Abstrict A desiccant assisted air conditioning apparatus incorporates an
absorption heat pump device to produce improved operating efficiency.
The heat pump device has circulation units 1 and 2 each of which
includes an evaporator, an absorber, a generator and a condenser
and heat exchangers provided by heat transfer pipe action. The absorber
in unit 1 operates at a higher temperature than the absorber in
the absorber in unit 2 so that heat transfer can occur through heat
transfer pipes acting as heat exchangers between the first evaporator
and the second absorber in the two units. The heat of condensation
from units 1 and 2 as well as the heat of absorption from unit
1 are used to heat regeneration air for regenerating the desiccant.
The heat of evaporation in unit 2 is utilized to produce chilled
water for cooling the process air in the air conditioning apparatus.
The use of heat enabled by the heat pump device achieves a high
level of energy conservation for performing desiccant assisted air
conditioning apparatus which operates at high efficiency.
Claims What is claimed is:
1. A desiccant assisted air conditioning apparatus including a
process air passage for flowing process air for dehumidification
through a desiccant and for delivery to a conditioning space; and
a regeneration air passage for flowing regeneration air for removing
moisture from said desiccant; and an absorption heat pump means
for providing cooling heat source for process air and heating source
for said regeneration air, said absorption heat pump means comprising:
a first circulation unit having a first evaporator, a first absorber,
a first generator and a first condenser for providing an absorption
refrigeration cycle operating at a first operating pressure;
a second circulation unit having a second evaporator, a second
absorber, a second generator and a second condenser for providing
an absorption refrigeration cycle operating at a second operating
pressure lower than said first operating pressure;
a heat exchanger provided between said first evaporator in said
first circulation unit and said second absorber in said second circulation
unit for performing a heat transfer between said first evaporator
and said second absorber;
a first heat medium passage means for introducing external heat
for providing generation heat for said absorption heat pump means
in which heat transfer medium flows in the order from said first
generator to said second generator,
a second heat medium passage means for extracting heat of condensation
in said first and second circulation unit and heat of absorption
in said first circulation unit which passes through said condenser
of said first and second circulation unit and said absorber in said
first circulation unit in series, and
a third heat medium passage means for extracting heat of evaporation
in said second circulation unit,
wherein the heat of condensation from said first circulation unit
and from said second circulation unit together with the heat of
absorption from said first circulation unit are utilized as heating
heat source for regenerating said desiccant, and the heat of evaporation
in said second circulation unit is utilized as cooling heat source
for cooling said process air prior to delivery to said conditioning
space.
2. A desiccant assisted air conditioning apparatus as claimed in
claim 1 wherein a sensible heat exchanger is provided between said
process air passage and said regeneration air passage for providing
heat transfer between pre-desiccant regeneration air and post-desiccant
process air.
3. A desiccant assisted air conditioning apparatus as claimed in
claim 2 wherein a heating medium passage is communicated with a
heating device disposed at a regeneration air inlet into said desiccant
for heating said pre-desiccant regeneration air, and a cooling medium
passage is communicated with a cooling device disposed in a process
air passage connecting said sensible heat exchanger and said conditioning
space for cooling said post-desiccant process air.
4. A desiccant assisted air conditioning apparatus as claimed in
claim 1 wherein said desiccant is a desiccant wheel alternatingly
communicating with said process air passage or said regeneration
air passage.
5. A desiccant assisted air conditioning apparatus including a
process air passage for flowing process air for dehumidification
through a desiccant and for delivery to a conditioning space; and
a regeneration air passage for flowing regeneration air for removing
moisture from said desiccant; and an absorption heat pump means
for providing cooling heat source for process air by way of a heating
device and heating heat source for said regeneration air by way
of cooling device; said absorption heat pump means comprising:
a lower pressure evaporator, and a higher pressure evaporator operating
at a higher operating pressure than said lower pressure evaporator;
a lower pressure absorber, and a higher pressure absorber operating
at a higher operating pressure than said lower pressure absorber,
a generator; a condenser; and heat exchanging means for providing
heat to said higher pressure evaporator by transferring the heat
of absorption from said lower pressure absorber to said higher pressure
evaporator; wherein a refrigerant condensed in said condenser is
branched off into said lower pressure evaporator and said higher
pressure evaporator, a refrigerant evaporated in said lower pressure
evaporator is absorbed in said lower pressure absorber, and a refrigerant
evaporated in said higher pressure evaporator is absorbed in said
higher pressure absorber, and said heating device is communicated
with a heating passage for heat exchanger with said higher pressure
absorber and said condenser, and said cooling device is provided
with a cooling passage for heat exchange with said lower pressure
a evaporator.
6. A desiccant assisted air conditioning apparatus as claimed in
claim 5 wherein a sensible heat exchanger is provided between said
process air passage and said regeneration air passage for providing
heat transfer between pre-desiccant regeneration air and post-desiccant
process air.
7. A desiccant assisted air conditioning apparatus as claimed in
claim 6 wherein a heating medium passage is communicated with a
heating device disposed at a regeneration air inlet into said desiccant
for heating said pre-desiccant regeneration air, and a cooling medium
passage is communicated with a cooling device disposed in a process
air passage connecting said sensible heat exchanger and said conditioning
space for cooling said post-desiccant process air.
8. A desiccant assisted air conditioning apparatus as claimed in
claim 5 wherein said desiccant is a desiccant wheel alternatingly
communicating with said process air passage or said regeneration
air passage.
9. A desiccant assisted air conditioning apparatus as claimed in
claim 1 wherein said absorption heat pump is operable without using
a cooling device to discard heat to ambient air.
10. A desiccant assisted air conditioning apparatus as claimed
in claim 5 wherein said absorption heat pump is operable without
using a cooling device to discard heat to ambient air.
11. A desiccant assisted air conditioning apparatus as claimed
in claim 1 wherein said absorption heat pump is operable with a
temperature difference of more than 10.degree. C. between condensation
temperature and absorption temperature.
12. A desiccant assisted air conditioning apparatus as claimed
in claim 5 wherein said absorption heat pump is operable with a
temperature difference of more than 10.degree. C. between condensation
temperature and absorption temperature.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to absorption heat pumps in general,
and relates in particular to an absorption heat pump utilized as
a heat source in a desiccant assisted air conditioning apparatus
and an air conditioning apparatus based on the heat pump device.
2. Description of the Related Art
Desiccant assisted air conditioning apparatus is well known, for
example in a U.S. Pat. No. 2700537. The system discloses a desiccant
assisted air conditioning apparatus requiring a heat source in a
temperature range of 100.degree.-150.degree. C. for regenerating
the desiccant (moisture adsorbent), and heat sources such as electric
heaters and boilers are primarily utilized. In recent years, desiccants
which can be regenerated at lower temperatures in a range of 60.degree.-80.degree.
C. have been developed, enabling the use of heat sources operating
at lower temperatures. FIG. 8 is a schematic representation of a
typical example of such improved desiccant assisted apparatus, and
FIG. 9 is a psychrometric chart showing the operation of this example
apparatus. In FIG. 8 the reference numeral 101 refers to a conditioning
space; 102 refers to a blower; 103 refers to a desiccant wheel;
104 refers to a sensible heat exchanger; 105 refers to a humidifier;
106 refers to a water supply pipe for the humidifier; 107-111 refer
to air ducts for conditioned air flows; 130 refers to a blower for
the regeneration air; 120 refers to a heat exchanger for hot water
and regeneration air (hot water heat exchanger); 121 refers to a
sensible heat exchanger; 122 123 refer to hot water pipes; and
124-129 refer to air ducts for regeneration air. In FIG. 8 circled
letters K-V represent the thermodynamic state of the air medium
being processed to correspond to respective sites shown in FIG.
9 SA designates supply air, RA designates return air, OA designates
outside air and EX designates exhaust air.
The operation of such an apparatus will be explained in the following.
In FIG. 8 the ambient air from the room 101 to be conditioned (process
air) is drawn through a passage 107 into a blower 102 to be pressurized
and is forwarded to a desiccant wheel 103 through a passage 108.
In the desiccant wheel 103 the humidity ratio of the ambient air
is lowered by the removal of moisture from the ambient air to the
moisture adsorbent in the desiccant wheel 103. During the process
of absorption, the heat of adsorption is released into the process
air which rises in temperature. The process air with a warmer temperature
and a lower humidity is forwarded through the passage 109 to the
sensible heat exchanger 104 and is cooled by heat exchange with
outside air (regeneration air). The cooled air is forwarded to a
humidifier 105 through a passage 110 to be cooled by such means
as water spray or evaporative humidifier in an isenthalpic process
and is returned to the conditioning room 101 through a passage 111.
The desiccant material takes in moisture during this process, and
it must be regenerated. In this example, this is performed as follows.
Outside air (regeneration air) OA is drawn into the blower 130 through
a passage 124 to be pressurized and forwarded to the sensible heat
exchanger 104 cools the process air and in the process raises its
own temperature. The warm air OA flows into a next sensible heat
exchanger 121 through a passage 125 and raises its temperature by
heat exchange with the spent high temperature regeneration air after
regeneration. The regeneration air from the heat exchanger 121 flows
into a hot water heat exchanger 120 through a passage 126 so that
its temperature rises to a range of 60.degree.-80.degree. C., and
its relative humidity is lowered. The regeneration air with a lowered
humidity passes through the desiccant wheel 103 to remove the moisture
from the desiccant wheel. Spent air from the desiccant 103 flows
through a passage 128 to enter the sensible heat exchanger 121 to
preheat the regeneration air prior to regeneration, and flows through
a passage 129 to be exhausted externally.
The above process can be explained with reference to the psychrometric
chart shown in FIG. 9. The ambient air in room 101 to be air conditioned
(air for processing: state K) is drawn into the blower 102 through
the passage 107 to be pressurized, and flows through the passage
108 to reach the desiccant wheel 103 so that its humidity ratio
will be lowered by the loss of moisture to the moisture adsorbent
in the desiccant wheel while its temperature rises (state L) by
the heat of adsorption. The air with a lower humidity and a higher
temperature flows through the passage 109 to reach the sensible
heat exchanger 104 and is cooled by heat exchange with the regeneration
air (state M). The cooled air flows through the passage 110 to reach
the humidifier 105 so that its temperature is lowered in an isenthalpic
manner by means of water spray or evaporative humidifier (state
P), and is returned through the passage 111 to the conditioning
space 101.
As explained above, a difference in enthalpy .DELTA.Q is generated
between the returned air (K) and the supply air (P) which is responsible
for cooling the conditioning space 101. The desiccant is regenerated
as follows. Outside air (OA: state Q) is withdrawn through the passage
124 into the blower 130 is pressurized, forwarded to the sensible
heat exchanger 104 cools the process air and raises its own temperature
(state R), flows into the passage 125 and the next heat sensible
exchanger 121 exchanges heat with the spent high temperature air
so that its own temperature rises (state S). Regeneration air from
the sensible heat exchanger 121 flows through the passage 126 to
reach the hot water heat exchanger 120 and is heated by the hot
water to a temperature between 60.degree.-80.degree. C., so that
its relative humidity is lowered (state T). The regeneration air
having a lowered humidity flows through the desiccant wheel 103
thereby losing its moisture (state U). Spent outgoing air from the
desiccant wheel 103 flows through the passage 128 to reach the sensible
heat exchanger 121 to preheat the regeneration air prior to regeneration
process, and lowers its own temperature (state V) and flows into
the passage 129 to be exhausted out as waste air.
The processes of regeneration of desiccant and dehumidification
of the ambient air described above is repeatedly performed to provide
the desiccant assisted air conditioning process. The conditioning
energy efficiency of such an apparatus is given by a value of coefficient
of performance (COP) which is obtained by dividing the enthalpy
difference .DELTA.Q (a measure of cooling effect) shown in FIG.
9 by regeneration heat .DELTA.H (i.e., COP=.DELTA.Q/.DELTA.H). However,
in the conventional desiccant assisted air conditioning apparatus,
even though the temperature of the hot water utilizable for heating
the regeneration air has been lowered compared with the earlier
apparatuss, the COP values for conventional desiccant assisted air
conditioning apparatuss is still lower than those of air conditioning
apparatuss based on other thermally driven refrigeration devices
(for example, double effect absorption chiller) for cooling and
dehumidification of ambient air. The reason is that the regeneration
of desiccant material still has been done by utilizing the high
temperature heat sources such as boiler, and the apparatus is still
operated at temperatures less than 100.degree. C., in which one
unit of high quality energy (excergy) of fuel is converted into
less than one unit.
SUMMARY OF THE INVENTION
According to the first embodiment of the invention, a desiccant
assisted air conditioning apparatus comprises: a process air passage
for flowing process air for dehumidification through a desiccant
and for delivery to a conditioning space; and a regeneration air
passage for flowing regeneration air for removing moisture from
the desiccant; and an absorption heat pump means for providing cooling
means for process air and heating means for the regeneration air;
the absorption heat pump means comprising: a first circulation unit
having a fist evaporator, a first absorber, a first generator and
a first condenser for providing an absorption refrigeration cycle
operating at a first operating pressure; a second circulation unit
having a second evaporator, a second absorber, a second generator
and a second condenser for providing an absorption refrigeration
cycle operating at a second operating pressure lower than the first
operating pressure; and a heat exchanger between the first evaporator
in the first circulation unit and the second absorber in the second
circulation unit between the first evaporator in the first circulation
unit and the second absorber in the second circulation unit for
performing a heat transfer between the first evaporator and the
second absorber; wherein the heat of condensation from the first
circulation unit and from the second circulation unit together with
the heat of absorption from the first circulation unit are utilized
as heating means for regenerating the desiccant, and the heat of
evaporation in the second circulation unit is utilized as cooling
means for cooling the process air prior to delivery to the conditioning
space.
According to the first aspect of the air conditioning apparatus
presented above, the heat pump device (including refrigeration devices)
is combined with a desiccant assisted air conditioning apparatus
to achieve a high level of energy conservation and system performance.
A sum of heat corresponding to the external heat input into the
system plus the heat of evaporation into the second circulation
unit is recovered by utilizing the heat of condensation generated
in the first and second circulation units and the heat of absorption
generated in the second circulation unit. This sum of heat is used
to produce hot water of 60.degree.-80.degree. C. for regeneration
of the desiccant material. Furthermore, the heat of evaporation
required for the second evaporator in the second circulation unit
is supplied by the chilled water to produce chilled water of about
15.degree. C. used as a cooling source for cooling the process air
in the air conditioning section of the system. The device configuration
presented is not only highly effective in conserving the primary
energy required for desiccant regeneration, but the cooling efficiency
for the air conditioning apparatus is also improved. The use of
all the heat sources enabled by the heat pump device achieves a
high level of energy conservation and performance for the desiccant
assisted air conditioning apparatus.
According another aspect, desiccant assisted air conditioning apparatus
including a process air passage for flowing process air for dehumidification
through a desiccant and for delivery to a conditioning space; and
a regeneration air passage for flowing regeneration air for removing
moisture from said desiccant; and an absorption heat pump means
for providing cooling heat source for process air by way of a heating
device and heating heat source for said regeneration air by way
of cooling cevice; said absorption heat pump means comprising:
a lower pressure evaporator, and a higher pressure evaporator operating
at a higher operating pressure than said lower pressure evaporator;
a lower pressure absorber, and a higher pressure absorber operating
at a higher operating pressure than said lower pressure absorber;
a generator; a condenser; and heat exchanging means for providing
heat to said higher pressure evaporator by transferring the heat
of absorption from said lower pressure absorber to said higher pressure
evaporator; wherein a refrigerant evaporated in said lower pressure
evaporator is absorbed in said lower pressure absorber, and a refrigerant
evaporated in said higher pressure evaporator is absorbed in said
higher pressure absorber, and said heating device is communicated
with a heating passage for heat exchange with said higher pressure
absorber and said condenser, and said cooling device is provided
with a cooling passage for heat exchange with said lower pressure
evaporator.
According to the second aspect, the same level of energy conservation
as in the first embodiment is obtained through the recovery of a
sum of heat, i.e. overall heat input into the system plus the heat
of evaporation in the lower pressure evaporator in the second circulation
unit, in the form of the heat of condensation in the first and second
circulation units and the heat of absorption in the high pressure
absorber in the second circulation unit. This sum of heat is used
to produce hot water in the high range of 80.degree.-100.degree.
C. for desiccant regeneration. As in the first embodiment, the heat
of evaporation required by the low pressure evaporator is utilized
so that chilled water of about 10.degree. C. is produced for use
in cooling the process air in the air conditioning section of the
system. The configuration of the heat pump device in this embodiment
offers an advantage that the solution concentration can be adjusted
according to the pressure selected so as to produce hot water of
higher temperatures and chilled water of lower temperatures. A solution
of higher concentration in the lower pressure absorber is achieved,
and consequently the absorption temperature is raised and the operating
temperature of the high pressure evaporator is also raised, resulting
that the absorption temperature in the high pressure absorber is
elevated. The overall result is that further degree of energy conservation
can be achieved for the same amount of heat input into the desiccant
assisted air conditioning apparatus so that a higher temperature
can be generated in the hot water.
Therefore, it is evident that the desiccant assisted air conditioning
apparatus of the present invention, the consumption of heating energy
to drive the overall system is significantly reduced, compared with
the conventional air conditioning apparatuss based on double effect
absorption chiller, and consistently higher values of the coefficient
of performance are obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a first embodiment of the
desiccant assisted air conditioning apparatus of the present invention
combining the heat pump device section and the air conditioning
section utilizing the desiccant.
FIG. 2 is a Duhring's diagram showing the operational cycles of
the heat pump device of the first embodiment.
FIG. 3 is a psychrometric chart showing the desiccant assisted
air conditioning cycle in the first embodiment.
FIG. 4 is a schematic representation of a second embodiment of
the desiccant assisted air conditioning apparatus of the present
invention.
FIG. 5 is a Duhring's diagram showing the operational cycles of
the heat pump device of the second embodiment.
FIG. 6 is schematic representation of a third embodiment of the
desiccant assisted air conditioning apparatus of the present invention.
FIG. 7 is a Duhring's diagram showing the operational cycles of
the heat pump device of the third embodiment.
FIG. 8 is a schematic representation of a conventional desiccant
assisted air conditioning apparatus.
FIG. 9 a psychrometric chart of the conventional desiccant assisted
air conditioning apparatus shown in FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first embodiment of the preferred embodiment will be explained
below with reference to FIGS. 1 to 3. FIG. 1 is a schematic representation
of the basic configuration of the desiccant assisted air conditioning
apparatus of the present invention. The heat pump device section
of the apparatus comprises a first circulation unit to provide an
absorption refrigeration cycle including a first evaporator 3; a
first absorber 1; a first generator 2; a first condenser 4; and
a heat exchanger 5 between the solution passages to and from the
first absorber 1 and the first generator 2 and a second circulation
unit including a second evaporator 13; a second absorber 11; a second
generator 12; a second condenser 14; a heat exchanger 15 between
the solution passages to and from the second absorber 11 and the
second generator 12. The second absorber 11 of the second circulation
unit is operated at a lower pressure than the first absorber 1 of
the first circulation unit. A heat exchanger 21 in the form of a
heat transfer pipe is provided between the first evaporator 3 in
the first circulation unit and the second absorber 11 in the second
circulation unit. A heat transfer passages 51 52 53 and 54 for
flowing heat transfer medium such as hot water or chilled water
to extracting the heat of condensation generated in the first and
second circulation units and the heat of absorption generated in
the first circulation unit for use as a heat source for the air
condining section of the apparatus. Heat transfer meadium performs
heat exchange by being flown through the passages 51 52 53 and
54 from the heat transfer pipe 30 of the first absorber 1 to the
heat transfer pipe 31 of the second condenser 14 and then to the
heat transfer pipe 32 of the first condenser 4. FIG. 1 shows that
the hot water pipe and the chilled water pipe, i.e., heat tranfer
passages 51 52 53 and 54 of the absorption heat pump device are
connected to a desiccant assisted air conditioning apparatus respectively
through a hot water pump 150 and a chilled water pump 160.
The air conditioning section of the desiccant assisted air conditioning
apparatus shown in FIG. 1 is constructed as follows: the conditioning
space 101 is communicated with the intake of the blower 102 through
the passage 107; the outlet of the blower 102 is communicated with
the desiccant wheel 103 through the passage 108; the discharge for
the process air from the desiccant wheel 103 is communicated with
the sensible heat exchanger 104 for the regeneration air through
the passage 109; the outlet for the process air from the heat exchanger
104 is communicated with the chilled water heat exchanger 115 through
the passage 110; the outlet for the process air from the chilled
water heat exchanger 115 is communicated with the humidifier 105
through the passage 119; and the outlet for the process air from
the humidifier 105 is communicated with the conditioning space 101
through the passage 111; thereby completing a processing cycle for
the process air.
In the meanwhile, the processing route for the regeneration air
is as follows: outside air is introduced by connecting the intake
of the blower 130 through the passage 124; the outlet of the blower
130 is communicated with the sensible heat exchanger 104 heat-exchangeable
with the process air; the outlet for the regeneration air from the
sensible heat exchanger 104 is communicated with the inlet of the
low temperature side of another heat exchanger 121 through a passage
125; the outlet of the low temperature side of the sensible heat
exchanger 121 is communicated with the hot water heat exchanger
120 through the passage 126; the outlet for the regeneration air
of the hot water heat exchanger 120 is communicated with the inlet
of the regeneration air from the desiccant wheel 103 through the
passage 127; the outlet for the regeneration air of the desiccant
wheel 103 is connected to the inlet of the high temperature side
of the sensible heat exchanger 121 through the passage 128; the
outlet of the high temperature side of the sensible heat exchanger
121 is communicated with the external space through the passage
129 so that outside air can be introduced for use as regeneration
air. The hot water inlet of the hot water heat exchanger 120 is
communicated with the outlet of the absorber 1 of the first circulation
unit in the hot water passage of the absorption heat pump through
the passage 122. The hot water outlet of the hot water heat exchanger
120 is communicated with the inlet of the condenser 14 in the second
circulation unit in the hot water passage of the absorption heat
pump through the passage 123 and the hot water pump 150. The chilled
water inlet of the chilled water heat exchanger 115 is communicated
with the outlet of the evaporator 13 in the second circulation unit
in the chilled water passage of the absorption heat pump through
the passage 117 and the chilled water outlet of the chilled water
heat exchanger 115 is communicated with the inlet of the evaporator
13 in the second circulation unit in the chilled water passage of
the absorption heat pump through the passage 118 and the pump 160.
In FIG. 1 the circled alphabetical designations K-V refer to the
thermodynamic states of the air corresponding to those in FIG. 3
and SA designates supply air, RA designates return air, OA designates
outside air and EX designates exhaust air.
The operational cycle of the absorption heat pump device of such
a configuration will be explained below. The solution in the first
circulation unit is heated in the generator 2 by a heat medium through
the heat transfer pipe 34 which was heated by an external heat
source (not shown) and supplied through the passage 61 to generate
a vapor of the refrigerant, and after becoming concentrated, is
delivered to the first absorber 1 through the first heat exchanger
5. In the first absorber 1 the solution absorbs the refrigerant
vapor evaporated in the first evaporator 3 and after being diluted,
returns to the first generator 2 again through the first heat exchanger
5 by the pumping action of the pump 6. In the first absorber 1
the absorption heat generated during the process is utilized by
heat exchange through a teat transfer medium in the heat transfer
pipe 30 such as hot water. The vapor of the refrigerant generated
in the first generator 2 enters into the first condenser 4 to be
condensed. In the first condenser 4 the heat of condensation generated
during the process is transferred to a teat transfer medium (hot
water) through the heat transfer pipe 32. The condensed refrigerant
flows into the first evaporator 3 to be evaporated. In the first
evaporator 3 a quantity of heat corresponding to the evaporation
heat generated during the process is transferred through the heat
transfer pipe 21 from the second absorber 11 in the second circulation
unit. In the heat transfer pipe 21 of the first absorber 1 it is
permissible to configure the heat transfer pipes so that the refrigerant
is evaporated directly in the second evaporator 13 without resorting
to a heat tranfer medium, the result produced is the same.
The solution in the second circulation unit is heated in the second
generator 12 by the same heating medium as in the first circulation
unit and supplied through the passage 62 and the heat transfer pipe
35 to generate a vapor of the refrigerant, becomes concentrated
and is delivered to the second absorber 11 through the second heat
exchanger 15. In the second absorber 11 the solution absorbs the
refrigerant vapor evaporated in the second evaporator 13 and after
becoming diluted, returns to the second generator 12 again through
the heat exchanger 15 by the pumping action of the pump 16. In the
second absorber 11 the absorption heat generated during the process
is transferred to the first evaporator 3 through the heat transfer
pipe 21. The vapor of the refrigerant generated in the second generator
12 enters into the second condenser 14 to be condensed. The heat
of condensation generated in the second condenser 14 is utilized
by transferring the heat to the heat transfer medium through the
heat transfer pipe 31. Since the heat transfer medium flows from
the condenser heat transfer pipe 30 of the second absorber 11 then
to the heat transfer pipe 31 of the second condenser 14 then back
to the absorption heat transfer pipe 32 of the first condenser 4
in succession, the absorption temperature of the solution in the
first circulation unit becomes lower than the condensation temperature
of the refrigerant in the first and second circulation units. The
condensed refrigerant is delivered to the second evaporator 13 to
be evaporated. In the second evaporator 13 the heat of evaporation
is transferred to a heat tranfer medium such as chilled water through
the heat transfer pipe 33.
The operation of the absorption heat pump section of the desiccant
assisted air conditioning will be explained with reference to FIG.
2. FIG. 2 is a Duhring's diagram showing the operational cycle of
the absorption heat pump device shown in FIG. 1. This is a typical
example of a lithium bromide-water working fluid system commonly
used in the absorption chiller. The alphabetical designations shown
in this drawing are related to various conditions of the solution
or refrigerant, and the corresponding designations are also shown
in FIG. 1.
The solution in the first circulation unit is heated in the first
generator 2 by an external heater to generate a vapor of the refrigerant,
and after becoming concentrated (150.degree. C. in FIG. 2), it flows
into the first heat exchanger 5 (state d) to be delivered to the
first absorber 1. In the first absorber 1 the solution absorbs
the refrigerant evaporated in the evaporator 3 and after becoming
diluted (state a), it is heated again in the first heat exchanger
5 (state b) to return to the first generator 2. The vapor of the
refrigerant generated in the first generator 2 enters into the first
condenser 4 to be condensed (state f). The heat of condensation
generated in the first condenser 4 is transferred to the hot water
by the heat transfer pipe 32 acting as a heat exchanger.
The condensed refrigerant is forwarded to the first evaporator
3 to be evaporated (state e). In the first evaporator 3 a quantity
of heat corresponding to the heat of evaporation is transferred
from the second absorber 11 of the second circulation unit through
the heat transfer pipe 21 (state A). The solution in the second
circulation unit is heated in the second generator 12 by the heat
supplied from an external source through the heat transfer pipe
35 to generate a vapor of the refrigerant, and after becoming concentrated
(state C), it flows into the second heat exchanger 15 (state D)
to be delivered to the second absorber 11. In the second absorber
11 the solution absorbs the refrigerant evaporated in the second
evaporator 13 (state E), and after becoming diluted (state A), it
is heated again in the second heat exchanger 15 (state B) to return
to the second generator 12. In the second absorber 11 the heat
of absorption generated during the process is transferred to the
first evaporator 3 (state e) in the first circulation unit through
the heat transfer pipe 21. The vapor of the refrigerant generated
in the second generator 12 enters into the second condenser 14 to
be condensed (state F). The condensed refrigerant (state F) is forwarded
to the second evaporator 13 to be condensed (state F). The condensed
refrigerant is delivered to the second evaporator 13 to be evaporated
(state E).
The absorption heat pump of the configuration described above produces
a high level of energy conservation, and gives a highly efficient
thermal performance by efficient utilization of heat as explained
below. The high temperature heat supplied by the external heater
to the first generator 2 in the first circulation unit is used for
concentrating the refrigerant in the first circulation unit, and
the heat possessed by the vapor of the refrigerant generated in
the process is recovered in and extracted from the first condenser
4 as the heat of condensation. The concentrated solution absorbs
the vapor evaporated in the first evaporator 1 in the first absorber
11 and the heat of absorption is also utilized. As well, the high
temperature input heat supplied from external source to the second
generator 12 in the second circulation unit is used to concentrate
the solution in the second circulation unit, and the heat possessed
by the vapor is recovered in and extracted from the second condenser
14 as the heat of condensation to produce hot water of about 60.degree.-80.degree.
C. In the second evaporator 13 in the second circulation unit, the
heat of evaporation in a form of chilled water of about 15.degree.
C. is extracted for cooling. Also, the heat of absorption generated
in the second absorber 11 in the second circulation unit is utilized
as the heat of evaporation in the first circulation unit. The hot
water thus generated in the absorption heat pump device is used
for desiccant regeneration, and the chilled water is utilized for
cooling the process air.
Overall heat balance of the operational cycle shows that the heat
input consists of the high temperature external heat input into
the first and second generators 2 12 in the first and second circulation
units and a quantity of heat extracted from the chilled water in
the second evaporator 13 in the second circulation unit, whereas,
the heat output during the cycle is the absorption heat in the first
circulation unit and the condensation heat in the first and second
circulation units. In other words, the hot water receives not only
the high temperature heat input from the external heater in the
first circulation unit but also the heat extracted from the chilled
water in the second circulation unit, therefore the amount of heat
available for heating is increased beyond the amount of heat supplied
externally to the generators 2 12 in the first and second circulation
units. Therefore, it has been demonstrated that a heat pump effect
has been achieved in the thermal cycles produced in the present
apparatus.
Next, the operation of an air conditioning apparatus combining
the absorption heat pump device presented above with desiccant assisted
conditioning section will be explained.
FIG. 3 is a psychrometric chart showing the operation of the air
conditioning section of the apparatus shown in FIG. 1. The operation
of the air conditioning apparatus is as follows. Referring to FIG.
1 ambient air (process air) from the conditioning room 101 is withdrawn
through the passage 107 into the blower 102 to be pressurized, and
the pressurized air is forwarded to the desiccant wheel 103 through
the passage 108 wherein the humidity ratio in the process air is
lowered by having the moisture in the ambient air removed by the
moisture adsorbent in the desiccant wheel 103. Heat released during
the adsorption process raises the temperature of the process air.
The process air with lower humidity and higher temperature is forwarded
to the sensible heat exchanger 104 through the passage 109 and cooled
by heat exchange with the outside air (regeneration air). The cooled
process air is delivered through the passage 110 to the chilled
water heat exchanger 115 for further cooling. The cooled process
air is delivered to the humidifier 105 for cooling isenthalpically
by water spray or evaporative humidifier, and the cooled process
air is returned to the conditioning space 101 through the passage
111.
The desiccant material becomes loaded with moisture in the above
process, and it is necessary to be regenerated. In this embodiment,
this is performed using the outside air as regeneration air as follows.
Outside air (OA) is withdrawn into the blower 130 through the passage
124 to be pressurized, and the pressurized outside air is delivered
to the sensible heat exchanger 104 through the passage 124 to cool
the process air. The regeneration air, having raised its own temperature,
is forwarded to the next sensible heat exchanger 121 through the
passage 125 wherein heat exchange takes place with the high temperature
spent regeneration air to further raise its own temperature, and
the regeneration air exiting the sensible heat exchanger 121 flows
into the hot water heat exchanger 120 through the passage 126. At
this point the temperature of the regeneration air is raised to
60.degree.-80.degree. C. by the hot water, and its relative humidity
is decreased.
This process corresponds to the sensible heat change of the regeneration
air, and the specific heat of the regeneration air is extremely
low compared with that of hot water, resulting in a large variation
in the air temperature. Therefore, even if the flow rate of the
hot water is decreased (resulting in variations in temperature of
the hot water), heat exchange process can take place quite efficiently.
Accordingly, the condensation temperature of the heat pump at the
inlet side of the hot water in the second circulation unit can be
set lower than the absorption temperature of the first circulation
unit at the outlet of the hot water. By adopting such an approach,
the pressure and temperature requirements in the generator 2 in
the first circulation unit can be lowered, and the heat input load
of water into the generator 2 in the first circulation unit can
be also lightened. By making the useable temperature difference
of the hot water to be large, the flow rate can be decreased, and
therefore the transport load of water is also lowered.
The regeneration air exiting from the hot water heat exchanger
120 has a lower relative humidity than before, and in the process
of flowing through the desiccant wheel 103 removes the moisture
therefrom, thus performing regeneration of the desiccant material.
Spent air which has passed through the desiccant wheel 103 flows
into the sensible heat exchanger 121 through the passage 128 preheats
the outside air and is exhausted through the passage 129 to outside
environment.
The process to this point will be explained with reference to psychrometric
chart in FIG. 3. The air to be processed for the conditioning space
101 (process air: state K) is withdrawn through the passage 107
into the blower 102 to be pressurized, and the pressurized process
air is forwarded to the desiccant wheel 103 through the passage
108. The humidity ratio in the process air is lowered by absorption
of moisture in the process air into the moisture adsorbent in the
desiccant wheel 103 and its temperature is raised by absorbing
the heat of adsorption (state L). The process air, having its humidity
lowered and temperature raised, is delivered to the sensible heat
exchanger 104 through the passage 109 and undergoes heat exchange
with outside air (regeneration air) to lower its temperature (state
M). The cooled process air is forwarded to the chilled water heat
exchanger 115 through the passage 110 to be further cooled (state
N). The cooled process air is delivered to the humidifier 105 through
the passage 119 and its temperature is lowered isenthalpically by
water spray or evaporative humidifier (state P), and the process
air is returned to the conditioning space 101 through the passage
111. During the process described above, an enthalpy difference
.DELTA.Q between the return air (state K) and the supply air (state
P) is generated to provide the driving force for cooling the conditioning
space 101.
Regeneration process of the desiccant follows the following states.
Outside air for regeneration (OA: state Q) is withdrawn into the
blower 130 through the passage 124 to be pressurized, and is delivered
to the sensible heat exchanger 104 to cool the process air while
raising its own temperature (state R), and flows into the next sensible
heat exchanger 121 through the passage 125 and, in exchanging heat
with the high temperature spent air, raises its own temperature
(state S). Regeneration air leaving the heat exchanger 121 flows
into the hot water heat exchanger 120 through the passage 126 so
that its temperature is raised to 60.degree.-80.degree. C., and
its relative humidity is decreased (state T). Regeneration air having
lower relative humidity passes through the desiccant wheel 103 to
remove the moisture therefrom (state U).
Spent air which has passed through the desiccant wheel 103 flows
into the sensible heat exchanger 121 through the passage 128 and
preheats regeneration air exiting from the sensible heat exchanger
104 and lowers its own temperature (state V). Spent air is exhausted
to outside environment through the passage 129. The process cycles
described above, i.e. , regeneration of desiccant on the one hand
and dehumidification and cooling of process air on the other, is
repeatedly carried out to provide desiccant assisted air conditioning
of the conditioning space. It is a common practice to utilize exhaust
air from the conditioning room as regeneration air, and in this
invention also, there is no problem in recycling the exhaust room
air for regeneration air, and the same result will be obtained.
The COP value to indicate the energy efficiency of the desiccant
regeneration having the present configuration can be calculated
by dividing the enthalpy difference .DELTA.Q in FIG. 3 by the amount
of heat input used for regeneration purpose. However, the heat input
.DELTA.H added to regeneration air by the hot water heat exchanger
includes that amount of heat .DELTA.Q supplied by the chilled water
heat exchanger which extracts the heat from the process air by means
of the absorption heat pump effect through the chilled water heat
exchanger 115 and the second evaporator 13 in the second circulation
unit. Therefore, the actual amount of heat supplied to the overall
system is obtained by subtracting .DELTA.q from .DELTA.H, which
is denoted by .DELTA.h which corresponds to the sensible heat change
generated in going from state X to state T.
It therefore follows that COP is given by the following expression:
Comparing COP in FIG. 3 with the conventional COP in FIG. 9 it
can be seen that in the present embodiment the cooling effect denoted
by .DELTA.Q in the numerator is increased by an amount equal to
.DELTA.q, and that the heat input indicated by the denominator is
lowered by an amount equal to .DELTA.q, thereby leading to a significant
increase in the final COP.
Sample calculation of COP for the present apparatus will be outlined
below. Assuming that COP for the refrigeration effect of absorption
heat pump to be about 0.3 and that COP for the conventional desiccant
assisted air conditioning is 1.0 the present COP can be obtained
as follows. Letting the heat input from an external heat source
into the absorption pump to be 1.0 the heat pump effect adds a
heat input of 1.3 to the hot water, and when this heat is used to
operate the desiccant assisted air conditioning, heat input for
the refrigeration effect is given by:
wherein, .DELTA.q is refrigeration effect.
Therefore, the present COP is obtained as:
(cooling effect)/(heat input to absorption heat pump)
=1.6/1.0
=1.6
This value is far in excess of COP of 1.2 for the double effect
absorption chiller of conventional design, thus indicating the present
apparatus is operating at quite a high level of energy conservation.
In summary review, it can be concluded that the overall performance
of the air conditioning apparatus is improved by a high level of
energy utilization demonstrated in the first embodiment. That is,
a sum of heat corresponding to the high temperature external input
heat into the generators in the first and second circulation units
plus the heat of evaporation in the second circulation unit is utilized
as a heating heat source of an intermediate temperature range of
60.degree.-80.degree. C. for desiccant regeneration in a form of
the heat of condensation in the first circulation unit and the absorption
heat in the second circulation unit. Further, the evaporation heat
absorbed in the evaporator in the second circulation unit is utilized
as a cooling heat source of approximately 15.degree. C. for cooling
the process air in the desiccant assisted air conditioning cycle
of the apparatus. The result is energy conservation in desiccant
regeneration as well as improved cooling effect.
In the following, a second embodiments of desiccant assisted air
conditioning apparatus will be presented with reference to FIGS.
4 to 7.
FIG. 4 is a schematic representation of the basic configuration
of a desiccant assisted air conditioning apparatus of the present
invention. The absorption heat pump section comprises: a lower pressure
evaporator 203; a higher pressure evaporator 213 which operates
at a higher pressure than the low pressure evaporator 203; a low
pressure absorber 201; a high pressure absorber 211 which operates
at a higher pressure than the low pressure absorber 201; a generator
201; a condenser 204; a first heat exchanger 205; and a second heat
exchanger 215. The apparatus is configured by including a heat transfer
pipe 221 acting as a heat exchanger for heat transfer between the
low pressure absorber 201 and the high pressure evaporator 213 so
that the heat of absorption generated in the low pressure absorber
201 is used to heat the high pressure evaporator 213 and the refrigerant
evaporated in the low pressure evaporator 203 is absorbed by the
low pressure absorber 201 and the refrigerant evaporated in the
high pressure evaporator 213 is absorbed in the high pressure absorber
211.
The solution passage for the absorption heat pump device is as
follows. The solution exiting the low pressure absorber 201 flows
into the generator 202 through the first heat exchanger 205 and
the second heat exchanger 215 and further flows into the high pressure
absorber 211 through the second heat exchanger 215 to return to
the low pressure absorber 201 through the first heat exchanger 205.
The refrigerant passage for the absorption heat pump device is
as follows. The refrigerant vapor generated in the generator 202
enters into the condenser 204 and the condensed refrigerant exiting
the condenser 204 splits into two paths. The refrigerant in one
path flows into the low pressure evaporator 203 through a constricting
device 207 and is evaporated in the low pressure evaporator 203
and the evaporated vapor flows into the low pressure absorber 201
to be absorbed into the solution flow. The refrigerant in the other
path flows into the high pressure evaporator 213 through the constricting
device 217 and after being evaporated in the high pressure evaporator
213 enters into the high pressure absorber 211 to be absorbed into
the solution flow.
The heat transfer medium passage for flowing heat transfer medium
(hot water) for extracting the absorption heat from the high pressure
absorber and the heat of condensation from the condenser as heating
source is arranged so that hot water flows from the absorption heat
transfer pipe 230 to the condensation heat transfer pipe 231 in
this order to provide heat exchange, and the heat transfer medium
passage for flowing heat transfer medium (chilled water) for supplying
the heat of evaporation to the low pressure evaporator from the
chilled water is connected to the heat transfer pipe 232 of the
low pressure evaporator 203. In FIG. 4 the hot water pipe and the
chilled water pipe from the absorption heat pump device are connected
to the desiccant assisted air conditioning apparatus through the
respective hot water pump 150 and chilled water pump 160.
The air conditioning section of the apparatus shown in FIG. 4 is
the same as that shown in FIG. 1 and the explanations are omitted.
The air conditioning section and the absorption pump device are
connected as follows.
The hot water inlet (for heat transfer medium) of the heater 120
is connected to the outlet of the condenser 4 in the hot water passage
of the absorption heat pump through the passage 122 the hot water
outlet of the heater 120 is connected to the inlet of the high pressure
absorber 11 through the water pump 150 in the hot water passage
of the absorption heat pump. The chilled water inlet of the chilled
water heat exchanger 115 is connected to the outlet of the low pressure
evaporator 203 through the passage 117 in the chilled water passage,
the chilled water outlet of the chilled water heat exchanger 115
is connected to the inlet of the low pressure evaporator 203 through
the passage 118 and the pump 160 in the chilled water passage of
the absorption heat pump device. In the drawing, the circled alphabet
letters denote thermodynamic conditions of the air at the respective
locations, and SA designates supply air, RA designates return air,
OA designates outside air and EX designates exhaust air.
The absorption cycle of the absorption heat pump device in the
desiccant air conditioning apparatus will be explained below. The
solution in the first circulation unit is heated in the generator
202 by a heating medium heated by an external heat source (not shown)
through the heat transfer pipe 233 generates a vapor of the refrigerant
and becomes more concentrated. The concentrated solution enters
the high pressure absorber 211 through the second heat exchanger
215. The solution in the high pressure absorber 211 absorbs the
vapor evaporated in the high pressure evaporator to become diluted,
and is delivered to the low pressure absorber 201 through the first
heat exchanger 205. In the low pressure absorber 201 the solution
absorbs the vapor of the refrigerant evaporated in the low pressure
evaporator 203 and becomes diluted. The weak solution returns to
the generator 202 through the first heat exchanger 205 and the second
heat exchanger 215 by the action of the pump 206. In the high pressure
absorber 211 the absorption heat generated in the process is utilized
as heat source for desiccant regeneration by heat exchange through
the heat transfer pipe 230 with heat transfer medium such as hot
water.
In the low pressure absorber 201 the heat of absorption generated
in the process is used within the internal cycle as heating source
for the high pressure evaporator 213 by heat exchange through the
heat transfer pipe 221. The vapor of the refrigerant generated in
the generator 202 enters into the condenser 204 to be condensed.
In the condenser 204 the heat of condensation is extracted by heat
exchange through the heat transfer pipe 231 with a heat transfer
medium such as hot water for regenerating the desiccant material.
The condensed refrigerant in the condenser 204 is split into two
paths. In one path, the refrigerant flows into the low pressure
evaporator 203 through the constricting device 207 and after extracting
the heat in the heat transfer pipe 232 from a heat transfer medium
(such as chilled water) and evaporating, flows into the low pressure
absorber 201 to be absorbed into the solution flow. In the other
path, the refrigerant flows into the high pressure evaporator 213
through the constricting device 217 and after removing the heat
from the low pressure absorber 201 through the heat transfer pipe
221 and evaporating, the vapor flows into the high pressure absorber
211 to be absorbed into the solution flow. In this case, in the
heat transfer pipe 221 of the low pressure absorber 201 it is permissible
to arrange so that evaporation can take place directly in the high
pressure evaporator 213 without resorting to a heat transfer medium
to achieve the same results.
In this embodiment also, the apparatus is configured so that the
condensation temperature of the refrigerant becomes higher than
the absorption temperature in the high pressure absorber by flowing
the heat transfer medium (hot water) in the direction from the high
pressure absorption heat transfer pipe 230 to the condensation heat
transfer pipe 231. Therefore, when the apparatus is operated so
that the outlet temperature of the hot water is fixed, and the useable
temperature difference of the hot water is made large, the operating
pressure of the high pressure absorber is lowered, and thereby lowering
the evaporation temperature of the high pressure evaporator which
leads to lowering in the solution temperature in the low pressure
absorber, offerring an advantage that the apparatus can be operated
at a low overall solution concentration. In the desiccant regeneration
arrangement used in the present invention, the sensible heat change
is used to heat the regeneration air, therefore a large variation
of the useable temperature difference of the hot water is permissible.
On the other hand, if the heat transfer medium (hot water) is made
to flow from the condensation heat transfer pipe 231 to the high
pressure absorption heat transfer pipe 230 the solution temperature
in the high pressure absorber becomes higher than the condensation
temperature of the refrigerant. However, in case that there is an
upper limit to the pressure rise in the generator 202 and it is
desired to have a high outlet temperature of the hot water, the
hot water passage of the configuration presented above has an advantage
that the pressure in the generator does not increase, because the
operating pressure in the high pressure absorber becomes high, causing
the evaporation temperature in the high pressure evaporator to rise
and the solution temperature in the low pressure absorber also to
rise, though the overall solution concentration becomes high in
the absorption heat transfer pipe device.
The operation of the heat pump section of the desiccant assisted
air conditioning apparatus will be explained with reference to FIG.
5. FIG. 5 is a Duhring's diagram showing the operational cycle of
the absorption heat pump device. The operating apparatus is based
on a typical example of a commonly used lithium bromide-water system.
The circled designations refer to the various conditions of the
solution and the refrigerant, and the same designations are also
given in FIG. 4. The solution is heated in the generator 202 by
an external heater, generates a refrigerant vapor, and after becoming
concentrated (state d: 150.degree. C. in FIG. 5) reaches the high
pressure absorber 211 (state e) through the second heat exchanger
215. In the high pressure absorber 211 the solution absorbs the
evaporated refrigerant in the high pressure evaporator 213 and
after becoming diluted (state f), the solution is cooled (state
g) by passing through the first heat exchanger 205 and flows into
the low pressure absorber 201 to absorb the refrigerant evaporated
in the low pressure evaporator 203. And after becoming diluted (state
a), the solution is heated by flowing into the first heat exchanger
205 (state b) and then to the second heat exchanger 215 (state c)
and returns to the generator 202. The vapor of the refrigerant generated
in the generator 202 enters into the condenser 204 and is condensed
(state h). The condensed refrigerant splits into two paths. The
refrigerant in one path flows into the low pressure evaporator 203
through the constricting device 207 and after extracting the heat
through the heat transfer pipe 232 (from the heat transfer medium
such as chilled water) and evaporating (state j), the refrigerant
flows into the low pressure absorber 201 and is absorbed into the
solution flow. The refrigerant in the other path flows into the
high pressure evaporator 213 through the constricting device 217
and after removing the heat of absorption from the low pressure
absorber 201 and evaporating (state k), flows into the high pressure
absorber 211 and is absorbed into the solution flow. The absorption
heat (state a) generated in the low pressure absorber 201 is transported
to the high pressure evaporator 213 to evaporate the refrigerant.
The heat pump device of the configuration presented above produces
the following heat utilization effects. The high temperature heat
externally supplied to the generator 202 is used to concentrate
the solution, and the heat possessed by the vapor generated in the
process is removed as condensation heat from the condenser 204
and the concentrated solution absorbs the refrigerant evaporated
in the high pressure evaporator 213 and the absorption heat generated
in the process is removed from the high pressure absorber 211 in
a form of hot water in a range of 80.degree.-100.degree. C. In the
low pressure evaporator 203 the heat of evaporation is supplied
from the chilled water acting as a heating source to produce chilled
water of about 10.degree. C. The heat of absorption generated in
the low pressure absorber 201 is utilized within the apparatus as
evaporation heat for the high pressure evaporator 213.
It is seen that the hot water produced in the heat pump device
is utilized for desiccant regeneration, and the chilled water is
utilized for cooling the process air. The heat balance in the overall
apparatus indicates that the heat input into the cycle is a sum
of the high temperature external heat supplied from an outside source
and the heat extracted from the chilled water in the low pressure
evaporator 203 and the heat output from the cycle is a heat inputted
into the hot water, which is a sum of the heat of absorption removed
from the high pressure absorber 211 and the heat of condensation
removed from the condenser 204. Therefore, hot water receives heat
removed from the chilled water in the low pressure evaporator 203
in addition to the high temperature external heat, and the total
heat supplied is higher than the heat supplied to the generator
from the outside source. Therefore, the cycle of the apparatus provides
a heat pump effect as demonstrated.
The operational behavior of the desiccant assisted air conditioning
apparatus having the heat pump device of the above configuration
is the same as that in the first embodiment shown in FIG. 1 and
can be explained with the use of a psychrometric chart shown in
FIG. 3 so the explanations will be omitted.
The coefficient of performance (COP) of this embodiment is given
by a value obtained by cooling effect .DELTA.Q in FIG. 3 by the
regeneration heat input. As shown by an example related to FIG.
1 it is given by 1.6 (cooling effect)/1.0 (heat input into the
absorption heat pump device)=1.6. This value is much higher than
a value of 1.2 which is typical of conventional double effect asorption
chiller, and shows the high degree of energy conservation.
As demonstrated above, the heat of absorption generated in the
high pressure absorber and the heat of condensation generated in
the condenser, either in a heat pump device or in a refrigerator,
can be used as heat source for desiccant regeneration purposes,
and the heat of evaporation required in the low pressure evaporator
can be used as a cooling source to produce chilled water for cooling
the process air in the air conditioning purposes.
FIG. 6 is a schematic representation of the basic configuration
of a third embodiment of the present invention. The absorption heat
pump section comprises the following components: a lower pressure
evaporator 203; a higher pressure evaporator 213 which operates
at a higher pressure than the low pressure evaporator 203; a low
pressure absorber 201; a high pressure absorber 211 which operates
at a higher pressure than the low pressure absorber 201; a generator
201; a condenser 204; a first heat exchanger 205; and a second heat
exchanger 215. The apparatus is configured so that, on the one hand,
the high pressure evaporator 213 is heated by the heat of absorption
generated in the low pressure absorber 201 by having a heat transfer
pipe 221 acting as a heat exchanger device for the low pressure
absorber 201 and the high pressure evaporator 213 and that the
refrigerant generated in the low pressure evaporator 203 is absorbed
by the low pressure absorber 201 and that the vapor evaporated in
the high pressure evaporator 213 is absorbed by the high pressure
absorber 211.
The solution passage for the absorption heat pump device is as
follows. The solution exiting the low pressure absorber 201 flows
into the high pressure absorber 211 through the first heat exchanger
205. The solution exiting the high pressure absorber 211 flows into
the generator 202 through the second heat exchanger 215 and the
solution exiting the generator 202 returns to the low pressure absorber
201 through the second heat exchanger 215 and first heat exchanger
205. The refrigerant passage for the absorption heat pump device
is as follows. The vapor of the refrigerant generated in the generator
202 enters into the condenser 204 and the condensed medium exiting
the condenser 204 splits into two paths. The refrigerant in one
path flows into the low pressure evaporator 203 through a constricting
device 207 and evaporate in the low pressure evaporator 203 and
then flows into the low pressure absorber 201 to be absorbed into
the solution flow. The refrigerant in the other path flows into
the high pressure evaporator 213 through the constricting device
217 and the evaporated refrigerant from the high pressure evaporator
213 enters into the high pressure absorber 211 to be absorbed into
the solution flow. The hot water passage of the heat transfer medium
(hot water) for removing the absorption heat from the high pressure
absorber and the condensation heat from the condenser for use as
heating source is constructed so that heat exchange is performed
by successively flowing from the condenser heat transfer pipe 231
then to the absorption heat transfer pipe 230 of the high pressure
absorber 230. The chilled water passage of the heat transfer medium
(chilled water) for supplying the evaporation heat to the low pressure
evaporator for use as cooling source is constructed by connecting
to heat transfer pipe 232. In FIG. 6 the hot water passage and
the chilled water passage of the heat pump device are connected
to the desiccant assisted air conditioning apparatus through a hot
water pump 150 and a chilled water pump 160 respectively.
The air conditioning section of the desiccant assisted air conditioning
apparatus shown in FIG. 6 is the same as the shown in FIG. 1 or
FIG. 4 and the explanations will be omitted. The air conditioning
section and the absorption heat pump are connected as follows.
The inlet for the heat transfer medium (hot water) for the heater
120 is connected to the outlet of the high pressure absorber 211
in the hot water passage of the absorption heat pump through the
passage 122 and the hot water outlet of the heater 120 is connected
to the inlet of the high pressure condenser 204 in the hot water
passage of the absorption heat pump through the passage 123 and
the water pump 150. The chilled water inlet of the chilled water
heat exchanger 115 is connected to the outlet of the low pressure
evaporator 203 through the passage 117 in the chilled water passage,
and the chilled water outlet of the chilled water heat exchanger
115 is connected to the inlet of the low pressure evaporator 203
in the chilled water passage of the absorption heat pump device
through the passage 118 and the pump 160. In the drawing, the circled
alphabet letters denote various thermodynamic conditions of the
process air corresponding to FIG. 4 and SA designates supply air,
RA designates return air, OA designates outside air and EX designates
exhaust air.
The operational cycle of the absorption heat pump device in the
desiccant air conditioning apparatus will be explained below. The
solution is heated by an external source of heat (not shown) in
the generator 202 through the heat transfer pipe 233 generates
a refrigerant vapor and becomes concentrated. The concentrated solution
enters the high pressure absorber 211 through the second heat exchanger
215 and the first heat exchanger 205. In the low pressure absorber
201 the solution absorbs the refrigerant evaporated in the low
pressure evaporator 203 and after becoming diluted, the solution
is pumped by the pump 206 to reach the high pressure absorber 211
through the first heat exchanger 205. In the high pressure absorber
211 the solution absorbs the vapor evaporated in the high pressure
evaporator 213 to become diluted, and is returned by the pump 216
to the generator 202 through the second heat exchanger 215. In the
high pressure absorber 211 the absorption heat generated in the
process is utilized as heat source for desiccant regeneration by
heat exchange through the heat transfer pipe 230 with heat transfer
medium such as hot water.
The heat of absorption generated in the low pressure absorber 201
is used within the internal cycle for heating the high pressure
evaporator 213 by heat exchange through the heat transfer pipe 221.
The vapor of the refrigerant generated in the generator 202 enters
into the condenser 204 to be condensed. In the condenser 204 the
heat of condensation is used to regenerate the desiccant material
by removing the heat through heat exchange process in the heat transfer
pipe 231 with a heat transfer medium such as hot water. The condensed
refrigerant in the condenser 204 is split into two paths. In one
path, the refrigerant flows into the low pressure evaporator 203
through the constricting device 207 and after utilizing the heat
in the heat transfer pipe 232 from a heat transfer medium (such
as chilled water) and evaporating, flows into the low pressure absorber
201 to be absorbed into the solution flow. In the other path, the
refrigerant flows into the high pressure evaporator 213 through
the constricting device 217 and after removing heat from the low
pressure absorber 201 (in the heat transfer pipe 221) and evaporating,
flows into the high pressure absorber 211 to be absorbed into the
solution flow.
The operation of the heat pump section of the desiccant assisted
air conditioning apparatus will be explained with reference to FIG.
7. FIG. 7 is a Duhring's diagram showing the absorption heat pump
operational cycle of the apparatus shown in FIG. 6. This operating
system is also based on a typical example of a commonly used lithium
bromide-water working fluid system. The circled designations refer
to the conditions of the solution and the refrigerant, and the same
designations are also given.
The solution is heated in the generator 202 by an external heater,
generates a vapor, and after becoming concentrated (state d: 150.degree.
C. in FIG. 7) the solution reaches the low pressure absorber 201
through the second heat exchanger 215 (state e) and the first heat
exchanger 205 (state g). In the low pressure absorber 201 the solution
absorbs the refrigerant evaporated in the low pressure evaporator
201 and after becoming diluted (state a), the solution flows into
the first heat exchanger 205 (state b), to reach the high pressure
absorber 211. In the high pressure absorber 211 the solution absorbs
the vapor evaporated in the high pressure evaporator 213 and after
becoming diluted (state f), is delivered to the second heat exchanger
215 to be heated (state c), and then the solution returns to the
generator 202. The vapor of the refrigerant generated in the generator
202 enters into the condenser 204 and is condensed (state h). The
condensed refrigerant splits into two paths. The refrigerant in
one path flows into the low pressure evaporator 203 through the
constricting device 207 and after utilizing the heat from the heat
transfer medium (such as chilled water) through the heat transfer
pipe 232 and evaporating (state j), the refrigerant flows into the
low pressure absorber 201 and is absorbed into the solution flow.
The refrigerant in the other path flows into the high pressure evaporator
213 through the constricting device 217 and after removing the
heat of absorption from the low pressure absorber 201 through the
heat transfer pipe 221 and evaporating (state k) flows into the
high pressure absorber 211 for absorption into the solution flow.
The absorption heat (state a) generated in the low pressure absorber
201 is transferred to the high pressure evaporator 213 to evaporate
the refrigerant.
Compared with the absorption heat pump device shown in FIG. 4
the heat pump of the present embodiment produces a solution of higher
concentration in the low pressure absorber, and consequently the
absorption temperature is raised and the operating temperature of
the high pressure evaporator is also raised, resulting that the
absorption temperature in the high pressure absorber is elevated.
The overall result is that a higher temperature can be achieved
in the hot water.
In the heat pump device of the present embodiment also, the heat
input into the operational cycle consists of the external high temperature
heat input into the generator 2 and the heat extracted from the
chilled water in the low pressure evaporator 203 and the output
heat consists of the heat of absorption generated in the high pressure
absorber 211 and the heat of condensation generated in the condenser
4 therefore, the hot water receives not only the external heat
input but also the heat recovered from the chilled water, and the
total available amount of heat for heating is larger than the external
heat alone. Therefore, the cycle of the apparatus provides a heat
pump effect as demonstrated.
The operational behavior of the air conditioning apparatus incorporating
the absorption heat pump device and the effect on energy conservation
are the same as those explained with reference to FIG. 4 and can
be explained similarly using the psychrometric chart shown in FIG.
3.
In the present embodiment also, the heat of absorption generated
in the high pressure absorber and the heat of condensation generated
in the condenser, which can be either a heat pump device or a refrigerator,
are used as heat source in the desiccant regeneration process, and
the heat of evaporation in the low pressure evaporator is utilized
in producing the chilled water used in cooling the process air in
the air conditioning process.
Although the foregoing embodiments were illustrated in terms of
understanding, and should not be construed to limit the scope of
the present invention. |