Abstrict An improved air recirculation and conditioning system for recirculating
and dehumidifying air within a living space is disclosed. In accordance
with one aspect of the present invention the system diverts a portion
of the air recirculated through a return and removes moisture from
that portion of the air before mixing the drier air with the air
in the return. In accordance with another aspect of the invention
the system makes use of a standard water heater as a source of heat
to heat a regenerative air stream to regenerate a desiccant wheel
of the system. Finally, in accordance with another aspect of the
present invention, the system externally draws all of the air for
the regenerative air stream and exhausts the regenerative air stream
to an air space external of the living space within which the air
is being treated.
Claims What is claimed is:
1. In combination with a central air conditioning system including
an evaporator coil for removing some of the moisture from air passing
through said coil, an improved air recirculation and conditioning
system for recirculating and dehumidifying air within a living space,
said system comprising:
conduit means for transmitting air derived entirely from said living
space back to said living space;
air recirculating means for drawing only air from said living space
through said conduit means and said evaporator coil; and
a dehumidification apparatus for removing latent heat and a portion
of associated sensible heat only from air recirculated from and
to said living space, said dehumidification apparatus comprising:
(a) an enclosure defining (i) an air treatment passageway, coupled
to said conduit means, for transmitting a treated air stream so
that air passing through said air treatment passageway is derived
entirely from a portion of the air transmitted through said conduit
means, treated in said air treatment passageway so as to remove
some of the moisture from the treated air stream, subsequently mixed
with the remaining portion of air in said conduit means and then
passed through said evaporator coil so as to remove additional moisture
from said mixed air, and (ii) a regenerative air passageway for
transmitting a regenerative air stream derived entirely from and
exhausted externally with respect to said living space;
(b) desiccant means for transferring moisture from the air treatment
passageway to the regenerative air passageway;
(c) means for creating said treated air stream through said air
treatment passageway so that air derived entirely from said portion
of the air transmitted through said conduit means passes through
said desiccant means before being mixed with the remaining portion
of air in said conduit means; and
(d) means for creating said regenerative air stream through said
regenerative air passageway so that air derived entirely externally
with respect to said living space passes through said desiccant
means before exhausting to a space external with respect to said
living space.
2. A system according to claim 1 wherein said means for creating
said treated air stream through said air treatment passageway draws
air so that the air drawn through said air treatment passageway
is at a relatively lower flow rate than air drawn through said conduit
by said air recirculating means.
3. A system according to claim 2 wherein said means for creating
said treated air stream draws air so that the treated air stream
is at a flow rate of between about 10% to 20% of the flow rate of
air drawn through said conduit by said air recirculating means.
4. A system according to claim 1 wherein said desiccant means
includes a desiccant wheel assembly comprising (1) a wheel including
a desiccant material and means for mounting said wheel so that at
any one moment (a) a portion of said wheel is positioned in said
air treatment passageway so that said treated air stream passes
through said portion of said wheel and (b) a different portion of
said wheel is positioned in said regenerative air passageway so
that said regenerative air stream passes through said different
portion of said wheel, and (2) means for rotating the wheel about
its axis so that said wheel rotates relative to said passageways.
5. A system according to claim 1 wherein said apparatus further
includes heater means disposed in said regenerative air passageway
for supplying heat to said regenerative air stream, wherein said
means for creating said regenerative air stream through said regenerative
air passageway draws air derived externally with respect to said
living space through said heater means and said desiccant means
before exhausting the air to a space external with respect to said
living space.
6. A system according to claim 5 wherein said heater means includes
heat radiating means, adapted to circulate hot water within said
regenerative air passageway, for using hot water to heat said air.
7. A system according to claim 6 further including means for connecting
said heat radiating means to a water heater.
8. A system according to claim 7 wherein said heat radiating means
includes a tube, disposed in said regenerative air passageway, for
circulating said hot water within said regenerative air passageway.
9. A system according to claim 1 further including heat exchanger
means for transferring heat from said air treatment passageway to
said regenerative air passageway, wherein said means for creating
said treated air stream through said air treatment passageway passes
air derived from said living space through said desiccant means
and said heat exchanger means before being mixed with air in said
conduit, and said means for creating said regenerative air stream
through said regenerative air passageway draws air derived externally
with respect to said living space through said heat exchanger means
and said desiccant means before exhausting said regenerative air
stream to a space external with respect to said living space.
10. A system according to claim 9 wherein said heat exchanger
means includes a heat exchanger assembly for cooling air transmitted
through said air treatment passageway after moisture is removed
from the air by said desiccant means and heating air transmitted
through said second passageway prior to regenerating said desiccant
material.
11. A system according to claim 10 wherein said heat exchanger
assembly includes (1) a heat wheel including a heat absorptive material,
(2) means for mounting said wheel so that at any one moment (a)
a portion of said heat wheel is positioned in said air treatment
passageway so that air of said treated air stream passes through
said portion of said heat wheel and (b) a different portion of said
heat wheel is positioned in said regenerative air passageway so
that air of said regenerative air stream passes through said different
portion of said heat wheel, and (3) means for rotating the wheel
about its axis so that said wheel rotates relative to said passageways.
12. A system according to claim 1 further including an air conditioning
unit including an evaporation coil disposed in said conduit for
cooling the mixture of said air passing through said conduit and
said treated air stream, wherein said air recirculating means includes
an air conditioning circulation blower.
13. A system according to claim 12 wherein said air conditioning
unit further includes a thermostat for controlling the temperature
of air in said living space, and said apparatus further includes
a humidistat, independent of said thermostat, for controlling the
humidity of air in said living space.
14. The combination of claim 1 wherein said enclosure defines
said air treatment passageway so that air passing through said air
treatment passageway is approximately between about 10% and 20%
of the air transmitted through said conduit means.
15. In combination with an air recirculation and conditioning system
for recirculating and dehumidifying air within a living space, said
system being of the type comprising: an evaporator coil for removing
some of the moisture from air transmitted through said coil; conduit
means for recirculating air derived entirely from said living space,
and transmitting the recirculated air through said evaporator coil
and back to said living space; and air recirculating means for drawing
air, derived entirely from said living space, through said conduit
means and said evaporator coil; and a dehumidification apparatus
for removing latent heat and a portion of associated sensible heat
from a portion of recirculated air entirely derived from said conduit
means, said dehumidification apparatus comprising:
(a) an enclosure defining (i) an air treatment passageway, coupled
to said conduit means, for transmitting a treated air stream so
that air passing through said air treatment passageway is derived
entirely from a portion of the air being transmitted through said
conduit means, treated in said air treatment passageway so as to
remove moisture from said air, subsequently mixed with the remaining
air in said conduit and then passed through said evaporator coil
so as to remove additional moisture from the mixed air, and (ii)
a regenerative air passageway for transmitting a regenerative air
stream derived entirely from and exhausted externally with respect
to said living space;
(b) desiccant means for transferring moisture from the air treatment
passageway to the regenerative air passageway;
(c) heat exchanger means for transferring sensible heat from said
air treatment passageway to said regenerative air passageway;
(d) heater means, disposed in said regenerative air passageway
between said desiccant means and said heat exchanger means, for
supplying heat to said regenerative air stream;
(e) means for creating said treated air stream through said air
treatment passageway so that said portion of air derived entirely
from said conduit means passes through said desiccant means and
then said heat exchanger means before being mixed with the remaining
portion of air in said conduit means; and
(f) means for creating said regenerative air stream through said
regenerative air passageway so that air entirely derived externally
with respect to said living space passes first through said heat
exchanger means; then through said heater means and then through
said desiccant means before exhausting to a space external with
respect to said living space.
16. The combination of claim 15 wherein said enclosure defines
said air treatment passageway so that air passing through said air
treatment passageway is approximately between about 10% and about
20% of the air transmitted through said conduit means.
17. A method of recirculating, dehumidifying and cooling air within
a living space, said method comprising the steps of:
transmitting only air entirely derived from said living space through
conduit means;
drawing only a portion of said air from said conduit means and
passing said air portion through an air treatment passageway wherein
said air portion is passed through desiccant means for transferring
moisture from the air treatment passageway to a regenerative air
passageway so as to reduce the moisture content of said air portion,
while simultaneously passing a regenerative air stream entirely
derived externally of said living space through said regenerative
air passageway so as to absorb moisture transferred from said air
treatment passageway to said regenerative air passageway and entirely
exhausted externally of said living space;
mixing said air portion having a reduced moisture content with
the air in said conduit means so as to provide a mixed air flow;
and
passing said mixed air flow through an air conditioning evaporator
coil and into said living space.
18. The method according to claim 17 wherein said step of drawing
only a portion of said air from said conduit means and passing said
air portion through an air treatment passageway includes the step
of drawing between about 10% and about 20% of the air from said
conduit means.
Description The present invention relates generally to air recirculating and
conditioning systems, and more particularly to an improved, economically
designed and efficient dehumidifying system for use with conventional
central air conditioning (A/C) systems.
With much of the country, particularly in the Southeastern portion
of the United States experiencing hot summers, more and more homes
and commercial buildings are being provided with central air conditioning
systems. Unfortunately, on extremely humid days, as is often the
case in the Southeast, and areas along the Gulf coast, these central
air conditioning systems, while cooling the air provided to the
living space, are inadequate with respect to the removal of moisture,
i.e., latent heat, since the cooled air provided is at or near 100%
relative humidity. Such systems control only temperature with humidity
control reduction as a by-product of a cold evaporator coil. A typical
air conditioning system alone cannot dehumidify more than allowed
by its coil design ratio. Thus, in order to remove more moisture
with a conventional air conditioning system one must use a larger
capacity system and operate the thermostat of the system at a lower
setting so as to lower the dew point in order to provide greater
moisture condensation. However, this results in excessive cooling,
is counter productive to any passive cooling techniques that may
be employed, and may result in uncomfortable, cold-clammy environments
and cause excessive energy use. For example, A/C energy typically
increases as much as 15% as the thermostat is reduces by 1.degree.
F.
One suggestion of reducing the relative humidity of air delivered
to a living space is to first cool the air to a dew point below
the desired temperature as described and then reheat the air to
the desired temperature with a heater, such as the condenser heat
from a condenser coil of the air conditioning unit. While this approach
is workable, it does not increase the efficiency of the system because
the air must be cooled below the desired temperature. In some systems,
such as spot dehumidifiers, the air is reheated with electrically
driven resistance coils further increasing the costs. This latter
approach is obviously energy inefficient.
Further, spot dehumidifiers provide heat into the room. The typical
electric spot dehumidifier, for example, adds roughly 2400 BTU of
heat to the home for every pound of water that it condenses out
of the air. Such spot dehumidifiers also require a sump or bucket
for draining the water removed from the air, which is inconvenient
for the user, as well as potentially messy if the water is not timely
or inadequately drained.
It is also known to use heat exchangers in ventilating and air
conditioning systems for transferring heat from the incoming outside
air to the exhausted inside air, thus reducing the heat load of
the fresh air. This process, however, can bring moisture from the
outside air into the living space.
Various suggestions have been made to dehumidify or condition air.
See, for example, U.S. Pat. Nos. 2723837; 2926502; 3009684;
3144901; 3470708; 3965695; 4060913; 4062129; 4180126;
and 4719761.
Systems for conditioning and dehumidifying air which operate as
the open-cycle type are described in U.S. Pat. Nos. 2723837; 2926502;
3144901; 3470703 and 4180126. Generally, in such systems an
air stream to be conditioned passes through an air permeable drying
wheel of a hygroscopic or desiccant material which absorbs moisture
from the air substantially adiabatically. The dried air will therefore
be at a higher temperature. The dried warmer air then flows through
a rotating heat exchange mass so as to cool the air by removing
sensible heat. The dried and cooled air then can be further cooled
to the desired temperature and reconstituted to a desired humidity
by evaporating water therein. The hygroscopic or desiccant material
of the drying wheel is cyclically regenerated by a regenerative
air stream. During regeneration, the regenerative air stream first
can be cooled by evaporative cooling and then passed through the
heat exchange mass thereby cooling the latter. Thereafter, the regenerative
air stream is heated by means of an external heat source to a temperature
sufficiently high to regenerate the hygroscopic material of the
drying wheel, passed in thermal exchange relation to the hygroscopic
material, and then discharged into the atmosphere (see U.S. Pat.
No. 3144901). The usual external heat source for providing an
external heat input for the regeneration step is an especially provided,
open flame, natural gas burner (see, for example, U.S. Pat. No.
3470708). One suggestion is to use solar-derived energy to provide
the necessary heat (see U.S. Pat. No. 4180126) although this is
not always practical since not all building structures provided
with central air conditioning can accommodate solar collectors and
solar heat storage devices. Further, such additional structures,
while providing some savings with respect to energy use, add substantial
additional costs to the system.
U.S. Pat. No. 4719761 (Cromer) describes a recirculating air
cooling system provided with a desiccant material used to contact
and evaporate moisture into dry feed air prior to passing the feed
air over the cooling coils of the air conditioner so as to increase
the dew point (moisture content) of the feed air. This increases
the amount of moisture removed by the cooling system. The desiccant
material is used to absorb moisture from the moisture saturated
air leaving the cooling coil and deliver the moisture to the feed
air. The patentee believes the system will remove more moisture
from the recirculated air at a higher average temperature of the
evaporator coil, while providing the same enthalpy exchange as a
conventional air conditioner. To the extent that the system removes
moisture before exhausting the air back to the living space makes
it similar to other dehumidification systems requiring drainage
of excess moisture.
It is an object of the present to substantially reduce or overcome
the above-identified problems of the prior art.
Another object of the present invention is to provide an improved
air recirculating and conditioning system for reducing the humidity
of air within an enclosed living space.
And another object of the present invention is to provide an improved
air dehumidification system which is energy efficient.
And another object of the present invention is to provide an improved
air dehumidification system which is capable of use with standard
central air conditioning systems.
Yet another object of the present invention is to provide an improved
air dehumidification system of the open-cycle type.
Still another object of the present invention is to provide an
improved air dehumidification system of the open cycle type which
can easily be installed for most enclosed living spaces without
substantial construction and associated costs.
And yet another object of the present invention is to provide an
improved air dehumidification system of the open cycle type which
utilizes a standard hot water heater as a heat source for the regenerative
air stream.
And still another object of the present invention is to provide
an improved air dehumidification system of the open cycle type for
use with an enclosed living space which draws and exhausts the regenerative
air stream externally from the living space so as to have little
direct effect on the temperature and humidity within the living
space.
These and other objects of the present invention are achieved by
an improved air recirculation and conditioning system for recirculating
and dehumidifying air within a living space. In accordance with
one aspect of the present invention the system diverts a portion
of the air recirculated through a return and removes moisture from
that portion of the air before mixing the drier air with the air
in the return. In accordance with another aspect of the invention
the system makes use of a standard water heater as a source of heat
to heat a regenerative air stream to regenerate a desiccant wheel
of the system. Finally, in accordance with another aspect of the
present invention, the system externally draws all of the air for
the regenerative air stream and exhausts the regenerative air stream
to an air space external of the living space within which the air
is being treated.
Other objects of the present invention will in part be obvious
and will in part appear hereinafter. The invention accordingly comprises
the apparatus possessing the construction, combination of elements,
and arrangement of parts which are exemplified in the following
detailed disclosure, and the scope of the application of which will
be indicated in the claims.
For a fuller understanding of the nature and objects of the present
invention, reference should be had to the following detailed description
taken in connection with the accompanying drawings wherein:
FIG. 1 is a schematic view of the air circulation and conditioning
system of the present invention;
FIG. 2 is a cross-sectional view taken along line 2--2 in FIG.
1; and
FIG. 3 is a perspective view of an example of the air circulation
and conditioning system of the present invention connected for use
with a typical hot water heater in an enclosed living space such
as a house.
In the drawings the same numerals are used to designate the same
or similar parts.
Referring to FIGS. 1 and 2 the system shown is intended for residential
or light commercial installations, although the invention should
not be construed to be limited to those applications. As shown the
system includes a dehumidifier of the open-cycle type specifically
configured to operate with a standard return duct of an air recirculation
system, which as shown is used with a central A/C system.
The system, shown at 10 generally includes desiccant means, in
the form of a rotatable desiccant wheel 20 mounted on shaft 22
and driven at a constant speed by motor 24. The system also includes
heat exchange means, in the form of a rotatable heat exchange wheel
26 also driven at a constant speed by motor 24 through shaft 22
and suitable gears 28. Desiccant wheel 20 can be of a commercial
type, such as one manufactured by either Airxchange, Inc. of Rockland,
Mass. or Seiby Giken Co. Ltd. of Japan, specifically designed for
the present application. The heat exchange wheel 26 can also be
of a commercial type, such as fin or honeycomb type. The wheels
20 and 26 are suitably enclosed by partitions 30. The latter are
used to define a first air treatment passageway 32 and a second
or regenerative air passageway 34 parallel with and separate from
the first passageway, such that a portion of each wheel is disposed
in each passageway at any one moment. Seals 36 are provided around
the entire peripheral edges of the portions of the wheels disposed
in the passageways in a suitable manner in order to insure that
all of the air passing through each passageway passes through the
portion of each wheel disposed in each passageway.
Means, in the form of a blower 40 is provided for creating an
air treatment stream (designated by arrows 38) through the air treatment
passageway 32 in the direction shown (left to right in FIG. 1) so
that air flows from the air intake 42 through the portion of desiccant
wheel 20 in passageway 32 through the portion of the heat exchange
wheel 26 in passageway 32 and out the air output 44. Means, in the
form of blower 46 is also provided for creating a regenerative
air stream (designated by the arrows 48) through the regenerative
air passageway 34 in the direction shown (opposite to the direction
of air stream 38 and thus right to left in FIG. 1) so that air flows
from the air intake 50 through the portion of the heat exchange
wheel 26 in passageway 34 through the portion of the desiccant
wheel 20 in passageway 34 and out the air output 52.
As described above, the regenerative air stream can be heated by
heater means, such as an open flame, natural gas burner (see U.S.
Pat. No. 3470708) or solar derived heat (see U.S. Pat. No. 4180126)
prior to passing the air stream through the desiccant wheel 20 so
that a greater amount of moisture absorbed by the portion of the
desiccant wheel 20 while it was disposed in the air treatment passageway
32 will be absorbed by the regenerative air stream as that portion
of the wheel passes through the regenerative air passageway 34.
To the extent described the system is known. However, in accordance
with one aspect of the present invention the system 10 is coupled
to a standard air recirculation system, i.e., the return conduit
60 so that the blower 40 draws a portion of the air drawn from
the enclosed living space 62 and passing through the return into
the air intake 42 and forces it through the air passageway 32 and
out the air output 44 where it mixes with the air passing through
the return conduit 60 before being forced back into the living space
62. In addition, for reasons which will be more apparent hereinafter
the air intake 50 and air output 52 are connected so that the air
for the regenerative air stream 48 is externally derived and is
exhausted to a space external from the living space 62. Finally,
as will be more evident hereinafter, because the air treatment stream
38 is derived from only a portion of the return air stream, the
system can be compact and easily installed in a typical residence
or small commercial establishment, and use a relatively small source
of heat for the heater means, indicated at 54 in FIG. 1. In this
latter regard, the heat source is preferably hot water tapped from
a standard hot water heater described in FIG. 3.
Accordingly, means 54 is preferably a coil properly connected to
a hot water heater so that hot water circulated though the coil
will heat the stream 48 before the water is returned to the hot
water heater. As shown in FIG. 1 the means for drawing air through
the return conduit 60 can be a standard blower 70 for drawing air
through the return conduit back into the living space 62. The mixed
air provided by the blower can be passed through an evaporator coil
72 of a central A/C system to further reduce the temperature and
humidity of the air returned to the living space 62.
In order to control the operation of the system a humidistat control
80 positioned in living space 62 can be suitably connected to
simultaneously turn on motor 24 blowers 40 and 46 blower 70 and
water circulation pump 85 (so that the latter allows water to circulate
through the coil, designated at 54) when the relative humidity within
the enclosed living space 62 exceeds the setting of the humidistat.
Such a control can be independent of a thermostat control 90 used
to control the central A/C system 104 which would necessarily include
blower 70 and coil 72 and separately operate the blower 70 when
the A/C system was on.
As an example of typical parameters of the system the desiccant
wheel 20 is rotated at a much slower speed than the heat exchange
wheel, with the former rotated at a rate of about 8 to 12 rph, while
the latter is rotated at a rate of about 20 to 30 rpm. The blower
70 is sized to draw air through the return conduit 60 at a flow
rate of about 1000 to 1200 scfm (Typical for a 36000 btu/m A/C
unit). The blowers 40 and 46 are preferably of equal capacity, with
the air flow of the air treatment stream being about 10% to 20%
of that of the return air stream in conduit 60. In the present example,
an air flow of 150 scfm for each air stream 38 and 48 would be adequate.
Therefore, if the incoming air through the return conduit is at
a temperature of 78.degree. F. at 50% relative humidity, i.e., a
dew point of 57.9.degree. F. (specific humidity=0.0102 lb/lb), the
air forming the air treatment stream 38 will pass through the desiccant
wheel 20 and exit the wheel at a higher temperature and lower dew
point, e.g., 101.degree. F. at 14% relative humidity, i.e., a dew
point of 42.degree. F. The air stream is then cooled by the heat
exchange wheel 26 to a temperature of, for example, 91.degree. F.
at 20% relative humidity, i.e., at a dew point of 42.degree. F.
The air stream exiting the air output 44 of the passageway 32 is
thus at a higher temperature than the temperature passing through
the conduit 60 but at a lower humidity level. As a consequence
when the two air streams are mixed the resulting mixed air will
be at a slightly higher temperature, at approximately 79.5.degree.
F., than the original air entering the conduit 60 but at a lower
humidity level, at approximately 44% relative humidity, i.e., at
a dew point of 55.9.degree. F. (Specific humidity=0.0095 lb/lb).
However, the mixed air can be further cooled and have additional
moisture removed by passing the mixed air over an evaporation coil
72 of a standard A/C system, typically provided, for example, in
residential central A/C system.
In order to regenerate the desiccant wheel 20 air is drawn from
a space which is external from the air space 62 and exhausted to
a space also external from the living space 62 so that the moisture
added to the regenerative air stream will have no affect on the
humidity level of the air within the living space. The air intake
50 for example, can be attached so as to draw air from a crawl
space, the basement or from the outdoors. Similarly, the air output
52 can be coupled to a crawl space, the basement or the outdoors
so that the air is exhausted to a different area from the living
space.
In addition, since only a portion of the air from the return conduit
is drawn through the air treatment passageway, the requirements
for heating the regenerative air stream 48 is lowered to the point
where the heater means 54 can include a circulating coil attached
to a standard water heater. The coil can be constructed to provide
a flow of approximately 1 to 2 gallons per minute at a temperature
of approximately 150.degree. F. when the pump 85 is actuated. At
this flow level, and at the levels described above, incoming air
at a temperature of about 88.degree. F. at 60% relative humidity,
will be heated to about 98.degree. F. after passing through the
heat exchange wheel 26 and subsequently raised to about 140.degree.
F. after passing through the coil indicated at 54. The warm air
is then passed through the portion of the desiccant wheel 20 disposed
in the regenerative air passageway 34 where a substantial portion
of the moisture previously absorbed by the desiccant material is
reabsorbed by the air stream. This results in cooling the stream
to a temperature of approximately 117.degree. F. This warm, wet
air exhausted through the output 52 does not directly affect the
air within the enclosed living space 62 since the regenerative air
stream is externally derived from the living space and similarly
exhausted to an external space.
As shown by the example in FIG. 3 the system can be designed so
that it can be easily installed within a residential home. The system
10 is positioned, for example, in the basement of a home in which
an A/C system is used to cool upper floors of the structure. Accordingly,
the air intake 50 is open to the basement area, while the air output
52 is connected though a pipe to the outside air through the window
100. The air intake 42 of the air treatment passageway (not specifically
shown in FIG. 3) is connected through a pipe 102 to one side of
an central A/C system 104 wherein air is drawn into the system
from the upper air intake 106 which receives an air input from the
enclosed living space in the upper floors. The air output 44 of
the air treatment passageway (also not specifically shown in FIG.
3) is connected through the pipe 108 to the input of a blower 70
before being passed through an evaporator coil 72 whereupon the
cooler and drier air is returned through the return air duct 110
to the living space on the upper floors. As previously described,
the heater means 54 can be a circulating coil (not shown in FIG.
3) which receives hot water from a hot water heater shown at 112
through the hot water pipe 114 and returns water to the heater
through the hot water return 116.
The system thus described has several advantages. In the example
given, the system will provide approximately 70 to 90 pints per
day of dehumidification capacity. The system 10 easily can be installed
with standard central A/C systems and provides whole house dehumidification,
in contrast to that provided at selected locations by spot dehumidifiers.
The system 10 can operate independently of the A/C system 104 (except
that the blower 70 would be used for both systems). Thus, temperature
and humidity control can be uncoupled from one another. This allows
independent control of the entire home temperature and humidity
set points, in contrast to air conditioning systems which control
only temperature with humidity reduction as a by-product of a cold
evaporator coil.
By design the system 10 is far more efficient with respect to heat
or load added to the air conditioning system 104 as compared to
the electric dehumidifiers of the prior art. The typical spot electric
dehumidifier when used in the home adds roughly 2400 BTUs of heat
to the home for every pound of water that it condenses out of the
home air. The present system described in the example above adds
about 700 BTUs of heat to the home for every pound of water it removes
from the home air. Operating costs of the system 10 should be less
than an equivalent electric spot dehumidifier given that its energy
source is a gas fired water heater (4 to 1 typical ratio for electric
to gas price). The coefficient of performance (COP) is defined as
the ratio of latent heat associated with the water removed to the
power input. Comparing the system 10 of the type described in the
example given above, to a standard electric vapor compression dehumidifier,
the COP's are:
System 10 has an COP=0.55 using a gas input; while a standard electric
dehumidifier has a COP=0.60 using an electric input.
Thus, on an energy basis the two are about equal but on a cost
basis the system 10 costs about 75% less to operate. In addition,
the central electric A/C cent's energy cost will be substantially
less with the desiccant dehumidifier system of the present invention
as compared to an electric spot dehumidifier. The electric dehumidifier
adds about four times more sensible heat load onto the home A/C
system than the desiccant unit. The system rejects the water removed
and heat absorbed by the regenerative air stream to a space external
from the enclosed living space for which the system 10 is used,
without the need for a sump or bucket for drainage as is common
with electric spot dehumidifiers.
Finally, a standard hot water heater can be used as a heat source
for heating the regenerative air stream further making it easily
adapted for residential and light commercial applications.
Since certain changes may be made in the above apparatus without
departing from the scope of the invention herein involved, it is
intended that all matter contained in the above description or shown
in the accompanying drawing shall be interpreted in an illustrative
and not in a limiting sense. |