U.S. patent application number 12/693724 was filed with the patent office on 2010-08-05 for liquid circulation heating system and method of controlling the same.
This patent application is currently assigned to PANASONIC CORPORATION. Invention is credited to Yasuhiko ISAYAMA, Kazuo NAKATANI.
Application Number | 20100193156 12/693724 |
Document ID | / |
Family ID | 42062557 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100193156 |
Kind Code |
A1 |
NAKATANI; Kazuo ; et
al. |
August 5, 2010 |
LIQUID CIRCULATION HEATING SYSTEM AND METHOD OF CONTROLLING THE
SAME
Abstract
A liquid circulation heating system includes a heat pump for
producing a heated liquid and a heating radiator. The heat pump has
a heat pump circuit in which a compressor, a radiator, a
decompressor, and an evaporator are connected in series. The heat
pump circuit is charged with a zeotropic refrigerant mixture of at
least two refrigerants having different boiling points. The system
is configured so that the composition ratio of a higher boiling
point refrigerant in the refrigerant circulating through the heat
pump circuit increases when the liquid supplied to the radiator has
a relatively high temperature.
Inventors: |
NAKATANI; Kazuo; (Osaka,
JP) ; ISAYAMA; Yasuhiko; (Osaka, JP) |
Correspondence
Address: |
HAMRE, SCHUMANN, MUELLER & LARSON P.C.
P.O. BOX 2902
MINNEAPOLIS
MN
55402-0902
US
|
Assignee: |
PANASONIC CORPORATION
Osaka
JP
|
Family ID: |
42062557 |
Appl. No.: |
12/693724 |
Filed: |
January 26, 2010 |
Current U.S.
Class: |
165/63 ;
62/324.6; 62/434; 62/512 |
Current CPC
Class: |
F24D 11/0214 20130101;
F24D 19/1039 20130101; F24D 3/18 20130101; Y02B 30/12 20130101 |
Class at
Publication: |
165/63 ; 62/512;
62/324.6; 62/434 |
International
Class: |
F25B 29/00 20060101
F25B029/00; F25B 43/00 20060101 F25B043/00; F25B 13/00 20060101
F25B013/00; F25D 17/02 20060101 F25D017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2009 |
JP |
2009-019233 |
Claims
1. A liquid circulation heating system for performing air-heating
by heating a liquid to produce a heated liquid and releasing heat
of the heated liquid from a heating radiator, the system comprising
a heat pump circuit for circulating a refrigerant, wherein the heat
pump circuit includes a refrigerant radiator for heating the liquid
by radiating heat from the refrigerant to produce the heated
liquid, the heat pump circuit is charged with a zeotropic
refrigerant mixture of at least two refrigerants having different
boiling points, as the refrigerant, and the liquid circulation
heating system is configured so that a composition ratio of a
higher boiling point refrigerant in the refrigerant circulating
through the heat pump circuit increases when the liquid supplied to
the refrigerant radiator has a relatively high temperature.
2. The liquid circulation heating system according to claim 1,
wherein the heat pump circuit further includes: a compressor for
compressing the refrigerant; a decompressor for decompressing the
refrigerant; an evaporator for evaporating the refrigerant; and a
vapor-liquid separator for separating the refrigerant into a gas
refrigerant and a liquid refrigerant, and the liquid circulation
heating system further comprises a controller for performing a
control operation to reduce an amount of the liquid refrigerant in
the vapor-liquid separator when the liquid supplied to the
refrigerant radiator has a relatively high temperature.
3. The liquid circulation heating system according to claim 2,
wherein the vapor-liquid separator is an accumulator provided
between the evaporator and the compressor.
4. The liquid circulation heating system according to claim 3,
wherein the decompressor is an expansion valve, and the controller
reduces an opening of the expansion valve when the liquid supplied
to the refrigerant radiator has a relatively high temperature.
5. The liquid circulation heating system according to claim 3,
wherein the heat pump circuit further includes, between the
evaporator and the accumulator, a heater for heating the
refrigerant to be fed to the accumulator from the evaporator, and
the controller increases an amount of the heating applied to the
refrigerant by the heater when the liquid supplied to the
refrigerant radiator has a relatively high temperature.
6. The liquid circulation heating system according to claim 5,
wherein the heat pump circuit further includes a bypass passage
that bypasses the decompressor, and the heater is a heat exchanger
for exchanging heat between the refrigerant flowing through the
bypass passage and the refrigerant to be fed to the accumulator
from the evaporator.
7. The liquid circulation heating system according to claim 2,
wherein the decompressor includes: a first expansion valve for
decompressing the refrigerant after the refrigerant radiates heat
in the refrigerant radiator; and a second expansion valve for
further decompressing the refrigerant after the refrigerant is
decompressed by the first expansion valve, the vapor-liquid
separator is a receiver provided between the first expansion valve
and the second expansion valve, and the controller reduces an
opening of the first expansion valve and increases an opening of
the second expansion valve when the liquid supplied to the
refrigerant radiator has a relatively high temperature.
8. The liquid circulation heating system according to claim 1,
further comprising: a supply pipe for guiding the liquid from the
heating radiator to the refrigerant radiator; and a recovery pipe
for guiding the heated liquid from the refrigerant radiator to the
heating radiator.
9. The liquid circulation heating system according to claim 1,
further comprising: a tank for storing the produced heated liquid;
a supply pipe for guiding the liquid from a lower portion of the
tank to the refrigerant radiator; a recovery pipe for guiding the
heated liquid from the refrigerant radiator to an upper portion of
the tank; a feed pipe for feeding the heated liquid stored in the
tank to the heating radiator; and a return pipe for returning the
heated liquid to the tank after the heated liquid radiates heat in
the heating radiator.
10. The liquid circulation heating system according to claim 1,
further comprising: a tank for storing the produced heated liquid;
a supply pipe for guiding the liquid from a lower portion of the
tank to the refrigerant radiator; a recovery pipe for guiding the
heated liquid from the refrigerant radiator to an upper portion of
the tank; a heat exchanger, disposed in the tank, for exchanging
heat between the heated liquid stored in the tank and a heat
transfer liquid; a feed pipe for feeding the heat transfer liquid
to the heating radiator after the heat transfer liquid is heated in
the heat exchanger; and a return pipe for returning the heat
transfer liquid to the heat exchanger after the heat transfer
liquid radiates heat in the heating radiator.
11. The liquid circulation heating system according to claim 1,
wherein the liquid is water, and the heated liquid is hot
water.
12. A method of controlling a liquid circulation heating system for
performing air-heating by heating a liquid to produce a heated
liquid and releasing heat of the heated liquid from a heating
radiator, wherein the liquid circulation heating system includes a
heat pump circuit for circulating a refrigerant, and the heat pump
circuit includes: a refrigerant radiator for heating the liquid by
radiating heat from the refrigerant to produce the heated liquid; a
compressor for compressing the refrigerant; a decompressor for
decompressing the refrigerant; an evaporator for evaporating the
refrigerant; and a vapor-liquid separator for separating the
refrigerant into a gas refrigerant and a liquid refrigerant, the
heat pump circuit is charged with a zeotropic refrigerant mixture
of at least two refrigerants having different boiling points, as
the refrigerant, and the method comprises the step of controlling
an operation of the decompressor to reduce an amount of the liquid
refrigerant in the vapor-liquid separator when the liquid supplied
to the refrigerant radiator has a relatively high temperature.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a liquid circulation
heating system for performing air-heating using a liquid and to a
method of controlling the system.
[0003] 2. Description of Related Art
[0004] Conventionally, there has been known a liquid circulation
heating system for producing hot water by a boiler or an electric
heater and performing air-heating using the hot water produced. In
recent years, the use of a heat pump capable of producing hot water
with high efficiency has been considered as an alternative heat
source to a boiler and an electric heater. For example, JP
2008-39306 A proposes a liquid circulation heating system for
producing hot water by a heat pump and storing the produced hot
water in a hot water storage tank. In this liquid circulation
heating system, the hot water stored in the hot water storage tank
is fed to, for example, a heating radiator placed indoors to
radiate its heat, and then returned to the hot water storage
tank.
[0005] The heat pump has a heat pump circuit for circulating a
refrigerant. The heat pump circuit includes, for example, a
compressor, a radiator, an expansion valve, and an evaporator,
which are connected by pipes. Heat is exchanged between a
refrigerant and water in the radiator so as to heat the water, and
thereby hot water is produced.
SUMMARY OF THE INVENTION
[0006] In the liquid circulation heating system, when the flow rate
of the hot water fed to the heating radiator is high, the
temperature of the water that flows from the heating radiator
presumably does not drop so much. In this case, the temperature of
the water supplied to the radiator of the heat pump rises. When the
temperature of the water supplied to the radiator rises, the high
pressure of the refrigeration cycle increases, as shown by a dotted
line in FIG. 2.
[0007] When the high pressure of the refrigeration cycle increases,
however, the increased pressure may exceed the upper limit pressure
for ensuring the normal operation of the components of the heat
pump.
[0008] In view of the above circumstances, it is an object of the
present invention to provide a liquid circulation heating system
capable of suppressing an increase in the high pressure of the
refrigeration cycle when the temperature of the liquid supplied to
the refrigerant radiator rises.
[0009] When the temperature of the liquid supplied to the
refrigerant radiator rises, a high boiling point refrigerant causes
a smaller increase in the high pressure of the refrigeration cycle
than a low boiling point refrigerant does. Moreover, when a mixture
of these high and low boiling point refrigerants is used, how much
the high pressure of the refrigeration cycle increases as the
temperature of the liquid supplied to the refrigerant radiator
rises is determined by the mixture ratio between these
refrigerants. Accordingly, the inventors of the present invention
have considered that the increase in the high pressure of the
refrigeration cycle can be suppressed by actively taking advantage
of the phenomenon that when a zeotropic refrigerant mixture of
refrigerants having different boiling points is used as a
refrigerant, the composition of the refrigerant circulating through
the heat pump circuit changes. The present invention has been made
in view of the above circumstances.
[0010] The present invention provides a liquid circulation heating
system for performing air-heating by heating a liquid to produce a
heated liquid and releasing heat of the heated liquid from a
heating radiator. This system includes a heat pump circuit for
circulating a refrigerant, and this heat pump circuit includes a
refrigerant radiator for heating the liquid by radiating heat from
the refrigerant to produce the heated liquid. The heat pump circuit
is charged with a zeotropic refrigerant mixture of at least two
refrigerants having different boiling points, as the refrigerant.
The system is configured so that a composition ratio of a higher
boiling point refrigerant in the refrigerant circulating through
the heat pump circuit increases when the liquid supplied to the
refrigerant radiator has a relatively high temperature.
[0011] The present invention also provides a method of controlling
a liquid circulation heating system for performing air-heating by
heating a liquid to produce a heated liquid and releasing heat of
the heated liquid from a heating radiator. The liquid circulation
heating system includes a heat pump circuit for circulating a
refrigerant, and the heat pump circuit includes: a refrigerant
radiator for heating the liquid by radiating heat from the
refrigerant to produce the heated liquid; a compressor for
compressing the refrigerant; a decompressor for decompressing the
refrigerant; an evaporator for evaporating the refrigerant; and a
vapor-liquid separator for separating the refrigerant into a gas
refrigerant and a liquid refrigerant. The heat pump circuit is
charged with a zeotropic refrigerant mixture of at least two
refrigerants having different boiling points, as the refrigerant.
This method includes the step of controlling an operation of the
decompressor to reduce an amount of the liquid refrigerant in the
vapor-liquid separator when the liquid supplied to the refrigerant
radiator has a relatively high temperature.
[0012] The present invention makes it possible to suppress the
increase in the high pressure of the refrigeration cycle when the
temperature of the liquid supplied to the refrigerant radiator
rises.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic configuration diagram of a liquid
circulation heating system according to a first embodiment of the
present invention.
[0014] FIG. 2 is a Mollier diagram of a heat pump.
[0015] FIG. 3 is a diagram for explaining the fact that an increase
in the high pressure of the refrigeration cycle is suppressed due
to a change in the composition of the refrigerant circulating
through the heat pump circuit.
[0016] FIG. 4 is a schematic configuration diagram of a liquid
circulation heating system according to a second embodiment of the
present invention.
[0017] FIG. 5 is a schematic configuration diagram of a liquid
circulation heating system according to a third embodiment of the
present invention.
[0018] FIG. 6 is a schematic configuration diagram of a heat pump
of a first modification.
[0019] FIG. 7 is a schematic configuration diagram of a heat pump
of a second modification.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings. It should be
noted, however, that the embodiments described below are merely
examples of the present invention, and should not be construed to
limit the scope of the present invention.
First Embodiment
[0021] FIG. 1 shows a liquid circulation heating system 1A
according to a first embodiment of the present invention. This
liquid circulation heating system 1A heats a liquid to produce a
heated liquid, releases heat of the heated liquid from a heating
radiator 3, and thereby performs air-heating, for example, in a
room. Specifically, the liquid circulation heating system 1A
includes the heating radiator 3, a heat pump 2 for producing the
heated liquid, and an overall controller 5 for controlling the
entire system.
[0022] In the present embodiment, the heating radiator 3 is
connected directly to the heat pump 2 by a supply pipe 31 and a
recovery pipe 32 to be described later, so that the liquid flows
without stopping. In the liquid circulation heating system 1A
having such a configuration, the hot water produced can be used
directly for air-heating. Therefore, heat radiation loss is
reduced, and as a result, energy conservation can be achieved. As
the liquid, for example, an antifreeze liquid containing propylene
glycol or the like dissolved in water can be used, but water is
preferably used because it is available at low cost and in large
quantities. The following description will be made on the
assumption that the liquid is water and the heated liquid is hot
water.
[0023] The heat pump 2 has a heat pump circuit 20 for circulating a
refrigerant. This heat pump circuit 20 includes a compressor 21 for
compressing the refrigerant, a radiator (refrigerant radiator) 22
for radiating heat from the compressed refrigerant, an expansion
valve 23 serving as a decompressor for decompressing the
refrigerant that has radiated heat, and an evaporator 24 for
evaporating the decompressed refrigerant. These components 21 to 24
are connected in series by pipes. The heat pump 2 includes a heat
pump controller (corresponding to a controller of the present
invention) 26 for controlling the compressor 21 and the expansion
valve 23 according to an instruction from the overall controller
5.
[0024] In the radiator 22, heat is exchanged between the
refrigerant and the water flowing through the radiator 22 so as to
heat the water, and thereby hot water is produced. In the
evaporator 24, heat is exchanged between the refrigerant and air
blown by a fan 25, and thereby the refrigerant absorbs heat.
[0025] In the present embodiment, the heat pump circuit 20 is
charged with, as a refrigerant, a zeotropic refrigerant mixture of
at least two refrigerants having different boiling points. A
zeotropic refrigerant mixture means a refrigerant in which the
mixture composition of a gas refrigerant is different from that of
a liquid refrigerant in a vapor-liquid equilibrium state (i.e., the
mixture ratio between the at least two refrigerants in the gas
refrigerant is different from that in the liquid refrigerant). When
a comparison is made between the gas refrigerant and the liquid
refrigerant, the gas refrigerant contains a higher percentage of a
low boiling point refrigerant, while the liquid refrigerant
contains a higher percentage of a high boiling point refrigerant.
Examples of such a mixed refrigerant include R407C that is a
mixture of R32, R125, and R134a, a mixture of R32 and HFO-1234yf
(2,3,3,3-tetrafluoropropene), and a mixture of R32, HFO-1234yf, and
R125.
[0026] It is preferable to use a zeotropic refrigerant mixture
including a high boiling point refrigerant and a low boiling point
refrigerant, with a difference in boiling point therebetween being
20.degree. C. or more. For example, in the case of R407C containing
a high boiling point refrigerant consisting of R32 (having a
boiling point of -52.degree. C.) and R125 (having a boiling point
of -49.degree. C.) and a low boiling point refrigerant that is
R134a (having a boiling point of -26.degree. C.), a difference in
boiling point between these high and low boiling point refrigerants
is 23.degree. C.
[0027] Further, in the present embodiment, an accumulator 27 is
provided between the evaporator 24 and the compressor 21. This
accumulator 27 separates the refrigerant evaporated in the
evaporator 24 into a gas refrigerant and a liquid refrigerant, and
serves as the vapor-liquid separator of the present invention. In
the present embodiment, a zeotropic refrigerant mixture is used.
Therefore, a liquid refrigerant, which is rich in a high boiling
point refrigerant, is accumulated in the bottom portion of the
accumulator 27. For example, in the case where the zeotropic
refrigerant mixture is a mixture of R32 (having a boiling point of
-52.degree. C.) and HFO-1234yf (having a boiling point of
-29.degree. C.), a liquid refrigerant, which is rich in HFO-1234yf,
is accumulated in the bottom portion of the accumulator 27.
[0028] The heating radiator 3 is a device for radiating heat from
hot water flowing therethrough, and has an inlet for allowing the
hot water to flow thereinto, and an outlet for allowing the hot
water that has radiated its heat to flow therefrom. As the heating
radiator 3, for example, a radiator to be placed in a room of a
building may be used. A hot water panel to be laid on a floor also
may be used.
[0029] The outlet of the heating radiator 3 is connected to the
radiator 22 by the supply pipe 31 for supplying water to the
radiator 22. The inlet of the heating radiator 3 is connected to
the radiator 22 by the recovery pipe 32 for recovering hot water
produced in the radiator 22. The supply pipe 31 is provided with an
incoming water temperature sensor 72 for detecting the temperature
of water (hereinafter referred also as an "incoming water
temperature") to be supplied to the radiator 22. The supply pipe 31
also is provided with a pump 61 on the upstream side of the
incoming water temperature sensor 72. The incoming water
temperature sensor 72 is connected to the heat pump controller 26.
On the other hand, the recovery pipe 32 is provided with a hot
water temperature sensor 71 for detecting the temperature of the
hot water produced in the radiator 22. When the pump 61 is rotated,
the water is guided from the heating radiator 3 to the radiator 22
by the supply pipe 31, and the hot water produced in the radiator
22 is guided from the radiator 22 to the heating radiator 3 by the
recovery pipe 32.
[0030] The overall controller 5 includes a microcomputer, a digital
signal processor (DSP), or the like, and is connected to the
above-mentioned heat pump controller 26, the hot water temperature
sensor 71, and the pump 61, respectively.
[0031] Next, the control operations performed by the overall
controller 5 and the heat pump controller 26 are described
specifically.
[0032] When a user turns on a heating switch (not shown), the
overall controller 5 rotates the pump 61 and sends an operation
start signal to the heat pump controller 26. Thereby, water is
heated in the radiator 22 to produce hot water, and the produced
hot water is fed to the heating radiator 3. Thus, air-heating is
performed.
[0033] The overall controller 5 controls the rotational rate of the
pump 61 to regulate the flow rate of the water flowing through the
supply pipe 31 so that the temperature of the water detected by the
hot water temperature sensor 71 becomes a specified temperature
(for example, 70.degree. C.).
[0034] When the temperature of the water (incoming water
temperature) supplied to the radiator 22 is relatively high, the
heat pump controller 26 performs a control operation to reduce the
amount of the liquid refrigerant in the accumulator 27.
Specifically, when the temperature detected by the incoming water
temperature sensor 72 is higher than a predetermined temperature
(for example, 55.degree. C.), the heat pump controller 26 reduces
the opening of the expansion valve 23. When the opening of the
expansion valve 23 is reduced, the refrigerant absorbs heat
efficiently in the evaporator 24 and the dryness of the refrigerant
flowing into the accumulator 27 increases. Thereby, the amount of
the liquid refrigerant remaining in the accumulator 27 decreases.
As a result, the composition ratio of the high boiling point
refrigerant in the refrigerant circulating through the heat pump
circuit 20 increases, which thereby suppresses the increase in the
high pressure of the refrigeration cycle.
[0035] With reference to FIG. 3, the above-described phenomenon is
explained below by taking, as an example, the case where the
zeotropic refrigerant mixture is a mixture of R32 and HFO-1234yf.
In FIG. 3, full lines indicate the case where the refrigerant is
R32 alone and the case where the refrigerant is HFO-1234yf alone, a
single-dashed line indicates the case where the composition ratio
of HFO-1234yf in the mixed refrigerant circulating through the heat
pump circuit 20 has a certain value, and a double-dashed line
indicates the case where the composition ratio of HFO-1234yf is
higher than the certain value.
[0036] First, it is assumed that the high pressure of the
refrigeration cycle is located at Point a on the single-dashed line
when the incoming water temperature is low. If the amount of the
liquid refrigerant in the accumulator 27 is fixed, the composition
of the refrigerant circulating through the heat pump circuit 20
does not change. Therefore, when the incoming water temperature
rises to, for example, 65.degree. C., the high pressure of the
refrigeration cycle shifts from Point a to Point b along the
single-dashed line. In the present embodiment, however, the amount
of the liquid refrigerant remaining in the accumulator 27
decreases. As a result, the composition ratio of the high boiling
point refrigerant in the refrigerant circulating through the heat
pump circuit 20 increases, and thus the high pressure of the
refrigeration cycle shifts from Point a to Point c on the
double-dashed line. Accordingly, the increase in the high pressure
of the refrigeration cycle can be suppressed when the incoming
water temperature rises.
[0037] That is, when the opening of the expansion valve 23 is
reduced, Point A shifts to the right in the Mollier diagram of FIG.
2 and thus the dryness increases. Thereby, the amount of the liquid
refrigerant remaining in the accumulator 27 decreases. As a result,
the composition ratio of the high boiling point refrigerant in the
refrigerant circulating through the heat pump circuit 20 increases,
which thereby suppresses the increase in the high pressure of the
refrigeration cycle.
[0038] It should be noted that the liquid refrigerant in the
accumulator 27 does not necessarily have to disappear completely.
When the amount of the liquid refrigerant in the accumulator 27
decreases to some extent, the heat pump controller 26 may stop
reducing the opening of the expansion valve 23 to maintain it.
Second Embodiment
[0039] FIG. 4 shows a liquid circulation heating system 1B
according to a second embodiment of the present invention. In the
present embodiment, the same components as those in the first
embodiment are designated by the same reference numerals and no
further description is given.
[0040] The liquid circulation heating system 1B of the second
embodiment has basically the same configuration as the liquid
circulation heating system 1A of the first embodiment, except that
the heating radiator 3 and the radiator 22 are connected via the
hot water storage tank 8.
[0041] Furthermore, as a refrigerant charged in the heat pump
circuit 20, the same refrigerant as that described in the first
embodiment also is used in the present embodiment, and therefore
the description of the zeotropic refrigerant mixture is not
repeated here. The same description also is not repeated in the
following embodiment and modifications.
[0042] The hot water storage tank 8 is a vertically cylindrical
closed casing and is filled with water. The lower portion of the
hot water storage tank 8 is connected to the radiator 22 by the
supply pipe 31, and the upper portion thereof is connected to the
radiator 22 by the recovery pipe 32.
[0043] When the pump 61 is rotated, the water is guided from the
lower portion of the hot water storage tank 8 to the radiator 22 by
the supply pipe 31, and the hot water produced in the radiator 22
is guided from the radiator 22 to the upper portion of the hot
water storage tank 8 by the recovery pipe 32. Thereby, the produced
hot water is stored in the hot water storage tank 8 from the top
thereof. On the peripheral surface of the hot water storage tank 8,
hot water temperature sensors 74 for determining how much hot water
remains in the tank 8 are provided separately from each other in
the vertical direction. The hot water temperature sensors 74 are
connected to the overall controller 5.
[0044] In the present embodiment, a heat exchanger 92 for hot water
supply is provided at an upper position in the hot water storage
tank 8, and a water inlet pipe 91 and a hot water outlet pipe 93
are connected to this heat exchanger 92. That is, in the present
embodiment, the produced hot water can be used as a heat source for
hot water supply. In addition, a heater 85 for re-heating the hot
water also is provided at an upper position in the hot water
storage tank 8.
[0045] The inlet of the heating radiator 3 is connected to the
upper portion of the hot water storage tank 8 by a feed pipe 81,
and the outlet of the heating radiator 3 is connected to the lower
portion of the hot water storage tank 8 by a return pipe 82. In the
present embodiment, a circulation pump 66 is provided in the return
pipe 82, but the circulation pump 66 may be provided in the feed
pipe 81. The circulation pump 66 is connected to the overall
controller 5. When the circulation pump 66 is rotated, the hot
water stored in the hot water storage tank 8 is fed to the heating
radiator 3 through the feed pipe 81, and the hot water is returned
to the hot water storage tank 8 through the return pipe 82 after
radiating heat in the heating radiator 3.
[0046] Next, the control operations performed by the overall
controller 5 and the heat pump controller 26 are described
specifically.
[0047] (Hot Water Storage Operation)
[0048] When the overall controller 5 determines that the amount of
hot water remaining in the tank is less than the required amount
based on the temperature detected by the hot water temperature
sensors 74, for example, during nighttime hours (for example, from
23:00 to 7:00), it rotates the pump 61, and sends an operation
start signal to the heat pump controller 26. Thereby, water is
heated in the radiator 22 to produce hot water, and the produced
hot water is stored in the hot water storage tank 8. The overall
controller 5 also controls the rotational rate of the pump 61 to
regulate the flow rate of the water flowing through the supply pipe
31 so that the temperature of the water detected by the hot water
temperature sensor 71 becomes a specified temperature (for example,
70.degree. C.).
[0049] When the temperature of the water (incoming water
temperature) supplied to the radiator 22 is relatively high, the
heat pump controller 26 performs a control operation to reduce the
amount of the liquid refrigerant in the accumulator 27.
Specifically, when the temperature detected by the incoming water
temperature sensor 72 is higher than a predetermined temperature
(for example, 55.degree. C.), the heat pump controller 26 reduces
the opening of the expansion valve 23. When the opening of the
expansion valve 23 is reduced, the refrigerant absorbs heat
efficiently in the evaporator 24 and the dryness of the refrigerant
flowing into the accumulator 27 increases. Thereby, the amount of
the liquid refrigerant remaining in the accumulator 27 decreases.
As a result, the composition ratio of the high boiling point
refrigerant in the refrigerant circulating through the heat pump
circuit 20 increases, which thereby suppresses the increase in the
high pressure of the refrigeration cycle.
[0050] That is, when the opening of the expansion valve 23 is
reduced, Point A shifts to the right in the Mollier diagram of FIG.
2 and thus the dryness increases. Thereby, the amount of the liquid
refrigerant remaining in the accumulator 27 decreases. As a result,
the composition ratio of the high boiling point refrigerant in the
refrigerant circulating through the heat pump circuit 20 increases,
which thereby suppresses the increase in the high pressure of the
refrigeration cycle.
[0051] It should be noted that the liquid refrigerant in the
accumulator 27 does not necessarily have to disappear completely.
When the amount of the liquid refrigerant in the accumulator 27
decreases to some extent, the heat pump controller 26 may stop
reducing the opening of the expansion valve 23 to maintain it.
[0052] (Air-Heating Operation)
[0053] When a user turns on a heating switch (not shown), the
overall controller 5 rotates the circulation pump 66. Thereby, the
hot water stored in the hot water storage tank 8 is fed to the
heating radiator 3, where heat is radiated from the hot water.
Thus, air-heating is performed.
[0054] In the liquid circulation heating system 1B of the second
embodiment described above, high-temperature hot water stored in
the hot water storage tank 8 can be fed to the heating radiator 3
even during the early stage of the air-heating operation.
Therefore, air-heating can be started immediately after the heating
switch is turned on.
Third Embodiment
[0055] FIG. 5 shows a liquid circulation heating system 1C
according to a third embodiment of the present invention. In the
present embodiment, the same components as those in the first and
second embodiments are designated by the same reference numerals
and no further description is given.
[0056] In the liquid circulation heating system 1C of the third
embodiment, hot water stored in the hot water storage tank 8 can be
used directly for hot water supply. Specifically, the water inlet
pipe 91 is connected to the lower portion of the hot water storage
tank 8, and the hot water outlet pipe 93 is connected to the upper
portion of the hot water storage tank 8. At an upper position in
the hot water storage tank 8, a heat exchanger 83 for exchanging
heat between the hot water stored in the hot water storage tank 8
and a heat transfer liquid (secondary liquid) is provided. The heat
exchanger 83 is connected to the heating radiator 3 by the feed
pipe 81 and the return pipe 82. When the circulation pump 66 is
rotated, the heat transfer liquid heated in the heat exchanger 83
is fed to the heating radiator 3 through the feed pipe 81, and the
heat transfer liquid is returned to the heat exchanger 83 through
the return pipe 82 after radiating heat in the heating radiator 3.
As the heat transfer liquid, for example, an antifreeze liquid can
be used, but water preferably is used because it is available at
low cost and in large quantities.
[0057] Since the overall controller 5 performs control in the same
manner as in the second embodiment, the description thereof is not
repeated here. It should be noted, however, that during the
air-heating operation, the heat transfer liquid that has exchanged
heat with the hot water stored in the hot water storage tank 8
radiates heat in the heating radiator 3, that is, the heat of the
hot water is transferred to the heating radiator 3 by the heat
transfer liquid, and thereby air-heating is performed.
[0058] In the liquid circulation heating system 1C having such a
configuration, the temperature in the lower portion of the hot
water storage tank 8 can be kept low because of the water supplied
from the water inlet pipe 91. Therefore, the low-temperature water
can be supplied to the radiator 22, and thus the efficiency of the
heat pump 2 can be enhanced.
(First Modification)
[0059] In each of the above embodiments, a heat pump 2A as shown in
FIG. 6 also can be employed. In this heat pump 2A, when the
temperature of the water (incoming water temperature) supplied to
the radiator 22 is relatively high, the refrigerant to be fed to
the accumulator 27 from the evaporator 24 is heated.
[0060] Specifically, the heat pump circuit 20 includes a heat
exchanger (heater) 29 between the evaporator 24 and the accumulator
27, and a bypass passage 29A that bypasses the expansion valve 23
so as to pass through the heat exchanger 29. With this
configuration, the heat exchanger 29 exchanges heat between the
refrigerant flowing through the bypass passage 29A and the
refrigerant to be fed to the accumulator 27 from the evaporator 24.
The bypass passage 29 is provided with an open/close valve 29B on
the upstream side of the heat exchanger 29. The open/close valve
29B is connected to the heat pump controller 26, and usually is
closed by the heat pump controller 26.
[0061] When the temperature detected by the incoming water
temperature sensor 72 is higher than a predetermined temperature,
the heat pump controller 26 opens the open/close valve 29B. When
the open/close valve 29B is opened, the refrigerant that has been
evaporated in the evaporator 24 is heated further in the heat
exchanger 29, and the dryness of the refrigerant flowing into the
accumulator 27 increases. Thereby, the amount of the liquid
refrigerant remaining in the accumulator 27 decreases. As a result,
the composition ratio of the high boiling point refrigerant in the
refrigerant circulating through the heat pump circuit 20 increases,
which thereby suppresses the increase in the high pressure of the
refrigeration cycle.
[0062] That is, when the open/close valve 29B is opened, Point A
shifts to the right in the Mollier diagram of FIG. 2 and thus the
dryness increases. Thereby, the amount of the liquid refrigerant
remaining in the accumulator 27 decreases. As a result, the
composition ratio of the high boiling point refrigerant in the
refrigerant circulating through the heat pump circuit 20 increases,
which thereby suppresses the increase in the high pressure of the
refrigeration cycle.
[0063] It should be noted that the liquid refrigerant in the
accumulator 27 does not necessarily have to disappear completely.
When the amount of the liquid refrigerant in the accumulator 27
decreases to some extent, the heat pump controller 26 may stop
increasing the opening of the open/close valve 29B to maintain
it.
[0064] When the incoming water temperature is relatively high, it
is only desirable that the amount of the heating applied to the
refrigerant to be fed to the accumulator 27 from the evaporator 24
by the heat exchanger 29 increase. The open/close valve 29B does
not necessarily have to be closed completely in its initial
state.
[0065] In the first modification, the heat exchanger 29 is used as
the heater of the present invention, but the heater of the present
invention is not limited to the heat exchanger. For example, it may
be an electric heater, or the like. If the heat exchanger 29 and
the bypass passage 29A are provided as in the case of the first
modification, however, the refrigerant to be fed to the accumulator
27 from the evaporator 24 can be heated by utilizing the heat of
the refrigerant that has passed through the radiator 22.
(Second Modification)
[0066] In each of the above embodiments, a heat pump 2B as shown in
FIG. 7 also can be employed. In this heat pump 2B, a first
expansion valve 23A and a second expansion valve 23B are used as
the decompressor of the present invention. The refrigerant is
decompressed by the first expansion valve 23A after radiating heat
in the radiator 22, and further decompressed by the second
expansion valve 23B after being decompressed by the first expansion
valve 23A. A receiver 28 is provided between the first expansion
valve 23A and the second expansion valve 23B. This receiver 28
separates the refrigerant decompressed by the first expansion valve
23A into a gas refrigerant and a liquid refrigerant, and serves as
the vapor-liquid separator of the present invention.
[0067] When the temperature detected by the incoming water
temperature sensor 72 is higher than a predetermined temperature,
the heat pump controller 26 reduces the opening of the first
expansion valve 23A and increases the opening of the second
expansion valve 23B. When the opening of the first expansion valve
23A is reduced and the opening of the second expansion valve 23B is
increased, the refrigerant absorbs heat efficiently in the
evaporator 24 and the dryness of the refrigerant flowing into the
receiver 28 increases. Thereby, the amount of the liquid
refrigerant remaining in the receiver 28 decreases. As a result,
the composition ratio of the high boiling point refrigerant in the
refrigerant circulating through the heat pump circuit 20 increases,
which thereby suppresses the increase in the high pressure of the
refrigeration cycle.
[0068] It should be noted that the liquid refrigerant in the
receiver 28 does not necessarily have to disappear completely. When
the amount of the liquid refrigerant in the receiver 28 decreases
to some extent, the heat pump controller 26 may stop controlling
the openings of the first expansion valve 23A and the second
expansion valve 23B to maintain them.
(Other Modifications)
[0069] In each of the above embodiments and modifications, the heat
pump controller 26 serves as the controller of the present
invention. In the case where the incoming water temperature sensor
72 is connected to the overall controller 5, the heat pump
controller 26 and the overall controller 5 may serve as the
controller of the present invention.
[0070] As the decompressor of the present invention, an expander
for recovering power from the expanding refrigerant also can be
used.
[0071] Furthermore, it is also possible, by using fraction
separation, membrane separation, or the like, to increase the
composition ratio of the high boiling point refrigerant in the
refrigerant circulating through the heat pump circuit 20 when the
water supplied to the radiator 22 has a relatively high
temperature.
[0072] The invention may be embodied in other forms without
departing from the spirit or essential characteristics thereof. The
embodiments disclosed in this specification are to be considered in
all respects as illustrative and not limiting. The scope of the
invention is indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are intended to be
embraced therein.
* * * * *