Technical Field
[0001] The present invention relates to a heat pump and a dehumidifying apparatus, and more
particularly to a heat pump with a high COP and a dehumidifying apparatus which has
such a heat pump.
Background Art
[0002] As shown in FIG. 17, there has heretofore been available a desiccant air-conditioning
apparatus having a heat pump as a heat source. The air-conditioning apparatus shown
in FIG. 17 employs a compression type heat pump HP including a compressor 260 as the
heat pump. The air-conditioning apparatus has a path for process air A from which
moisture is adsorbed by a desiccant wheel 103, and a path for regeneration air B which
is heated by a heating source and then passes through the desiccant wheel 103 which
has adsorbed the moisture, to desorb the moisture from the desiccant for thereby regenerating
the desiccant. The air-conditioning apparatus has an air-conditioner having a sensible
heat exchanger 104 for exchanging heat between the process air from which moisture
has been adsorbed and the regeneration air before it regenerates the desiccant of
the desiccant wheel 103 and also before it is heated by the heating source, and also
has the compression type heat pump HP. The regeneration air of the air-conditioner
for regenerating the desiccant is used as a high-temperature heat source in the compression
type heat pump HP, and is heated by a heating unit 220. The process air of the air-conditioner
is used as a low-temperature heat source in the compression type heat pump HP, and
is cooled by a cooling unit 210.
[0003] Here, operation of the compression type heat pump HP shown in FIG. 17 will be described
below with reference to a Mollier diagram shown in FIG. 18. The diagram shown in FIG.
18 is a Mollier diagram in the case where HFC134a is used as the refrigerant. A point
a represents a state of the refrigerant evaporated by the cooling unit 210, and the
refrigerant is in the form of a saturated vapor. The refrigerant has a pressure of
4.2 kg/cm
2, a temperature of 10°C, and an enthalpy of 148.83 kcal/kg. A point b represents a
state of the vapor drawn and compressed by the compressor 260, i.e., a state at the
outlet port of the compressor 260. In this state, the refrigerant has a pressure of
19.3 kg/cm
2 and a temperature of 78°C, and is in the form of a superheated vapor. The refrigerant
vapor is cooled in the heating unit (as a cooling unit or a condenser from the viewpoint
of the refrigerant) 220 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 19.3 kg/cm
2 and a temperature of 65°C. Under this pressure, the refrigerant is further 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 122.97 kcal/kg. The
refrigerant liquid is depressurized by an expansion valve 250 to a saturation pressure
of 4.2 kg/cm
2 at a temperature of 10°C. The refrigerant is delivered as a mixture of the refrigerant
liquid and the vapor at a temperature of 10°C to the cooling unit (as an evaporator
from the viewpoint of the refrigerant) 210, where 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
260 again, and the above cycle is repeated.
[0004] The heat pump used in the above conventional air-conditioning apparatus does not
have an excellent COP because the cooling effect of a refrigerant in a refrigerant
cycle is not necessarily large. In the conventional air-conditioning apparatus, the
sensible heat exchanger 104 for preliminarily cooling the process air before the process
air is cooled by the cooling unit 210 plays an important role. However, since the
sensible heat exchanger generally occupies a large volume in the system, it is difficult
to construct the system, and the system unavoidably becomes large in size.
[0005] It is therefore an object of the present invention to provide a heat pump having
a high COP and a dehumidifying apparatus which has a high COP and a compact structure.
Disclosure of Invention
[0006] This object is achieved by a heat pump and a dehumidifying apparatus as defined in
the appended claims.
[0007] According to an aspect of the present invention, as shown in FIGS. 1 and 2, for example,
there is provided a heat pump HP 1 in which a pressurizer 260, a condenser 220, and
an evaporator 210 are interconnected via refrigerant paths 201 - 207, the heat pump
comprising: means disposed in the refrigerant path interconnecting the condenser 220
and the evaporator 210, for alternately evaporating and condensing a refrigerant repeatedly
under an intermediate pressure which is located intermediately between a pressure
to be pressurized by the pressurizer 260 and a pressure which has been pressurized
by the pressurizer 260 (from a point e to a point f1 and from a point f1 to a point
g1a and the like in FIG. 3).
[0008] The heat pump may be arranged such that while the refrigerant is alternately being
evaporated and condensed repeatedly as shown in a flow diagram shown in FIG. 9 and
a corresponding Mollier diagram shown in FIG. 10, for example, the condensed refrigerant
is condensed after it is depressurized to a second intermediate pressure lower than
the previous intermediate pressure (from a point g2 to a point E in FIG. 10). For
example, the heat pump may have two means for alternately evaporating and condensing
the refrigerant repeatedly as shown in a flow diagram shown in FIG. 12 and a corresponding
Mollier diagram shown in FIG. 13, and the heat pump may be arranged such that the
evaporation pressure and the condensation pressure in one of the means is made lower
than the evaporation pressure and the condensation pressure in the other means, and
while the refrigerants are alternately being evaporated and condensed repeatedly by
the respective means, the condensed refrigerants are concurrently depressurized to
an evaporation pressure in the evaporator (from a point g2 to a point j1 and from
a point G2 to a point j in FIG. 13).
[0009] According to an aspect of the present invention, there is provided a dehumidifying
air-conditioning apparatus comprising: a moisture adsorbing device 103 for removing
moisture from process air and for being regenerated by desorbing moisture therefrom
with regeneration air; and a heat pump HP1 having a condenser 220, an evaporator 210,
and a thin pipe group interconnecting the condenser 220 and the evaporator 210; wherein
the thin pipe group is arranged so as to introduce a refrigerant condensed by the
condenser 220 to the evaporator 210 and to bring the refrigerant into alternate contact
with the process air and the regeneration air.
[0010] As shown in FIG. 12 or FIG. 14, for example, there may be two of the above thin pipe
group, the refrigerant path for introducing the refrigerant from the condenser to
the thin pipe groups may be branched into two passages which are connected respectively
to the two of the thin pipe groups, and refrigerant pipes extending from the respective
thin pipe groups may be joined to each other at the inlet of the evaporator or directly
in the evaporator.
[0011] According to another aspect of the present invention, as shown in FIGS. 1 and 2,
for example, there is provided a heat pump comprising: a pressurizer 260 for raising
a pressure of a refrigerant; an evaporator 210 for cooling a low-temperature heat
source fluid A with heat of evaporation of the refrigerant to be pressurized by the
pressurizer 260; a condenser 220 for heating a high-temperature heat source fluid
B with heat of condensation of the refrigerant pressurized by the pressurizer 260;
and a first heat exchanger 300a for exchanging heat between the low-temperature heat
source fluid A upstream of the evaporator 210 and a cooling fluid; wherein the first
heat exchanger 300a has a first compartment 310 through which the low-temperature
heat source fluid A flows, a second compartment 320 through which the cooling fluid
flows, and refrigerant passages 251A1 - A9, 252A1 - A9 extending through the first
compartment 310 and the second compartment 320, the refrigerant passages 251A1 - A9,
252A1 - A9 being connected to the condenser 220 through a first restriction 330, extending
alternately through the first compartment 310 and the second compartment 320 repeatedly,
and then being connected to the evaporator 210 through a second restriction 250. The
cooling fluid should preferably comprise the high-temperature heat source fluid B..Particularly,
the cooling fluid which is to exchange heat with the cold heat source fluid upstream
of the evaporator in the first heat exchanger 300a should preferably comprise the
high-temperature heat source fluid B upstream of the condenser 220.
[0012] In the refrigerant passage, the refrigerant typically flows in one direction as a
whole. This means that the refrigerant flows in substantially one direction through
the refrigerant passage when views as a whole even though the refrigerant may locally
flow back due to turbulences or may be vibrated in the flowing direction due to pressure
waves produced by bubbles or instantaneous interruptions. The refrigerant passage
comprises a heat exchange tube, for example, and extends alternately through the first
compartment and the second compartment. Therefore, the refrigerant which flows in
one direction as a whole is alternately evaporated and condensed repeatedly. The expression
that the refrigerant passage extends alternately through the first compartment and
the second compartment means that the refrigerant passage does not run through the
first compartment and the second compartment only once, but the refrigerant passage
runs through the first compartment and the second compartment once and then runs at
least once through the second compartment or the first compartment. In the first compartment,
the low-temperature heat source fluid exchanges heat with the refrigerant, and in
the second compartment, the high-temperature heat source fluid exchanges heat with
the refrigerant. Typically, the refrigerant is at least partly evaporated in the refrigerant
passage which extends through the first compartment, and the refrigerant in the vapor
phase is at least partly evaporated in the refrigerant passage which extends through
the second compartment.
[0013] With the above arrangement, since the refrigerant passes through the first and second
compartments a plurality of times, the refrigerant will not completely be dried out
even if it is evaporated in the refrigerant passage extending through the first compartment.
[0014] In the heat pump, the first compartment 310 and the second compartment 320 may be
arranged such that the low-temperature heat source fluid A and the cooling fluid flow
as counterflows; the refrigerant passage in the first compartment 310 and the second
compartment 320 may have at least a pair of a first compartment extending portions
251A1 and a second compartment extending portions 252A1 in a first plane PA which
is substantially perpendicular to the flows of the low-temperature heat source fluid
A and the cooling fluid, at least a pair of a first compartment extending portions
251B1 and a second compartment extending portions 252B1 in a second plane PB, different
from the first plane PA, which is substantially perpendicular to the flows of the
low-temperature heat source fluid A and the cooling fluid, and an intermediate restriction
331 disposed in a transitional location from the first plane PA to the second plane
PB.
[0015] In the portion of the refrigerant passage which extends through the first compartment,
at least a portion of the refrigerant is typically evaporated. That portion of the
refrigerant passage may thus be referred to as an evaporating section. In the portion
of the refrigerant passage which extends through the second compartment, at least
a portion of the refrigerant is typically condensed. That portion of the refrigerant
passage may thus be referred to as a condensing section. The pair which is mentioned
above refers to a pair of the evaporating section and the condensing section (or the
condensing section and the evaporating section). Since the heat pump has the intermediate
restriction, the pressure in the refrigerant passage in the first plane and the pressure
in the refrigerant passage in the second plane may have different values. Since the
low-temperature heat source fluid and the cooling fluid flow as counterflows, the
different pressures become progressively lower in the downstream direction of the
low-temperature heat source fluid or in the upstream direction of the cooling fluid.
Therefore, the low-temperature heat source fluid and the cooling fluid perform counterflow
heat exchange therebetween, resulting in an extremely high heat exchange efficiency.
[0016] In the above heat pump, the intermediate restriction 331 may be located in a position
where the refrigerant passage has extended through the second compartment 320 as shown
in FIG. 1, for example, or the intermediate restriction 331 may be located in a position
where the refrigerant passage has extended through the first compartment 310 as shown
in FIG. 6, for example.
[0017] For example, as shown in FIG. 12, the heat pump may further comprise a second heat
exchanger 300d2 for exchanging heat between the low-temperature heat source fluid
A upstream of the evaporator 210 and the cooling fluid; wherein the second heat exchanger
300d2 has a third compartment 310B through which the low-temperature heat source fluid
A flows, a fourth compartment 320B through which the cooling fluid flows, and a refrigerant
passage extending through the third compartment 310B and the fourth compartment 320B,
the refrigerant passage being connected to the condenser 220 through a third restriction
330B, extending alternately through the third compartment 310B and the fourth compartment
320B repeatedly, and then being connected to the evaporator 210 through a fourth restriction
340B; and the third compartment 310B is disposed downstream of the first compartment
310A with respect to the low-temperature heat source fluid A, and the fourth compartment
320B is disposed upstream of the second compartment 320A with respect to the cooling
fluid. The cooling fluid should preferably comprise the high-temperature heat source
fluid B. Particularly, the cooling fluid which is to exchange heat with the cold heat
source fluid upstream of the evaporator in the second heat exchanger 300d2 should
preferably comprise the high-temperature heat source fluid B upstream of the condenser
220.
[0018] With the above arrangement, since the heat pump has the second heat exchanger 300d2,
the heat pump can operate under a pressure different from the pressure of the first
heat exchanger, thus increasing an overall heat exchange efficiency.
[0019] For example, as shown in FIG, 9, the heat pump may further comprise a third heat
exchanger 300c2 for exchanging heat between the low-temperature heat source fluid
A upstream of the evaporator 210 and the cooling fluid; wherein the third heat exchanger
300c2 has a fifth compartment 310B through which the low-temperature heat source fluid
A flows, a sixth compartment 320B through which the cooling fluid flows, and a refrigerant
passage extending through the fifth compartment 310B and the sixth compartment 320B,
the refrigerant passage being connected to the refrigerant passage of the first heat
exchanger 300c1 through a fifth restriction 340, extending alternately through the
fifth compartment 310B and the sixth compartment 320B repeatedly, and then being connected
to the evaporator 210 through the second restriction 250; and the fifth compartment
310B is disposed downstream of the first compartment 310A with respect to the low-temperature
heat source fluid A, and the sixth compartment 320B is disposed upstream of the second
compartment 320A with respect to the cooling fluid. The cooling fluid should preferably
comprise the high-temperature heat source fluid B. Particularly, the cooling fluid
which is to exchange heat with the cold heat source fluid upstream of the evaporator
in the third heat exchanger 300c2 should preferably comprise the high-temperature
heat source fluid B upstream of the condenser 220.
[0020] According to still another aspect of the present invention, as shown in FIGS. 1,
6, 9, and 12, for example, there is provided a dehumidifying apparatus comprising:
the above heat pump; and a moisture adsorbing device 103 disposed upstream of the
first heat exchanger with respect to the low-temperature heat source fluid A and having
a desiccant for adsorbing moisture from the low-temperature heat source fluid A.
[0021] The low-temperature heat source fluid is typically the process air of the air-conditioning
apparatus. Since the air-conditioning apparatus has a moisture adsorbing device, the
humidity of the low-temperature heat source fluid can be lowered. The high-temperature
heat source fluid is typically outside air as regeneration air.
[0022] The present dehumidifying apparatus should preferably be arranged so as to desorb
the moisture of the desiccant with the high-temperature heat source fluid B which
is heated by the condenser 220.
[0023] As shown in FIG. 3, for example, the object of the present invention can also be
achieved by a method of transferring heat from a low-temperature heat source fluid
A to a high-temperature heat source fluid B, the method comprising: a first step of
evaporating a refrigerant by cooling a low-temperature heat source under a predetermined
low pressure of 4.2 kg/cm
2 (from a point j to a point a) ; a second step of raising a pressure of the refrigerant
which has been evaporated in the first step to a predetermined high pressure of 19.3
kg/cm
2 (from the point a to a point b); a third step of condensing the refrigerant pressurized
in the second step under the predetermined high pressure to heat a high-temperature
heat source fluid with heat of condensation (from the point b to a point d); a fourth
step of depressurizing the refrigerant which has been condensed in the third step
to a first intermediate pressure between the predetermined high pressure and the predetermined
low pressure (from the point d, a point c to a point e); a fifth step of repeatedly
evaporating the refrigerant depressurized in the fourth step by cooling the low-temperature
heat source fluid and condensing the refrigerant by heating the high-temperature heat
source fluid; and a sixth step of providing the refrigerant which has been condensed
in the fifth step as the refrigerant to be evaporated in the first step. The transfer
of heat is typically performed by the pumping of heat.
[0024] As shown in FIG. 3, for example, the repeated evaporation and condensation in the
fifth step is achieved by evaporation by cooling the low-temperature heat source fluid
A (from the point e to a point f1, from a point h1 to a point f2, from a point h2
to a point f3, from a point h3 to a point h4) and condensation by heating the high-temperature
heat source fluid B (from the point f1 to a point g1a, from a point g1b to the point
h1, from a point f2 to a point g2a, from a point g2b to the point h2, and the like).
In the example shown in FIG. 3, the sixth step is a step (from a point h4 to the point
j) of providing, as the refrigerant to be evaporated in the first step, the refrigerant
which has been condensed (from the point f4 to the point h4) by heating the high-temperature
heat source fluid B.
[0025] There may be provided a dehumidifying method comprising the above method of pumping
heat, and, as shown in FIG. 4, for example, an eleventh step of adsorbing, with a
desiccant, moisture contained in the low-temperature heat source fluid before it is
cooled by evaporating the refrigerant in the fifth step (from a point K to a point
L) ; and a twelfth step of desorbing moisture from the desiccant which has adsorbed
the moisture in the eleventh step, with the high-temperature heat source fluid which
has been heated by condensing the refrigerant in the third step (from a point T to
a point U).
[0026] The present application is based on Japanese patent application No. 11-245022 filed
on August 31, 1999, which is incorporated herein as part of the disclosure of the
present application.
[0027] The present invention can more fully be understood based on the following detailed
description. Further applications of the present invention will become more apparent
from the following detailed description. However, the following detailed description
and specific examples will be described as preferred embodiments only for the purpose
of explaining the present invention. It is evident to a person skilled in the art
that various changes and modifications can be made to the embodiments in the following
detailed description within the spirit and scope of the present invention.
[0028] The applicant has no intention to dedicate any of the embodiments described below
to the public, and any of the disclosed modifications and alternatives which may not
be included in the scope of the claims constitutes part of the invention under the
doctrine of equivalent.
Brief Description of Drawings
[0029]
FIG. 1 is a flow diagram of a heat pump according to a first embodiment of the present
invention and a dehumidifying air-conditioning apparatus having the heat pump;
FIGS. 2 (a) and 2(b) are schematic side elevational and cross-sectional plan views,
respectively, of a heat exchanger suitable for use in the heat pump shown in FIG.
1;
FIG. 3 is a Mollier diagram of the heat pump shown in FIG. 1;
FIG. 4 is a psychrometric chart illustrative of operation of the dehumidifying air-conditioning
apparatus shown in FIG. 1;
FIG. 5 is a cross-sectional front elevational view schematically showing an example
of an actual structure of a dehumidifying air-conditioning apparatus having a heat
pump according to the first embodiment of the present invention;
FIG. 6 is a flow diagram of a heat pump according to a second embodiment of the present
invention and a dehumidifying air-conditioning apparatus having the heat pump;
FIG. 7 is a Mollier diagram of the heat pump shown in FIG. 6;
FIG. 8 is a cross-sectional front elevational view schematically showing an example
of an actual structure of a dehumidifying air-conditioning apparatus having a heat
pump according to the second embodiment of the present invention;
FIG. 9 is a flow diagram of a heat pump according to a third embodiment of the present
invention and a dehumidifying air-conditioning apparatus having the heat pump;
FIG. 10 is a Mollier diagram of the heat pump shown in FIG. 9;
FIG. 11 is a cross-sectional front elevational view schematically showing an example
of an actual structure of a dehumidifying air-conditioning apparatus having a heat
pump according to the third embodiment of the present invention;
FIG. 12 is a flow diagram of a heat pump according to a fourth embodiment of the present
invention and a dehumidifying air-conditioning apparatus having the heat pump;
FIG. 13 is a Mollier diagram of the heat pump shown in FIG. 12;
FIG. 14 is a cross-sectional front elevational view schematically showing an example
of an actual structure of a dehumidifying air-conditioning apparatus having a heat
pump according to the fourth embodiment of the present invention;
FIGS. 15(a) and 15(b) are schematic plan and side views, respectively, showing a heat
exchanger suitable for use in a heat pump according to an embodiment of the present
invention;
FIG. 16 is a diagram showing the relationship between the number of stages of a heat
exchange tube and the temperature effectiveness;
FIG. 17 is a flowchart of a conventional heat pump and a conventional dehumidifying
air-conditioning apparatus; and
FIG. 18 is a Mollier diagram of the conventional heat pump shown in FIG. 17.
Best Mode for Carrying Out the Invention
[0030] Embodiments of the present invention will be described below with reference to the
accompanying drawings. Identical or corresponding components are designated by the
identical or like reference characters throughout drawings, and will not be described
repetitively.
[0031] FIG. 1 is a flow diagram of a heat pump HP1 according to a first embodiment of the
present invention and a dehumidifying air-conditioning apparatus having the heat pump
HP1. The dehumidifying air-conditioning apparatus is an air-conditioning apparatus
which employs a desiccant. FIGS. 2(a) and 2(b) are schematic side elevational and
partial cross-sectional plan views, respectively, showing an example of a structure
of a first heat exchanger used in the air-conditioning apparatus shown in FIG. 1.
FIG. 3 is a refrigerant Mollier diagram of a heat pump HP1 included in the air-conditioning
apparatus shown in FIG. 1. FIG. 4 is a psychrometric chart of the air-conditioning
apparatus shown in FIG. 1.
[0032] Structural details of the heat pump according' to the first embodiment and the dehumidifying
air-conditioning apparatus having the heat pump will be described below with reference
to FIG. 1. The air-conditioning apparatus lowers the humidity of process air with
a desiccant to maintain a comfortable environment in an air-conditioned space 101
supplied with the process air. In FIG. 1, devices related to the process air will
be described along a path for the process air A from the air-conditioned space 101.
A path 107 connected to the air-conditioned space 101, an air blower 102 connected
to the path 107 for circulating the process air, a path 108, a desiccant wheel 103
filled with a desiccant, a path 109, a first compartment 310 in a first heat exchanger
300a according to the present invention, a path 110, a refrigerant evaporator (as
a cooling unit from the viewpoint of the process air) 210, and a path 111 are arranged
in the order named so as to return the process air to the air-conditioned space 101.
[0033] A path 124, an air blower 140 for circulating regeneration air, a path 125, a second
compartment 320 of the heat exchanger 300a for exchanging heat between the regeneration
air flowing into a desiccant wheel 103 and the process air flowing out of the desiccant
wheel, a path 126, a refrigerant condenser (as a heating unit from the viewpoint of
the regeneration air) 220, a path 127, the desiccant wheel 103, and a path 128 are
successively arranged in the order named along a path for the regeneration air B from
an outside space OA so as to discharge the regeneration air as an exhaust air EX into
the outside space.
[0034] Devices of the heat pump HP1 will be described below along a path for the refrigerant
from the refrigerant evaporator 210. In FIG. 1, the refrigerant evaporator 210, a
path 207, a compressor 260 for compressing the refrigerant which has been evaporated
into a vapor by the refrigerant evaporator 210, a path 201, the refrigerant condenser
220, a path 202, a restriction 330, the heat exchanger 300a, a path 204, a restriction
250, and a path 206 are arranged in the order named so as to return the refrigerant
to the refrigerant evaporator 210. The heat pump HP1 is thus constructed.
[0035] The desiccant wheel 103 comprises a thick disk-shaped wheel which is rotatable about
a rotational axis AX, and a desiccant is filled into the wheel with gaps for allowing
a gas to pass therethrough. For example, the desiccant wheel 103 comprises a number
of tubular dry elements bounded to each other so that their central axes extend parallel
to the rotational axis AX. The wheel is arranged so as to rotate in one direction
about the rotational axis AX and also to allow the process air A and the regeneration
air B to flow into and out of the desiccant wheel 103 parallel to the rotational axis
AX. Each of the dry elements is positioned so as to alternately contact the process
air A and the regeneration air B according to rotation of the wheel 103. Generally,
the desiccant wheel 103 is arranged so that the process air A and the regeneration
air B flow as counterflows parallel to the rotational axis AX through respective substantially
half areas of the circular desiccant wheel 103.
[0036] Since the air-conditioning apparatus is arranged so that the compression type heat
pump HP1 simultaneously cools the process air of the desiccant air-conditioner and
heats the regeneration air thereof, the compression type heat pump HP1 produces a
cooling effect on the process air based on the drive energy applied from an external
source to the compression type heat pump HP1, and the desiccant is regenerated with
heat which is the sum of heat pumped from the process air by the heat pump action
and the drive energy of the compression type heat pump HP1. Therefore, the drive energy
applied from the external source can be used in multiple ways for high energy saving
effects. The energy saving effects are further increased by the heat exchanger 300a
for exchanging heat between the process air and the regeneration air.
[0037] Structural details of the heat exchanger 300a suitable for use in the heat pump HP1
will be described below with reference to FIGS. 2(a) and 2 (b) . FIG. 2 (a) is a side
elevational view showing a plate-fin-tube heat exchanger as viewed in the longitudinal
direction of the tubes as refrigerant passages, with some plate fins being shown fragmentarily.
The symbol "x" at the centers of circular cross sections of tubes indicates that the
refrigerant flows from the viewer toward the sheet of FIG. 2(a), and the symbol "•"
at the centers of circular cross sections of tubes indicates that the refrigerant
flows toward the viewer from the sheet of FIG. 2(a). FIG. 2(b) is a cross-sectional
view taken along a line X - X of FIG. 2(a). In FIG. 2(b), the heat exchanger 300a
has a first compartment 310 for allowing the process air A to pass therethrough and
a second compartment 320 for allowing outside air as the regeneration air to pass
therethrough, and the first and second compartments 310, 320 are positioned adjacent
to each other with a single partition wall 301 being interposed therebetween.
[0038] In FIG. 2(a), the process air A is supplied from the upper side through the path
109 to the first compartment 310 and discharged from the lower side of the first compartment
310 through the path 110. The regeneration air B is supplied from the lower side through
the path 125 to the second compartment 320 and discharged from the upper side of the
second compartment 320 through the path 126. As shown in FIG. 2(a), the heat exchanger
300 has a plurality of substantially parallel heat exchange tubes as refrigerant passages
in each of a plurality of different planes PA, PB, PC, ... which are substantially
horizontal (i.e., perpendicular to the sheet of FIG. 2(a)).
[0039] As shown in FIG. 2(b), the plurality of heat exchange tubes extend through the first
compartment 310, the second compartment 320, and the partition wall 301 which separates
those compartments from each other. The heat exchange tubes disposed in the plane
PA shown in FIG, 2(a), for example, have portions extending through the first compartment
310, as shown in FIG. 2(b), and such portions are referred to as an evaporating section
251 as a first refrigerant passage. The plurality of evaporating sections are denoted
by the respective reference numerals 251A1, 251A2, 251A3, --- 251A9 (in the illustrated
example, nine tubes are disposed in the single plane PA). Hereinafter, these evaporating
sections are denoted by the single reference numeral 251 in the case where it is not
necessary to discuss a plurality of evaporating sections separately. The heat exchange
tubes disposed in the plane PA also have portions extending through the second compartment
320, and such portions are referred to as a condensing section 252 as a second refrigerant
passage. The plurality of condensing sections are denoted by the respective reference
numerals 252A1, 252A2, 252A3, ··· 252A9. Hereinafter, these condensing sections are
denoted by the single reference numeral 252 in the case where it is not necessary
to discuss a plurality of condensing sections separately. The evaporating section
251A1 and the condensing section 252A1, 251A2 and 252A2, 251A3 and 252A3, ··· 251A9
and 252A9 serve as a pair of a first compartment extending portion and a second compartment
extending portion, respectively, and constitute refrigerant passages.
[0040] Further, as shown in FIG. 2(b), the heat exchange tubes disposed in the plane PB
have a plurality of portions extending through the first compartment 310, and such
portions are referred to as evaporating sections 251B1, 251B2, 251B3, ··· 251B8 (in
the illustrated example, eight tubes are disposed in the plane PB). The heat exchange
tubes disposed in the plane PB also have portions extending through the second compartment
320, and such portions, which constitute a pair of refrigerant passages with the above
evaporating sections, are referred to as condensing sections 252B1, 252B2, 252B3,
... 252B8 as second refrigerant passages. Refrigerant passages are also provided in
the plane PC as with the plane PB, which is not shown.
[0041] In the heat exchanger shown in FIGS. 2(a) and 2(b), the evaporating section 251A1
and the condensing section 252A1 are paired with each other and formed by a single
tube as an integral passage. The evaporating sections 251A1, 251A3, ··· and the condensing
sections 252A2, 252A3, ···, and the evaporating sections 251B1, 251B2, 251B3, ···
and the condensing sections 252B1, 252B2, 252B3, ··· are similarly constructed. This
feature, together with the fact that the first compartment 310 and the second compartment
320 are positioned adjacent to each other with the single partition wall 301 being
interposed therebetween, is effective in making the heat exchanger 300a small and
compact as a whole.
[0042] In the heat exchanger shown in FIGS. 2(a) and 2(b), the evaporating sections 251A,
251B, 251C are successively arranged in the order named from the upper side of FIG.
2(a), and the condensing sections 252A, 252B, 252C are also successively arranged
in the order named from the upper side of FIG. 2 (a) . In the plane PA, the evaporating
sections are arrayed in the order of 251A1 - 251A9 from the left to the right in FIG.
2(a), and the condensing sections are also arrayed in the order of 252A1 - 252A9 from
the left to the right in FIG. 2(a).
[0043] As shown in FIG. 2(b), the end of the condensing section 252A1 (remote from the partition
wall 301) and the end of the condensing section 252A2 (remote from the partition wall
301) are connected to each other by a U tube. The end of the evaporating section 251A2
and the end of the evaporating section 251A3 are similarly connected to each other
by a U tube.
[0044] Therefore, the refrigerant flowing in one direction from the evaporating section
251A1 to the condensing section 252A1 as a whole is introduced into the condensing
section 252A2 by the U tube, and then flows into the evaporating section 251A2, from
which the refrigerant flows into the evaporating section 251A3 via the U tube. In
this manner, the refrigerant passages including the evaporating sections and the condensing
sections extend through the first compartment 310 and the second compartment 320,
alternately and repetitively. In other words, the refrigerant passages are provided
as a group of meandering thin pipes. A group of meandering thin pipes pass through
the first compartment 310 and the second compartment 320, and are held in alternate
contact with the process air and the regeneration air.
[0045] In FIG. 2(a), the right-hand end of the refrigerant passage in the plane PA, i.e.,
the end of the condensing section 252A9, and the right-hand end of the refrigerant
passage in the plane PB, i.e., the end of the condensing section 252B8, are connected
to each other via an orifice 331 which serves as a restriction. The left-hand end
of the refrigerant passage in the plane PB, i.e., the end of the condensing section
252B1, and the left-hand end of the refrigerant passage in the plane PC, i.e., the
end of the condensing section 252C1 (not shown) are connected to each other via an
orifice 332 which serves as a restriction.
[0046] In FIG. 2(a), the process air A flows downwardly into the first compartment 310 through
a duct 109, and then flows downwardly out of the first compartment 310. In FIG. 2(a),
outside air used as the regeneration air B flows upwardly into the second compartment
320 through a duct 125, and then flows upwardly out of the second compartment 320.
[0047] With the heat exchanger thus constructed, the refrigerant introduced into the evaporating
section 251A1 is partly evaporated in the evaporating section 251A1, and flows in
a wet state into the condensing section 252A1. The refrigerant is reversed in direction
by the U tube, and flows into the condensing section 252A2 where the refrigerant is
condensed. The condensed refrigerant then flows into the evaporating section 251A2,
where the refrigerant is partly evaporated, then reversed in direction by the U tube,
and flows into the evaporating section 251A3. The refrigerant is thus alternately
evaporated and condensed repeatedly until it reaches the condensing section 252A9
in the final row in the plane PA. The refrigerant is then depressurized by the restriction
331, and flows into the condensing section 252B8 in the plane PB.
[0048] Then, the refrigerant similarly passes alternately through the condensing sections
and the evaporating sections in the plane PB while being condensed and evaporated
repeatedly therein until the refrigerant reaches the final condensing section 252B1
in the plane PB. The refrigerant is then depressurized by the restriction 332, and
flows into the condensing section 252Cl in the plane PC.
[0049] An evaporating pressure in the evaporating section 251A and a condensing pressure
in the condensing section 252A, i.e., first intermediate pressures, or pressures in
the evaporating sections 251B and the condensing sections 252B, i.e., second intermediate
pressures, are determined by the temperature of the process air A and the temperature
of the outside air used as the regeneration air B. Since the heat exchanger 300a shown
in FIGS. 2(a) and 2(b) utilizes heat transfer by way of evaporation and condensation,
the heat exchanger has an excellent rate of heat transfer. Further, since the heat
exchanger has a very high efficiency of heat exchange as it performs a heat exchange
on the counterflow principles. Since the refrigerant is forcibly caused to flow in
substantially one direction as a whole in the refrigerant passages, from the evaporating
section 251 to the condensing section 252 or from the condensing section 252 to the
evaporating section 251, the efficiency of heat exchange between the process air and
the regeneration air (outside air) is very high. The expression "the refrigerant flows
in substantially one direction as a whole" means that the refrigerant flows in substantially
one direction in the refrigerant passages when viewed as a whole even though the refrigerant
may locally flow back due to turbulences or be vibrated in the flowing direction due
to pressure waves produced by bubbles or instantaneous interruptions. In the present
embodiment, the refrigerant is forced to flow in one direction under the pressure
increased by the compressor 260.
[0050] When the high-temperature fluid is cooled, i.e., the heat exchanger is used for cooling
the high-temperature fluid, the efficiency φ of heat exchange is defined by
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 T, 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 φ of heat exchange is defined
by
[0051] The inner surface of the heat exchange tube used in the evaporating section 251 and
the condensing section 252 should preferably comprise a high-performance heat-transfer
surface by forming therein spiral grooves such as linear grooves like those grooves
which are found in the inner surface of a barrel of a rifle. The refrigerant liquid
flowing through the heat exchange tube usually flows so as to wet the inner surface
thereof. The spiral grooves disturb the boundary layer of the flow of the refrigerant
liquid, resulting in an increased rate of heat transfer.
[0052] The process air flows through the first compartment 310. The fins mounted on the
outer surface of the heat exchange tube in the first compartment 310 should preferably
be arranged in the form of louvers to disturb the flow of the fluid flowing through
the first compartment 310. Similarly, the fins in the second compartment 320 should
also preferably be arranged to disturb the flow of the fluid flowing through the second
compartment 320. The fins should preferably be made of aluminum or copper or an alloy
thereof.
[0053] First, flows of the refrigerant between the devices will be described below with
reference to FIG. 1, and then operation of the heat pump HP1 will be described below
with reference to FIG. 3.
[0054] In FIG. 1, a refrigerant vapor compressed by the refrigerant compressor 260 is introduced
into the regeneration air heating unit (refrigerant condenser) 220 via the refrigerant
vapor pipe 201 connected to the discharge port of the compressor. The refrigerant
vapor compressed by the compressor 260 is increased in temperature by the heat of
compression, and the heat of the refrigerant vapor heats the regeneration air. Heat
is removed from the refrigerant vapor itself, and the refrigerant vapor is condensed.
[0055] The refrigerant condenser 220 has a refrigerant outlet connected by the refrigerant
path 202 to the inlet of the evaporating section 251A1 in the heat exchanger 300a.
The restriction 330 is disposed on the refrigerant path 202 near the inlet of the
evaporating section 251A1.
[0056] In FIG. 1, only the evaporating section 251A1 and the condensing section 252A1 paired
therewith are shown as being positioned between the restriction 330 and the restriction
331 of the heat exchanger 330a. Although the evaporating section 251A1 and the condensing
section 252A1 are a minimum requirement, a plurality of evaporating sections and condensing
sections are typically arranged in one plane, e.g., the plane PA, as described above
with reference to FIGS. 2(a) and 2 (b) .
[0057] The refrigerant liquid that flows out of the refrigerant condenser (as a heating
unit from the viewpoint of the regeneration air) 220 is depressurized by the restriction
330 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 251A1, where
the refrigerant liquid flows so as to wet the inner wall surface of the tube in the
evaporating section 251A1 and is evaporated to cool the process air which flows through
the first compartment 310.
[0058] The evaporating section 251A1 and the condensing section 252A1 are constructed as
a continuous tube. Specifically, since the evaporating section 251A1 and the condensing
section 252A1 are provided as an integral passage, the evaporated refrigerant vapor
(and the refrigerant liquid which has not been evaporated) flows into the condensing
section 252A2. In this time, heat is removed from the refrigerant vapor by the outside
air flowing through the second compartment 320, and the refrigerant vapor is condensed.
[0059] As described above, the heat exchanger 300a has the evaporating section as the refrigerant
passage extending through the first compartment 310 and the condensing section as
the refrigerant passage extending through the second compartment 320 (at least one
pair of them, e.g., denoted by 251A9 and 252A9) in the first plane PA, and also has
the condensing section as the refrigerant passage extending through the second compartment
320 and the evaporating section as the refrigerant passage extending through the first
compartment 310 (at least one pair of them, e.g., denoted by 252B8 and 251B8) in the
second plane PB. The heat exchanger 300a has the intermediate restriction 331 in a
transitional location position where the refrigerant moves from the condensing section
252A9 in the plane PA to the condensing section 252B8 in the plane PB. Specifically,
the intermediate restriction 331 is located in a position where the refrigerant passage
has extended through the second compartment 320.
[0060] In the first embodiment, the heat pump HP1 has intermediate restrictions 331, 332,
333 which interconnect condensing sections in the different planes, and a plurality
of pairs of condensing sections and evaporating sections which are disposed downstream
of the restriction 333. Thus, the heat pump HP1 is arranged such that the refrigerant
in the liquid phase flows out of the heat exchanger 300a finally through the condensing
section.
[0061] The final condensing section of the heat exchanger 300a has its outlet connected
to an expansion valve 250 as a second restriction via the refrigerant liquid pipe
204. The expansion valve 250 is connected to the refrigerant evaporator (as a cooling
unit from the viewpoint of the process air) 210 via the refrigerant pipe 206.
[0062] The restriction 250 may be positioned at any position from the condensing section
to the inlet of the refrigerant evaporator 210, but should preferably be positioned
just in front of the inlet of the refrigerant evaporator 210. It is because a heat
insulating material of the refrigerant pipe needs to be thickened as temperature of
the refrigerant flowing out of the restriction 250 is considerably lower than the
atmospheric temperature. The refrigerant liquid condensed in the condensing section
is depressurized by the restriction 250, and expanded and lowered in temperature.
The refrigerant is then introduced into the refrigerant evaporator 210 where the refrigerant
is evaporated to cool the process air with heat of evaporation. The restrictions 330,
250 may comprise orifices, capillary tubes, expansion valves, or the like. The intermediate
restrictions 331, 332, 333 usually comprise orifices.
[0063] The refrigerant which has been evaporated into a vapor in the refrigerant evaporator
210 is introduced into the suction side of the refrigerant compressor 260, and thus
the above cycle is repeated.
[0064] The behavior of the refrigerant in the evaporating sections and the condensing sections
of the heat exchanger 300a will be described below with reference to FIG. 2(b). The
refrigerant flows into the evaporating section 251A1 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
251A1, it is heated by the process air and enters the condensing section 252A1 while
increasing the vapor phase thereof. In the condensing section 252A1, the refrigerant
heats the regeneration air. In this time, heat is removed from the refrigerant itself,
and while the refrigerant in the vapor phase is being condensed, the refrigerant flows
into the next condensing section 252A2. While the refrigerant is flowing through the
condensing section 252A2, heat is further removed from the refrigerant by the regeneration
air, and the refrigerant in the vapor phase is further condensed. Thereafter, the
refrigerant flows into the next evaporating section 251A2. In this manner, the refrigerant
flows through the refrigerant passages while changing in phase between the vapor phase
and the liquid phase. Thus, heat is exchanged between the process air as a low-temperature
heat source fluid in the heat pump HP1 and the regeneration air as a high-temperature
heat source fluid in the heat pump HP1.
[0065] Next, operation of the heat pump HP1 will be described below with reference to FIG.
3. FIG. 3 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.
[0066] For illustrative purposes, it is assumed that the refrigerant passage is constituted
by a pair of the evaporating section 251A1 and the condensing section 252A1 in the
plane PA, the restriction 331, the condensing section 252B2 and the evaporating section
251B2, and the evaporating section 251B1 and the condensing section 252B1 in the plane
PB, the restriction 332, the condensing section 252C1 and the evaporating section
251C1, and the evaporating section 251C2 and the condensing section 252C2 in the plane
PC, the restriction 333, the condensing section 252D2 and the evaporating section
251D2, and the evaporating section 251D1 and the condensing section 252D1 in the plane
PD, and reaches the restriction 250.
[0067] In FIG. 3, a point "a" represents a state of the refrigerant at the outlet port of
the refrigerant evaporator 210, and the refrigerant is in the form of a saturated
vapor. The refrigerant has a pressure of 4.2 kg/cm
2, a temperature of 10°C, and an enthalpy of 148.83 kcal/kg. A point b represents a
state of the vapor drawn and compressed by the compressor 260, i.e., a state at the
outlet port of the compressor 260. In the point b, the refrigerant has a pressure
of 19.3 kg/cm
2 and a temperature of 78°C, and is in the form of a superheated vapor.
[0068] The refrigerant vapor is cooled in the refrigerant condenser 220 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 19.3 kg/cm
2 and a temperature of 65°C. Under this pressure, the refrigerant is further 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 122.97 kcal/kg.
[0069] The refrigerant liquid is depressurized by the restriction 330 and flows into the
evaporating section 251A1 in the heat exchanger 300a. This state is indicated at a
point e on the Mollier diagram. The temperature of the refrigerant liquid is slightly
higher than the temperature of the outside air. The pressure of the refrigerant liquid
is a first intermediate pressure according to the present invention, i.e., is of an
intermediate value between 4.2 kg/cm
2 and 19.3 kg/cm
2 in the present embodiment. The refrigerant liquid is a mixture of the liquid and
the vapor because part of the liquid is evaporated.
[0070] In the evaporating section 251A1, the refrigerant liquid is evaporated under the
first 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 part of the liquid
is evaporated, the refrigerant liquid remains in a considerable amount.
[0071] The refrigerant in the state represented by the point f1 flows into the condensing
section 252A1. In the condensing section 252A1, heat is removed from the refrigerant
by the outside air which flows through the second compartment 320, and the refrigerant
reaches a state represented by a point g1a.
[0072] The refrigerant in the state at the point g1a is depressurized by the restriction
331, and reaches a state represented by a point g1b. In the point g1b, the refrigerant
has a second intermediate pressure which is lower than the pressure at the point g1a.
Then, heat is removed from the refrigerant in the condensing section 252B2, and the
refrigerant reaches a state represented by a point h1 while increasing its liquid
phase. Then, the refrigerant flows into the evaporating section 251B2, where the refrigerant
increases its vapor phase and reaches a state represented by a point f2. Thereafter,
the refrigerant flows into the condensing section 252B1. In the condensing section
252B1, heat is removed from the refrigerant by the outside air flowing through the
second compartment 320, and reaches a state represented by a point g2a.
[0073] The refrigerant in the state at the point g2a is depressurized by the restriction
332, and reaches a state represented by a point g2b. In the point g2b, the refrigerant
has a third intermediate pressure which is lower than the pressure at the point g2a.
Then, heat is removed from the refrigerant in the condensing section 252C2, and the
refrigerant reaches a state represented by a point h2 while increasing its liquid
phase. Thereafter, the refrigerant flows into the evaporating section 251C2.
[0074] The refrigerant is depressurized , by the intermediate restriction 333, then flows
through the refrigerant passages in the condensing section, the evaporating section,
the evaporating section, and the condensing section, and reaches a state represented
by a point h4 on the Mollier diagram. On the Mollier diagram, the point h4 is on the
saturated liquid curve. In this point, the refrigerant has a temperature of 30°C and
an enthalpy of 109.99 kcal/kg.
[0075] The refrigerant liquid at the point h4 is depressurized to 4.2 kg/cm
2, which is a saturated pressure at a temperature of 10°C, by the restriction 250.
The refrigerant flows as a mixture of the refrigerant liquid and the vapor at a temperature
of 10°C into the refrigerant evaporator 210, where the refrigerant removes heat from
the process air and is evaporated into a saturated vapor at the state represented
by the point a on the Mollier diagram. The evaporated vapor is drawn again by the
compressor 260, and thus the above cycle is repeated.
[0076] In the heat exchanger 300a, as described above, the refrigerant goes through changes
of the evaporated state from the point e to the point f1 or from the point h1 to the
point f2 in the evaporating section 251, and goes through changes of the condensed
state from the point f1 to the point g1a or from the point g1b to the point h1 in
the condensing section 252. Since the refrigerant transfers heat by way of evaporation
and condensation, the rate of heat transfer is very high.
[0077] In the compression type heat pump HP1 .including the compressor 260, the refrigerant
condenser (regeneration air heating unit) 220, the restrictions 330, 250, and the
refrigerant evaporator 210, when the heat exchanger 300a is not provided, the refrigerant
at the state represented by the point d in the refrigerant condenser 220 is returned
to the refrigerant evaporator 210 through the restrictions. Therefore, the enthalpy
difference that can be used by the refrigerant evaporator 210 is only 148.83 - 122.97
= 25.86 kcal/kg. With the heat pump HP1 according to the present embodiment which
has the heat exchanger 300a, however, the enthalpy difference that can be used by
the refrigerant evaporator 210 is 148.83 - 109.99 = 38.84 kcal/kg. Thus, the amount
of vapor that is circulated to the compressor under the same cooling load and the
required power can be reduced by 33 %. Consequently, the heat pump HP1 according to
the present embodiment can perform the same operation as with a well-known subcooled
cycle.
[0078] Operation of the dehumidifying air-conditioning apparatus having the heat pump HP1
will be described below with reference to FIG. 4. FIG. 1 will be referred to for structural
details. In FIG. 4, the alphabetical letters K - N and Q - U represent states of air
in various regions, and correspond to the encircled letters in the flow diagram shown
in FIG. 1. The psychrometric chart shown in FIG. 4 is also applicable to a dehumidifying
air-conditioning apparatus according to another embodiment of the present invention
which will be described later on.
[0079] First, the flow of the process air A will be described below. In FIG. 4, the process
air (in a state K) from the air-conditioned space 101 is drawn via the process air
path 107 into the air blower 102, and delivered via the process air path 108 into
the desiccant wheel 103. The moisture of the process air is adsorbed by the desiccant
in the dry elements of the desiccant wheel 103. The absolute humidify of the process
air is reduced, and the dry-bulb temperature thereof is increased by heat of adsorption
by the desiccant, so that the process air reaches a state L. The process air flows
through the process air path 109 into the first compartment 310 in the heat exchanger
300a, where the process air is cooled, with the constant absolute humidity, by the
refrigerant evaporated in the evaporating section 251 (FIG. 2). The process air then
reaches a state M, and flows via the path 110 into the cooling unit 210. In the cooling
unit 210, the process air is further cooled, with constant absolute humidity, and
reaches a state N. The process air is then dried and cooled, and returned as process
air SA having a suitable humidity and a suitable temperature via the duct 111 into
the air-conditioned space 101.
[0080] The flow of the regeneration air B will be described below. The regeneration air
B (in a state Q) from the outside space OA is drawn via the regeneration air path
124, and flows via the path 125 into the second compartment 320 of the heat exchanger
300a. In the second compartment 320, the regeneration air exchanges heat with the
process air (in a state L) flowing through the second compartment 310 indirectly through
the refrigerant which flows through the evaporating section 251 and the condensing
section 252 as the refrigerant passage in the heat exchanger 300a. As a result of
the heat exchange, the regeneration air is increased in dry-bulb temperature and reaches
a state R. The regeneration air is then delivered via the path 126 into the refrigerant
condenser (as a heating unit from the viewpoint of the regeneration air) 220, where
the regeneration air is heated and increased in dry-bulb temperature to reach a state
T. The regeneration air is then delivered via the path 127 into the desiccant wheel
103, where moisture is removed (desorbed) from the desiccant in the dry elements,
so that the desiccant is regenerated. The regeneration air is increased in absolute
humidity and lowered in dry-bulb temperature due to heat of desorption of the moisture
from the desiccant, and reaches a state U. As described above, the regeneration air
is then discharged through the path 128 as the exhaust air EX.
[0081] From an air cycle in the psychrometric chart shown in FIG. 4, it can be shown that,
in the air-conditioning apparatus described above, the amount of heat H applied to
the regeneration air to regenerate the desiccant, the amount of heat q pumped from
the process air, and the drive energy h of the compressor are related to each other
by H = q + h.
[0082] A mechanical arrangement of the dehumidifying air-conditioning apparatus described
above will be described below with reference to FIG. 5. In FIG. 5, devices of the
dehumidifying air-conditioning apparatus are housed in a cabinet 700. The cabinet
700 comprises a housing made of thin steel sheets in the form of a rectangular parallelepiped,
for example, and has an inlet port for process air RA which is opened in the center
of a vertically upper ceiling panel thereof. A filter 501 is provided at the inlet
port for preventing dusts in the air-conditioned space from entering the dehumidifying
air-conditioning apparatus. The air blower 102 is disposed inwardly of the filter
501 in the cabinet 700, and has its inlet port communicating with the process air
inlet port of the cabinet through the filter 501.
[0083] The air blower 102 has an outlet port directed vertically downwardly, and the desiccant
wheel 103 is disposed below the air blower 102 with the rotational axis AX being vertically
oriented. The desiccant wheel 103 is operatively coupled through a belt, a chain,
or the like to an electric motor 105 as an actuator with its rotatable shaft being
vertically oriented, and can be rotated at a low speed of about one revolution per
several minutes. Since the desiccant wheel 103 is rotatable in a substantially horizontal
plane about the vertical rotational axis AX, the dehumidifying air-conditioning apparatus
is compact with its height reduced.
[0084] The outlet port of the air blower 102 is connected to the desiccant wheel via a passage
108. The passage 108 is divided from the other parts by thin steel sheets which are
similar to those of the cabinet, 700, for example. The process air flows into about
one half (semicircular region) of the circular desiccant wheel 103.
[0085] The first compartment 310 of the heat exchanger 300a, i.e., the evaporating section
251, is disposed downwardly below one half (semicircular region) of the desiccant
wheel 103 through which the process air flows. The desiccant wheel 103 and the first
compartment 310 are connected to each other by a path 109 defined as a space between
the desiccant wheel 103 horizontally disposed and tubes horizontally disposed (and
fins mounted thereon) of the evaporating section in FIG. 7.
[0086] The refrigerant evaporator 210 with horizontal cooling pipes is disposed downwardly
below the first compartment 310. In FIG. 7, a path 110 is defined as a space between
the first compartment 310 and the refrigerant evaporator 210. Since the first compartment
310 and the refrigerant evaporator 210 are integrally combined with each other, the
space therebetween is joined to the heat exchanger 300a and the refrigerant evaporator
210. Vertically below the refrigerant evaporator 210, there is disposed a starting
portion of a path 111 extending horizontally on the bottom of the cabinet 700. The
path 111 changes its direction and is directed upwardly and isolated from the paths
109, 108 by partition walls, and finally reaches the ceiling panel of the cabinet
700, i.e., an air supply port SA which is opened alongside of the inlet port for the
process air RA.
[0087] An inlet port for introducing outside air OA is opened in a lower side panel of the
cabinet 700, and a filter 502 is provided at the inlet port for blocking dust carried
by the outside air. A space defined inwardly of the filter 502 serves as a path 124,
in which the compressor 260 is installed. While the air blower 140 is disposed between
the outside air inlet port and the heat exchanger 300a in FIG. 1, the air blower 140
is disposed between the desiccant wheel 103 and a regeneration air outlet port in
FIG. 5 as described later on. The air blower 140 may be placed in any of these positions
as long as it can circulate the regeneration air.
[0088] The second compartment 320 of the heat exchanger 300a is disposed vertically above
the compressor 260. The condenser 220 is disposed above the second compartment 320
of the heat exchanger 300a. In this example, the second compartment 320 of the heat
exchanger 300a and the condenser 220 have common fins and are integrally constructed.
The intermediate restrictions 331, 332, 333 are mounted on the ends of the condensing
sections that extend through the second compartment 320 and arranged along the cabinet
700.
[0089] About one half (semicircular region) of the circular desiccant wheel 103 through
which the regeneration air flows is disposed vertically above the condenser 220.
[0090] The space vertically above the latter half region of the desiccant wheel 103 serves
as a path 128 where the air blower 140 is located. The air blower 140 has an outlet
port disposed at the ceiling panel of the cabinet 700 adjacent to the process air
inlet port. The outlet port of the air blower 140 serves as a port for discharging
the used regeneration air into the outside space.
[0091] Since the heat exchanger 300a utilizes heat transfer by way of evaporation and condensation
and exchanges heat between the process air and the regeneration air substantially
on the counterflow principle, the heat pump HP1 and hence the dehumidifying air-conditioning
apparatus can be arranged in a compact size.
[0092] Structural details of a heat pump HP2 according to a second embodiment and the dehumidifying
air-conditioning apparatus incorporating the heat pump will be described below with
reference to FIG. 6. A heat exchanger 300b is the same as the heat exchanger according
to the first embodiment except that the intermediate restrictions 331, 332, 333 are
disposed in the evaporating section.
[0093] Specifically, the heat exchanger 300b has the condensing section as the refrigerant
passage extending through the second compartment 320 and the evaporating section as
the refrigerant passage extending through the first compartment 310 (at least one
pair of them, e.g., denoted by 252A1 and 251A1) in the first plane PA, and also has
the evaporating section as the refrigerant passage extending through the first compartment
310 and the condensing section as the refrigerant passage extending through the second
compartment 320 (at least one pair of them, e.g., denoted by 251B1 and 252B1) in the
second plane PB. The heat exchanger 300a has the intermediate restriction 331 in a
transitional location where the refrigerant moves from the evaporating section 251A1
in the plane PA to the evaporating section 251B1 in the plane PB. Specifically, the
intermediate restriction 331 is located in a position where the refrigerant passage
has extended through the first compartment 310.
[0094] As with the heat exchanger 300a, in the heat exchanger 300b, the refrigerant circulating
in a heat pump cycle is utilized, typically in the total amount thereof, for repeatedly
exchanging heat alternately through pairs of evaporating and condensing sections which
are connected in series. Therefore, heat can sufficiently be exchanged between the
process air and the regeneration air when a small fraction of the flowing refrigerant
is evaporated and condensed. Usually, in the evaporating section, the refrigerant
liquid remains unevaporated in a considerable amount. Consequently, even through the
intermediate restrictions 331, 332, 333 are disposed in the evaporating section, necessary
pressure differences can be developed in the refrigerant passage in the respective
planes (PA, PB, PC, ...).
[0095] Operation of the heat pump HP2 according to the second embodiment will be described
below with reference to FIG. 7. In FIG. 7, the transitions from the point "a" to the
point e are identical to those shown in FIG. 3 and will not be described below. The
refrigerant in the state represented by the point e which flows into an evaporating
section 251A1 in the heat exchanger 300b is a mixture of the liquid and the vapor
with part of the liquid being evaporated under the first intermediate pressure, as
described above with reference to FIG. 3.
[0096] The refrigerant is further evaporated in the evaporating section, and reaches a point
f1 nearer to the saturated vapor curve in the wet region on the Mollier diagram. The
refrigerant in this state flows into the condensing section, where the refrigerant
is condensed. Then, refrigerant reaches a point g1 nearer to the saturated liquid
curve though in the wet region. Then, the refrigerant flows into the evaporating section,
goes toward the saturated vapor curve within the wet region to reach a point h1a.
Up to this point, the refrigerant undergoes changes substantially under the first
intermediate pressure.
[0097] The refrigerant in the state indicated by the point h1a is depressurized' by the
restriction 331, and reaches a point h1b under the second intermediate pressure. Specifically,
the refrigerant flows from the evaporating sections as the refrigerant passages in
the plane PA into the evaporating sections as the refrigerant passages in the plane
PB. This refrigerant is evaporated under the second intermediate pressure in the evaporating
section, and reaches a point f2. The refrigerant is then repeatedly similarly evaporated
and condensed alternately, and depressurized by the intermediate restriction 333.
Thereafter, the refrigerant flows through the evaporating and condensing sections,
and reaches a point g4 on the Mollier diagram which corresponds to the point h4 in
FIG. 3. On the Mollier diagram, the point g4 is on the saturated liquid curve. In
this point, the refrigerant has a temperature of 30°C and an enthalpy of 109.99 kcal/kg.
[0098] As in the case of FIG. 3, the refrigerant liquid at the point g4 is depressurized
to 4.2 kg/cm
2, which is a saturated pressure at a temperature of 10°C, by the restriction 250.
The refrigerant flows as a mixture of the refrigerant liquid and the vapor at a temperature
of 10°C into the refrigerant evaporator 210, where the refrigerant removes heat from
the process air and is 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
260, and thus the above cycle is repeated.
[0099] In the heat exchanger 300b, as described above, the refrigerant repeatedly goes alternately
through changes of vapor phase and changes of liquid phase. Since the refrigerant
transfers heat by way of evaporation and condensation, the rate of heat transfer is
very high, as with the heat exchanger 300a.
[0100] The enthalpy difference that can be used by the refrigerant evaporator 210 is remarkably
larger than that in the conventional heat pump. Thus, the amount of vapor that is
circulated to the compressor under the same cooling load and the required power can
be reduced by 33 %, as in the case of FIG. 3.
[0101] Operation of the dehumidifying air-conditioning apparatus with the heat pump HP2
will not be described below as it is qualitatively the same as described above with
reference to the psychrometric chart of FIG. 4.
[0102] FIG. 8 shows a mechanical arrangement of a heat pump HP2 according to the second
embodiment of the present invention and a dehumidifying air-conditioning apparatus
having the heat pump HP2. In the present embodiment, the intermediate restrictions
331, 332, 333 are mounted on the ends of the evaporating sections that extend through
the first compartment 310 and arranged along a partition wall which defines the vertically
upward portion of the process air path 111. Other mechanical details of the present
embodiment are identical to those shown in FIG. 5.
[0103] A heat pump HP3 according to a third embodiment of the present invention and a dehumidifying
air-conditioning apparatus incorporating the heat pump HP3 will be described below
with reference to FIG. 9. In the present embodiment, a heat exchanger 300c for exchanging
heat between the process air flowing out of the desiccant wheel 103 and the regeneration
air flowing into the condenser 220 is divided into a heat exchanger 300c1 which is
located upstream with respect to the flow of the process air and a heat exchanger
300c2 which is located downstream with respect to the flow of the process air. The
heat exchanger 300c1 corresponds to the first heat exchanger according to the present
invention, and the heat exchanger 300c2 corresponds to a third heat exchanger according
to the present invention.
[0104] As with the first embodiment or the third embodiment, the heat exchanger 300c1 may
be a heat exchanger with the intermediate restrictions 331, 332, 333. In the example
shown in FIG. 9, however, the heat exchanger 300c1 has no intermediate restrictions.
In this embodiment, a refrigerant passage alternately extending through the first
compartment 310 and the second compartment 320 repeatedly includes a first evaporating
section, a first condensing section, a folded second condensing section, a second
evaporating section, a folded third evaporating section, and a third condensing section.
The heat exchanger 300c2 may be a heat exchanger with the intermediate restrictions
331, 332, 333. Either the heat exchanger 300c1 or the heat exchanger 300c2 may be
a heat exchanger with intermediate restrictions.
[0105] The heat pump HP3 is arranged such that the refrigerant flowing out of the third
condensing section of the heat exchanger 300c1 is introduced into the heat exchanger
300c2 via a pipe that bypasses the heat exchanger 300c1. In the embodiment shown in
FIG. 9, the heat exchanger 300c2 is fully identical in structure to the heat exchanger
300c1.
[0106] The refrigerant pipe extending from the third condensing section of the heat exchanger
300cl has a restriction 340 that serves as a fifth restriction. Specifically, the
heat exchanger 300c1 and the heat exchanger 300c2 are connected via the restriction
340 in series with each other in the direction in which the refrigerant flows. The
fifth restriction 340 is connected to the first evaporating section of the heat exchanger
300c2. The third condensing section of the heat exchanger 300c2 is connected to the
restriction 250.
[0107] The compartment of the heat exchanger 300c2 for passing the process air therethrough
serves as a fifth compartment, and the compartment of the heat exchanger 300c2 for
passing the regeneration air serves as a sixth compartment. The process air which
has flowed out of the desiccant wheel flows from the first compartment into the fifth
compartment. The regeneration air which has been introduced from the outside space
flows from the sixth compartment into the second compartment and then into the condenser
220.
[0108] Operation of the heat pump HP3 will be described below with reference to FIG. 10.
The heat pump HP3 operates in the same manner as with the first and second embodiments
up to the point e. The refrigerant at the point e is partly evaporated under the first
intermediate pressure in the first evaporating section, and then reaches a point f1
in the wet region. The refrigerant from the point f1 is condensed in the first and
second condensing sections, and reaches a point g1 on or near a saturated liquid curve.
The refrigerant at the point g1 is partly evaporated in the second and third evaporating
sections, and reaches a point f2. The refrigerant is condensed in the third condensing
section, and reaches a point g2 on or near the saturated liquid curve.
[0109] The refrigerant at the point g2 is depressurized by the restriction 340, and reaches
a point E under the second intermediate pressure. The refrigerant then flows into
the first evaporating section of the heat exchanger 300c2. Thereafter, the refrigerant
changes its state in the same manner as with the refrigerant in the heat exchanger
300c1, and reaches to a point G2 which corresponds to the point g4 shown in FIG. 3.
The refrigerant is depressurized by the restriction 250, and reaches the state at
a point j. Subsequently, the heat pump HP3 operates in the same manner as with the
first and second embodiments.
[0110] FIG. 11 shows a mechanical arrangement of the heat pump HP3 according to the third
embodiment of the present invention and a dehumidifying air-conditioning apparatus
having the heat pump HP3. In the present embodiment, the heat pump is free of the
intermediate restrictions 331, 332, 333, but has the restriction 340 provided between
the heat exchanger 300c1 and the heat exchanger 300c2. Other mechanical details of
the present embodiment are identical to those shown in FIGS. 5 and 8.
[0111] A heat pump HP4 according to a fourth embodiment of the present invention and a dehumidifying
air-conditioning apparatus incorporating the heat pump HP4 will be described below
with reference to FIG. 12. In the present embodiment, a heat exchanger 300d for exchanging
heat between the process air flowing out of the desiccant wheel 103 and the regeneration
air flowing into the condenser 220 is divided into a heat exchanger 300d1 which is
located upstream with respect to the flow of the process air and a heat exchanger
300d2 which is located downstream with respect to the flow of the process air. The
heat exchanger 300d1 corresponds to the first heat exchanger according to the present
invention, and the heat exchanger 300d2 corresponds to the second heat exchanger according
to the present invention.
[0112] As with the first embodiment or the second embodiment, the heat exchanger 300d1 may
be a heat exchanger with the intermediate restrictions 331, 332, 333. In the example
shown in FIG. 12, however, the heat exchanger 300d1 has no intermediate restrictions.
The heat exchanger 300d1 and the heat exchanger 300d2 are of substantially the same
structure as the heat exchanger 300cl and the heat exchanger 300c2.
[0113] According to the third embodiment, the heat exchanger 300cl and the heat exchanger
300c2 are connected in series with each other via the restriction 340. According to
the present embodiment, however, the heat exchanger 300d1 and the heat exchanger 300d2
have respective restrictions 330A, 330B connected to their inlets and respective restrictions
340A, 340B connected to their outlets, and are arranged in parallel with each other.
Specifically, a refrigerant path 202 extending from the condenser 220 is branched
into two paths connected respectively to the restrictions 330A, 330B. The restrictions
340A, 340B are connected to the refrigerant outlets of the heat exchanger 300c1 and
the heat exchanger 300c2, and joined to a path 204 which is connected to the restriction
250. Either one of the restrictions 250, 340B may be dispensed with.
[0114] Operation of the heat pump HP4 will be described below with reference to FIG. 13.
In FIG. 13, the transitions to the point d are identical to those in the first, second
and third embodiments. The refrigerant at a point d is divided from the path 202 into
two paths, which deliver a substantially one half of the refrigerant to the restriction
330A and the remainder to the restriction 330B.
[0115] The refrigerant delivered to the restriction 330A is depressurized to the first intermediate
pressure by the restriction 330A, and reaches a point e. The refrigerant at the point
e is partly evaporated under the first intermediate pressure in the first evaporating
section of the heat exchanger 300d1, and reaches a point f1 in the wet region. The
refrigerant from the point f1 is condensed in the first and second condensing sections,
and reaches a point g1 on or near a saturated liquid curve. The refrigerant at the
point g1 is partly evaporated in the second and third evaporating sections, and reaches
a point f2. The refrigerant is condensed in the third condensing section, and reaches
a point g2 on or near the saturated liquid curve. The refrigerant at the point g2
is depressurized by the restriction 340A and the restriction 250, and reaches a point
j1. The pressure at the point j1 is the same as the evaporating pressure in the evaporator
210.
[0116] Of the refrigerant at the point d, the refrigerant delivered to the restriction 330B
is depressurized to an intermediate pressure lower than the first intermediate pressure
by the restriction 330B, and reaches a point E. This is because the third compartment
of the heat exchanger 300d2 for passing the process air is positioned downstream of
the first compartment of the heat exchanger 300d1 with respect to the flow of the
process air, and the fourth compartment of the heat exchanger 300d2 for passing the
regeneration air is positioned upstream of the second compartment of the heat exchanger
300d1 with respect to the flow of the regeneration air, so that the evaporating temperature
or the condensing temperature is low.
[0117] The refrigerant in the state at the point E changes its state in the same manner
as the refrigerant in the heat exchanger 300d1, and finally reaches a point G2 on
or near the saturated liquid curve. The refrigerant at the point G2 is depressurized
by the restriction 340B and the restriction 250, and reaches a point j. The pressure
at the point j is the same as the evaporating pressure in the evaporator 210. The
mixture of the refrigerants at the points j1, j is evaporated in the evaporator 210.
[0118] FIG. 14 shows a mechanical arrangement of the heat pump HP4 according to the fourth
embodiment of the present invention and a dehumidifying air-conditioning apparatus
having the heat pump HP4. In the present embodiment, the heat pump HP4 is free of
the intermediate restrictions 331, 332, 333, and the restrictions 330A, 330B are connected
to the respective inlets of the heat exchanger 300d1 and the heat exchanger 300d2
and the restrictions 340A, 340B are connected to the respective outlets of the heat
exchanger 300d1 and the heat exchanger 300d2. Other mechanical details of the present
embodiment are identical to those according to the first, second and third embodiments.
[0119] A structure of the first, second and third heat exchangers according to the present
invention will be described below with reference to FIGS. 15(a) and 15(b), from the
different viewpoint from the above description with reference to FIGS. 2(a) and 2(b).
FIG. 15(a) is a plan view showing the heat exchanger as viewed in the direction in
which the process air and the regeneration air are flowing, and FIG. 15 (b) is a side
elevational view showing the heat exchanger as viewed in a direction perpendicular
to the flows of the process air and the regeneration air. In FIG. 15(a), the process
air flows from the viewer toward the sheet, and the regeneration air from the sheet
toward the viewer. In the heat exchanger, tubes are disposed in eight rows in each
of the four planes PA, PB, PC, PD which lie perpendicularly to the flows of the process
air and the regeneration air. Thus, the tubes are arranged in four tiers and eight
rows along the flows of the process air and the regeneration air.
[0120] An intermediate restriction 331 is disposed in a transitional location from the first
plane PA to the next plane PB. An intermediate restriction 332 (not shown) is disposed
in a transitional location from the plane PB to the plane PC. An intermediate restriction
333 is disposed in a transitional location from the plane PC to the plane PD. While
one restriction is provided in a transitional location from one plane to the next
plane, tube rows in the plane PA may be arranged in a plurality of layers. In such
an arrangement, an intermediate restriction is disposed in a transitional location
from each layer to the next layer. Planes prior and subsequent to an intermediate
restriction are referred to as first and second planes, respectively.
[0121] Heat exchangers each having tubes in eight rows and four layers (tiers) as shown
in FIGS. 15(a) and 15(b) may be arranged in parallel with each other or in series
with each other with respect to the flows of the process air and the regeneration
air, depending on the amount of the process air and the regeneration air.
[0122] In the Mollier diagram shown in FIG. 3, for example, the cycle is effective even
if the refrigerant is repeatedly evaporated and condensed into a subcooled region
beyond the saturated liquid curve. In view of the heat exchange between the flows
of the process air and the regeneration air, however, the refrigerant should preferably
change its phase in the wet region. With the heat exchanger shown in FIG. 2 or FIG.
15, therefore, the heat transfer area of the first evaporating section connected to
the restriction 330 should preferably be larger than the heat transfer area of the
subsequent evaporating section. Furthermore, since the refrigerant flowing into the
restriction 250 is preferably in the saturated or subcooled region, the heat transfer
area of the condensing section connected to the restriction 250 should preferably
be larger than the heat transfer area of the prior condensing section.
[0123] The relationship between the total temperature effectiveness (heat exchange efficiency)
and the number of stages of the heat exchange tubes along the flow of the process
air or the regeneration air which are divided by the intermediate restrictions, which
can be referred to the number of layers or the number of lines and corresponds to
the number of planes in FIG. 15, will be described below with reference to FIG. 16.
If the temperature effectiveness per one stage is 0.400, for example, then the total
temperature effectiveness is about 0.67 for three stages, about 0.72 for four stages,
about 0.77 for five stages, and about 0.80 for six stages. Further increases in the
number of stages do not result in any appreciable increases in the total temperature
effectiveness. Therefore, it is preferable to use about four stages from the standpoint
of cost effectiveness.
[0124] In the above embodiments, the compressor is used as a pressurizer. However, a pressurizer
may comprise an absorber for absorbing a refrigerant with an absorbent solution, a
pump for pressurizing the absorbent solution which has absorbed the refrigerant, and
a generator for generating the refrigerant from the pressurized absorbent solution,
which are used in an absorption chiller.
Industrial Applicability
[0125] According to the present invention, as described above, since the refrigerant repeatedly
passes alternately through refrigerant passages which extend through first and second
compartments, the refrigerant flowing through an evaporator or a condenser passes
through the first and second compartments a plurality of times, and can be used a
plurality of times to exchange heat between a low-temperature heat source fluid and
a high-temperature heat source fluid. Therefore, the refrigerant will not be completely
dried out even if it is evaporated in the refrigerant passage extending through the
first compartment.