finned for efficiency, it being understood that the solid desiccant
wheel can be substituted for by the packed type desiccant of FIG.
3 when employing heat pipes for energy transfer.
FIG. 7 is a psychometric graph of this desiccant dehumidification
plus sensible cooling process without reheat, compared with a conventional
refrigeration process using sensible cooling and dehumidification
plus reheat.
FIG. 8 is a diagram of said conventioanl process, and
FIG. 9 is a diagram of this invention and its desiccant dehumification.
PREFERRED EMBODIMENT
Referring now to the drawings, this invention provides a Desiccant
Assisted Air Conditioner which is characterized by desiccant dehumification
plus sensible cooling. As shown generally in FIG. 1 of the drawings,
minimum, approximately 25%, outside air (OSA) enters through dehumidifiying
means D, while maximum, approximately 75%, return air (RA) is recirculated,
both entering through a cooling coil 9 of a sensible cooling refrigeration
means R to be discharged as supply air (SA) into an occupied space
or the like to be air conditioned thereby. Since there is a continuous
induction of outside air (25%), there is an exhaust duct 10 controlled
by a variable damper and control means 11 which controls the exhaust
of relief air as may be required, this relief air being usefully
employed in the after cooling means C which characterizes this invention.
As shown, there is a variable damper and control means 12 controlling
the inlet of outside air (OSA) that is mixed with the recirculated
return air (RA) so that the required volume of air is replaced and
so that the mixed air is not less than about 55.degree. F. at the
entry through the refrigeration coil 9. Accordingly, there is an
outside air inlet duct 13 for induction of minimum outside air to
be dehumidified, there is an outside air inlet duct 14 for induction
of maximim outside air to be mixed with the dehumidified air from
duct 13 there is a supply air duct 15 into the air conditioned
space, there is a return air duct 16 from the air conditioned space,
and there is the exhaust duct 10 and variable damper control means
11 that separates the required volume of return air from duct 16.
The damper control means 11 and 12 operate independently and/or
together, and inversely proportion the two columns of air as may
be required upon demand for 100% air circulation through the cooling
coil 9.
Referring now to the graph of FIG. 7 and to the diagrams of FIGS.
8 and 9 return air (RA) enters through the refrigeration cooling
coil 9 at 2 and is discharged as supply air (SA) at 3. However,
in the case of the conventional process shown in FIG. 8 the refrigeration
energy line extends to 4 whereas the refrigeration energy line
in this process shown in FIG. 9 extends only to 3; a substantially
lower energy use without the requirement for reheating. Note the
absence of a reheating coil in FIG. 9. In practice, the energy saving
with this invention can be 10% to 15% and reheating after refrigeration
is eliminated.
The dehumidifier means D can vary in form and mode of operation
as may be required, and is of the regeneration type having a dehumifying
section 20 in the outside air inlet duct 13 and having a regenerating
section 21 in a separate outside air duct 22. The dehumidifying
section 20 discharges through a heat exchanger 23 and into the outside
air inlet duct 14 ahead of the refrigeration cooling coil 9 whereby
the heat rise due to desiccant dehumidification is reduced and/or
removed from the induced column of air through duct 13. Heat exchanger
23 is part of the after cooling means C as will be described. As
shown in FIG. 2 approximately one third of the desiccant wheel
is devoted to the inlet duct 13 for the induction of minimum outside
air, while two third of the desiccant wheel is devoted to regeneration
of the moisture saturated desiccant, by means of heated or tempered
air delivered through duct 22 wherein waste heat is recovered from
the refrigeration means R. As shown in FIGS. 1 and 2 the desiccant
dehumidifier means D is a solid desiccant wheel, whereas the dehumidifier
means D' shown in FIGS. 3 and 4 is a packed type apparatus which
is stationary. The desiccant wheel 25 of FIGS. 1 and 2 revolves
by means of a variable speed motor and control means 26.
In FIGS. 3 and 4 of the drawings the packed type desiccant dehumidifier
D' is comprised of stationary sections 20' and 21' for dehumidifying
and regeneration respectively. As shown, a desiccant spray bar 27
supplied with desiccant from a desuperheating means 28 discharges
through the core of regenerating section 21' and into a sump 29
from which it flows through a spraybar 30 for discharge through
the core of the dehumidifying section 20' and into a sump 31 from
which it is circulated by a pump P through a cooling coil 32 immersed
in the sump 29 and recirculated through the desuperheating means
28. As shown, the hot suction refrigeration gas passes through the
desuperheating means 28 for decreasing its temperature, thereby
removing its superheat while causing an increase in the temperature
of the spent desiccant, to assist in its subsequent regeneration
by liberating the moisture therefrom. In practice, a portion of
the refrigeration gas discharge is routed through the desuperheater
means 28 a part of the refrigeration coil, where heat is removed.
This cooler desuperheated gas returns to the compressor and is mixed
with the discharge gas to produce a cooler more dense mixture that
passes over the motor and its windings to remove more heat than
possible with gas that is not desuperheated. The dehumidified air
passing through the dehumidifier section 20 or 20' experiences a
heat rise that is reduced if not eliminated by the after cooling
means C as will be described.
The refrigeration means R is shown for refrigeration only, though
it may be a heat pump means when so desired. There is a compressor
and variable speed motor means 33 to direct compressed refrigerant
through a condenser coil 34 from which it discharges through a capillary
tube 35 and expands through the cooling coil 9. The above described
desuperheating means 28 connection is adjacent to the refrigerant
discharge so that much of the oil passing through the compressor
will be entrained with the gas flowing into the coil of the desuperheater
means 28. This oil will then be carried with the gas and returned
to the compressor to be mixed with the oil returning from the motor
and integral separating elements, all of which are cooled thereby.
The resulting drop in compressor temperature will cause less superheating
of the suction gas and a greater mass flow rate. The increase in
cooling effect is greater than the increase in power consumed, thereby
producing a substantial increase in desuperheating effect. In accordance
with this invention, liquid injection into the comnpressor is at
36 into the compressor shell, which does not decrease compressor
capacity, as a full suction volume will have been taken into the
compressor shell before the liquid flashes or expands. Power consumption
and system charge will only be marginally higher, approximately
1.degree. to 2.degree..
The refrigeration means R absorbs heat from the two columns of
air emanating from the inlet duct 13 and recirculation duct 14
by means of the evaporative cooling coil 9. Refrigerated air passing
through coil 9 is delivered by a blower 37 through the duct 15 as
supply air (SA). The minimum outside air (OSA) entering through
duct 13 experiences a significant heat rise as it is dehumidified
when passing through the dehumidifier section 20 (20'), and this
unwanted heat is immediately removed by the after cooling means
C And, the refrigeration means R dissipates heat from the condenser
coil 34 placed in the outside air (OSA) inlet duct 22 so as to
heat that column of air for desiccant regeneration by passing the
same through the regenerating section 21 (21') of the dehumidifier
means D. The column of air passing through the regenerating section
takes on moisture and is exhausted at 38. Supplemental heat can
be applied to the column of air in duct 22 as by heater means 39
an electrical heater as shown.
Referring now to the embodiment of FIGS. 1 and 2 the after cooling
means C involves the exhaust duct 10 that is supplied with relief
air by variable speed blower means 40' that draws return air from
duct 16. A portion of all of the exhaust air (25%) is available
as relief air. The air exhausted through duct 10 is demumidified
as it comes from the air conditioned building space, and accordingly
will support an evaporative cooling process for its further cooling.
Accordingly, evaporative cooling means 41 is provided in the relief
air duct 40 following a relief air damper and control means 42
that selects the required volume of relief air for reducing and/or
eliminating the heat rise experienced through the dehumidifier section
20 (20').
In accordance with this invention, the column of evaporatively
cooled relief air is discharged through the heat exchanger 23 to
absorb the heat rise discharge from the dehumidifier section 20
(20'), controlling and/or reducing the induction air temperature
from duct 13 so that air temperature ahead of the cooling coil 19
is at or less than 55.degree. F., thereby precluding icing. It is
otherwise difficult to employ refrigeration for dehumidification
if the cooling surfaces must be below freezing to obtain desired
results, because condensed moisture will freeze on the cooling coils
and cannot be drained off during operation. Moreover, ice or frost
build-up reduces efficiency and impedes air flow.
In accordance with this invention, discharge of relief air at an
elevated temperature from heat exchanger 23 is conducted to the
outside air (OSA) inlet duct 22 by a transfer duct 43 where it is
mixed with inducted outside air and delivered through duct 22 by
a blower means 44. Accordingly, the heat energy absorbed from the
heat exchanger 23 supplements waste heat of refrigeration from condenser
coil 34. This total heat energy is then available for desiccant
regeneration in the section 21 (21') of the dehumidifier means D,
after which it is exhausted at 38. Thus, it will be seen that relief
air through duct 40 is advantageously employed as it progresses
through the process of evaporative cooling in order to absorb unwanted
heat resulting from dehumidification at heat exchanger 23 and through
the process of heat absorption in said heat exhanger 23 and usefully
employed in the desiccant regeneration process at regeneration section
21 (21') of the dehumidfying means D.
Referring now to the embodiment of FIGS. 5 and 6 the after cooling
means C' involves the relief air duct 40' that draws a portion ar
all of the exhaust air from the exhaust duct 10. As in the embodiment
of FIGS. 1 and 2 the air exhausted through duct 10 is return air
(RA) which remains substantially dehumidified as it comes from the
air conditioned building space, and accordingly will support an
evaporative cooling process for its further cooling. Accordingly,
the evaporative cooling means 41 is employed following the variable
air damper and control means 11 as hereinabove described. In accordance
with this embodiment, heat pipes 50 replace the heat exchanger 23
and transfer duct 43 the relief air duct now exhausting directly
to atmosphere as shown. The heat pipes 50 are combined with and
operate between the relief air duct 40' and discharge of the minimum
outside air (OSA) inlet duct 13 at the discharge thereof into the
recirculation duct 14 after the heat rise from the dehumidifier
section 20 (20'). The heat pipes 50 are characterized by a hot end
52 for absorbtion of heat and by a cold end 51 for dissipation of
heat. In other words, there is a "heat in" end 52 and
a "heat out" end 51. In carrying out this invention the
"heat out" cold end 51 of each heat pipe is placed in
the relief air duct 40' following the evaporative cooling means
41 and the "heat in" hot end 52 of each heat pipe is
placed in the discharge of the inlet duct 13 following the dehumidifier
section 20 (20'). Accordingly, there is a heat transfer that occurs
between ducts 40' and 13 and controlled so as to reduce the induction
air temperature from duct 13 so that air temperature ahead of the
cooling coil 9 is at or no less than 55.degree. F.
Transfer of heat energy from the discharge end of the inlet duct
13 and the exhaust or relief air duct 40' is by means of a bank
comprised of a multiplicity of heat pipes, the cold ends 51 in the
form of heat dissipaters placed in the exhaust discharge of duct
40' and the hot ends 52 in the form of heat absorbers placed in
the discharge of duct 13 into the duct 14 ahead of the evaporative
cooling coil 9. In practice, the heat pipes are short lengths of
heat conductive material, tubing sealed at their ends, having fitting
tubular wicks 54 and charged with a refrigerant 55 a gas-liquid.
A temperature differential between the ends of each pipe causes
the refrigerant 55 liquid to migrate by capillary action to the
warmer end where evaporation thereof takes place and absorbs heat.
The resultant refrigerant vapor then returns through the hollow
tube center of the wick and to the cooler end of the pipe, where
it gives up the heat carried thereby, by condensing into the wick
in order to repeat the cycle. This heat transfer process is efficient,
as the heat pipes 50 are sealed and have no moving parts and require
little or no maintainance.
As shown in FIG. 6a, the heat pipes 50' are finned at 56 for most
efficient heat energy transfer.
In accordance with this invention, control means is provided to
coordinate the air column circulation of the several columns of
moving air involved. In practice, there are two basic types or modes
of operation which may be implemented in utilizing the several embodiments
hereinabove disclosed, the control means K as shown in FIG. 1 which
employs Constant Volume Variable Temperature control, and the control
means K' as shown in FIG. 5 wich employs Variable Volume Constant
Temperature control. In each of said control means K and K' there
are means repsonsive to both temperature and humidity and which
together govern the operation of the various means involved. As
shown, there is a control means K (K') responsive to the air conditioned
space temperature and humidity as by temperature sensor means means
60 and humidity sensor means 61 and responsive to outside air temperature
and mixed intake air temperature as by temperature sensor means
62 and 63 placed in the ouside air inlet duct 14 and at the entry
or mixed air into the evaporator cooling coil 9. A feature of this
invention is that the refrigeration and dehumidification function
outputs vary according to the temperature and humidity requirements
in response to the aforesaid sensor means. And the air volume or
air temperature may be inversely employed according to either of
the types or modes of operation, as next described.
Referring now to the Constant Volume Variable Temperature mode
of operation shown in FIG. 1 of the drawings, minimum outside air
intake through duct 13 is adjustably controlled by a fixed damper
64 while the drive motor 65 operates the blower 37 at a constant
speed for delivery of supply air through duct 15. The control means
K coordinates the temperature and humidity information from sensor
means 60-63; so as to control the variable speed motor 26 driving
the desiccant wheel 25 through inverter means 66 increased speed
removing more moisture; so as to inversely control the positions
of the damper and control means 11 and 12 through actuator means
67 and 68 in order for example to maximize cooling with outside
air; so as to control the speed of the blower means 40', through
an actuator 70 in order to provide air flow commensurate with the
position of the damper and control means 11; so as to control the
position of damper and control means 42 with repsect to the position
of damper and control means 11 and 12 through actuator means 69;
so as to control the speed of the compressor and motor means 33
of the refrigeration means, through an inverter means 71 in order
to avoid cycling losses; and so as to control the speed of variable
speed motor 72 driving the blower 44 through an inverter means
72 in order to control the air temperature for desiccant regeneration
and/or rejection of compressor heat; all as circumstances require,
it being understood that state of the art means are implemented
for the functions hereinabove described.
Referring now to the Variable Volume Constant Temperature mode
of operation shown in FIG. 5 of the drawings, minimum outside air
intake through duct 13 is by blower means 75 controlled for a variable
rate of intake volume driven at a variable rate of intake volume
by a variable speed motor 76 having inverter means 77 while the
blower 37 is driven by a variable speed motor 65 controlled by an
inverter means 77' responsive to the control means K'. The inverter
means 66 varies the speed of the desiccant wheel 50 the inverter
means 71 varies the speed of the compressor means 33 the inverter
means 78 varies the speed of the blower 44 and motor 72 the actuator
means 67 and 68 control the positions of damper and control means
11 and 12 the inverter means 70 controls the speed of blower means
40', and the actuator means 69 controls the position of damper and
control means 42 all as hereinabove described with respect to the
Constant Volume Variable Temperature Control. The control means
K' coordinates the temperature and humidity information from sensor
means 60-63 so as to control the motors and dampers as shown, and
further so as to control the speed of motor 65 through the inverter
means 77 all as circumstances require, it being understood that
state of the art means are implemented for the functions herein
described.
Referring now to the embodiment of FIG. 3 of the drawings, the
packed type desiccant dehumidifier and desuperheater 28 are operated
at variable outputs by control of variable speed motor 78 through
an inverter means 79 responsive to the control means K (K'), all
as circumstances may require, it being understood that state of
the art means are employed for the functions herein described.
Having described only the typical preferred forms and applications
of my invention, I do not wish to be limited or restricted to the
specific details herein set forth, but wish to reserve to myself
any modification or variations that may appear to those skilled
in the art as set forth within the limits of the following claims. |