U.S. patent application number 10/468832 was filed with the patent office on 2004-06-24 for heat pump and dehumidifying air-conditioning apparatus.
Invention is credited to Inaba, Hideo, Maeda, Kensaku, Nishikawa, Shunro.
Application Number | 20040118133 10/468832 |
Document ID | / |
Family ID | 18918904 |
Filed Date | 2004-06-24 |
United States Patent
Application |
20040118133 |
Kind Code |
A1 |
Maeda, Kensaku ; et
al. |
June 24, 2004 |
Heat pump and dehumidifying air-conditioning apparatus
Abstract
A dehumidifying air-conditioning apparatus comprises a
pressurizer (4) for raising a pressure of a refrigerant, a
condenser (5) for condensing the refrigerant to heat a
high-temperature heat source fluid, and an evaporator (1) for
evaporating the refrigerant to cool process air to a temperature
lower than its dew point. The dehumidifying air-conditioning
apparatus further comprises a refrigerant path branched into a
plurality of branched refrigerant paths (42, 43, 44) between the
condenser (5) and the evaporator (1). A first heat exchanging
portion (21) is disposed in the branched refrigerant path for
evaporating the refrigerant under an intermediate pressure between
the condensing pressure of the condenser (5) and the evaporating
pressure of the evaporator (1) to cool the process air by
evaporation of the refrigerant under the intermediate pressure. A
second heat exchanging portion (22) is disposed in the branched
refrigerant path for condensing the refrigerant under an
intermediate pressure between the condensing pressure of the
condenser (5) and the evaporating pressure of the evaporator (1) to
heat the process air by condensation of the refrigerant under the
intermediate pressure. The first heat exchanging portion (21), the
evaporator (1), the second heat exchanging portion (22) are
connected in the order named by paths (30, 31, 32, 33, 34).
Inventors: |
Maeda, Kensaku;
(Asaichi-cho, Ohta-ku, JP) ; Inaba, Hideo;
(Okayama-shi, JP) ; Nishikawa, Shunro;
(Yokohama-shi, JP) |
Correspondence
Address: |
ARMSTRONG, KRATZ, QUINTOS, HANSON & BROOKS, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
18918904 |
Appl. No.: |
10/468832 |
Filed: |
September 23, 2003 |
PCT Filed: |
March 1, 2002 |
PCT NO: |
PCT/JP02/01897 |
Current U.S.
Class: |
62/93 ; 62/176.1;
62/324.1 |
Current CPC
Class: |
F24F 3/1405 20130101;
F24F 3/153 20130101; F25B 5/00 20130101 |
Class at
Publication: |
062/093 ;
062/324.1; 062/176.1 |
International
Class: |
F25D 017/06; F25D
017/04; F25B 049/00; F25B 013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2001 |
IL |
142051 |
Jan 24, 2002 |
IL |
147812 |
Claims
1. A heat pump comprising: a pressurizer for raising a pressure of
a refrigerant; a condenser for condensing said refrigerant to heat
a high-temperature heat source fluid; an evaporator for evaporating
said refrigerant to cool a low-temperature heat source fluid; a
refrigerant path branched into a plurality of branched refrigerant
paths between said condenser and said evaporator; a first heat
exchanging portion disposed in said branched refrigerant path
between said condenser and said evaporator for evaporating said
refrigerant under an intermediate pressure between the condensing
pressure of said condenser and the evaporating pressure of said
evaporator to cool said low-temperature heat source fluid by
evaporation of said refrigerant under said intermediate pressure; a
second heat exchanging portion disposed in said branched
refrigerant path between said condenser and said evaporator for
condensing said refrigerant under an intermediate pressure between
the condensing pressure of said condenser and the evaporating
pressure of said evaporator to heat said low-temperature heat
source fluid by condensation of said refrigerant under said
intermediate pressure; a low-temperature heat source fluid path
connecting said first heat exchanging portion, said evaporator,
said second heat exchanging portion in the order named.
2. A dehumidifying air-conditioning apparatus comprising: a
pressurizer for raising a pressure of a refrigerant; a condenser
for condensing said refrigerant to heat a high-temperature heat
source fluid; an evaporator for evaporating said refrigerant to
cool process air to a temperature lower than its dew point; a
refrigerant path branched into a plurality of branched refrigerant
paths between said condenser and said evaporator; a first heat
exchanging portion disposed in said branched refrigerant path
between said condenser and said evaporator for evaporating said
refrigerant under an intermediate pressure between the condensing
pressure of said condenser and the evaporating pressure of said
evaporator to cool said process air by evaporation of said
refrigerant under said intermediate pressure; a second heat
exchanging portion disposed in said branched refrigerant path
between said condenser and said evaporator for condensing said
refrigerant under an intermediate pressure between the condensing
pressure of said condenser and the evaporating pressure of said
evaporator to heat said process air by condensation of said
refrigerant under said intermediate pressure; a process air path
connecting said first heat exchanging portion, said evaporator,
said second heat exchanging portion in the order named.
3. A dehumidifying air-conditioning apparatus according to claim 2,
wherein said branched refrigerant paths extend through the interior
of said evaporator in parallel, respectively, and are joined to
each other at the downstream side of said evaporator.
4. A dehumidifying air-conditioning apparatus according to claim 3,
further comprising an ejector provided on a branched refrigerant
path for a refrigerant which exchanges heat with process air having
a high temperature, for pressurizing a refrigerant which exchanges
heat with process air having a low temperature by a refrigerant
which has passed through said branched refrigerant path.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat pump and a
dehumidifying air-conditioning apparatus, and more particularly to
a heat pump with a high coefficient of performance (COP) and a
dehumidifying air-conditioning apparatus which has such a heat pump
and a high moisture removal per energy consumption.
BACKGROUND ART
[0002] FIG. 10 is a flow diagram of a conventional air-conditioning
system. As shown in FIG. 10, there has heretofore been available a
dehumidifying air-conditioning apparatus having a compressor 201
for compressing a refrigerant, a condenser 202 for condensing the
compressed refrigerant with outside air OA, an evaporator 204 for
depressurizing the condensed refrigerant with an expansion valve
203 and evaporating the refrigerant to cool process air from an
air-conditioned space 100 to a temperature lower than its dew
point, and a reheater 205 for reheating the process air, which has
been cooled to a temperature lower than its dew point, at the
downstream side of the condenser 202 with the refrigerant upstream
of the expansion valve 203. The refrigerant is condensed in the
condenser 202 and the reheater 205. With the illustrated
dehumidifying air-conditioning apparatus, a heat pump HP is
constituted by the compressor 201, the condenser 202, the reheater
205, the expansion valve 203, and the evaporator 204. The heat pump
HP pumps heat from the process air which flows through the
evaporator 204 into the outside air OA which flows through the
condenser 202.
[0003] FIG. 11 is a Mollier diagram in the case where HFC134a is
used as the refrigerant in the conventional dehumidifying
air-conditioning apparatus. In FIG. 11, a point a represents a
state of the refrigerant evaporated by the evaporator 204, and the
refrigerant is in the form of a saturated vapor. The refrigerant
has a pressure of 0.34 MPa, a temperature of 5.degree. C., and an
enthalpy of 400.9 kJ/kg. A point b represents a state of the vapor
drawn and compressed by the compressor 201, i.e., a state at the
outlet port of the compressor 201. In the point b, the refrigerant
is in the form of a superheated vapor.
[0004] The refrigerant vapor is cooled in the condenser 202 and
reaches a state represented by a point c in the Mollier diagram. In
the point c, the refrigerant is in the form of a saturated vapor
and has a pressure of 0.94 MPa and a temperature of 38.degree. C.
Under this pressure, the refrigerant is cooled and condensed to
reach a state represented by a point d. In the point d, the
refrigerant is in the form of a saturated liquid and has the same
pressure and temperature as those in the point c. The saturated
liquid has an enthalpy of 250.5 kJ/kg.
[0005] The refrigerant liquid is depressurized by the expansion
valve 203 to a saturation pressure of 0.34 MPa at a temperature of
5.degree. C. and reaches a state represented by the point e. The
refrigerant at the point e is delivered as a mixture of the
refrigerant liquid and the vapor at a temperature of 5.degree. C.
to the evaporator 204, in which the mixture removes heat from
process air and is evaporated to reach a state of the saturated
vapor, which is represented by the point a in the Mollier diagram.
The saturated vapor is drawn into the compressor 201 again, and the
above cycle is repeated.
[0006] FIG. 12 is a psychrometric chart showing an air-conditioning
cycle in the conventional dehumidifying air-conditioning apparatus.
In FIG. 12, the alphabetical letters K, L, M correspond to the
encircled letters in FIG. 10. As shown in FIG. 12, in the
conventional dehumidifying air-conditioning apparatus, air (in a
state K) from the air-conditioned space 100 is cooled to a
temperature lower than its dew point to lower the dry bulb
temperature thereof and lower the absolute humidity thereof, and
reaches a state L. The state L is on a saturation curve in the
psychrometric chart. The air in the state L is reheated by the
reheater 205 to increase the dry bulb temperature thereof and keep
the absolute humidity thereof constant, and reaches a state M.
Then, the air is supplied to the air-conditioned space 100. The
state M is lower in both of absolute humidity and dry bulb
temperature than the state K.
[0007] With the conventional dehumidifying air-conditioning
apparatus described above, since it is necessary to considerably
cool the air to its dew point, about half of the cooling effect of
the evaporator in the heat pump is consumed to remove a sensible
heat load from the air, so that the moisture removal (the
dehumidifying performance) per electric power consumption is low.
If a single-stage compressor is used as the compressor in the heat
pump, then it produces a one-stage compression-type refrigerating
cycle, resulting in a low coefficient of performance (COP) and a
large amount of electric power consumed per amount of moisture
removal.
DISCLOSURE OF INVENTION
[0008] The present invention has been made in view of the above
drawbacks. It is therefore an object of the present invention to
provide a heat pump with a high coefficient of performance (COP)
and a dehumidifying air-conditioning apparatus which consumes a
small amount of energy per amount of moisture removal.
[0009] In order to attain the above object, according to a first
aspect of the present invention, there is provided a heat pump
comprising: a pressurizer for raising a pressure of a refrigerant;
a condenser for condensing the refrigerant to heat a
high-temperature heat source fluid; an evaporator for evaporating
the refrigerant to cool a low-temperature heat source fluid; a
refrigerant path branched into a plurality of branched refrigerant
paths between the condenser and the evaporator; a first heat
exchanging portion disposed in the branched refrigerant path
between the condenser and the evaporator for evaporating the
refrigerant under an intermediate pressure between the condensing
pressure of the condenser and the evaporating pressure of the
evaporator to cool the low-temperature heat source fluid by
evaporation of the refrigerant under the intermediate pressure; a
second heat exchanging portion disposed in the branched refrigerant
path between the condenser and the evaporator for condensing the
refrigerant under an intermediate pressure between the condensing
pressure of the condenser and the evaporating pressure of the
evaporator to heat the low-temperature heat source fluid by
condensation of the refrigerant under the intermediate pressure; a
low-temperature heat source fluid path connecting the first heat
exchanging portion, the evaporator, the second heat exchanging
portion in the order named.
[0010] According to a second aspect of the present invention, there
is provided a dehumidifying air-conditioning apparatus comprising:
a pressurizer for raising a pressure of a refrigerant; a condenser
for condensing the refrigerant to heat a high-temperature heat
source fluid; an evaporator for evaporating the refrigerant to cool
process air to a temperature lower than its dew point; a
refrigerant path branched into a plurality of branched refrigerant
paths between the condenser and the evaporator; a first heat
exchanging portion disposed in the branched refrigerant path
between the condenser and the evaporator for evaporating the
refrigerant under an intermediate pressure between the condensing
pressure of the condenser and the evaporating pressure of the
evaporator to cool the process air by evaporation of the
refrigerant under the intermediate pressure; a second heat
exchanging portion disposed in the branched refrigerant path
between the condenser and the evaporator for condensing the
refrigerant under an intermediate pressure between the condensing
pressure of the condenser and the evaporating pressure of the
evaporator to heat the process air by condensation of the
refrigerant under the intermediate pressure; a process air path
connecting the first heat exchanging portion, the evaporator, the
second heat exchanging portion in the order named.
[0011] With the above arrangement, the low-temperature heat source
fluid can be precooled in the first heat exchanging portion prior
to cooling in the evaporator. The low-temperature heat source fluid
can be heated in the second heat exchanging portion after cooling
in the evaporator with use of the heat in precooling. When process
air is used as the low-temperature heat source and is cooled to a
temperature lower than its dew point by the evaporator, it is
possible to provide a dehumidifying air-conditioning apparatus
which consumes a small amount of energy per amount of moisture
removal.
[0012] Further, with the branched refrigerant paths, the operative
temperature of the refrigerant can gradually be changed to achieve
a high efficiency of heat exchange. When the high-temperature fluid
is cooled, i.e., the heat exchanger is used for cooling the
high-temperature fluid, the efficiency .phi. of heat exchange is
defined by
.phi.=(TP1-TP2)/(TP1-TC1)
[0013] where the temperature of the high-temperature fluid at the
inlet of the heat exchanger is represented by TP1, the temperature
thereof at the outlet of the heat exchanger by TP2, the temperature
of the low-temperature fluid at the inlet of the heat exchanger is
represented by TC1, and the temperature thereof at the outlet of
the heat exchanger by TC2. When the low-temperature fluid is to be
heated, i.e., when the heat exchanger is used to heat the
low-temperature fluid, the efficiency .phi. of heat exchange is
defined by
.phi.=(TC2-TC1)/(TP1-TC1)
[0014] According to a preferred aspect of the present invention,
the branched refrigerant paths extend through the interior of the
evaporator in parallel, respectively, and are joined to each other
at the downstream side of the evaporator. In this case, there may
be provided an ejector on a branched refrigerant path for a
refrigerant which exchanges heat with process air having a high
temperature, for pressurizing a refrigerant which exchanges heat
with process air having a low temperature by a refrigerant which
has passed through the branched refrigerant path.
[0015] With the above arrangement, since the operative temperature
of the evaporator is increased to improve the theoretical cooling
effect, the theoretical work of compression is reduced to achieve a
high efficiency. Further, the specific volume of the refrigerant is
reduced to increase the flow rate of the refrigerant drawn by the
pressurizer. Therefore, an amount of moisture removal is increased
according to the improved cooling effect, and hence a high
efficiency can be achieved.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a schematic view showing a whole arrangement of an
air-conditioning system according to a first embodiment of the
present invention;
[0017] FIG. 2 is a flow diagram of a dehumidifying air-conditioning
apparatus according to the first embodiment of the present
invention;
[0018] FIG. 3 is an enlarged view showing branched refrigerant
paths in a heat exchanger of the dehumidifying air-conditioning
apparatus shown in FIG. 2;
[0019] FIG. 4A is a perspective view showing a heat exchanger and
an evaporator in the case where a refrigerant path is not branched,
as viewed from a front side;
[0020] FIG. 4B is a perspective view showing a heat exchanger and
an evaporator in the case where a refrigerant path is not branched,
as viewed from a rear side;
[0021] FIG. 5 is a Mollier diagram of a heat pump included in the
dehumidifying air-conditioning apparatus shown in FIG. 2;
[0022] FIG. 6 is a psychrometric chart showing an air-conditioning
cycle in the dehumidifying air-conditioning apparatus shown in FIG.
2;
[0023] FIG. 7 is a graph showing the relationship between the
number of branched refrigerant paths and the temperature efficiency
in a dehumidifying air-conditioning apparatus according to the
present invention;
[0024] FIG. 8 is a flow diagram of a dehumidifying air-conditioning
apparatus according to a second embodiment of the present
invention;
[0025] FIG. 9 is a Mollier diagram of a heat pump included in the
dehumidifying air-conditioning apparatus shown in FIG. 8;
[0026] FIG. 10 is a flow diagram of a conventional dehumidifying
air-conditioning apparatus;
[0027] FIG. 11 is a Mollier diagram of a heat pump included in the
conventional dehumidifying air-conditioning apparatus; and
[0028] FIG. 12 is a psychrometric chart showing an air-conditioning
cycle in the conventional dehumidifying air-conditioning
apparatus.
BEST MODE FOR CARRYING OUT THE INVENTION
[0029] A dehumidifying air-conditioning apparatus according to a
first embodiment of the present invention will be described below
with reference to FIGS. 1 through 6. FIG. 1 is a schematic view
showing a whole arrangement of an air-conditioning system according
to the first embodiment of the present invention, and FIG. 2 is a
flow diagram of a dehumidifying air-conditioning apparatus
according to the first embodiment of the present invention. The
dehumidifying air-conditioning apparatus in the first embodiment
serves to cool process air to a temperature lower than its dew
point for dehumidifying the air. The dehumidifying air-conditioning
apparatus includes a heat pump HP1 therein. The dehumidifying
air-conditioning apparatus lowers the humidity of the process air
to maintain a comfortable environment in an air-conditioned space
100 supplied with the process air.
[0030] As shown in FIG. 1, the dehumidifying air-conditioning
apparatus mainly comprises an indoor unit 10 and an outdoor unit 20
installed outside of the air-conditioned space 100 (outdoor). The
indoor unit 10 in the dehumidifying air-conditioning apparatus
comprises a refrigerant evaporator 1 for evaporating a refrigerant,
a heat exchanger 2 for exchanging heat between the refrigerant and
the process air, and an air blower 3 for circulating the process
air. The heat exchanger 2 performs a heat exchange between process
air flowing into the evaporator 1 and process air flowing out of
the evaporator 1, indirectly with the refrigerant. The heat
exchanger 2 has a first heat exchanging portion 21 for evaporating
the refrigerant to cool the process air, and a second heat
exchanging portion 22 for condensing the refrigerant to heat the
process air. The outdoor unit 20 in the dehumidifying
air-conditioning apparatus comprises a pressurizer (compressor) 4
for raising a pressure of the refrigerant, a refrigerant condenser
5 for cooling and condensing the refrigerant, and an air blower 6
for circulating the cooling air.
[0031] Process air paths, which are paths for circulating process
air, include a path 30 connecting the air-conditioned space 100 and
the first heat exchanging portion 21 in the heat exchanger 2, a
path 31 connecting the first heat exchanging portion 21 and the
evaporator 1, a path 32 connecting the evaporator 1 and the second
heat exchanging portion 22 in the heat exchanger 2, a path 33
connecting the second heat exchanging portion 22 and the air blower
3, and a path 34 connecting the air blower 3 and the
air-conditioned space 100. Thus, the first heat exchanging portion
21 in the heat exchanger 2, the evaporator 1, and the second heat
exchanging portion 22 in the heat exchanger 2 are connected in the
order named by the process air paths.
[0032] Refrigerant paths include a path 40 connecting the
evaporator 1 and the compressor 4, a path 41 connecting the
compressor 4 and the condenser 5, and a path connecting the
condenser 5 and the evaporator 1. The path connecting the condenser
5 and the evaporator 1 is branched into a plurality of branched
refrigerant paths at the downstream side of the condenser 5. In
FIG. 2, three branched refrigerant paths 42, 43, 44 are formed at
the downstream side of the condenser 5. The branched refrigerant
paths 42, 43, 44 are joined to one path 45 at the upstream side of
the evaporator 1.
[0033] Outside air OA is introduced as cooling air through the path
46 into the condenser 5. The outside air OA removes heat from the
refrigerant which is condensed, and the heated outside air OA is
drawn through the path 47 into the air blower 6, from which the air
is discharged through the path 48 as exhaust air EX.
[0034] The branched refrigerant paths 42, 43, 44 penetrate the
first heat exchanging portion 21 and the second heat exchanging
portion 22 in the heat exchanger 2, respectively. An evaporating
section 51 for evaporating the refrigerant to cool the process air
which flows through the first heat exchanging portion 21 is
provided in the first heat exchanging portion 21 of the heat
exchanger 2. A condensing section 52 for condensing the refrigerant
to heat (reheat) the process air which flows through the second
heat exchanging portion 22 is provided in the second heat
exchanging portion 22 of the heat exchanger 2. Restrictions 11, 12,
13 are disposed on the respective branched refrigerant paths 42,
43, 44 at the upstream side of the first heat exchanging portion
21. Restrictions 14, 15, 16 are disposed on the respective branched
refrigerant paths 42, 43, 44 at the downstream side of the second
heat exchanging portion 22. The restrictions 11-16 may comprise
orifices, capillary tubes, expansion valves, or the like.
[0035] FIG. 3 is an enlarged view showing the branched refrigerant
paths 42, 43, 44 in the heat exchanger 2 of the dehumidifying
air-conditioning apparatus shown in FIG. 2. The refrigerant paths
including the evaporating section 51 and the condensing section 52
penetrate the first heat exchanging portion 21 and the second heat
exchanging portion 22 in the heat exchanger 2, alternately and
repeatedly. Specifically, as shown in FIG. 3, the refrigerant path
42 has an evaporating section 61a, a condensing section 62a, a
condensing section 62b, an evaporating section 61b, an evaporating
section 61c, and a condensing section 62c. The refrigerant path 43
has an evaporating section 63a, a condensing section 64a, a
condensing section 64b, an evaporating section 63b, an evaporating
section 63c, and a condensing section 64c. The refrigerant path 44
has an evaporating section 65a, a condensing section 66a, a
condensing section 66b, an evaporating section 65b, an evaporating
section 65c, and a condensing section 66c.
[0036] The heat exchanger 2 has the first heat exchanging portion
21 for allowing the process air before flowing through the
evaporator 1 to pass therethrough, and the second heat exchanging
portion 22 for allowing the process air after flowing through the
evaporator 1 to pass therethrough. The first heat exchanging
portion 21 and the second heat exchanging portion 22 form
respective separate spaces, each in the form of a rectangular
parallelepiped. The evaporator 1 is disposed between the first heat
exchanging portion 21 and the second heat exchanging portion 22.
FIGS. 4A and 4B show the arrangement of a heat exchanger and an
evaporator in the case where a refrigerant path is not branched,
for reference. FIG. 4A is a perspective view as viewed from the
front side, and FIG. 4B is a perspective view as viewed from the
rear side.
[0037] The first heat exchanging portion 21 and the second heat
exchanging portion 22 have a plurality of substantially parallel
heat exchange tubes as refrigerant passages in each of a plurality
of planes which lie perpendicularly to the flow of the process air.
Tubes 67 are provided across the evaporator 1 between the
corresponding sections, for example, the evaporating section 61a
and the condensing section 62a, the evaporating section 61b and the
condensing section 62b, and the evaporating section 61c and the
condensing section 62c (see FIG. 4B). Thus, the corresponding
evaporating and condensing sections are connected to each other.
The ends of the evaporating sections 61b, 61c, the ends of the
evaporating sections 63b, 63c, and the ends of the evaporating
sections 65b, 65c are connected to each other by a U tube 68.
Similarly, the ends of the condensing sections 62a, 62b, the ends
of the condensing sections 64a, 64b, and the ends of the condensing
sections 66a, 66b are connected to each other by a U tube 69 (see
FIG. 4A).
[0038] With the above arrangement, for example, in the refrigerant
path 42, the refrigerant flowing in one direction from the
evaporating section 61a to the evaporating section 62a is
introduced into the condensing section 62b by the U tube 69. The
refrigerant introduced into the condensing section 62b then flows
into the evaporating section 61b, from which the refrigerant flows
into the evaporating section 61c via the U tube 68 and further
flows into the condensing section 62c. In this manner, the
refrigerant passages are provided as a group of meandering thin
pipes. A group of meandering thin pipes pass through the first heat
exchanging portion 21 and the second heat exchanging portion 22,
and are held in alternate contact with the process air which has a
higher temperature and the process air which has a lower
temperature.
[0039] As shown in FIGS. 1 and 2, a drain pan 7 is provided in the
indoor unit 10 of the dehumidifying air-conditioning apparatus. The
drain pan 7 is preferably located below not only the evaporator 1,
but also the heat exchanger 2. Particularly, the drain pan 7 is
preferably disposed below the first heat exchanging portion 21
because the process air is mainly precooled in the first heat
exchanging portion 21 and some moisture may possibly be condensed
in the first heat exchanging portion 21.
[0040] The flow of the refrigerant in the devices will be described
below with reference to FIGS. 2 and 3.
[0041] A refrigerant vapor pressurized by the compressor 4 is
introduced into the condenser 5 via the refrigerant pipe 41
connected to the discharge port of the compressor 4. The
refrigerant vapor compressed by the compressor 4 is cooled and
condensed by the outside air OA as cooling air. The refrigerant
liquid flowing out of the condenser 5 is branched into the branched
refrigerant paths 42, 43, 44. The refrigerants similarly flow
through the respective refrigerant paths 42, 43, 44. Therefore, the
refrigerant flowing through the refrigerant path 42 will mainly be
described below, and the refrigerants flowing through the other
refrigerant paths 43, 44 will not be described in detail below.
[0042] The refrigerant flowing through the refrigerant path 42 is
depressurized by the restriction 11 and expanded so as to be partly
evaporated (flashed). The refrigerant which is a mixture of the
liquid and the vapor reaches the evaporating section 61a, where the
refrigerant liquid flows so as to wet the inner wall surface of the
tube in the evaporating section 61a. The refrigerant flows into the
evaporating section 61a in the liquid phase. The refrigerant may be
a refrigerant liquid which has been partly evaporated to slightly
contain a vapor phase. While the refrigerant liquid is flowing
through the evaporating section 61a, it is evaporated to cool
(precool) the process air before flowing into the evaporator 1. The
refrigerant itself is heated while increasing the vapor phase
thereof.
[0043] As described above, the evaporating section 61a and the
condensing section 62a are constructed as a continuous tube.
Specifically, since the evaporating section 61a and the condensing
section 62a are provided as an integral passage, the refrigerant
vapor evaporated in the evaporating section 61a (and the
refrigerant liquid which has not been evaporated) flows into the
condensing section 62a, and heats (reheats) the process air, which
has been cooled and dehumidified in the evaporator 1 and has a
temperature lower than the process air in the evaporating section
61a. At this time, heat is removed from the evaporated refrigerant
vapor itself, and while the evaporated refrigerant vapor in the
vapor phase is condensed, the refrigerant flows into the next
condensing section 62b. While the refrigerant is flowing through
the condensing section 62b, heat is further removed from the
refrigerant by the process air having a lower temperature, and the
refrigerant in the vapor phase is further condensed.
[0044] The condensed refrigerant liquid flows into the next
evaporating section 61b and the subsequent evaporating section 61c
to cool (precool) the process air before flowing into the
evaporator 1 in the same manner as described above. Thereafter, the
refrigerant vapor flows into the condensing section 62c to heat
(reheat) the process air. In this manner, the refrigerant flows
through the branched refrigerant path while changing in phase
between the vapor phase and the liquid phase. Thus, heat is
exchanged between the process air before being cooled by the
evaporator 1 and the process air which has been cooled by the
evaporator 1 to lower its absolute humidity.
[0045] The refrigerant liquid condensed in the condensing section
62c is depressurized and expanded by the restriction 14 provided at
the downstream side of the second heat exchanging portion 22, for
thereby lowering its pressure. Then, the refrigerant liquid is
joined to the refrigerants which have flowed through the other
branched refrigerant liquid paths 43, 44. The joined refrigerant
liquid enters the evaporator 1 to be evaporated to cool the process
air with heat of evaporation. The refrigerant which has been
evaporated into a vapor in the evaporator 1 is introduced into the
suction side of the compressor 4 through the path 40, and thus the
above cycle is repeated.
[0046] Next, operation of the heat pump HP1 included in the
dehumidifying air-conditioning apparatus according to the first
embodiment of the present invention will be described below with
reference to FIG. 5. FIG. 5 is a Mollier diagram of the heat pump
HP1 included in the dehumidifying air-conditioning apparatus shown
in FIG. 2. The diagram shown in FIG. 5 is a Mollier diagram in the
case where HFC134a is used as the refrigerant. In the Mollier
diagram, the horizontal axis represents the enthalpy, and the
vertical axis represents the pressure. In addition to the above
refrigerant, HFC407C and HFC410A are suitable refrigerants for the
heat pump and the dehumidifying air-conditioning apparatus
according to the present invention. These refrigerants have an
operating pressure region shifted toward a higher pressure side
than HFC134a.
[0047] In FIG. 5, a point a represents a state of the refrigerant
which has been evaporated by the evaporator 1 shown in FIG. 2, and
the refrigerant is in the form of a saturated vapor. The
refrigerant has a pressure of 0.234 MPa, a temperature of 5.degree.
C., and an enthalpy of 395.1 kJ/kg. A point b represents a state of
the vapor drawn and compressed by the compressor 4, i.e., a state
at the outlet port of the compressor 4. In the point b, the
refrigerant has a pressure of 0.706 MPa and is in the form of a
superheated vapor.
[0048] The refrigerant vapor at the point b is cooled in the
condenser 5 and reaches a state represented by a point c in the
Mollier diagram. In the point c, the refrigerant is in the form of
a saturated vapor and has a pressure of 0.706 MPa and a temperature
of 38.degree. C. Under this pressure, the refrigerant is cooled and
condensed to reach a state represented by a point d. In the point
d, the refrigerant is in the form of a saturated liquid and has the
same pressure and temperature as those in the point c. The
saturated liquid has an enthalpy of 237.4 kJ/kg.
[0049] The refrigerant liquid is branched into the branched
refrigerant liquid paths 42, 43, 44, and the branched refrigerant
liquids flow into the heat exchanger 2. First, the refrigerant
flowing through the refrigerant path 43 will be described below.
The refrigerant liquid is depressurized by the restriction 12 and
flows into the evaporating section 63a in the first heat exchanging
portion 21. This state is indicated at a point e on the Mollier
diagram. The refrigerant liquid is a mixture of the liquid and the
vapor because a part of the liquid is evaporated. The pressure of
the refrigerant liquid is an intermediate pressure between the
condensing pressure in the condenser 5 and the evaporating pressure
in the evaporator 1, i.e., is of an intermediate value between
0.234 MPa and 0.706 MPa in the present embodiment.
[0050] In the evaporating section 63a, the refrigerant liquid is
evaporated under the intermediate pressure, and reaches a state
represented by a point f1, which is located intermediately between
the saturated liquid curve and the saturated vapor curve, under the
intermediate pressure. In the point f1, while a part of the liquid
is evaporated, the refrigerant liquid remains in a considerable
amount. The refrigerant in the state represented by the point f1
flows into the condensing sections 64a, 64b. In the condensing
sections 64a, 64b, heat is removed from the refrigerant by the
process air which has a low temperature and flows through the
second heat exchanging portion 22, and the refrigerant reaches a
state represented by a point g1.
[0051] The refrigerant in the state represented by the point g1
flows into the evaporating sections 63b, 63c, where heat is removed
from the refrigerant. The refrigerant increases its liquid phase
and reaches a state represented by a point f2. Then, the
refrigerant flows into the condensing section 64c, where the
refrigerant increases its liquid phase and reaches a state
represented by a point g2. On the Mollier diagram, the point g2 is
on the saturated liquid curve. In this point, the refrigerant has a
temperature of 18.degree. C. and an enthalpy of 209.5 kJ/kg.
[0052] The refrigerant liquid at the point g2 is depressurized to
0.234 MPa, which is a saturated pressure at a temperature of
5.degree. C., by the restriction 15, and reaches a state
represented by a point h. The refrigerant at the point h flows as a
mixture of the refrigerant liquid and the vapor at a temperature of
5.degree. C. into the evaporator 1, where the refrigerant removes
heat from the process air to thus be evaporated into a saturated
vapor at the state indicated by the point a on the Mollier diagram.
The evaporated vapor is drawn again by the compressor 4, and thus
the above cycle is repeated.
[0053] In the same manner as described above, the refrigerant
flowing into the refrigerant path 42 passes through the restriction
11, the evaporating sections, the condensing sections, and the
restriction 14. The refrigerant goes through states represented by
points j, i1, k1, i2, and k2 and reaches the a state represented by
a point l. The refrigerant flowing into the refrigerant path 44
passes through the restriction 13, the evaporating sections, the
condensing sections, and the restriction 16. The refrigerant goes
through states represented by points m, n1, o1, n2, and o2 and
reaches a state represented by a point P.
[0054] In the heat exchanger 2, as described above, the refrigerant
goes through changes of the evaporated state from the point e to
the point f1 or from the point g1 to the point f2 in the
evaporating section 51, and goes through changes of the condensed
state from the point f1 to the point g1 or from the point f2 to the
point g2 in the condensing section 52. Since the refrigerant
transfers heat by way of evaporation and condensation, the rate of
heat transfer is very high and the efficiency of heat exchanger is
high.
[0055] In the vapor compression type heat pump HP1 including the
compressor 4, the condenser 5, the restrictions 11-16, and the
evaporator 1, when the heat exchanger 2 is not provided, the
refrigerant at the state represented by the point d in the
condenser 5 is returned to the evaporator 1 through the
restrictions. Therefore, the enthalpy difference that can be used
by the evaporator 1 is only 395.1-237.4=157.7 kJ/kg. With the heat
pump HP1 according to the present embodiment which has the heat
exchanger 2, however, the enthalpy difference that can be used by
the evaporator 1 is 395.1-209.5=185.6 kJ/kg. Thus, the amount of
refrigerant that is circulated to the compressor under the same
cooling load and the required power can be reduced by 15%
(=1-157.7/185.6). Consequently, the heat pump HP1 according to the
present embodiment can perform the same operation as with a
well-known subcooled cycle.
[0056] FIG. 6 is a psychrometric chart showing an air-conditioning
cycle in the dehumidifying air-conditioning apparatus shown in FIG.
2. In FIG. 6, the alphabetical letters K, X, L, M correspond to the
encircled letters in FIG. 2.
[0057] In FIG. 6, the process air (in a state K) from the
air-conditioned space 100 flows through the path 30 into the first
heat exchanging portion 21 in the heat exchanger 2, where the
process air is cooled to a certain extent by the refrigerant that
is evaporated in the evaporating section 51. This process can be
referred to as precooling because the process air is preliminarily
cooled before being cooled to a temperature lower than its dew
point by the evaporator 1. While the process air is being precooled
in the evaporating section 51, a certain amount of moisture is
removed from the air to lower the absolute humidity of the air, and
then air reaches a point X on the saturation curve. Alternatively,
the air may be precooled to an intermediate point between the point
K and the point X. Further, the air may be precooled to a point
that is shifted beyond the point X slightly toward a lower humidity
on the saturation curve.
[0058] The process air precooled by the first heat exchanging
portion 21 is introduced through the path 31 into the evaporator 1,
where the air is cooled to a temperature lower than its dew point
by the refrigerant which has been depressurized by the restrictions
14-16 and is evaporated at a low temperature. Moisture is removed
from the air to lower the absolute humidity and the dry bulb
temperature of the air, and the air reaches a point L. Although the
thick line representing a change from the point X to the point L is
plotted as being remote from the saturation curve for illustrative
purpose in FIG. 6, it is actually aligned with the saturation
curve.
[0059] The process air in the state represented by the point L
flows through the path 32 into the second heat exchanging portion
22 in the heat exchanger 2, where the process air is heated, with
the constant absolute humidity, by the refrigerant condensed in the
condensing section 52, and reaches a point M. The process air in
the point M has a sufficiently lower absolute humidity than the
process air in the point K, a dry bulb temperature which is not
excessively lower than the process air in the point K, and a
suitable relative humidity. The process air in the point M is then
drawn by the air blower 3 and returned to the air-conditioned space
100 through the path 34.
[0060] In the air cycle on the psychrometric chart shown in FIG. 6,
the amount of heat which has precooled the process air in the first
heat exchanging portion 21, i.e., the amount AH of heat which has
reheated the process air in the second heat exchanging portion 22,
represents the amount of heat recovered, and the amount of heat
which has cooled the process air in the evaporator 1 is represented
by .DELTA.Q. The cooling effect for cooling the air-conditioned
space 100 is represented by .DELTA.i.
[0061] As described above, in the heat exchanger 2, the process air
is precooled by evaporation of the refrigerant in the evaporating
section 51, and the process air is reheated by condensation of the
refrigerant in the condensing section 52. The refrigerant
evaporated in the evaporating section 51 is condensed in the
condensing section 52. The same refrigerant is thus evaporated and
condensed to perform a heat exchange indirectly between the process
air before being cooled in the evaporator 1 and the process air
after being cooled in the evaporator 1.
[0062] In the embodiment described above, the same refrigerant is
used as a heat transfer medium in the evaporator for cooling the
process air to a temperature lower than its dew point, the
precooler for precooling the process air, and the reheater for
reheating the process air. Therefore, the refrigerant system is
simplified. The refrigerant is positively circulated because the
pressure difference between the evaporator and the condenser can be
utilized. Since a boiling phenomenon with a phase change is applied
to heat exchanges for precooling and reheating the process air, a
high heat transfer efficiency can be achieved.
[0063] In the embodiment described above, the refrigerant path is
branched into the three branched refrigerant paths. However, the
present invention is not limited to three branched refrigerant
paths. The refrigerant path may be branched into any number of
branched refrigerant paths. FIG. 7 is a graph showing the
relationship between the number of branched refrigerant paths and
the temperature efficiency in a dehumidifying air-conditioning
apparatus according to the present invention. It is inferred from
FIG. 7 that the temperature efficiency can be improved when the
number of branched refrigerant paths is larger. Thus, when a
plurality of branched refrigerant paths are provided, the operative
temperature of the refrigerant can gradually be changed to achieve
a high efficiency of heat exchange.
[0064] A dehumidifying air-conditioning apparatus according to a
second embodiment of the present invention will be described below
with reference to FIGS. 8 and 9. FIG. 8 is a flow diagram of a
dehumidifying air-conditioning apparatus according to the second
embodiment of the present invention, and FIG. 9 is a Mollier
diagram of a heat pump HP2 included in the dehumidifying
air-conditioning apparatus shown in FIG. 8. In FIGS. 8 and 9, like
parts and components are denoted by the same reference numerals and
characters as those of the first embodiment and will not be
described below.
[0065] In the present embodiment, a refrigerant path is branched
into a plurality of refrigerant paths at the downstream side of the
condenser 5 to form branched refrigerant paths 142, 143, 144. The
present embodiment differs from the first embodiment in that these
branched refrigerant paths 142, 143, 144 extend to the interior of
an evaporator 101, respectively, and joined to each other at the
downstream side of the evaporator 101. Among these branched
refrigerant paths 142, 143, 144, the refrigerant path for the
refrigerant which exchanges heat with the process air having a high
temperature, i.e., the branched refrigerant path 142, has an
ejector 8 provided thereon for pressurizing the refrigerant which
exchanges heat with the process air having a low temperature, i.e.,
the refrigerant that has passed through the refrigerant path
144.
[0066] In FIG. 9, a point a represents a state of the refrigerant
which has been evaporated by the evaporator 101 shown in FIG. 8,
and the refrigerant is in the form of a saturated vapor. The
refrigerant has a pressure of 0.262 MPa, a temperature of 8.degree.
C., and an enthalpy of 396.8 kJ/kg. A point b represents a state of
the vapor drawn and compressed by the compressor 4, i.e., a state
at the outlet port of the compressor 4. In the point b, the
refrigerant has a pressure of 0.706 MPa and is in the form of a
superheated vapor.
[0067] The refrigerant vapor is cooled in the condenser 5 and
reaches a state represented by a point c in the Mollier diagram. In
the point c, the refrigerant is in the form of a saturated vapor
and has a pressure of 0.706 MPa and a temperature of 38.degree. C.
Under this pressure, the refrigerant is cooled and condensed to
reach a state represented by a point d. In the point d, the
refrigerant is in the form of a saturated liquid and has the same
pressure and temperature as those in the point c. The saturated
liquid has an enthalpy of 237.4 kJ/kg.
[0068] The refrigerant liquid is depressurized by the restriction
12 and reaches a state represented by a point e on the Mollier
diagram. The pressure of the refrigerant liquid is an intermediate
pressure between the condensing pressure in the condenser 5 and the
evaporating pressure in the evaporator 101, i.e., is of an
intermediate value between 0.262 MPa and 0.706 MPa in the present
embodiment. Then, the refrigerant flows alternately through the
evaporating sections in the first heat exchanging portion 21 and
the condensing sections in the second heat exchanging portion 22
and goes through states represented by points f1, g1, f2, and g2.
Thereafter, the refrigerant is depressurized by the restriction 15
to a saturation pressure of 0.262 MPa at a temperature of 8.degree.
C. and reaches a state represented by the point h. The refrigerant
at the point h is delivered as a mixture of the refrigerant liquid
and the vapor at a temperature of 8.degree. C. to the evaporator
101, in which the mixture removes heat from the process air and is
evaporated to reach a state of the saturated vapor, which is
represented by the point a in the Mollier diagram. The saturated
vapor is drawn into the compressor 4 again, and the above cycle is
repeated.
[0069] The refrigerant flowing into the refrigerant path 142 passes
through the restriction 11, the evaporating sections, the
condensing sections, and the restriction 14. The refrigerant goes
through states represented by points j, i1, k1, i2, and k2 and
reaches the a state represented by a point 1. The refrigerant in
the state represented by the point 1 flows into the evaporator 101,
where the refrigerant removes heat from the process air to be
evaporated and reaches a state indicated by the point q on the
Mollier diagram. The refrigerant flowing into the refrigerant path
144 passes through the restriction 13, the evaporating sections,
the condensing sections, and the restriction 16. The refrigerant
goes through states represented by points m, n1, o1, n2, and o2 and
reaches a state represented by a point P.
[0070] The refrigerant in the state represented by the point p
flows into the evaporator 101, where the refrigerant removes heat
from the process air to be evaporated and reaches a state indicated
by the point r on the Mollier diagram. The refrigerant in the state
represented by the point r is pressurized by the ejector 8 provided
on the refrigerant path 142. Specifically, in the ejector 8, the
refrigerant at a low pressure in the state represented by the point
r is pressurized by the refrigerant at a high pressure in the state
represented by the point q. As a result, the refrigerant in the
state represented by the point r and the refrigerant in the state
represented by the point q reach a state of the saturated vapor,
which is represented by the point a in the Mollier diagram. In this
manner, with the ejector 8, since the operative temperature of the
evaporator is increased to improve the theoretical cooling effect,
the theoretical work of compression is reduced to achieve a high
efficiency. Further, the specific volume of the refrigerant is
reduced to increase the flow rate of the refrigerant drawn by the
compressor. Therefore, an amount of moisture removal is increased
according to the improved cooling effect, and hence a high
efficiency can be achieved.
[0071] In the vapor compression type heat pump HP2 including the
compressor 4, the condenser 5, the restrictions 11-16, and the
evaporator 101, when the heat exchanger 2 is not provided, the
refrigerant at the state represented by the point d in the
condenser 5 is returned to the evaporator 101 through the
restrictions. Therefore, the enthalpy difference that can be used
by the evaporator 101 is only 396.8-237.4=159.4 kJ/kg. With the
heat pump HP2 according to the present embodiment which has the
heat exchanger 2, however, the enthalpy difference that can be used
by the refrigerant evaporator 101 is 396.8-209.5=187.3 kJ/kg. Thus,
the amount of refrigerant that is circulated to the compressor
under the same cooling load and the required power can be reduced
by 15% (=1-159.4/187.3). Consequently, the heat pump HP2 according
to the present embodiment can perform the same operation as with a
well-known subcooled cycle.
[0072] While the present invention has been described in detail
with reference to the preferred embodiments thereof, it would be
apparent to those skilled in the art that many modifications and
variations may be made therein without departing from the spirit
and scope of the present invention. For example, the number of the
evaporating sections on the respective branched refrigerant paths
in the first heat exchanging portion and the number of the
condensing sections on the respective branched refrigerant paths in
the second heat exchanging portion are not limited to the
illustrated examples. With respect to the order of the refrigerant
paths in the heat exchanger, the refrigerant may be introduced into
the heat exchanger from the second heat exchanging portion in place
of the first heat exchanging portion. In this case, the second heat
exchanging portion, the first heat exchanging portion, and the
second heat exchanging portion are arranged in the order named, so
that the number of paths can be increased. Further, the
dehumidifying air-conditioning apparatus according to the above
embodiments has been described as the dehumidifying
air-conditioning apparatus for air-conditioning a space. However,
the dehumidifying air-conditioning apparatus according to the
present invention is applicable not only to the air-conditioned
space, but also to other spaces that need to be dehumidified.
INDUSTRIAL APPLICABILITY
[0073] The present invention is suitable for use in a heat pump
with a high coefficient of performance (COP) and a dehumidifying
air-conditioning apparatus which has such a heat pump and a high
moisture removal per energy consumption.
* * * * *