U.S. patent application number 13/202605 was filed with the patent office on 2011-12-15 for heat pump system.
This patent application is currently assigned to DAIKIN EUROPE N.V.. Invention is credited to Masahiro Honda.
Application Number | 20110302947 13/202605 |
Document ID | / |
Family ID | 42665290 |
Filed Date | 2011-12-15 |
United States Patent
Application |
20110302947 |
Kind Code |
A1 |
Honda; Masahiro |
December 15, 2011 |
HEAT PUMP SYSTEM
Abstract
A heat pump system includes a refrigerant circuit, an inlet
temperature sensor measuring a heat exchanger inlet temperature of
an aqueous medium in a usage-side heat exchanger of the refrigerant
circuit, an outlet temperature sensor measuring a heat exchanger
outlet temperature of the aqueous medium in the usage-side heat
exchanger, a variable-capacity circulating pump circulating the
aqueous medium inside a hot-water circuit of a loop, and a
controller. The controller controls refrigerant-side circulation
rate in the refrigerant circuit to bring a temperature of the
aqueous medium at the outlet of the usage-side heat exchanger to a
targeted first target temperature, and operating capacity of the
circulating pump to bring a medium temperature differential of the
aqueous medium between the outlet and the inlet of the usage-side
heat exchanger to a targeted second target temperature
differential.
Inventors: |
Honda; Masahiro; (Oostende,
BE) |
Assignee: |
DAIKIN EUROPE N.V.
Oostende
BE
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
42665290 |
Appl. No.: |
13/202605 |
Filed: |
February 23, 2010 |
PCT Filed: |
February 23, 2010 |
PCT NO: |
PCT/JP2010/001185 |
371 Date: |
August 22, 2011 |
Current U.S.
Class: |
62/324.6 |
Current CPC
Class: |
F25B 2313/003 20130101;
F25B 2600/13 20130101; F24D 19/1012 20130101; F24D 3/18 20130101;
F25B 2313/0315 20130101; F25B 2313/02741 20130101; F25B 2700/21163
20130101; F25B 2700/1933 20130101; F25B 2700/21162 20130101; F25B
2700/2106 20130101; Y02B 30/70 20130101; F25B 2313/0314 20130101;
F25B 2339/047 20130101; Y02B 30/745 20130101; Y02B 30/12 20130101;
F25B 2700/1931 20130101; F24D 3/02 20130101; F24D 2200/12 20130101;
F25B 13/00 20130101; F25B 2700/2104 20130101 |
Class at
Publication: |
62/324.6 |
International
Class: |
F25B 30/00 20060101
F25B030/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2009 |
JP |
2009-040980 |
Claims
1. A heat pump system comprising: a refrigerant circuit including a
compressor, a usage-side heat exchanger arranged to carry out heat
exchange between a refrigerant and an aqueous medium, an expansion
valve, and a heat-source-side heat exchanger are connected in a
loop; an inlet temperature sensor arranged to measure a heat
exchanger inlet temperature of the aqueous medium in the usage-side
heat exchanger; an outlet temperature sensor arranged to measure a
heat exchanger outlet temperature of the aqueous medium in the
usage-side heat exchanger; a variable-capacity circulating pump
arranged to circulate the aqueous medium inside a hot-water circuit
of the loop; and a controller configured to control
refrigerant-side circulation rate in the refrigerant circuit to
bring a temperature of the aqueous medium at the outlet of the
usage-side heat exchanger to a targeted first target temperature,
and operating capacity of the circulating pump to bring a medium
temperature differential of the aqueous medium between the outlet
and the inlet of the usage-side heat exchanger to a targeted second
target temperature differential.
2. The heat pump system as recited in claim 1, wherein the
controller is further configured to control operating capacity of
the circulating pump by carrying out PI control such that the
medium temperature differential at a current point in time is
brought into approximation with the second target temperature
differential.
3. The heat pump system as recited in claim 1, wherein air-warming
of a target space is carried out using hot water produced by
condensing the refrigerant in the usage-side heat exchanger.
4. The heat pump system as recited in claim 3, wherein the
controller is further configured to carry out a control in which
operating capacity of the circulating pump is decreased in a case
where the medium temperature differential is smaller than the
second target temperature differential and the temperature of the
aqueous medium at the outlet of the usage-side heat exchanger is
equal to or greater than the first target temperature, and a
control in which operating capacity of the circulating pump is
increased in a case where the medium temperature differential is
greater than the second target temperature differential.
5. The heat pump system as recited in claim 4, further comprising:
an air-temperature-setting element configured to set an air
temperature of a target space for which air-warming is to be
carried out; and an air-temperature-detecting element configured to
detect the air temperature of the target space, in a case where an
air temperature differential between a detected air temperature
detected by the air-temperature-detecting element and a set air
temperature set by the air-temperature-setting element is greater
than a predetermined third target temperature differential, the
controller being further configured to change the second target
temperature differential in the direction of a smaller medium
temperature differential.
6. The heat pump system as recited in claim 2, wherein air-warming
of a target space is carried out using hot water produced by
condensing the refrigerant in the usage-side heat exchanger.
7. The heat pump system as recited in claim 6, wherein the
controller is further configured to carry out a control in which
operating capacity of the circulating pump is decreased in a case
where the medium temperature differential is smaller than the
second target temperature differential and the temperature of the
aqueous medium at the outlet of the usage-side heat exchanger is
equal to or greater than the first target temperature, and a
control in which operating capacity of the circulating pump is
increased in a case where the medium temperature differential is
greater than the second target temperature differential.
8. The heat pump system as recited in claim 7, further comprising:
an air-temperature-setting element configured to set an air
temperature of a target space for which air-warming is to be
carried out; and an air-temperature-detecting element configured to
detect the air temperature of the target space, in a case where an
air temperature differential between a detected air temperature
detected by the air-temperature-detecting element and a set air
temperature set by the air-temperature-setting element is greater
than a predetermined third target temperature differential, the
controller being further configured to change the second target
temperature differential in the direction of a smaller medium
temperature differential.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat pump system for
circulating an aqueous medium.
BACKGROUND ART
[0002] Hydronic heating devices of a heat pump type like that
disclosed in Patent Citation 1 (Japanese Laid-open Patent
Application 2003-314838) are known in the prior art. This hydronic
heating device is provided with an outdoor unit of a heat pump
type; a water/refrigerant heat exchanger for bringing about heat
exchange between a refrigerant and water; an air-warming floor
panel or air-warming heat exchanger connected to the
water/refrigerant heat exchanger by a hot-water tube; and a
circulating pump for circulating hot water through the hot-water
tube.
SUMMARY OF THE INVENTION
[0003] However, a problem with such conventional hydronic heating
devices of a heat pump type is that in a case of a decrease in load
on the air-warming floor panel or air-warming heat exchanger which
warms the room, the outlet/inlet temperature differential of the
water/refrigerant heat exchanger becomes smaller, resulting in an
excessive temperature rise of the water being supplied to the
air-warming floor panel or air-warming heat exchanger, possibly
leading to auto-shutoff or poor energy efficiency of the unit, as
well as to diminished comfort.
[0004] An object of the present invention is to provide a heat pump
system that can adapt to changes in operating load and provide
comfortable air conditioning.
[0005] The heat pump system according to a first aspect of the
present invention is provided with a refrigerant circuit, an inlet
temperature sensor for measuring a heat exchanger inlet temperature
of an aqueous medium in a usage-side heat exchanger; an outlet
temperature sensor for measuring a heat exchanger outlet
temperature of the aqueous medium in the usage-side heat exchanger;
a variable-capacity circulating pump for circulating the aqueous
medium inside a hot-water circuit of loop form; and controller. The
refrigerant circuit is a circuit in which a compressor, a
usage-side heat exchanger for carrying out heat exchange between
the refrigerant and the aqueous medium, an expansion valve, and a
heat-source-side heat exchanger are connected in loop form. The
controller controls a refrigerant-side circulation rate in the
refrigerant circuit to bring a temperature of the aqueous medium at
the outlet of the usage-side heat exchanger to a targeted first
target temperature, and controls an operating capacity of the
circulating pump to bring a medium temperature differential of the
aqueous medium between the outlet and the inlet of the usage-side
heat exchanger to a targeted second target temperature
differential.
[0006] Specifically, in this heat pump system, as a first control,
the refrigerant-side circulation rate in the refrigerant circuit is
controlled to bring the temperature of the aqueous medium at the
outlet of the usage-side heat exchanger to a targeted first target
temperature, controlling the water temperature at the outlet side
of the usage-side heat exchanger to maintain it at a predetermined
temperature. Also, as a second control, the operating capacity of
the circulating pump is controlled to bring the medium temperature
differential of the aqueous medium between the outlet and the inlet
of the usage-side heat exchanger to a targeted second target
temperature differential, controlling the outlet/inlet temperature
differential to a predetermined temperature differential. In so
doing, excessive temperature fluctuations of the aqueous medium can
be reliably prevented, even in cases of decreased load on the
usage-side heat exchanger.
[0007] The heat pump system according to a second aspect of the
present invention is the heat pump system according to the first
aspect wherein the controller controls the operating capacity of
the pump by carrying out PI control such that the medium
temperature differential at a current point in time is brought into
approximation with the second target temperature differential.
[0008] According to the aspect described above, because temperature
control can take place so as to bring the medium temperature
differential at a current point in time into approximation with the
second target temperature differential and eliminate deviation
therebetween through PI control, excessive temperature rise of the
aqueous medium can be reliably prevented.
[0009] The heat pump system according to a third aspect of the
present invention is the heat pump system according to the first or
second aspect wherein air-warming of a target space is carried out
using hot water produced by condensing the refrigerant in the
usage-side heat exchanger.
[0010] According to the aspect described above, by using hot water
produced by condensing the refrigerant in the usage-side heat
exchanger for air-warming of a target space, an excessive rise in
the temperature of the aqueous medium can be reliably prevented,
even in cases of decreased load on the usage-side heat exchanger in
association with higher room temperature in the target space.
[0011] The heat pump system according to a fourth aspect of the
present invention is the heat pump system according to the third
aspect wherein the controller carries out a control to decrease the
operating capacity of the pump in a case where the medium
temperature differential is smaller than the second target
temperature differential, and the temperature of the aqueous medium
at the outlet of the usage-side heat exchanger is equal to or
greater than the first target temperature, and carries out a
control to increase the operating capacity of the pump in a case
where the medium temperature differential is greater than the
second target temperature differential.
[0012] According to the aspect described above, control is carried
out to decrease the operating capacity of the pump in a case where
the medium temperature differential is smaller than the second
target temperature differential, and moreover the temperature of
the aqueous medium at the outlet of the usage-side heat exchanger
is equal to or greater than the first target temperature, while
control is carried out to increase the operating capacity of the
pump in a case where the medium temperature differential is greater
than the second target temperature differential; whereby in a case
where the medium temperature differential is smaller than the
second target temperature differential, and the temperature of the
aqueous medium at the outlet of the usage-side heat exchanger is
equal to or greater than the first target temperature, it can be
decided that the load on the usage-side heat exchanger has
decreased, and excessive temperature rise of the aqueous medium can
be reliably prevented.
[0013] The heat pump system according to a fifth aspect of the
present invention is the heat pump system according to the fourth
aspect, further comprising air-temperature-setting means for
setting an air temperature of a target space for which air-warming
is to be carried out; and air-temperature-detecting means for
detecting the air temperature. In a case where an air temperature
differential between a detected air temperature detected by the
air-temperature-detecting means and a set air temperature set by
the air-temperature-setting means is greater than a predetermined
third target temperature differential, the controller changes the
second target temperature differential in the direction of a
smaller medium temperature differential.
[0014] According to the aspect described above, because in a case
where an air temperature differential between a detected air
temperature detected by the air-temperature-detecting means and a
set air temperature set by the air-temperature-setting means is
greater than a predetermined third target temperature differential,
the second target temperature differential is modified in the
direction of a smaller medium temperature differential, flow rate
control of the aqueous medium can take place in coordination with
room temperature, and excessive temperature rise of the aqueous
medium can be more reliably prevented, even in cases of decreased
load on the usage-side heat exchanger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a circuit diagram of a heat pump system according
to an embodiment of the present invention.
[0016] FIG. 2 is a flowchart of flow rate control of an aqueous
medium by the heat pump system of FIG. 1.
[0017] FIG. 3 is a flowchart of coordinated control of room
temperature and flow rate of the aqueous medium by the heat pump
system of FIG. 1.
DESCRIPTION OF EMBODIMENTS
[0018] Next, an embodiment of the heat pump system of the present
invention is described with reference to the drawings.
Embodiment
Overall Configuration
[0019] FIG. 1 is a view showing the general configuration of a heat
pump system 1 according to an embodiment of the present invention.
A heat pump system 1 is a device capable of utilizing a vapor
compression type heat pump cycle to carry out an operation to heat
an aqueous medium.
[0020] The heat pump system 1 is primarily provided with a heat
source unit 2, a usage unit 4a, a liquid refrigerant communication
tube 13, a gas refrigerant communication tube 14, a hot-water
air-warming unit 9a, an aqueous medium communication tube 15a, and
an aqueous medium communication tube 16a. The heat source unit 2
and the usage unit 4a are connected via the refrigerant
communication tubes 13, 14, and thereby constitute a
heat-source-side refrigerant circuit 20, while the usage unit 4a
and the hot-water air-warming unit 9a are connected via the aqueous
medium communication tubes 15a, 16a, and thereby constitute an
aqueous medium circuit 80a. HFC-410A, which is a type of HFC-based
refrigerant, is enclosed in the heat-source-side refrigerant
circuit 20 as the heat-source-side refrigerant, while an ester-type
or ether-based refrigerant machine oil that is compatible with the
HFC-based refrigerant is enclosed in the heat-source-side
refrigerant circuit 20 for lubricating a heat-source-side
compressor 21 (discussed later). Water is circulated as an aqueous
medium through the aqueous medium circuit 80a.
[0021] In this heat pump system 1, the heat-source-side compressor
21, a usage-side heat exchanger 41a for carrying out heat exchange
between the refrigerant and the aqueous medium, expansion valves
25, 42a, and a heat-source-side heat exchanger 24 are connected in
a loop, thereby constituting the single heat-source-side
refrigerant circuit 20.
[0022] The heat pump system 1 of FIG. 1 is further provided with a
room temperature controller 202 furnished to a room R where the
hot-water air-warming unit 9a is disposed; an air temperature
sensor 203; a hot-water controller 204; and a controller 201 for
controlling operation of the heat pump system 1 on the basis of
signals from the room temperature controller 202, the air
temperature sensor 203, the hot-water controller 204, and various
other sensors (an aqueous medium inlet temperature sensor 51a, an
aqueous medium outlet temperature sensor 52a, and others).
[0023] On the heat source unit 2 side, the controller 201 primarily
controls operation of the heat-source-side compressor 21, a
heat-source-side expansion valve 25, and the like; and on the usage
unit 4a side, controls operation of a usage-side flow rate
adjustment valve 42a, a circulating pump 43a, and the like.
[0024] The room temperature controller 202 is a controller for
setting the room temperature of the room R to a desired
temperature, and is furnished to an existing remote control or the
like. The room temperature controller 202 transmits a temperature
setting signal to the controller 201.
[0025] The air temperature sensor 203 detects the room temperature
of the room R and transmits a signal indicating the detected room
temperature to the controller 201.
[0026] The hot-water controller 204 is a controller for measuring
the water temperature of hot water supplied to the hot-water
air-warming unit 9a, and setting the water to a predetermined
temperature setting. The hot-water controller 204 transmits a
signal indicating current water temperature and a signal indicating
the water temperature setting to the controller 201.
[0027] <Heat Source Unit>
[0028] The heat source unit 2 is installed outdoors, and is
connected to the usage unit 4a via the refrigerant communication
tubes 13, 14 to constitute part of the heat-source-side refrigerant
circuit 20.
[0029] The heat source unit 2 has primarily a heat-source-side
compressor 21, an oil separation mechanism 22, a heat-source-side
switching mechanism 23, a heat-source-side heat exchanger 24, a
heat-source-side expansion valve 25, an intake return tube 26, a
subcooler 27, a heat-source-side accumulator 28, a liquid-side
shutoff valve 29 and a gas-side shutoff valve 30.
[0030] The heat-source-side compressor 21 is a mechanism for
compressing the heat-source-side refrigerant. The heat-source-side
compressor 21 used herein is an airtight compressor in which a
rotary-type, scroll-type, or other positive-displacement
compression element (not shown) housed in a casing (not shown) is
driven by a heat-source-side compressor motor 21a which is also
housed in the casing. A high-pressure space (not shown) filled by
the heat-source-side refrigerant after compression in the
compression element is formed inside the casing of the
heat-source-side compressor 21, and refrigeration machine oil is
stored in the high-pressure space. The rotation speed (i.e., the
operating frequency) of the heat-source-side compressor motor 21a
can be varied by an inverter apparatus (not shown), and the
capacity of the heat-source-side compressor 21 can thereby be
controlled.
[0031] The oil separation mechanism 22 is a mechanism for
separating refrigeration machine oil included in the
heat-source-side refrigerant that is discharged from the
heat-source-side compressor 21 and returning the refrigeration
machine oil to the intake of the heat-source-side compressor. The
oil separation mechanism 22 has primarily an oil separator 22a
provided to a heat-source-side discharge tube 21b of the
heat-source-side compressor 21; and an oil return tube 22b for
connecting the oil separator 22a and a heat-source-side intake tube
21c of the heat-source-side compressor 21. The oil separator 22a is
a device for separating refrigeration machine oil included in the
heat-source-side refrigerant that is discharged from the
heat-source-side compressor 21. The oil return tube 22b has a
capillary tube, and is a refrigerant tube for returning the
refrigeration machine oil separated from the heat-source-side
refrigerant in the oil separator 22a to the heat-source-side intake
tube 21c of the heat-source-side compressor 21.
[0032] The heat-source-side switching mechanism 23 is a four-way
switching valve capable of switching between a heat-source-side
radiating operation state in which the heat-source-side heat
exchanger 24 functions as a radiator of the heat-source-side
refrigerant, and a heat-source-side evaporating operation state in
which the heat-source-side heat exchanger 24 functions as a
evaporator of the heat-source-side refrigerant. The
heat-source-side switching mechanism 23 is connected to the
heat-source-side discharge tube 21b, the heat-source-side intake
tube 21c, a first heat-source-side gas refrigerant tube 23a
connected to the gas side of the heat-source-side heat exchanger
24, and a second heat-source-side gas refrigerant tube 23b
connected to the gas-side shutoff valve 30. The heat-source-side
switching mechanism 23 is capable of switching for communicating
the heat-source-side discharge tube 21b with the first
heat-source-side gas refrigerant tube 23a, and communicating the
second heat-source-side gas refrigerant tube 23b with the
heat-source-side intake tube 21c (this switching corresponding to
the heat-source-side radiating operation state, indicated by solid
lines in the heat-source-side switching mechanism 23 in FIG. 1).
The heat-source-side switching mechanism 23 is also capable of
switching for communicating the heat-source-side discharge tube 21b
with the second heat-source-side gas refrigerant tube 23b, and
communicating the first heat-source-side gas refrigerant tube 23a
with the heat-source-side intake tube 21c (this switching
corresponding to the heat-source-side evaporating operation state,
indicated by dashed lines in the heat-source-side switching
mechanism 23 in FIG. 1). The heat-source-side switching mechanism
23 is not limited to a four-way switching valve, and may configured
so as to have a function for switching the same directions of
heat-source-side refrigerant flow as those described above, through
the use of a combination of a plurality of solenoid valves or the
like, for example.
[0033] The heat-source-side heat exchanger 24 is a heat exchanger
for functioning as a radiator or evaporator of the heat-source-side
refrigerant by exchanging heat between the heat-source-side
refrigerant and outdoor air. A heat-source-side liquid refrigerant
tube 24a is connected to the liquid side of the heat-source-side
heat exchanger 24, and the first heat-source-side gas refrigerant
tube 23a is connected to the gas side thereof. The outdoor air for
heat exchange with the heat-source-side refrigerant in the
heat-source-side heat exchanger 24 is fed by a heat-source-side fan
32 which is driven by a heat-source-side fan motor 32a.
[0034] The heat-source-side expansion valve 25 is an electrical
expansion valve for performing such functions as depressurizing the
heat-source-side refrigerant flowing through the heat-source-side
heat exchanger 24, and is provided to the heat-source-side liquid
refrigerant tube 24a.
[0035] The intake return tube 26 is a refrigerant tube for
diverting a portion of the heat-source-side refrigerant flowing
through the heat-source-side liquid refrigerant tube 24a and
returning the diverted refrigerant to the intake of the
heat-source-side compressor 21, and in the present embodiment, one
end of the intake return tube 26 is connected to the
heat-source-side liquid refrigerant tube 24a, and the other end is
connected to the heat-source-side intake tube 21c. An intake return
expansion valve 26a, the opening degree of which can be controlled,
is provided to the intake return tube 26. The intake return
expansion valve 26a is composed of an electrical expansion
valve.
[0036] The subcooler 27 is a heat exchanger for exchanging heat
between the heat-source-side refrigerant flowing through the
heat-source-side liquid refrigerant tube 24a and the
heat-source-side refrigerant flowing through the intake return tube
26 (more specifically, the heat-source-side refrigerant that has
been depressurized by the intake return expansion valve 26a).
[0037] The heat-source-side accumulator 28 is provided to the
heat-source-side intake tube 21c, and is a container for
temporarily storing the heat-source-side refrigerant circulated
through the heat-source-side refrigerant circuit 20 before the
heat-source-side refrigerant is drawn into the heat-source-side
compressor 21 from the heat-source-side intake tube 21c.
[0038] The liquid-side shutoff valve 29 is a valve provided at the
connection between the heat-source-side liquid refrigerant tube 24a
and the liquid refrigerant communication tube 13. The gas-side
shutoff valve 30 is a valve provided at the connection between the
second heat-source-side gas refrigerant tube 23b and the gas
refrigerant communication tube 14.
[0039] Various sensors are provided to the heat source unit 2.
Specifically, the heat source unit 2 is provided with a
heat-source-side intake pressure sensor 33 for detecting a
heat-source-side intake pressure Ps1, which is the pressure of the
heat-source-side refrigerant in the intake of the heat-source-side
compressor 21; a heat-source-side discharge pressure sensor 34 for
detecting a heat-source-side discharge pressure Pd1, which is the
pressure of the heat-source-side refrigerant in the discharge of
the heat-source-side compressor 21; a heat-source-side heat
exchange temperature sensor 35 for detecting a heat-source-side
heat exchanger temperature Thx, which is the temperature of the
heat-source-side refrigerant in the liquid side of the
heat-source-side heat exchanger 24; and an outdoor air temperature
sensor 36 for detecting an outdoor air temperature To.
[0040] --Liquid Refrigerant Communication Tube--
[0041] The liquid refrigerant communication tube 13 is connected to
the heat-source-side liquid refrigerant tube 24a via the
liquid-side shutoff valve 29, and the liquid refrigerant
communication tube 13 is a refrigerant tube capable of directing
the heat-source-side refrigerant to the outside of the heat source
unit 2 from the outlet of the heat-source-side heat exchanger 24
which functions as a radiator of the heat-source-side refrigerant
when the heat-source-side switching mechanism 23 is in the
heat-source-side radiating operation state. The liquid refrigerant
communication tube 13 is also a refrigerant tube capable of
introducing the heat-source-side refrigerant from outside the heat
source unit 2 into the inlet of the heat-source-side heat exchanger
24 which functions as an evaporator of the heat-source-side
refrigerant when the heat-source-side switching mechanism 23 is in
the heat-source-side evaporating operation state.
[0042] --Gas Refrigerant Communication Tube--
[0043] The gas refrigerant communication tube 14 is connected to
the second heat-source-side gas refrigerant tube 23b via the
gas-side shutoff valve 30. The gas refrigerant communication tube
14 is a refrigerant tube capable of introducing the
heat-source-side refrigerant into the intake of the
heat-source-side compressor 21 from outside the heat source unit 2
when the heat-source-side switching mechanism 23 is in the
heat-source-side radiating operation state. The gas refrigerant
communication tube 14 is also a refrigerant tube capable of
directing the heat-source-side refrigerant to the outside of the
heat source unit 2 from the discharge of the heat-source-side
compressor 21 when the heat-source-side switching mechanism 23 is
in the heat-source-side evaporating operation state.
[0044] <Usage Unit>
[0045] The usage unit 4a is installed indoors, and is connected to
the heat source unit 2 via the refrigerant communication tubes 13,
14 to constitute a part of the heat-source-side refrigerant circuit
20. The usage unit 4a is also connected to the hot-water
air-warming unit 9a via the aqueous medium communication tubes 15a,
16a, and constitutes a part of the aqueous medium circuit 80a.
[0046] The usage unit 4a primarily has the usage-side heat
exchanger 41a, the usage-side flow rate adjustment valve 42a, and
the circulating pump 43a.
[0047] The usage-side heat exchanger 41a is a heat exchanger that
functions as a radiator for the heat-source-side refrigerant by
carrying out heat exchange between the heat-source-side refrigerant
and the aqueous medium. A usage-side liquid refrigerant tube 45a is
connected to the liquid side of the flow path along which the
heat-source-side refrigerant flows, while a usage-side gas
refrigerant tube 54a is connected to the gas side of the flow path
along which the heat-source-side refrigerant flows. A usage-side
water inlet tube 47a is connected to the inlet side of the flow
path along which the aqueous medium flows, and a usage-side water
outlet tube 48a is connected to the outlet side of the flow path
along which the aqueous medium flows. The liquid refrigerant
communication tube 13 is connected to the usage-side liquid
refrigerant tube 45a, the gas refrigerant communication tube 14 is
connected to the usage-side gas refrigerant tube 54a, the aqueous
medium communication tube 15a is connected to the usage-side water
inlet tube 47a, and the aqueous medium communication tube 16a is
connected to the usage-side water outlet tube 48a.
[0048] The usage-side flow rate adjustment valve 42a is an
electrical expansion valve whereby the flow rate of
heat-source-side refrigerant flowing through the usage-side heat
exchanger 41a can be varied by controlling the opening degree of
the usage-side flow rate adjustment valve 42a, and the usage-side
flow rate adjustment valve 42a is provided to the usage-side liquid
refrigerant tube 45a.
[0049] The circulation pump 43a is a mechanism for pressurizing the
aqueous medium, and the circulation pump 43a used herein is a pump
in which a centrifugal and/or positive-displacement pump element
(not shown) is driven by a circulation pump motor 44a. The
circulation pump 43a is provided to the usage-side water outlet
tube 48a. The rotation speed (i.e., the operating frequency) of the
circulation pump motor 44a can be varied by an inverter apparatus
(not shown), and the capacity of the circulation pump 43a can
thereby be controlled.
[0050] The usage unit 4a is thereby configured so that a hot-water
supply operation can be performed in which the usage-side heat
exchanger 41a is caused to function as a radiator of the
heat-source-side refrigerant introduced from the gas refrigerant
communication tube 14, whereby the heat-source-side refrigerant
radiated in the usage-side heat exchanger 41a is directed to the
liquid refrigerant communication tube 13, and the aqueous medium is
heated by radiation of the heat-source-side refrigerant in the
usage-side heat exchanger 41a.
[0051] Various sensors are provided to the usage unit 4a.
Specifically, the usage unit 4a is provided with a usage-side heat
exchange temperature sensor 50a for detecting a usage-side
refrigerant temperature Tsc1, which is the temperature of the
heat-source-side refrigerant in the liquid side of the usage-side
heat exchanger 41a; an aqueous medium inlet temperature sensor 51a
for detecting an aqueous medium inlet temperature Twr, which is the
temperature of the aqueous medium in the inlet of the usage-side
heat exchanger 41a; and an aqueous medium outlet temperature sensor
52a for detecting an aqueous medium outlet temperature Twl, which
is the temperature of the aqueous medium in the outlet of the
usage-side heat exchanger 41a.
[0052] --Hot-Water Air-Warming Unit--
[0053] The Hot-Water Air-Warming Unit 9a is Installed Indoors, is
Connected to the First Usage unit 4a via the aqueous medium
communication tubes 15a, 16a, and constitutes a portion of the
aqueous medium circuit 80a.
[0054] The hot-water air-warming unit 9a has primarily a heat
exchange panel 91a, and is composed of a radiator and/or a floor
heating panel and other components.
[0055] The heat exchange panel 91a is provided alongside a wall or
elsewhere indoors when configured as a radiator, and is provided
under the floor or elsewhere indoors when configured as a floor
heating panel. The heat exchange panel 91a is a heat exchanger for
functioning as a radiator or heater of the aqueous medium
circulated through the aqueous medium circuit 80a, and the aqueous
medium communication tube 16a is connected to the inlet of the heat
exchange panel 91a, and the aqueous medium communication tube 15a
is connected to the outlet of the heat exchange panel 91a.
[0056] <Aqueous Medium Communication Tubes>
[0057] The aqueous medium communication tube 15a is connected to
the outlet of a heat exchange panel 91a of the hot-water
air-warming unit 9a. The aqueous medium communication tube 16a is
connected to the inlet of the heat exchange panel 91a of the
hot-water air-warming unit 9a.
[0058] It is also possible for a hot-water storage unit to be
connected to the aqueous medium communication tubes 15a, 16a, in
parallel with the hot-water air-warming unit 9a.
[0059] <Hot-Water Air-Warming Operation>
[0060] Next, the hot-water air-warming operation of the heat pump
system 1 is described.
[0061] In a case where the hot-water air-warming operation of the
usage unit 4a is to be carried out, in the heat-source-side
refrigerant circuit 20, a heat-source-side switching mechanism 23
switches to an evaporation operation state (the state of the
heat-source-side switching mechanism 23 depicted by broken lines in
FIG. 1), and an intake return expansion valve 26a goes to a closed
state.
[0062] In such a state, in the heat-source-side refrigerant circuit
20, the heat-source-side refrigerant, currently at low pressure in
the refrigeration cycle, is drawn into the heat-source-side
compressor 21 through a heat-source-side intake tube 21c, where it
is compressed to high pressure in the refrigeration cycle, and
thereafter discharged to a heat-source-side discharge tube 21b. The
high-pressure heat-source-side refrigerant which has been
discharged into the heat-source-side discharge tube 21b undergoes
separation of the refrigerant machine oil in an oil separator 22a.
The refrigerant machine oil that was separated from the
heat-source-side refrigerant in the oil separator 22a is returned
to the heat-source-side intake tube 21c through an oil return tube
22b. Through the second heat-source-side gas refrigerant tube 23b
and the gas-side shutoff valve 30, the high-pressure
heat-source-side refrigerant from which the refrigerant machine oil
was separated is fed from the heat source unit 2 to the refrigerant
communication tube 14.
[0063] The high-pressure heat-source-side refrigerant fed to the
refrigerant communication tube 14 is then fed to the usage unit 4a.
The high-pressure heat-source-side refrigerant fed to the usage
unit 4a is then fed to the usage-side heat exchanger 41a. In the
usage-side heat exchanger 41a, the high-pressure heat-source-side
refrigerant fed to the usage-side heat exchanger 41a radiates heat
through heat exchange with the aqueous medium circulated through
the aqueous medium circuit 80a by the circulating pump 43a. Through
the usage-side flow rate adjustment valve 42a and the usage-side
liquid refrigerant tube 45a, the high-pressure heat-source-side
refrigerant that has radiated its heat in the usage-side heat
exchanger 41a is fed from the usage unit 4a to the liquid
refrigerant communication tube 13.
[0064] The heat-source-side refrigerant fed to the liquid
refrigerant communication tube 13 is fed to the heat source unit 2.
The heat-source-side refrigerant fed to the heat source unit 2 is
fed to a subcooler 27 through the liquid-side shutoff valve 29.
Because the heat-source-side refrigerant is not flowing in the
intake return tube 26, the heat-source-side refrigerant fed to the
subcooler 27 is fed to the heat-source-side expansion valve 25,
without having undergone heat exchange. The heat-source-side
refrigerant fed to the heat-source-side expansion valve 25 is
depressurized in the heat-source-side expansion valve 25 and
assumes a low-pressure, gas-liquid two-phase state, and is fed to
the heat-source-side heat exchanger 24 through the heat-source-side
liquid refrigerant tube 24a. In the heat-source-side heat exchanger
24, the low-pressure refrigerant fed to the heat-source-side heat
exchanger 24 undergoes heat exchange with outdoor air supplied by a
heat-source-side fan 32 and evaporates. The low-pressure
heat-source-side refrigerant having evaporated in the
heat-source-side heat exchanger 24 is fed to a heat-source-side
accumulator 28 through a first heat-source-side gas refrigerant
tube 23a and the heat-source-side switching mechanism 23. The
low-pressure heat-source-side refrigerant fed to the
heat-source-side accumulator 28 is again drawn into the
heat-source-side compressor 21 through the heat-source-side intake
tube 21c.
[0065] Meanwhile, in the aqueous medium circuit 80a, the aqueous
medium circulating through the aqueous medium circuit 80a is heated
by heat radiated from the heat-source-side refrigerant in the
usage-side heat exchanger 41a. The aqueous medium heated in the
usage-side heat exchanger 41a is drawn into the circulating pump
43a through the usage-side water outlet tube 48a; and, after being
pressurized, is fed from the usage unit 4a to the aqueous medium
communication tube 16a. The aqueous medium fed to the aqueous
medium communication tube 16a is fed to the hot-water air-warming
unit 9a.
[0066] The aqueous medium fed to the hot-water air-warming unit 9a
radiates heat in the heat exchange panel 91a, and thereby heats
indoor walls and the like, or indoor floors.
[0067] <Flow Rate Control of Aqueous Medium Circulating in
Aqueous Medium Circuit>
[0068] Flow rate control of the aqueous medium circulating through
the aqueous medium circuit 80a in the above-described hot-water
air-warming operation will be described referring to the flowcharts
of FIGS. 2 and 3.
[0069] In the heat pump system 1 of the present embodiment, first,
the controller 201 changes the operating frequency of the
compressor 21 to control the refrigerant circulation rate such that
the aqueous medium outlet temperature Twl at the outlet of the
usage-side heat exchanger 41a reaches a targeted first target
temperature Twls. Control of the refrigerant circulation rate is
carried out in parallel even during the following flow rate control
of the aqueous medium.
[0070] In association therewith, the controller 201 controls the
operating capacity of the circulating pump 43a to bring an
outlet/inlet temperature differential .DELTA.Tw (=Twl-Twr) of the
aqueous medium between the outlet and the inlet of the usage-side
heat exchanger 41a to a target aqueous medium outlet/inlet
temperature differential .DELTA.Tws which is a targeted second
target temperature differential.
[0071] Specifically, in Step S1 of FIG. 2, first, the rotating
speed R (i.e., the operating frequency) of the circulating pump
motor 44a is set to an initial value R0. Next, in Step S2, while
the rotating speed R of the circulating pump motor 44a is kept at
R0, the controller 201 controls the circulating pump 43a to operate
for a fixed duration.
[0072] Next, in Step S3, the controller 201 assesses whether the
outlet/inlet temperature differential .DELTA.Tw of the aqueous
medium at the outlet and the inlet of the usage-side heat exchanger
41a is greater than the target aqueous medium outlet/inlet
temperature differential .DELTA.Tws.
[0073] In a case where a state in which the aqueous medium
outlet/inlet temperature differential .DELTA.Tw is greater than the
target aqueous medium outlet/inlet temperature differential
.DELTA.Tws is maintained for a predetermined duration (YES in Step
S3), the flow rate of the aqueous medium circulating through the
aqueous medium circuit 80a is assessed as being low, and a control
is carried out to increase the operating capacity of the
circulating pump 43a by increasing the rotating speed
(specifically, the operating frequency) of the circulating pump
motor 44a (Steps S4-5). In the present embodiment, the controller
201 controls the operating capacity of the circulating pump 43a by
carrying out PI control to bring the outlet/inlet temperature
differential .DELTA.Tw at the current point in time into
approximation with the target aqueous medium outlet/inlet
temperature differential .DELTA.Tws.
[0074] Here, PI control refers to so-called proportional-integral
control, the input-output relationship of which is typically
depicted by Expression (1) below.
u(t)=kp{e(t).+-.(1/Ti).intg.e(t)dt} Expression (1)
Here,
[0075] u(t): a function of a manipulated variable with respect to
time t
[0076] kp: proportional gain
[0077] e(t): a function of deviation with respect to time t
[0078] Ti: integration time
[0079] An advantage of PI control is that deviation (error) does
not arise even if there are modifications of the target value or
steady disturbances.
[0080] Based on the aforedescribed basic expression (1) of PI
control, PI control is carried out to bring deviation EF
(=.DELTA.Tws-.DELTA.Tw) between the target temperature differential
.DELTA.Tws and the usage-side heat exchanger outlet/inlet
temperature differential .DELTA.Tw to zero. In this case, a value a
which is a correction value for the rotation speed R of the
circulating pump motor 44 is given by the following Expression
(2).
.alpha.=.alpha.#+Kc.times.{(EF-EF#)+Kic.times.(EF+EF#).DELTA.tc/2Tic}
Expression (2)
[0081] .alpha.#: previous .alpha.
[0082] EF: current deviation
[0083] EF#: previous deviation
[0084] Kc, Kic: gain
[0085] .DELTA.tc: sampling time
[0086] Tic: integration constant
[0087] Specifically, in Step S4, the controller 201 calculates a on
the basis of the above Expression (2).
[0088] Next, in Step S5, the controller 201 corrects the rotating
speed R of the circulating pump motor 44a to a rotating speed equal
to the current rotating speed plus a, and controls the operating
capacity of the circulating pump 43a. Thereafter, the process flow
returns to Step S2.
[0089] On the other hand, in a case where the aqueous medium
outlet/inlet temperature differential .DELTA.Tw is less than the
target aqueous medium outlet/inlet temperature differential
.DELTA.Tws (NO in Step S3), and the aqueous medium outlet
temperature Twl is equal to or greater than the targeted first
target temperature Twls (YES in Step S6), the flow rate of the
aqueous medium circulating through the aqueous medium circuit 80a
is assessed as being high, and PI control analogous to that
discussed above is carried out to decrease the operating capacity
of the circulating pump 43a by decreasing the rotating speed
(specifically, the operating frequency) of the circulating pump
motor 44a (Steps S7-8).
[0090] Specifically, in Step S7, the controller 201 calculates a on
the basis of the above Expression (2).
[0091] Next, in Step S8, the controller 201 corrects the rotating
speed R of the circulating pump motor 44a to a rotating speed equal
to the current rotating speed minus a, and controls the operating
capacity of the circulating pump 43a. Thereafter, the process flow
returns to Step S2.
[0092] Through flow rate control of the aqueous medium in the above
manner, it is possible to appropriately control the flow rate of
the aqueous medium circulating through the aqueous medium circuit
80a. The target aqueous medium outlet/inlet temperature
differential .DELTA.Tws is set with consideration to the design
parameter for heat exchange capability of the usage-side heat
exchanger 41a, and the like.
[0093] (Coordinated Control of Room Temperature and Flow Rate of
Aqueous Medium)
[0094] In a case where an air temperature differential .DELTA.Ta
(=Ts-Td) between a detected air temperature Td, which is the room
temperature inside the room R detected by the air temperature
sensor 203, and a set air temperature Ts that has been set by the
room temperature controller 202, is greater than a predetermined
third target temperature differential .DELTA.Tcs, the controller
201 carries out control to change the target aqueous medium
outlet/inlet temperature differential .DELTA.Tws in the direction
of a smaller aqueous medium outlet/inlet temperature differential
.DELTA.Tw.
[0095] Specifically, as depicted in the flowchart of FIG. 3, first,
in Step S31, the controller 201 sets the target aqueous medium
outlet/inlet temperature differential .DELTA.Tws to an initial
value T0.
[0096] Next, in Step S32, the controller 201 assesses whether the
air temperature differential .DELTA.Ta between the detected air
temperature Td and the set air temperature Ts that has been set by
the room temperature controller 202 is greater than the
predetermined third target temperature differential .DELTA.Tcs.
[0097] In a case where a state in which .DELTA.Ta is greater than
.DELTA.Tcs is maintained for a predetermined duration (YES in Step
S32), in Step S33, the controller 201 performs operation control in
the direction of a smaller aqueous medium outlet/inlet temperature
differential .DELTA.Tw by setting a new target aqueous medium
outlet/inlet temperature differential .DELTA.Tws that is equal to
the previous target aqueous medium outlet/inlet temperature
differential .DELTA.Tws minus a predetermined correction value
T.delta., and more specifically, controls the operating capacity of
the circulating pump 43a in the direction of an increased
circulation rate of the aqueous medium.
[0098] On the other hand, in a case where a state in which
.DELTA.Ta is greater than .DELTA.Tcs is not maintained for a
predetermined duration (NO in Step S32), the target aqueous medium
outlet/inlet temperature differential .DELTA.Tws is set to the
initial value T0.
[0099] Through flow rate control of the aqueous medium in
coordination with room temperature in this way, even if there has
been a decrease in load on the hot-water air-warming unit 9a or
other air-warming heat exchanger, excessive temperature rise of the
aqueous medium can be reliably prevented.
Features of the Present Embodiment
(1)
[0100] In the heat pump system 1 of the present embodiment, two
controls are carried out in parallel. As a first control, the
refrigerant-side circulation rate in the heat-source-side
refrigerant circuit 20 is controlled such that the temperature Twl
of the aqueous medium at the outlet of the usage-side heat
exchanger 41a is brought to the targeted first target temperature
Twls, controlling the water temperature at the outlet side of the
usage-side heat exchanger 41a so as to maintain it at a
predetermined temperature. In association therewith, as a second
control, the operating capacity of the circulating pump 43a is
controlled such that the medium temperature differential .DELTA.Tw
of the aqueous medium at the outlet and the inlet of the usage-side
heat exchanger 41a is brought to a targeted second target
temperature differential .DELTA.Tws, automatically controlling the
temperature differential between the outlet and the inlet, which in
a conventional heat pump system is fixed by manual adjustment
during installation and the like, to a predetermined temperature
differential. Because of this, even if there is a decline in the
load on the usage-side heat exchanger 41a, excessive temperature
fluctuations of the aqueous medium can be reliably prevented.
(2)
[0101] Consequently, even if there is a decline in the load on the
usage side, through PI control whereby the medium temperature
differential .DELTA.Tw, which is the temperature differential
between the outlet and the inlet of the usage-side heat exchanger
41a, is increased towards the second target temperature
differential .DELTA.Tws, the temperature can be prevented from
rising above the design temperature of intermediate hot-water
equipment of usage-side machinery such as the hot-water air-warming
unit 9a, and overheating or auto-shutoff of machinery can be
prevented. As a result, energy efficiency can be improved, and
comfort can be improved as well. Further, because water flow
adjustment of the circulating pump 43a is carried out
automatically, management and adjustment of the hot-water flow rate
is easy.
(3)
[0102] Also, in the heat pump system 1 of the present embodiment,
the controller 201 controls the operating capacity of the
circulating pump 43a by carrying out PI control so as to bring the
outlet/inlet temperature differential .DELTA.Tw at the current
point in time into approximation with the target aqueous medium
outlet/inlet temperature differential .DELTA.Tws.
[0103] Consequently, in the heat pump system 1 of the present
embodiment, through PI control as described above, temperature
control can take place such that deviation between the outlet/inlet
temperature differential .DELTA.Tw at the current point in time and
the target aqueous medium outlet/inlet temperature differential
.DELTA.Tws is eliminated, whereby excessive temperature rise of the
aqueous medium can be reliably prevented.
(4)
[0104] Further, in the heat pump system 1 of the present
embodiment, air-warming of the room R is carried out using hot
water produced by condensing the refrigerant in the usage-side heat
exchanger 41a. Because of this, even if the load on the usage-side
heat exchanger 41a has decreased due to a rise in room temperature
of the room R, excessive temperature rise of the aqueous medium can
be reliably prevented.
(5)
[0105] In the heat pump system 1 of the present embodiment, in a
case where the outlet/inlet temperature differential .DELTA.Tw is
less than the target aqueous medium outlet/inlet temperature
differential .DELTA.Tws, and the temperature Twl of the aqueous
medium at the outlet of the usage-side heat exchanger 41a is equal
to or greater than the targeted first target temperature Twls, the
controller 201 carries out control to decrease the operating
capacity of the circulating pump 43a; or if the outlet/inlet
temperature differential .DELTA.Tw is greater than the target
aqueous medium outlet/inlet temperature differential .DELTA.Tws,
carries out control to increase the operating capacity of the
circulating pump 43a.
[0106] Therefore, in a case where the outlet/inlet temperature
differential .DELTA.Tw is less than the target aqueous medium
outlet/inlet temperature differential .DELTA.Tws, and the
temperature Twl of the aqueous medium at the outlet of the
usage-side heat exchanger 41a is equal to or greater than the
targeted first target temperature Twls, it can be decided that the
load on the usage-side heat exchanger 41a has decreased, and
excessive temperature rise of the aqueous medium can be more
reliably prevented.
(6)
[0107] In the heat pump system 1 of the present embodiment, in a
case where the differential .DELTA.Ta (=Ts-Td) between the detected
air temperature Td detected by the air temperature sensor 203, and
the set air temperature Ts set by the room temperature controller
202, is greater than the predetermined third target temperature
differential .DELTA.Tcs, the controller 201 changes the target
aqueous medium outlet/inlet temperature differential .DELTA.Tws in
the direction of a smaller outlet/inlet temperature differential
.DELTA.Tw.
[0108] Through flow rate control of the aqueous medium in
coordination with room temperature, when the load on the usage-side
heat exchanger 41a has decreased due to the room temperature
becoming sufficiently higher than the set temperature, control is
thus carried out to change the target aqueous medium outlet/inlet
temperature differential .DELTA.Tws in the direction of a smaller
outlet/inlet temperature differential .DELTA.Tw, increasing the
operating capacity of the circulating pump 43a, whereby excessive
temperature rise of the aqueous medium can be more reliably
prevented.
[0109] Consequently, in a case where, e.g., the capability is
insufficient during warming up of the heat pump system 1, by
automatically modifying the target aqueous medium outlet/inlet
temperature differential .DELTA.Tws, it is possible to modify the
operating capacity of the circulating pump 43a. Consequently, the
need to modify the set air temperature Ts using the room
temperature controller 202 is eliminated.
Modified Examples
(A)
[0110] In the aforedescribed embodiment, in order to aid in
understanding of the invention, an example of a single usage unit
4a furnished on the usage side was depicted as one example of the
heat pump system 1 of the present invention, but the present
invention is not limited thereto, and it is possible for another
usage unit (an indoor air conditioning unit or the like) to be
connected in parallel with the usage unit 4a to the liquid
refrigerant communication tube 13 and the gas refrigerant
communication tube 14. In this case as well, by carrying out the
operation control of the aforedescribed embodiment, excessive
temperature rise of the aqueous medium can be reliably prevented,
even in a case of a decrease in load on the usage-side heat
exchanger 41a.
(B)
[0111] Further, in the heat pump system 1 of the aforedescribed
embodiment, the usage unit 4a is one in which direct heat exchange
is carried out between the refrigerant of the heat-source-side
refrigerant circuit 20 and the water of the aqueous medium circuit
80a by the usage-side heat exchanger 41a; however, the present
invention is not limited thereto, and may instead be configured as
a cascade-type heat pump system with a separate refrigerant circuit
intervening between the heat-source-side refrigerant circuit 20 and
the aqueous medium circuit 80a. In this case as well, by carrying
out the operation control of the aforedescribed embodiment,
excessive temperature rise of the aqueous medium can be reliably
prevented, even in a case of a decrease in load on the usage-side
heat exchanger 41a.
(C)
[0112] Also, in the heat pump system 1 of the aforedescribed
embodiment, a heat pump system for carrying out hot-water floor
air-warming was described by way of example, but the present
invention is not limited thereto. Specifically, the
heat-source-side switching mechanism 23 in the heat pump system 1
may be switched to reverse the flow of the refrigerant in the
heat-source-side refrigerant circuit 20, and air-cooling of the
room R may be carried out using the cold water generated by
evaporation of the refrigerant in the usage-side heat exchanger
41a. In this case, by carrying out the aforedescribed operation
control, excessive temperature drop of the aqueous medium can be
reliably prevented, even in a case of a decrease in load on the
usage-side heat exchanger 41a.
INDUSTRIAL APPLICABILITY
[0113] Various applications of the present invention in heat pump
systems for circulating aqueous media are possible.
REFERENCE SIGNS LIST
[0114] 1 Heat pump system [0115] 2 Heat source unit [0116] 4a Usage
unit [0117] 12 Discharge refrigerant communication tube [0118] 13
Liquid refrigerant communication tube [0119] 14 Gas refrigerant
communication tube [0120] 20 Heat-source-side refrigerant circuit
[0121] 21 Heat-source-side compressor [0122] 23 Heat-source-side
switching mechanism [0123] 24 Heat-source-side heat exchanger
[0124] 41a Usage-side heat exchanger [0125] 42a Usage-side flow
rate adjustment valve [0126] 43a Circulating pump [0127] 80a
Aqueous medium circuit [0128] 201 Controller [0129] 202 Room
temperature controller [0130] 203 Air temperature sensor [0131] 204
Hot-water controller
CITATION LIST
Patent Literature
[0131] [0132] <Patent Document 1> Japanese Laid-open Patent
Application 2003-314838
* * * * *