U.S. patent application number 14/442420 was filed with the patent office on 2015-11-19 for air-conditioning apparatus.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. The applicant listed for this patent is Takayoshi HONDA, Osamu MORIMOTO, Yuji MOTOMURA, Daisuke SHIMAMOTO. Invention is credited to Takayoshi HONDA, Osamu MORIMOTO, Yuji MOTOMURA, Daisuke SHIMAMOTO.
Application Number | 20150330673 14/442420 |
Document ID | / |
Family ID | 50933896 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150330673 |
Kind Code |
A1 |
HONDA; Takayoshi ; et
al. |
November 19, 2015 |
AIR-CONDITIONING APPARATUS
Abstract
All of pumps are in operation for a predetermined period of time
in an air-conditioning apparatus and, after that, the number of
pumps in operation is changed depending on an operation capacity
for indoor units each including a use side heat exchanger.
Inventors: |
HONDA; Takayoshi; (Tokyo,
JP) ; MOTOMURA; Yuji; (Tokyo, JP) ; SHIMAMOTO;
Daisuke; (Tokyo, JP) ; MORIMOTO; Osamu;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONDA; Takayoshi
MOTOMURA; Yuji
SHIMAMOTO; Daisuke
MORIMOTO; Osamu |
Tokyo
Tokyo
Tokyo
Tokyo |
|
JP
JP
JP
JP |
|
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
50933896 |
Appl. No.: |
14/442420 |
Filed: |
December 12, 2012 |
PCT Filed: |
December 12, 2012 |
PCT NO: |
PCT/JP2012/082128 |
371 Date: |
May 13, 2015 |
Current U.S.
Class: |
62/324.1 |
Current CPC
Class: |
F25B 2313/0231 20130101;
F24F 3/065 20130101; F25B 25/005 20130101; F25B 13/00 20130101;
F25B 2313/0312 20130101; Y02B 30/745 20130101; Y02B 30/70 20130101;
F25B 49/02 20130101; F25B 2313/0314 20130101; F25B 2600/13
20130101; F25B 2313/0233 20130101; F25B 2313/003 20130101 |
International
Class: |
F25B 13/00 20060101
F25B013/00 |
Claims
1. An air-conditioning apparatus comprising: at least one
intermediate heat exchanger that exchanges heat between heat source
side refrigerant and a heat medium different from the heat source
side refrigerant; a refrigeration cycle including a compressor, a
heat source side heat exchanger, at least one expansion valve, and
a refrigerant passage of the intermediate heat exchanger connected
by pipe through which the heat source side refrigerant flows; and a
heat medium circuit including a heat medium passage of the
intermediate heat exchanger, a plurality of pumps, and a plurality
of use side heat exchangers connected by pipe through which the
heat medium flows, wherein the air-conditioning apparatus includes
a heating only operation mode for supplying only heating energy to
the use side heat exchangers and a cooling only operation mode for
supplying only cooling energy to the use side heat exchangers, all
of the pumps are in operation for a predetermined period of time
and, after that, the number of pumps in operation is changed
depending on an operation capacity for indoor units each including
the use side heat exchanger, and during the heating only operation
mode or the cooling only operation mode, when the operation
capacity for the indoor units is greater than the predetermined
value X, and is greater than or equal to a value C determined based
on a differential, and any of the pumps is in non-operation, the
number of pumps in operation is changed by actuating the pump in
non-operation at minimum input power.
2-5. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to an air-conditioning
apparatus which is used as, for example, a multi-air-conditioning
apparatus for a building.
BACKGROUND ART
[0002] There have been air-conditioning apparatuses configured such
that refrigerant is circulated between an outdoor unit, serving as
a heat source unit, disposed outside, for example, a structure and
an indoor unit disposed in an indoor space in the structure in
order to convey cooling energy or heating energy to an
air-conditioned space, such as an indoor space, and perform a
cooling operation or a heating operation. Such air-conditioning
apparatuses are used as, for example, building
multi-air-conditioning apparatuses. As regards the refrigerant used
in those air-conditioning apparatuses, for example, HFC refrigerant
(e.g., R410A, R404A, R407C, and R134a) are often used. In addition,
natural refrigerant, such as carbon dioxide (CO.sub.2), have also
recently been used.
[0003] There have been other air-conditioning apparatuses typified
by a chiller system. Such an air-conditioning apparatus is
configured such that cooling energy or heating energy is produced
in a heat source unit disposed in an outdoor space, the cooling
energy or heating energy is transferred to a heat medium, such as
water or antifreeze, in a heat exchanger disposed in an outdoor
unit, and the heat medium is conveyed through a heat medium circuit
to a fan coil unit or a panel heater, serving as an indoor unit,
disposed in an air-conditioned space in order to perform the
cooling operation or the heating operation (refer to Patent
Literature 1, for example).
[0004] Such related-art air-conditioning apparatuses include an
air-conditioning apparatus configured such that refrigerant is
circulated through an indoor unit. In this air-conditioning
apparatus, if the refrigerant leaks into an indoor space where
people stay, a user may be affected by the leaked refrigerant. An
air-conditioning apparatus that conditions air by exchanging heat
between refrigerant and a heat medium, such as water or brine, and
allowing the heat medium after heat exchange to flow through an
indoor unit has been proposed to solve the above-described problem
(refer to Patent Literature 2, for example).
CITATION LIST
Patent Literature
[0005] Patent Literature 1: Japanese Unexamined Patent Application
Publication No. 2003-343936 (Page 5, FIG. 1, for example)
[0006] Patent Literature 2: Japanese Unexamined Patent Application
Publication No. 2010-084951 (Pages 5 and 6, FIG. 1, for
example)
SUMMARY OF INVENTION
Technical Problem
[0007] As described above, an air-conditioning apparatus configured
such that a heat medium, serving as a secondary refrigerant, flows
through an indoor unit typically uses a pump to circulate the heat
medium. The pump is typically inoperative at or below a certain
current (refer to FIG. 9). FIG. 9 includes graphs illustrating the
relationship between the flow rate of a heat medium and an input
voltage to the pump disposed in the air-conditioning apparatus
configured such that the heat medium, serving as a secondary
refrigerant, flows through the indoor unit. FIG. 9(a) is a graph
illustrating the relationship between an input current [A] and a
flow rate variable signal [V]. FIG. 9(b) is a graph illustrating
the relationship between the heat medium flow rate [L/min] and the
flow rate variable signal [V]. FIG. 9 demonstrates that the pump is
inoperative at or below a current indicated by a broken line Y.
[0008] Such an air-conditioning apparatus, therefore, performs
control to force the flow rate to be reduced by using a valve whose
opening degree can be controlled. Disadvantageously, power
consumption of the related-art air-conditioning apparatus during an
operation with a reduced heat medium flow rate is high relative to
the heat medium flow rate. In other words, this operation exhibits
low efficiency.
[0009] The present invention has been made to solve the
above-described disadvantage and provides an air-conditioning
apparatus that controls pumps depending on an operation mode of
each indoor unit.
Solution to Problem
[0010] The present invention provides an air-conditioning apparatus
including at least one intermediate heat exchanger that exchanges
heat between heat source side refrigerant and a heat medium
different from the heat source side refrigerant, a refrigeration
cycle including a compressor, a heat source side heat exchanger, at
least one expansion valve, and a refrigerant passage of the
intermediate heat exchanger connected by pipes through which the
heat source side refrigerant flows, and a heat medium circuit
including a heat medium passage of the intermediate heat exchanger,
a plurality of pumps, and a plurality of use side heat exchangers
connected by pipes through which the heat medium flows. All of the
pumps are in operation for a predetermined period of time and,
after that, the number of pumps in operation is changed depending
on an operation capacity for indoor units each including the use
side heat exchanger.
Advantageous Effects of Invention
[0011] The air-conditioning apparatus according to the present
invention controls the pumps depending on an operation mode of each
indoor unit.
[0012] Advantageously, an operation can be performed with pump
power consumption depending on the flow rate of the heat medium.
Thus, the efficiency of operation can be further increased.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 is an overall configuration diagram illustrating an
exemplary installation state of an air-conditioning apparatus
according to Embodiment of the present invention.
[0014] FIG. 2 is an overall configuration diagram illustrating an
exemplary installation state of the air-conditioning apparatus
according to Embodiment of the present invention.
[0015] FIG. 3 is a schematic circuit diagram illustrating an
exemplary circuit configuration of the air-conditioning apparatus
according to Embodiment of the present invention.
[0016] FIG. 4 is a refrigerant circuit diagram illustrating flows
of refrigerant in a cooling only operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0017] FIG. 5 is a refrigerant circuit diagram illustrating flows
of the refrigerant in a heating only operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0018] FIG. 6 is a refrigerant circuit diagram illustrating flows
of the refrigerant in a cooling main operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0019] FIG. 7 is a refrigerant circuit diagram illustrating flows
of the refrigerant in a heating main operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0020] FIG. 8 is a flowchart illustrating an exemplary control
process for changing the number of pumps operated in the
air-conditioning apparatus according to Embodiment of the present
invention.
[0021] FIG. 9 includes graphs illustrating the relationship between
the flow rate of a heat medium and an input voltage to a pump
disposed in an air-conditioning apparatus in which the heat medium,
serving as a secondary refrigerant, flows through an indoor
unit.
DESCRIPTION OF EMBODIMENTS
[0022] Embodiment of the present invention will be described below
with reference to the drawings.
[0023] FIGS. 1 and 2 are overall configuration diagrams each
illustrating an exemplary installation state of an air-conditioning
apparatus according to Embodiment of the present invention.
Examples of installation of the air-conditioning apparatus
according to Embodiment will be described with reference to FIGS. 1
and 2. This air-conditioning apparatus includes a refrigeration
cycle (a refrigerant circuit and a heat medium circuit), through
which refrigerants (heat source side refrigerant and a heat medium,
such as water or antifreeze) are circulated, to perform a cooling
operation or a heating operation. Note that the dimensional
relationship among components in FIG. 1 and the following figures
may be different from the actual one.
[0024] In FIG. 1, the air-conditioning apparatus according to
Embodiment includes a single heat source unit 1, serving as a heat
source device, a plurality of indoor units 2, and a relay unit 3
interposed between the heat source unit 1 and the indoor units 2.
The relay unit 3 exchanges heat between the heat source side
refrigerant and the heat medium. The heat source unit 1 is
connected to the relay unit 3 by refrigerant pipes 4 through which
the heat source side refrigerant is conveyed. The relay unit 3 is
connected to each indoor unit 2 by pipes (heat medium pipes) 5
through which the heat medium is conveyed. Cooling energy or
heating energy produced in the heat source unit 1 is delivered to
the indoor units 2 via the relay unit 3. The number of heat source
units 1 connected, the number of indoor units 2 connected, and the
number of relay units 3 connected are not limited to the numbers
illustrated in FIG. 1.
[0025] In FIG. 2, the air-conditioning apparatus according to
Embodiment includes a single heat source unit 1, serving as a heat
source device, a plurality of indoor units 2, and a plurality of
separated relay units 3 (a first relay unit 3a and second relay
units 3b) interposed between the heat source unit 1 and the indoor
units 2. The heat source unit 1 is connected to the first relay
unit 3a by the refrigerant pipes 4. The first relay unit 3a is
connected to the second relay units 3b by the refrigerant pipes 4.
Each of the second relay units 3b is connected to each indoor unit
2 by the pipes 5. Cooling energy or heating energy produced in the
heat source unit 1 is delivered to the indoor units 2 via the first
relay unit 3a and the second relay units 3b. The number of heat
source units 1 connected, the number of indoor units 2 connected,
and the number of relay units 3 connected are not limited to the
numbers illustrated in FIG. 2.
[0026] The heat source unit 1 is typically disposed in an outdoor
space 6 that is a space (e.g., a roof) outside a structure 9, such
as a building, and supplies cooling energy or heating energy to the
indoor units 2 via the relay unit 3. Each indoor unit 2 is disposed
in a living space 7 that is a space (e.g., a living room or a
server room) inside the structure 9 to which cooling air or heating
air can be conveyed, and supplies the cooling air or the heating
air to the living space 7, serving as an air-conditioned area. The
relay unit 3 includes a housing separate from housings of the heat
source unit 1 and the indoor units 2 so that the relay unit 3 can
be disposed in a different position (hereinafter, referred to as a
"non-living space 50") from those of the outdoor space 6 and the
living space 7. The relay unit 3 connects the heat source unit 1
and the indoor units 2 to transfer cooling energy or heating
energy, supplied from the heat source unit 1, to the indoor units
2.
[0027] The outdoor space 6 is assumed to be a place outside the
structure 9, for example, a roof as illustrated in FIGS. 1 and 2.
The non-living space 50 is assumed to be a place that is inside the
structure 9 but is different from the living space 7, for example,
a place (e.g., a space above a corridor) in which people do not
stay at all times, a space above a ceiling of a common zone, a
common space in which an elevator or the like is installed, a
machine room, a computer room, or a stockroom. The living space 7
is assumed to be a place that is inside the structure 9 and in
which people stay at all times, or many or a few people temporarily
stay, for example, an office, a classroom, a conference room, a
dining hall, or a server room.
[0028] Referring to FIGS. 1 and 2, the heat source unit 1 and the
relay unit 3 are connected using two refrigerant pipes 4. The relay
unit 3 and each indoor unit 2 are connected using two pipes 5.
Connecting the heat source unit 1 to the relay unit 3 using the two
refrigerant pipes 4 and connecting each indoor unit 2 to the relay
unit 3 using the two pipes 5 in this manner facilitate construction
of the air-conditioning apparatus according to Embodiment.
[0029] As illustrated in FIG. 2, the relay unit 3 may be separated
into a single first relay unit 3a and two second relay units 3b
derived from the first relay unit 3a. This configuration enables a
plurality of second relay units 3b to be connected to the single
first relay unit 3a. In this configuration, the first relay unit 3a
is connected to each second relay unit 3b by three refrigerant
pipes 4. Such a circuit will be described in detail later (refer to
FIG. 3).
[0030] Although FIGS. 1 and 2 illustrate the indoor units 2 of a
ceiling cassette type, the indoor units are not limited to this
type and may be of any type capable of sending heating air or
cooling air to the living space 7 directly or through a duct or the
like, for example, a ceiling concealed type or a ceiling suspended
type.
[0031] Although FIGS. 1 and 2 illustrate the heat source unit 1
disposed in the outdoor space 6, the arrangement is not limited to
this illustration. For example, the heat source unit 1 may be
disposed in an enclosed space, for example, a machine room with a
ventilation opening. The heat source unit 1 may be disposed inside
the structure 9 as long as waste heat can be exhausted through an
exhaust duct to the outside of the structure 9. Alternatively, if
the heat source unit 1 of a water-cooled type is used, the heat
source unit 1 may be disposed inside the structure 9. Even when the
heat source unit 1 is disposed in such a place, no problem in
particular will occur.
[0032] The relay unit 3 can be disposed near the heat source unit
1. If the distance between the relay unit 3 and each indoor unit 2
is too long, conveyance power for the heat medium would be
significantly large. Note that the effect of energy saving is
reduced in this case. As described above, the number of heat source
units 1 connected, the number of indoor units 2 connected, and the
number of relay units 3 connected are not limited to the numbers
illustrated in FIGS. 1 and 2. The numbers may be determined
depending on, for example, the structure 9 where the
air-conditioning apparatus according to Embodiment is
installed.
[0033] FIG. 3 is a schematic circuit diagram illustrating an
exemplary circuit configuration of the air-conditioning apparatus
(hereinafter, referred to as the "air-conditioning apparatus 100")
according to Embodiment of the present invention. The configuration
of the air-conditioning apparatus 100 will now be described in
detail with reference to FIG. 3. Referring to FIG. 3, the heat
source unit 1 and the relay unit 3 are connected by the refrigerant
pipes 4 through a first intermediate heat exchanger 15a and a
second intermediate heat exchanger 15b which are arranged in the
second relay unit 3b. The second relay unit 3b and each indoor unit
2 are connected by the pipes 5 through the first intermediate heat
exchanger 15a and the second intermediate heat exchanger 15b.
[Configuration of Air-Conditioning Apparatus 100]
[0034] The configurations and functions of components included in
the air-conditioning apparatus 100 will now be described. FIG. 3
and the following figures illustrate a case where the relay unit 3
is separated into the first relay unit 3a and the second relay unit
3b. The refrigerant pipes 4 and the pipes 5 will be described in
detail later.
(Heat Source Unit 1)
[0035] The heat source unit 1 includes a compressor 10, a four-way
valve 11, a heat source side heat exchanger (outdoor heat
exchanger) 12, and an accumulator 17 which are connected in series
by the refrigerant pipes 4. The heat source unit 1 further includes
a first connecting pipe 4a, a second connecting pipe 4b, a check
valve 13a, a check valve 13b, a check valve 13c, and a check valve
13d. The arrangement of the first connecting pipe 4a, the second
connecting pipe 4b, and the check valves 13a, 13b, 13c, and 13d
enables the heat source side refrigerant, allowed to flow into the
relay unit 3, to flow in a constant direction irrespective of an
operation requested by any indoor unit 2.
[0036] The compressor 10 sucks the heat source side refrigerant and
compresses the heat source side refrigerant into a high-temperature
high-pressure state and may be, for example, a
capacity-controllable inverter compressor.
[0037] The four-way valve 11 switches between a flow direction of
the heat source side refrigerant in the heating operation and a
flow direction of the heat source side refrigerant in the cooling
operation.
[0038] The heat source side heat exchanger 12 functions as an
evaporator in the heating operation or functions as a condenser in
the cooling operation to exchange heat between the heat source side
refrigerant and air supplied from an air-sending device (not
illustrated), such as a fan, so that the heat source side
refrigerant evaporates and gasifies or condenses and liquefies.
[0039] The accumulator 17, which is disposed on a suction side of
the compressor 10, stores an excess of refrigerant.
[0040] The check valve 13d, which is disposed to the refrigerant
pipe 4 located between the relay unit 3 and the four-way valve 11,
permits the heat source side refrigerant to flow only in a
predetermined direction (the direction from the relay unit 3 to the
heat source unit 1).
[0041] The check valve 13a, which is disposed to the refrigerant
pipe 4 located between the heat source side heat exchanger 12 and
the relay unit 3, permits the heat source side refrigerant to flow
only in a predetermined direction (the direction from the heat
source unit 1 to the relay unit 3).
[0042] The check valve 13b, which is disposed to the first
connecting pipe 4a, permits the heat source side refrigerant to
flow only in a direction from a point downstream of the check valve
13d to a point downstream of the check valve 13a.
[0043] The check valve 13c, which is disposed to the second
connecting pipe 4b, permits the heat source side refrigerant to
flow only in a direction from a point upstream of the check valve
13d to a point upstream of the check valve 13a.
[0044] The first connecting pipe 4a connects the refrigerant pipe 4
downstream of the check valve 13d and the refrigerant pipe 4
downstream of the check valve 13a in the heat source unit 1.
[0045] The second connecting pipe 4b connects the refrigerant pipe
4 upstream of the check valve 13d and the refrigerant pipe 4
upstream of the check valve 13a in the heat source unit 1.
[0046] Although FIG. 2 illustrates a case where the first
connecting pipe 4a, the second connecting pipe 4b, and the check
valves 13a, 13b, 13c, and 13d are arranged, the configuration is
not limited to the case. The air-conditioning apparatus 100 does
not necessarily have to include those components.
(Indoor Units 2)
[0047] The indoor units 2 each include a use side heat exchanger
26. The use side heat exchanger 26 is connected to a stop valve 24
and a flow control valve 25 arranged in the second relay unit 3b by
the pipes 5. The use side heat exchanger 26 exchanges heat between
the heat medium and air supplied from an air-sending device (not
illustrated), such as a fan, to produce heating air or cooling air
to be supplied to the air-conditioned area.
[0048] FIG. 3 illustrates a case where four indoor units 2 are
connected to the second relay unit 3b. An indoor unit 2a, an indoor
unit 2b, an indoor unit 2c, and an indoor unit 2d are illustrated
in that order from the bottom in FIG. 3. In addition, the use side
heat exchangers 26 are illustrated as a use side heat exchanger
26a, a use side heat exchanger 26b, a use side heat exchanger 26c,
and a use side heat exchanger 26d in that order from the bottom in
FIG. 3 so as to correspond to the indoor units 2a to 2d,
respectively. The number of indoor units 2 connected is not limited
to four, as illustrated in FIG. 3, as in the case of FIG. 1.
(Relay Unit 3)
[0049] The relay unit 3 is composed of the first relay unit 3a and
the second relay unit 3b which include separate housings. As
described above, this configuration enables a plurality of second
relay units 3b to be connected to the single first relay unit 3a.
The first relay unit 3a includes a gas-liquid separator 14 and an
expansion valve 16e. The second relay unit 3b includes the two
intermediate heat exchangers 15, four expansion valves 16, two
pumps 21, four flow switching valves 22, four flow switching valves
23, the four stop valves 24, and the four flow control valves
25.
[0050] The gas-liquid separator 14 is connected to one refrigerant
pipe 4 connecting to the heat source unit 1 and two refrigerant
pipes 4 connecting to the first and second intermediate heat
exchangers 15a and 15b in the second relay unit 3b. The gas-liquid
separator 14 separates the heat source side refrigerant supplied
from the heat source unit 1 into vapor refrigerant and liquid
refrigerant.
[0051] The expansion valve 16e, which is disposed between the
gas-liquid separator 14 and the refrigerant pipe 4 connecting an
expansion valve 16a and an expansion valve 16b, functions as a
pressure reducing valve or an expansion device to depressurize the
heat source side refrigerant such that the refrigerant is expanded.
The expansion valve 16e may be a component having a variably
controllable opening degree, for example, an electronic expansion
valve.
[0052] The first relay unit 3a includes a pressure sensor 39 and a
pressure sensor 40.
[0053] The pressure sensor 39, which is disposed to the refrigerant
pipe 4 connecting to a heat source side refrigerant inlet of the
gas-liquid separator 14, detects a pressure of the heat source side
refrigerant flowing from the heat source unit 1 into the first
relay unit 3a. More specifically, the pressure sensor 39 detects
the pressure of the heat source side refrigerant flowing into the
gas-liquid separator 14.
[0054] The pressure sensor 40, which is disposed to the refrigerant
pipe 4 connecting the expansion valve 16b, an expansion valve 16c,
and the first relay unit 3a, detects the pressure of the heat
source side refrigerant leaving the second relay unit 3b. More
specifically, the pressure sensor 40 detects the pressure of the
heat source side refrigerant flowing into the heat source unit
1.
[0055] The two intermediate heat exchangers 15 (the first
intermediate heat exchanger 15a and the second intermediate heat
exchanger 15b) each function as a condenser or an evaporator,
exchange heat between the heat source side refrigerant and the heat
medium, and supply cooling energy or heating energy produced by the
heat source unit 1 to the indoor units 2. The first intermediate
heat exchanger 15a is disposed between the gas-liquid separator 14
and an expansion valve 16d in the flow direction of the heat source
side refrigerant and is used to heat the heat medium. The second
intermediate heat exchanger 15b is disposed between the expansion
valves 16a and 16c in the flow direction of the heat source side
refrigerant and is used to cool the heat medium.
[0056] The four expansion valves 16 (the expansion valves 16a to
16d) each function as a pressure reducing valve or an expansion
device to depressurize the heat source side refrigerant such that
the refrigerant is expanded. The expansion valve 16a is disposed
between the expansion valve 16e and the second intermediate heat
exchanger 15b in a state where the heat source side refrigerant
flows through the expansion valve 16e. The expansion valve 16b is
disposed parallel to the expansion valve 16a. The expansion valve
16c is disposed between the second intermediate heat exchanger 15b
and the first relay unit 3a. The expansion valve 16d is disposed
between the first intermediate heat exchanger 15a and the expansion
valves 16a and 16b. Each of the four expansion valves 16 may be a
component having a variably controllable opening degree, for
example, an electronic expansion valve.
[0057] The two pumps 21 (a pump 21a and a pump 21b) each allow the
heat medium flowing through the pipe 5 to be circulated. The pump
(first pump) 21a is disposed to the pipe 5 located between the
first intermediate heat exchanger 15a and the flow switching valves
22. The pump (second pump) 21b is disposed to the pipe 5 located
between the second intermediate heat exchanger 15b and the flow
switching valves 22. Each of the pumps 21a and 21b may be of any
type, for example, a capacity-controllable pump.
[0058] Each of the four flow switching valves 22 (flow switching
valves 22a to 22d) is a three-way valve and switches between
passages for the heat medium. The flow switching valves 22 equal in
number to the (four in this case) indoor units 2 installed are
arranged. Each flow switching valve 22 is disposed on an inlet side
of a heat medium passage of the corresponding use side heat
exchanger 26 such that one of three ways is connected to the first
intermediate heat exchanger 15a, another one of the three ways is
connected to the second intermediate heat exchanger 15b, and the
other one of the three ways is connected to the stop valve 24. The
flow switching valve 22a, the flow switching valve 22b, the flow
switching valve 22c, and the flow switching valve 22d are
illustrated in that order from the bottom in FIG. 3 so as to
correspond to the respective indoor units 2.
[0059] Each of the four flow switching valves 23 (flow switching
valves 23a to 23d) is a three-way valve and switches between
passages for the heat medium. The flow switching valves 23 equal in
number to the (four in this case) indoor units 2 installed are
arranged. Each flow switching valve 23 is disposed on an outlet
side of the heat medium passage of the corresponding use side heat
exchanger 26 such that one of three ways is connected to the first
intermediate heat exchanger 15a, another one of the three ways is
connected to the second intermediate heat exchanger 15b, and the
other one of the three ways is connected to the flow control valve
25. The flow switching valve 23a, the flow switching valve 23b, the
flow switching valve 23c, and the flow switching valve 23d are
illustrated in that order from the bottom in FIG. 3 so as to
correspond to the respective indoor units 2.
[0060] Each of the four stop valves 24 (stop valves 24a to 24d) is
a two-way valve and opens or closes the pipe 5. The stop valves 24
equal in number to the (four in this case) indoor units 2 installed
are arranged. Each stop valve 24 is disposed on the inlet side of
the heat medium passage of the corresponding use side heat
exchanger 26 such that one of two ways is connected to the use side
heat exchanger 26 and the other one of the two ways is connected to
the flow switching valve 22. The stop valve 24a, the stop valve
24b, the stop valve 24c, and the stop valve 24d are illustrated in
that order from the bottom in FIG. 3 so as to correspond to the
respective indoor units 2.
[0061] Each of the four flow control valves 25 (flow control valves
25a to 25d) is a three-way valve and switches between passages for
the heat medium. The flow control valves 25 equal in number to the
(four in this case) indoor units 2 installed are arranged. Each
flow control valve 25 is disposed on the outlet side of the heat
medium passage of the corresponding use side heat exchanger 26 such
that one of three ways is connected to the use side heat exchanger
26, another one of the three ways is connected to a bypass 27, and
the other one of the three ways is connected to the flow switching
valve 23. The flow control valve 25a, the flow control valve 25b,
the flow control valve 25c, and the flow control valve 25d are
illustrated in that order from the bottom in FIG. 3 so as to
correspond to the respective indoor units 2.
[0062] Each bypass 27 is disposed so as to connect the flow control
valve 25 and the pipe 5 located between the stop valve 24 and the
use side heat exchanger 26. The bypasses 27 equal in number to the
indoor units 2 installed (four in this case, specifically, a bypass
27a, a bypass 27b, a bypass 27c, and a bypass 27d) are arranged.
The bypass 27a, the bypass 27b, the bypass 27c, and the bypass 27d
are illustrated in that order from the bottom in FIG. 3 so as to
correspond to the respective indoor units 2.
[0063] The second relay unit 3b further includes two first
temperature sensors 31, two second temperature sensors 32, four
third temperature sensors 33, four fourth temperature sensors 34, a
fifth temperature sensor 35, a pressure sensor 36, a sixth
temperature sensor 37, and a seventh temperature sensor 38.
Information detected by such detecting means is transmitted to a
controller (controller 60) that controls an operation of the
air-conditioning apparatus 100. The information is used to control,
for example, a driving frequency of the pumps 21 and switching
between passages for the heat medium flowing through the pipes
5.
[0064] The two first temperature sensors 31 (a first temperature
sensor 31a and a first temperature sensor 31b) each detect a
temperature of the heat medium flowing out of the corresponding
intermediate heat exchanger 15, that is, the heat medium at an
outlet of the intermediate heat exchanger 15. Each first
temperature sensor 31 may be a thermistor, for example. The first
temperature sensor 31a is disposed to the pipe 5 on an inlet side
of the pump 21a. The first temperature sensor 31b is disposed to
the pipe 5 on an inlet side of the pump 21b.
[0065] The two second temperature sensors 32 (a second temperature
sensor 32a and a second temperature sensor 32b) each detect the
temperature of the heat medium flowing into the corresponding
intermediate heat exchanger 15, that is, the heat medium at an
inlet of the intermediate heat exchanger 15. Each second
temperature sensor 32 may be a thermistor, for example. The second
temperature sensor 32a is disposed to the pipe 5 on the inlet side
of the first intermediate heat exchanger 15a. The second
temperature sensor 32b is disposed to the pipe 5 on the inlet side
of the second intermediate heat exchanger 15b.
[0066] Each of the four third temperature sensors 33 (third
temperature sensors 33a to 33d) is disposed on the inlet side of
the heat medium passage of the corresponding use side heat
exchanger 26 and detects the temperature of the heat medium flowing
into the use side heat exchanger 26. Each third temperature sensor
33 may be a thermistor or the like. The third temperature sensors
33 equal in number to the (four in this case) indoor units 2
installed are arranged. The third temperature sensor 33a, the third
temperature sensor 33b, the third temperature sensor 33c, and the
third temperature sensor 33d are illustrated in that order from the
bottom in FIG. 3 so as to correspond to the respective indoor units
2.
[0067] Each of the fourth temperature sensors 34 (fourth
temperature sensors 34a to 34d) is disposed on the outlet side of
the heat medium passage of the corresponding use side heat
exchanger 26 and detects the temperature of the heat medium flowing
out of the use side heat exchanger 26. Each fourth temperature
sensor 34 may be a thermistor or the like. The fourth temperature
sensors 34 equal in number to the (four in this case) indoor units
2 installed are arranged. The fourth temperature sensor 34a, the
fourth temperature sensor 34b, the fourth temperature sensor 34c,
and the fourth temperature sensor 34d are illustrated in that order
from the bottom in FIG. 3 so as to correspond to the respective
indoor units 2.
[0068] The fifth temperature sensor 35 is disposed on an outlet
side of a heat source side refrigerant passage of the first
intermediate heat exchanger 15a and detects a temperature of the
heat source side refrigerant flowing out of the first intermediate
heat exchanger 15a. The fifth temperature sensor 35 may be a
thermistor or the like.
[0069] The pressure sensor 36 is disposed on the outlet side of the
heat source side refrigerant passage of the first intermediate heat
exchanger 15a and detects the pressure of the heat source side
refrigerant flowing out of the first intermediate heat exchanger
15a. The pressure sensor 36 may be a pressure sensor or the
like.
[0070] The sixth temperature sensor 37 is disposed on an inlet side
of a heat source side refrigerant passage of the second
intermediate heat exchanger 15b and detects the temperature of the
heat source side refrigerant flowing into the second intermediate
heat exchanger 15b. The sixth temperature sensor 37 may be a
thermistor or the like.
[0071] The seventh temperature sensor 38 is disposed on an outlet
side of the heat source side refrigerant passage of the second
intermediate heat exchanger 15b and detects the temperature of the
heat source side refrigerant flowing out of the second intermediate
heat exchanger 15b. The seventh temperature sensor 38 may be a
thermistor or the like.
[0072] The pipes 5 through which the heat medium is conveyed
include the pipes 5 (hereinafter, referred to as "pipes 5a")
connected to the first intermediate heat exchanger 15a and the
pipes 5 (hereinafter, referred to as "pipes 5b") connected to the
second intermediate heat exchanger 15b. Each of the pipes 5a and 5b
branches into pipes (four pipes in this case) equal in number to
the indoor units 2 connected to the relay unit 3. The pipes 5a and
the pipes 5b are connected by the flow switching valves 22 and the
flow switching valves 23. Whether the heat medium conveyed through
the pipe 5a is allowed to flow into the use side heat exchanger 26
or the heat medium conveyed through the pipe 5b is allowed to flow
into the use side heat exchanger 26 is determined by controlling
the corresponding flow switching valves 22 and 23.
[0073] The air-conditioning apparatus 100 further includes the
controller 60 that controls operations of the components included
in the heat source unit 1, the relay unit 3, and the indoor units 2
on the basis of information from a remote controller for receiving
instructions from various detecting means and a user. The
controller 60 controls, for example, driving frequency of the
compressor 10 included in the heat source unit 1, a rotation speed
(including ON/OFF) of the air-sending device disposed near the heat
source side heat exchanger 12, and switching of the four-way valve
11 to perform any of operation modes, which will be described
later. Furthermore, the controller 60 controls a rotation speed
(including ON/OFF) of the air-sending device disposed near the use
side heat exchanger 26 included in each indoor unit 2.
[0074] In addition, the controller 60 controls driving of the pumps
21 arranged in the relay unit 3, opening degrees of the expansion
valves 16a to 16e, switching of the flow switching valves 22 and
the flow switching valves 23, opening and closing of the stop
valves 24, and switching of the flow control valves 25.
Specifically, the controller 60 has functions of flow control means
for controlling the flow rate of the heat medium in the relay unit
3, functions of passage determining means for determining a heat
medium passage, functions of ON/OFF control means for turning each
component on or off, and functions of control target value changing
means for appropriately changing a set target value based on
information from the various detecting means. The controller may be
provided for each unit. In such a case, the controllers may be
enabled to communicate with each other. The controller includes a
microcomputer.
[0075] In the air-conditioning apparatus 100, the compressor 10,
the four-way valve 11, the heat source side heat exchanger 12, the
refrigerant passage of the first intermediate heat exchanger 15a,
the refrigerant passage of the second intermediate heat exchanger
15b, and the accumulator 17 are connected by the refrigerant pipes
4 through which the refrigerant flows, thus providing the
refrigeration cycle. In addition, the heat medium passage of the
first intermediate heat exchanger 15a, the pump 21a, and the use
side heat exchangers 26 are sequentially connected by the pipes 5a
through which the heat medium flows, thus providing a heat medium
circuit. Similarly, the heat medium passage of the second
intermediate heat exchanger 15b, the pump 21b, and the use side
heat exchangers 26 are sequentially connected in series by the
pipes 5b through which the heat medium flows, thus providing
another heat medium circuit. Specifically, the plurality of use
side heat exchangers 26 are connected in parallel with each of the
intermediate heat exchangers 15, thus making the heat medium
circuit multiple systems.
[0076] The heat medium circuit for heating is provided with a
discharge valve 71a for discharging the heat medium from the heat
medium circuit. The discharge valve 71a is disposed to the pipe
5a.
[0077] The heat medium circuit for cooling is provided with a
discharge valve 71b for discharging the heat medium from the heat
medium circuit. The discharge valve 71b is disposed to the pipe
5b.
[0078] Specifically, in the air-conditioning apparatus 100, the
heat source unit 1 is connected to the relay unit 3 through the
first intermediate heat exchanger 15a and the second intermediate
heat exchanger 15b arranged in the relay unit 3, and the relay unit
3 is connected to the indoor units 2 through the first intermediate
heat exchanger 15a and the second intermediate heat exchanger 15b.
The first intermediate heat exchanger 15a and the second
intermediate heat exchanger 15b allow the heat source side
refrigerant, serving as a primary refrigerant, circulated through
the refrigeration cycle to exchange heat with the heat medium,
serving as a secondary refrigerant, circulated through the heat
medium circuit.
[0079] The kinds of refrigerant used in the refrigeration cycle and
the heat medium circuit will now be described. In the refrigeration
cycle, a non-azeotropic refrigerant mixture, such as R407C, a
near-azeotropic refrigerant mixture, such as R410A or R404A, or a
single refrigerant, such as R22 or R134a, can be used.
Alternatively, a natural refrigerant, such as carbon dioxide or
hydrocarbon, may be used. The use of the natural refrigerant as the
heat source side refrigerant can reduce the earth's greenhouse
effect caused by refrigerant leakage. In particular, the use of
carbon dioxide can improve heat exchange performance for heating or
cooling the heat medium in the arrangement in which the heat source
side refrigerant and the heat medium are allowed to flow in a
counter-current manner in the first intermediate heat exchanger 15a
and the second intermediate heat exchanger 15b as illustrated in
FIG. 3, because carbon dioxide in a supercritical state on a
high-pressure side exchanges heat without condensing.
[0080] As described above, the heat medium circuit is connected to
the use side heat exchangers 26 in the indoor units 2. Accordingly,
the air-conditioning apparatus 100 is premised on the use of a
highly safe heat medium in consideration of the leakage of the heat
medium into a room or the like in which the indoor unit 2 is
installed. As regards the heat medium, for example, water,
antifreeze, or a liquid mixture of water and antifreeze can be
used. The above-described configuration reduces a likelihood that
the refrigerant leaking from any pipe may enter an indoor space,
thus providing high reliability. Furthermore, a highly
heat-insulating fluorine inert liquid can be used as the heat
medium if the indoor unit 2 is installed in a place that dislikes
moisture, for example, a computer room.
(Refrigerant Pipes 4)
[0081] As will be described later, the air-conditioning apparatus
100 has several operation modes. In these operation modes, the heat
source side refrigerant flows through the refrigerant pipes 4
connecting the heat source unit 1 and the relay unit 3.
(Pipes 5)
[0082] In the several operation modes performed by the
air-conditioning apparatus 100, the heat medium, such as water or
antifreeze, flows through the pipes 5 connecting the relay unit 3
and the indoor units 2.
(Heat Source Side Refrigerant)
[0083] As regards the heat source side refrigerant, for example, a
hydrofluorocarbon (HFC) refrigerant, such as R410A, R407C, or
R404A, a hydrochlorofluorocarbon (HCFC) refrigerant, such as R22 or
R134a, refrigerant that contains a double bond in its chemical
formula and has a relatively low global warming potential, for
example, CF.sub.3CF.dbd.CH.sub.2, a mixture containing the
refrigerant, or a natural refrigerant, such as hydrocarbon, helium,
or carbon dioxide, can be used.
(Heat Medium)
[0084] As regards the heat medium, for example, brine (antifreeze),
water, a liquid mixture of brine and water, or a liquid mixture of
water and an additive with a high corrosion protection effect can
be used. In the air-conditioning apparatus 100, therefore, if the
heat medium leaks into the indoor space 7 through any indoor unit
2, the safety of the heat medium used is high. This contributes to
the improvement of safety.
[Operation Modes of Air-Conditioning Apparatus 100]
[0085] The operation modes performed by the air-conditioning
apparatus 100 will now be described.
[0086] The air-conditioning apparatus 100 enables each indoor unit
2, on the basis of an instruction from the indoor unit 2, to
perform the cooling operation or the heating operation. More
specifically, the air-conditioning apparatus 100 enables all of the
indoor units 2 to perform the same operation and also enables the
indoor units 2 to perform different operations. In other words, the
air-conditioning apparatus 100 is an air-conditioning apparatus
capable of performing the cooling operation and the heating
operation at the same time.
[0087] Four operation modes performed by the air-conditioning
apparatus 100, that is, a cooling only operation mode in which all
of the operating indoor units 2 perform the cooling operation, a
heating only operation mode in which all of the operating indoor
units 2 perform the heating operation, a cooling main operation
mode in which a cooling load is larger in a cooling and heating
mixed operation, and a heating main operation mode in which a
heating load is larger in the cooling and heating mixed operation
will be described below in accordance with the flows of the
refrigerant.
(Cooling Only Operation Mode)
[0088] FIG. 4 is a refrigerant circuit diagram illustrating the
flows of the refrigerant in the cooling only operation mode of the
air-conditioning apparatus 100. The cooling only operation mode
will be described on the assumption that, for example, a cooling
load is generated only in the use side heat exchangers 26a and 26b
in FIG. 4. In other words, FIG. 4 illustrates a case where no
cooling load is generated in the use side heat exchangers 26c and
26d. In FIG. 4, pipes indicated by thick lines correspond to pipes
through which the refrigerants (the heat source side refrigerant
and the heat medium) are circulated. Furthermore, solid-line arrows
indicate the direction of flow of the heat source side refrigerant
and broken-line arrows indicate the direction of flow of the heat
medium.
[0089] In the cooling only operation mode illustrated in FIG. 4, in
the heat source unit 1, the four-way valve 11 is switched so that
the heat source side refrigerant discharged from the compressor 10
flows into the heat source side heat exchanger 12. In the relay
unit 3, the pump 21a is in non-operation, the pump 21b is driven,
the stop valves 24a and 24b are opened, and the stop valves 24c and
24d are closed so that the heat medium is circulated between the
second intermediate heat exchanger 15b and the use side heat
exchangers 26 (the use side heat exchanger 26a and the use side
heat exchanger 26b). In this state, the compressor 10 is started to
operate.
[0090] First, the flow of the heat source side refrigerant in the
refrigeration cycle will be described.
[0091] Low-temperature low-pressure refrigerant is compressed into
high-temperature high-pressure gas refrigerant by the compressor 10
and is then discharged therefrom. The high-temperature
high-pressure gas refrigerant discharged from the compressor 10
passes through the four-way valve 11 and flows into the heat source
side heat exchanger 12. In the heat source side heat exchanger 12,
the refrigerant condenses and liquefies while transferring heat to
outdoor air, so that the refrigerant turns into high-pressure
liquid refrigerant. The high-pressure liquid refrigerant, which has
flowed out of the heat source side heat exchanger 12, passes
through the check valve 13a, flows out of the heat source unit 1,
passes through the refrigerant pipe 4, and flows into the first
relay unit 3a. The high-pressure liquid refrigerant, which has
flowed into the first relay unit 3a, flows into the gas-liquid
separator 14, passes through the expansion valve 16e, and then
flows into the second relay unit 3b.
[0092] The refrigerant, which has flowed into the second relay unit
3b, is expanded by the expansion valve 16a, so that the refrigerant
turns into low-temperature, low-pressure two-phase gas-liquid
refrigerant. The two-phase gas-liquid refrigerant flows into the
second intermediate heat exchanger 15b, acting as an evaporator,
removes heat from the heat medium circulated through the heat
medium circuit, so that the refrigerant turns into low-temperature
low-pressure gas refrigerant while cooling the heat medium. The gas
refrigerant, which has flowed out of the second intermediate heat
exchanger 15b, passes through the expansion valve 16c, flows out of
the second relay unit 3b and the first relay unit 3a, passes
through the refrigerant pipe 4, and flows into the heat source unit
1. The refrigerant, which has flowed into the heat source unit 1,
passes through the check valve 13d, the four-way valve 11, and the
accumulator 17, and is then again sucked into the compressor 10.
The expansion valves 16b and 16d are allowed to have such a small
opening degree that the refrigerant does not flow through the valve
and the expansion valve 16c is fully opened in order to prevent
pressure loss.
[0093] Next, the flow of the heat medium in the heat medium circuit
will be described.
[0094] In the cooling only operation mode, the pump 21a is in
non-operation and the heat medium is accordingly circulated through
the pipes 5b. The pump 21b allows the heat medium cooled by the
heat source side refrigerant in the second intermediate heat
exchanger 15b to flow through the pipes 5b. The heat medium,
pressurized by the pump 21b, leaving the pump 21b passes through
the flow switching valves 22 (the flow switching valve 22a and the
flow switching valve 22b) and the stop valves 24 (the stop valve
24a and the stop valve 24b) and flows into the use side heat
exchangers 26 (the use side heat exchanger 26a and the use side
heat exchanger 26b). In each use side heat exchanger 26, the heat
medium removes heat from indoor air to cool the air-conditioned
area, such as an indoor space, where the indoor unit 2 is
installed.
[0095] After that, the heat medium flows out of the use side heat
exchangers 26 and flows into the flow control valves 25 (the flow
control valve 25a and the flow control valve 25b). At this time,
each flow control valve 25 allows only the amount of heat medium
required to provide an air-conditioning load needed in the
air-conditioned area, such as an indoor space, to flow into the
corresponding use side heat exchanger 26. The other heat medium
flows through each of the bypasses 27 (the bypass 27a and the
bypass 27b) so as to bypass the use side heat exchanger 26.
[0096] The heat medium passing through each bypass 27 does not
contribute to heat exchange and merges with the heat medium leaving
the corresponding use side heat exchanger 26. The heat medium then
passes through the corresponding flow switching valve 23 (the flow
switching valve 23a or the flow switching valve 23b) and flows into
the second intermediate heat exchanger 15b and is then again sucked
into the pump 21b. Note that the air-conditioning load needed in
each air-conditioned area, such as an indoor space, can be provided
by controlling the difference between a temperature detected by the
third temperature sensor 33 and a temperature detected by the
fourth temperature sensor 34 at a target value.
[0097] In this case, it is unnecessary to supply the heat medium to
each use side heat exchanger 26 having no thermal load (including
thermo-off). Accordingly, the corresponding stop valve 24 is closed
to block the passage so that the heat medium does not flow into the
use side heat exchanger 26. In FIG. 4, the heat medium flows into
the use side heat exchanger 26a and the use side heat exchanger 26b
because these heat exchangers each have a thermal load. The use
side heat exchanger 26c and the use side heat exchanger 26d have no
thermal load and the corresponding stop valves 24c and 24d are
accordingly closed. When a cooling load is generated in the use
side heat exchanger 26c or the use side heat exchanger 26d, the
stop valve 24c or the stop valve 24d may be opened so that the heat
medium is circulated.
[0098] The same applies to the heating only operation mode, the
cooling main operation mode, and the heating only operation mode
which will be described later.
(Heating Only Operation Mode)
[0099] FIG. 5 is a refrigerant circuit diagram illustrating the
flows of the refrigerant in the heating only operation mode of the
air-conditioning apparatus 100. The heating only operation mode
will be described on the assumption that, for example, a heating
load is generated only in the use side heat exchangers 26a and 26b
in FIG. 5. In other words, FIG. 5 illustrates a case where no
heating load is generated in the use side heat exchangers 26c and
26d. In FIG. 5, pipes indicated by thick lines correspond to pipes
through which the refrigerants (the heat source side refrigerant
and the heat medium) are circulated. Furthermore, solid-line arrows
indicate the direction of flow of the heat source side refrigerant
and broken-line arrows indicate the direction of flow of the heat
medium.
[0100] In the heating only operation mode illustrated in FIG. 5, in
the heat source unit 1, the four-way valve 11 is switched so that
the heat source side refrigerant discharged from the compressor 10
flows into the relay unit 3 without passing through the heat source
side heat exchanger 12. In the relay unit 3, the pump 21a is
driven, the pump 21b is in non-operation, the stop valves 24a and
24b are opened, and the stop valves 24c and 24d are closed to
switch between the heat medium flow directions so that the heat
medium is circulated between the first intermediate heat exchanger
15a and the use side heat exchangers 26 (the use side heat
exchanger 26a and the use side heat exchanger 26b). In this state,
the compressor 10 is started to operate.
[0101] First, the flow of the heat source side refrigerant in the
refrigeration cycle will be described.
[0102] Low-temperature low-pressure refrigerant is compressed into
high-temperature high-pressure gas refrigerant by the compressor 10
and is then discharged therefrom. The high-temperature
high-pressure gas refrigerant discharged from the compressor 10
passes through the four-way valve 11, flows through the first
connecting pipe 4a, passes through the check valve 13b, and flows
out of the heat source unit 1. The high-temperature high-pressure
gas refrigerant, which has flowed out of the heat source unit 1,
passes through the refrigerant pipe 4 and flows into the first
relay unit 3a. The high-temperature high-pressure gas refrigerant,
which has flowed into the first relay unit 3a, flows into the
gas-liquid separator 14 and then flows into the first intermediate
heat exchanger 15a. The high-temperature high-pressure gas
refrigerant, which has flowed into the first intermediate heat
exchanger 15a, condenses and liquefies while transferring heat to
the heat medium circulated through the heat medium circuit, so that
the refrigerant turns into high-pressure liquid refrigerant.
[0103] The high-pressure liquid refrigerant leaving the first
intermediate heat exchanger 15a is expanded by the expansion valve
16d, so that the refrigerant turns into a low-temperature,
low-pressure two-phase gas-liquid state. The refrigerant in the
two-phase gas-liquid state, obtained by expanding through the
expansion valve 16d, passes through the expansion valve 16b, flows
through the refrigerant pipe 4, and then flows into the heat source
unit 1. The refrigerant, which has flowed into the heat source unit
1, passes through the check valve 13c and the second connecting
pipe 4b and then flows into the heat source side heat exchanger 12,
acting as an evaporator. The refrigerant, which has flowed into the
heat source side heat exchanger 12, removes heat from the outdoor
air in the heat source side heat exchanger 12, so that the
refrigerant turns into low-temperature low-pressure gas
refrigerant. The low-temperature low-pressure gas refrigerant
leaving the heat source side heat exchanger 12 passes through the
four-way valve 11 and the accumulator 17 and then returns to the
compressor 10. The expansion valve 16a, the expansion valve 16c,
and the expansion valve 16e are allowed to have such a small
opening degree that the refrigerant does not flow through the
valve.
[0104] Next, the flow of the heat medium in the heat medium circuit
will be described.
[0105] In the heating only operation mode, the pump 21b is in
non-operation and the heat medium is accordingly circulated through
the pipes 5a. The pump 21a allows the heat medium heated by the
heat source side refrigerant in the first intermediate heat
exchanger 15a to flow through the pipes 5a. The heat medium,
pressurized by the pump 21a, leaving the pump 21a passes through
the flow switching valves 22 (the flow switching valve 22a and the
flow switching valve 22b) and the stop valves 24 (the stop valve
24a and the stop valve 24b) and flows into the use side heat
exchangers 26 (the use side heat exchanger 26a and the use side
heat exchanger 26b). In each use side heat exchanger 26, the heat
medium transfers heat to the indoor air to heat the air-conditioned
area, such as an indoor space, where the indoor unit 2 is
installed.
[0106] After that, the heat medium flows out of the use side heat
exchangers 26 and flows into the flow control valves 25 (the flow
control valve 25a and the flow control valve 25b). At this time,
each flow control valve 25 allows only the amount of heat medium
required to provide an air-conditioning load needed in the
air-conditioned area, such as an indoor space, to flow into the
corresponding use side heat exchanger 26. The other heat medium
flows through each of the bypasses 27 (the bypass 27a and the
bypass 27b) so as to bypass the use side heat exchanger 26.
[0107] The heat medium passing through each bypass 27 does not
contribute to heat exchange and merges with the heat medium leaving
the corresponding use side heat exchanger 26. The heat medium then
passes through the corresponding flow switching valve 23 (the flow
switching valve 23a or the flow switching valve 23b) and flows into
the first intermediate heat exchanger 15a and is then again sucked
into the pump 21a. Note that the air-conditioning load needed in
each air-conditioned area, such as an indoor space, can be provided
by controlling the difference between a temperature detected by the
third temperature sensor 33 and a temperature detected by the
fourth temperature sensor 34 at a target value.
(Cooling Main Operation Mode)
[0108] FIG. 6 is a refrigerant circuit diagram illustrating the
flows of the refrigerant in the cooling main operation mode of the
air-conditioning apparatus 100. The cooling main operation mode
will be described on the assumption that, for example, a heating
load is generated in the use side heat exchanger 26a and a cooling
load is generated in the use side heat exchanger 26b in FIG. 6. In
other words, FIG. 6 illustrates a case where neither heating load
nor cooling load is generated in the use side heat exchangers 26c
and 26d. In FIG. 6, pipes indicated by thick lines correspond to
pipes through which the refrigerants (the heat source side
refrigerant and the heat medium) are circulated. Furthermore,
solid-line arrows indicate the direction of flow of the heat source
side refrigerant and broken-line arrows indicate the direction of
flow of the heat medium.
[0109] In the cooling main operation mode illustrated in FIG. 6, in
the heat source unit 1, the four-way valve 11 is switched so that
the heat source side refrigerant discharged from the compressor 10
flows into the heat source side heat exchanger 12. In the relay
unit 3, the pumps 21a and 21b are driven, the stop valves 24a and
24b are opened, and the stop valves 24c and 24d are closed so that
the heat medium is circulated between the first intermediate heat
exchanger 15a and the use side heat exchanger 26a and the heat
medium is circulated between the second intermediate heat exchanger
15b and the use side heat exchanger 26b. In this state, the
compressor 10 is started to operate.
[0110] First, the flow of the heat source side refrigerant in the
refrigeration cycle will be described.
[0111] Low-temperature low-pressure refrigerant is compressed into
high-temperature high-pressure gas refrigerant by the compressor 10
and is then discharged therefrom. The high-temperature
high-pressure gas refrigerant discharged from the compressor 10
passes through the four-way valve 11 and flows into the heat source
side heat exchanger 12. In the heat source side heat exchanger 12,
the refrigerant condenses while transferring heat to the outdoor
air, so that the refrigerant turns into a two-phase gas-liquid
refrigerant. The two-phase gas-liquid refrigerant, which has flowed
out of the heat source side heat exchanger 12, passes through the
check valve 13a, flows out of the heat source unit 1, passes
through the refrigerant pipe 4, and flows into the first relay unit
3a. The two-phase gas-liquid refrigerant, which has flowed into the
first relay unit 3a, flows into the gas-liquid separator 14 where
the refrigerant is separated into gas refrigerant and liquid
refrigerant. These refrigerants flow into the second relay unit
3b.
[0112] The gas refrigerant, obtained by separation through the
gas-liquid separator 14, flows into the first intermediate heat
exchanger 15a. The gas refrigerant, which has flowed into the first
intermediate heat exchanger 15a, condenses and liquefies while
transferring heat to the heat medium circulated through the heat
medium circuit, so that the refrigerant turns into liquid
refrigerant. The liquid refrigerant, which has flowed out of the
first intermediate heat exchanger 15a, passes through the expansion
valve 16d.
[0113] On the other hand, the liquid refrigerant, obtained by
separation through the gas-liquid separator 14, passes through the
expansion valve 16e. After that, the liquid refrigerant merges with
the liquid refrigerant leaving the expansion valve 16d after
condensation and liquefaction in the first intermediate heat
exchanger 15a. The refrigerant is then expanded by the expansion
valve 16a, so that the refrigerant turns into low-temperature,
low-pressure two-phase gas-liquid refrigerant. The refrigerant
flows into the second intermediate heat exchanger 15b.
[0114] The two-phase gas-liquid refrigerant removes heat from the
heat medium circulated through the heat medium circuit in the
second intermediate heat exchanger 15b, acting as an evaporator, so
that the refrigerant turns into low-temperature low-pressure gas
refrigerant while cooling the heat medium. The gas refrigerant,
which has flowed out of the second intermediate heat exchanger 15b,
passes through the expansion valve 16c, flows out of the second
relay unit 3b and the first relay unit 3a, passes through the
refrigerant pipe 4, and flows into the heat source unit 1. The
refrigerant, which has flowed into the heat source unit 1, passes
through the check valve 13d, the four-way valve 11, and the
accumulator 17, and is then again sucked into the compressor 10.
The expansion valve 16b is allowed to have such a small opening
degree that the refrigerant does not flow through the valve and the
expansion valve 16c is fully opened in order to prevent pressure
loss.
[0115] Next, the flow of the heat medium in the heat medium circuit
will be described.
[0116] In the cooling main operation mode, both the pump 21a and
the pump 21b are driven and the heat medium is accordingly
circulated through the pipes 5a and 5b. The pump 21a allows the
heat medium heated by the heat source side refrigerant in the first
intermediate heat exchanger 15a to flow through the pipes 5a. The
pump 21b allows the heat medium cooled by the heat source side
refrigerant in the second intermediate heat exchanger 15b to flow
through the pipes 5b.
[0117] The heat medium, pressurized by the pump 21a, leaving the
pump 21a passes through the flow switching valve 22a and the stop
valve 24a, and then flows into the use side heat exchanger 26a. The
heat medium transfers heat to the indoor air in the use side heat
exchanger 26a to heat the air-conditioned area, such as an indoor
space, where the indoor unit 2 is installed.
[0118] In addition, the heat medium, pressurized by the pump 21b,
leaving the pump 21b passes through the flow switching valve 22b
and the stop valve 24b, and then flows into the use side heat
exchanger 26b. The heat medium removes heat from the indoor air in
the use side heat exchanger 26b to cool the air-conditioned area,
such as an indoor space, where the indoor unit 2 is installed.
[0119] The heat medium, used for heating, flows into the flow
control valve 25a. At this time, the flow control valve 25a allows
only the amount of heat medium required to provide an
air-conditioning load needed in the air-conditioned area to flow
into the use side heat exchanger 26a. The other heat medium flows
through the bypass 27a so as to bypass the use side heat exchanger
26a. The heat medium passing through the bypass 27a does not
contribute to heat exchange and merges with the heat medium leaving
the use side heat exchanger 26a. The heat medium then passes
through the flow switching valve 23a and flows into the first
intermediate heat exchanger 15a and is then again sucked into the
pump 21a.
[0120] Similarly, the heat medium, used for cooling, flows into the
flow control valve 25b. At this time, the flow control valve 25b
allows only the amount of heat medium required to provide an
air-conditioning load needed in the air-conditioned area to flow
into the use side heat exchanger 26b. The other heat medium flows
through the bypass 27b so as to bypass the use side heat exchanger
26b. The heat medium passing through the bypass 27b does not
contribute to heat exchange and merges with the heat medium leaving
the use side heat exchanger 26b. The heat medium then passes
through the flow switching valve 23b and flows into the second
intermediate heat exchanger 15b and is then again sucked into the
pump 21b.
[0121] Throughout this mode, the flow switching valves 22 (the flow
switching valve 22a and the flow switching valve 22b) and the flow
switching valves 23 (the flow switching valve 23a and the flow
switching valve 23b) allow the warm heat medium (the heat medium
used for the heating load) and the cold heat medium (the heat
medium used for the cooling load) to flow into the use side heat
exchanger 26a having the heating load and the use side heat
exchanger 26b having the cooling load, respectively, without mixing
with each other. Note that the air-conditioning load needed in each
air-conditioned area, such as an indoor space, can be provided by
controlling the difference between a temperature detected by the
third temperature sensor 33 and a temperature detected by the
fourth temperature sensor 34 at a target value.
(Heating Main Operation Mode)
[0122] FIG. 7 is a refrigerant circuit diagram illustrating the
flows of the refrigerant in the heating main operation mode of the
air-conditioning apparatus 100. The heating main operation mode
will be described on the assumption that, for example, a heating
load is generated in the use side heat exchanger 26a and a cooling
load is generated in the use side heat exchanger 26b in FIG. 7. In
other words, FIG. 7 illustrates a case where neither heating load
nor cooling load is generated in the use side heat exchangers 26c
and 26d. In FIG. 7, pipes indicated by thick lines correspond to
pipes through which the refrigerants (the heat source side
refrigerant and the heat medium) are circulated. Furthermore,
solid-line arrows indicate the direction of flow of the heat source
side refrigerant and broken-line arrows indicate the direction of
flow of the heat medium.
[0123] In the heating main operation mode illustrated in FIG. 7, in
the heat source unit 1, the four-way valve 11 is switched so that
the heat source side refrigerant discharged from the compressor 10
flows into the relay unit 3 without passing through the heat source
side heat exchanger 12. In the relay unit 3, the pumps 21a and 21b
are driven, the stop valves 24a and 24b are opened, and the stop
valves 24c and 24d are closed so that the heat medium is circulated
between the first intermediate heat exchanger 15a and the use side
heat exchanger 26a and the heat medium is circulated between the
second intermediate heat exchanger 15b and the use side heat
exchanger 26b. In this state, the compressor 10 is started to
operate.
[0124] First, the flow of the heat source side refrigerant in the
refrigeration cycle will be described.
[0125] Low-temperature low-pressure refrigerant is compressed into
high-temperature high-pressure gas refrigerant by the compressor 10
and is then discharged therefrom. The high-temperature
high-pressure gas refrigerant discharged from the compressor 10
passes through the four-way valve 11, flows through the first
connecting pipe 4a, passes through the check valve 13b, and flows
out of the heat source unit 1. The high-temperature high-pressure
gas refrigerant, which has flowed out of the heat source unit 1,
passes through the refrigerant pipe 4 and flows into the first
relay unit 3a. The high-temperature high-pressure gas refrigerant,
which has flowed into the first relay unit 3a, flows into the
gas-liquid separator 14 and then flows into the first intermediate
heat exchanger 15a. The high-temperature high-pressure gas
refrigerant, which has flowed into the first intermediate heat
exchanger 15a, condenses and liquefies while transferring heat to
the heat medium circulated through the heat medium circuit, so that
the refrigerant turns into high-pressure liquid refrigerant.
[0126] The high-pressure liquid refrigerant leaving the first
intermediate heat exchanger 15a is expanded by the expansion valve
16d, so that the refrigerant turns into a low-temperature,
low-pressure two-phase gas-liquid state. The refrigerant in the
two-phase gas-liquid state, obtained by expanding through the
expansion valve 16d, is divided into a flow to the expansion valve
16a and a flow to the expansion valve 16b. As regards the
refrigerant flowing through the expansion valve 16a, the
refrigerant is further expanded by the expansion valve 16a, so that
the refrigerant turns into low-temperature, low-pressure two-phase
gas-liquid refrigerant. The refrigerant flows into the second
intermediate heat exchanger 15b, acting as an evaporator. The
refrigerant, which has flowed into the second intermediate heat
exchanger 15b, removes heat from the heat medium in the second
intermediate heat exchanger 15b, so that the refrigerant turns into
low-temperature low-pressure gas refrigerant. The low-temperature
low-pressure gas refrigerant leaving the second intermediate heat
exchanger 15b passes through the expansion valve 16c.
[0127] As regards the refrigerant, expanded by the expansion valve
16d, flowing through the expansion valve 16b, the refrigerant
merges with the refrigerant which has passed through the second
intermediate heat exchanger 15b and the expansion valve 16c, so
that the low-temperature low-pressure refrigerant exhibits a higher
quality. The refrigerant after merging flows out of the second
relay unit 3b and the first relay unit 3a, passes through the
refrigerant pipe 4, and flows into the heat source unit 1. The
refrigerant, which has flowed into the heat source unit 1, passes
through the check valve 13c and the second connecting pipe 4b and
flows into the heat source side heat exchanger 12, acting as an
evaporator. The refrigerant, which has flowed into the heat source
side heat exchanger 12, removes heat from the outdoor air in the
heat source side heat exchanger 12, so that the refrigerant turns
into low-temperature low-pressure gas refrigerant. The
low-temperature low-pressure gas refrigerant leaving the heat
source side heat exchanger 12 flows through the four-way valve 11
and the accumulator 17 and then returns to the compressor 10. The
expansion valve 16e is allowed to have such a small opening degree
that the refrigerant does not flow through the valve.
[0128] Next, the flow of the heat medium in the heat medium circuit
will be described.
[0129] In the heating main operation mode, both the pump 21a and
the pump 21b are driven and the heat medium is accordingly
circulated through the pipes 5a and 5b. The pump 21a allows the
heat medium heated by the heat source side refrigerant in the first
intermediate heat exchanger 15a to flow through the pipes 5a. The
pump 21b allows the heat medium cooled by the heat source side
refrigerant in the second intermediate heat exchanger 15b to flow
through the pipes 5b.
[0130] The heat medium, pressurized by the pump 21a, leaving the
pump 21a passes through the flow switching valve 22a and the stop
valve 24a and then flows into the use side heat exchanger 26a. The
heat medium transfers heat to the indoor air in the use side heat
exchanger 26a to heat the air-conditioned area, such as an indoor
space, where the indoor unit 2 is installed.
[0131] In addition, the heat medium, pressurized by the pump 21b,
leaving the pump 21b passes through the flow switching valve 22b
and the stop valve 24b and then flows into the use side heat
exchanger 26b. The heat medium removes heat from the indoor air in
the use side heat exchanger 26b to cool the air-conditioned area,
such as an indoor space, where the indoor unit 2 is installed.
[0132] The heat medium leaving the use side heat exchanger 26a
flows into the flow control valve 25a. At this time, the flow
control valve 25a allows only the amount of heat medium required to
provide an air-conditioning load needed in the air-conditioned
area, such as an indoor space, to flow into the use side heat
exchanger 26a. The other heat medium flows through the bypass 27a
so as to bypass the use side heat exchanger 26a. The heat medium
passing through the bypass 27a does not contribute to heat exchange
and merges with the heat medium leaving the use side heat exchanger
26a. The heat medium then passes through the flow switching valve
23a and flows into the first intermediate heat exchanger 15a and is
then again sucked into the pump 21a.
[0133] Similarly, the heat medium leaving the use side heat
exchanger 26b flows into the flow control valve 25b. At this time,
the flow control valve 25b allows only the amount of heat medium
required to provide an air-conditioning load needed in the
air-conditioned area, such as an indoor space, to flow into the use
side heat exchanger 26b. The other heat medium flows through the
bypass 27b so as to bypass the use side heat exchanger 26b. The
heat medium passing through the bypass 27b does not contribute to
heat exchange and merges with the heat medium leaving the use side
heat exchanger 26b. The heat medium then passes through the flow
switching valve 23b and flows into the second intermediate heat
exchanger 15b and is then again sucked into the pump 21b.
[0134] Throughout this mode, the flow switching valves 22 (the flow
switching valve 22a and the flow switching valve 22b) and the flow
switching valves 23 (the flow switching valve 23a and the flow
switching valve 23b) allow the warm heat medium and the cold heat
medium to flow into the use side heat exchanger 26a having the
heating load and the use side heat exchanger 26b having the cooling
load, respectively, without mixing with each other. Note that the
air-conditioning load needed in each air-conditioned area, such as
an indoor space, can be provided by controlling the difference
between a temperature detected by the third temperature sensor 33
and a temperature detected by the fourth temperature sensor 34 at a
target value.
[0135] As described above, while the heating load is generated in
any of the use side heat exchangers 26a to 26d in the
air-conditioning apparatus 100, the corresponding one of the flow
switching valves 22a to 22d and the corresponding one of the flow
switching valves 23a to 23d are switched to the passage connected
to the first intermediate heat exchanger 15a for heating. While the
cooling load is generated in any of the use side heat exchangers
26a to 26d, the corresponding one of the flow switching valves 22a
to 22d and the corresponding one of the flow switching valves 23a
to 23d are switched to the passage connected to the second
intermediate heat exchanger 15b for cooling. Thus, the heating
operation or the cooling operation can be freely performed in each
indoor unit 2.
[0136] Each of the flow switching valves 22a to 22d and the flow
switching valves 23a to 23d may be a component that can switch
between passages, for example, a three-way valve capable of
switching between flow directions in a three-way passage or a
combination of two two-way valves, such as on-off valves, for
opening and closing a two-way passage. Alternatively, a component
capable of changing a flow rate in a three-way passage, for
example, a stepping-motor-driven mixing valve, may be used, or, a
combination of two components capable of changing a flow rate in a
two-way passage, for example, two electronic expansion valves, may
be used as each of the flow switching valves. In this case, water
hammer caused when a passage is suddenly opened or closed can be
prevented.
[0137] Although FIGS. 3 to 7 illustrate the case where the flow
control valves 25a to 25d are mixing valves arranged downstream of
the use side heat exchangers 26a to 26d, the flow control valves
25a to 25d may be arranged on an upstream side of the use side heat
exchangers 26a to 26d.
[Control for Changing Number of Pumps 21 Operated in
Air-Conditioning Apparatus 100]
[0138] FIG. 8 is a flowchart illustrating an exemplary control
process for changing the number of pumps 21 operated in the
air-conditioning apparatus 100. Control for changing the number of
operated pumps 21 at a low flow rate in the air-conditioning
apparatus 100 will be described with reference to FIG. 8. The
controller 60 performs the control process for changing the number
of operated pumps 21.
(STEP 1)
[0139] In STEP 1, the air-conditioning apparatus 100 starts an
air-conditioning operation and the compressor 10 is actuated. Just
after actuation of the compressor 10, for example, a maximum number
of pumps 21 are operated in order to allow an extra amount of heat
medium to flow in the air-conditioning apparatus 100.
(STEP 2)
[0140] In STEP 2, the maximum number of pumps 21 (the two pumps 21a
and 21b in FIGS. 3 to 7) are started to operate. An accumulated
period of operating time of each pump is recorded.
(STEP 3)
[0141] In STEP 3, the current operation is repeated until a
predetermined period of time elapses.
(STEP 4)
[0142] In STEP 4, whether all of the pumps 21 are used for cooling
or heating, that is, whether the operation mode is the cooling only
operation mode or the heating only operation mode is
determined.
[0143] If the operation mode is the cooling only operation mode or
the heating only operation mode, the process proceeds to STEP 5. If
NO, the current operation is maintained.
(STEP 5)
[0144] In STEP 5, whether a capacity for operating the indoor units
2 (operation capacity for the indoor units 2) is less than or equal
to a predetermined value X is determined. The predetermined value X
is a reference for changing the number of operated pumps 21. The
predetermined value X is set to any value based on actual
performance of the air-conditioning apparatus 100.
[0145] If the operation capacity is less than or equal to the
predetermined value X, the process proceeds to STEP 6. If NO, the
process proceeds to STEP 10.
[0146] The predetermined value X is set to any value based on flow
rate characteristics of the pumps 21, the length of the water pipes
5, and the capacities of the indoor units 2 connected.
(STEP 6)
[0147] STEP 6 is processing to be performed when it is determined
that the amount of heat medium circulated is too much relative to
the operation capacity for the indoor units 2.
[0148] In this case, whether the maximum number of pumps 21 have
been operated is determined.
[0149] If it is determined that the maximum number of pumps 21 have
been operated, the process proceeds to STEP 7. If NO, the process
proceeds to STEP 9.
(STEP 7)
[0150] In STEPs 7 and 8, rotation control is performed to equalize
the periods of operating time of the pumps 21.
[0151] In STEP 7, priorities assigned to the operated pumps 21 are
determined.
[0152] The pump 21 assigned a lower priority is stopped.
[0153] The priority assigned to each of the pumps 21 is determined
based on the accumulated period of operating time of the pump 21.
Alternatively, the number of times the pump 21 is actuated may be
counted for each of the pumps 21 and the priority assigned to each
of the pumps 21 may be determined based on the number of times the
pump 21 is actuated.
(STEP 8)
[0154] In STEP 8, the pump 21 assigned a lower priority is stopped
and the process proceeds to STEP 9.
[0155] For example, if the pumps 21a and 21b are operated and the
pump 21a is assigned a lower priority than the pump 21b, the pump
21a is stopped in STEP 8a.
[0156] For example, if the pumps 21a and 21b are operated and the
pump 21b is assigned a lower priority than the pump 21a, the pump
21b is stopped in STEP 8b.
(STEP 9)
[0157] In STEP 9, whether the operation capacity for the indoor
units 2 has changed is determined.
[0158] If the operation capacity for the indoor units 2 has
changed, the process is returned to STEP 4 in order to make a
determination.
(STEP 10)
[0159] In STEPs 10 to 12, control for changing the number of
operated pumps 21 from one to two pumps because of an increase in
operation capacity for the indoor units 2 is performed.
[0160] In STEP 10, whether the operation capacity for the indoor
units 2 is greater than the predetermined value X and is greater
than or equal to a value (hereinafter, referred to as a "value C")
that takes a differential into account is determined.
[0161] The differential is provided to stabilize an operation.
Providing the differential can reduce frequent changing of the
number of operated pumps 21.
[0162] If the operation capacity (.SIGMA.Qj) for the indoor units 2
is greater than the predetermined value X and is greater than or
equal to the value C, the process proceeds to STEP 11. If NO, the
process proceeds to STEP 9 without doing anything.
[0163] The value C is used to reduce frequent changing of the
number of operated pumps 21 and is set to any value based on the
actual performance of the air-conditioning apparatus 100. In other
words, the value C is used to reduce the number of times the pump
21 is actuated or stopped. The value C is determined based on the
flow rate characteristics (maximum circulation amount) of each pump
21 and a permissible total length of pipes (pressure loss in the
entire water circuit).
(STEP 11)
[0164] In STEP 11, whether the maximum number of pumps 21 are
operated is determined.
[0165] If the maximum number of pumps 21 are operated, the process
proceeds to STEP 9 without doing anything.
[0166] If the number of operated pumps 21 is not equal to the
maximum number, the process proceeds to STEP 12.
(STEP 12)
[0167] In STEP 12, the pump 21 in non-operation is actuated. The
pump 21 is actuated at minimum input power (minimum voltage) in
order to suppress a sudden increase in water pressure.
[0168] Then, the process proceeds to STEP 9.
[0169] The control is terminated by stopping the compressor 10.
[0170] Although Embodiment has been described with respect to the
control for changing the number of pumps 21 in the use of the two
pumps 21, the number of pumps 21 is not limited to two. Similar
control for changing the number of pumps 21 in the use of three or
more pumps 21 can be achieved.
[0171] In the use of three or more pumps 21, the number of operated
pumps 21 is defined in STEPs 6 to 8. The pump 21 is stopped in
order of increasing priority depending on the operation capacity
for the indoor units 2.
[0172] As described above, the air-conditioning apparatus 100 is
configured such that the number of operated pumps 21 is changed
depending on the operation capacity for the indoor units 2
connected. Thus, a highly efficient operation with reduced pump
power consumption is achieved. Such an advantage is particularly
great when the heat medium flows at a low flow rate. Additionally,
since the current operation mode of the indoor unit 2 connected is
taken into consideration, the efficiency of operation can be
further increased.
[0173] Although Embodiment has been described with respect to the
case where both the first temperature sensors 31 and the second
temperature sensors 32 are arranged, it is only required that
either of the first temperature sensors 31 and the second
temperature sensors 32 are arranged in order to control the pumps
21a and 21b. The other temperature detecting means may be
eliminated.
[0174] As regards the heat source side refrigerant, for example,
hydrofluorocarbon (HFC) refrigerant, such as R410A, R407C, or
R404A, hydrochlorofluorocarbon (HCFC) refrigerant, such as R22 or
R134a, refrigerant that contains a double bond in its chemical
formula and has a relatively low global warming potential, for
example, CF.sub.3CF.dbd.CH.sub.2, a mixture containing the
refrigerant, or natural refrigerant, such as hydrocarbon, helium,
or carbon dioxide, can be used in Embodiment as described above.
The refrigerant is not limited to any of those examples. In
addition, although Embodiment has been described with respect to
the case where the heat source unit 1 includes the accumulator 17,
the air-conditioning apparatus 100 will act in the same way and
offer the same advantages if the accumulator 17 is eliminated.
[0175] Each of the heat source side heat exchanger 12 and the use
side heat exchangers 26 is often typically provided with an
air-sending device, such as a fan, to send air in order to promote
condensation or evaporation. The configuration is not limited to
such a case. For example, a heat exchanger that uses radiation, for
example, a panel heater, can be used as the use side heat exchanger
26 and a water-cooled heat exchanger that transfers heat through
water or antifreeze can be used as the heat source side heat
exchanger 12. Any type of heat exchanger capable of transferring
heat or removing heat may be used.
[0176] Although the case where the flow switching valve 22, the
flow switching valve 23, the stop valve 24, and the flow control
valve 25 are arranged for each use side heat exchanger 26 has been
described above, the configuration is not limited to this case. For
example, a plurality of flow switching valves 22, a plurality of
flow switching valves 23, a plurality of stop valves 24, and a
plurality of flow control valves 25 may be connected to each use
side heat exchanger 26. In this case, the flow switching valves 22,
the flow switching valves 23, the stop valves 24, and the flow
control valves 25 connected to the same use side heat exchanger 26
may be operated in the same way as described above. Although the
case where the two intermediate heat exchangers 15 are arranged has
been described above, any number of intermediate heat exchangers
may be arranged. Three or more intermediate heat exchangers capable
of cooling or/and heating the heat medium may be arranged.
[0177] Although the case where each flow control valve 25, each
third temperature sensor 33, and each fourth temperature sensor 34
are arranged within the second relay unit 3b has been described
above, one or all of these components may be arranged within the
corresponding indoor unit 2. The arrangement of these components
within the second relay unit 3b facilitates maintenance because,
for example, the valves and pumps for the heat medium are
accommodated in the same housing. On the other hand, the
arrangement of these components within the indoor unit 2 allows the
components to be manageable because the components can be dealt
with like an expansion valve in a related-art direct-expansion
indoor unit. In addition, since the components are arranged near
the use side heat exchanger 26, a thermal load in the indoor unit 2
can be effectively controlled without being affected by heat loss
in an extension pipe.
REFERENCE SIGNS LIST
[0178] 1 heat source unit, 2 indoor unit, 2a indoor unit, 2b indoor
unit, 2c indoor unit, 2d indoor unit, 3 relay unit, 3a first relay
unit, 3b second relay unit, 4 refrigerant pipe, 4a first connecting
pipe, 4b second connecting pipe, 5 pipe, 5a pipe, 5b pipe, 6
outdoor space, 7 living space, 9 structure, 10 compressor, 11
four-way valve, 12 heat source side heat exchanger, 13a check
valve, 13b check valve, 13c check valve, 13d check valve, 14
gas-liquid separator, 15 intermediate heat exchanger, 15a first
intermediate heat exchanger, 15b second intermediate heat
exchanger, 16 expansion valve, 16a expansion valve, 16b expansion
valve, 16c expansion valve, 16d expansion valve, 16e expansion
valve, 17 accumulator, 21 pump, 21a pump (first pump), 21b pump
(second pump), 22 flow switching valve, 22a flow switching valve,
22b flow switching valve, 22c flow switching valve, 22d flow
switching valve, 23 flow switching valve, 23a flow switching valve,
23b flow switching valve, 23c flow switching valve, 23d flow
switching valve, 24 stop valve, 24a stop valve, 24b stop valve, 24c
stop valve, 24d stop valve, 25 flow control valve, 25a flow control
valve, 25b flow control valve, 25c flow control valve, 25d flow
control valve, 26 use side heat exchanger, 26a use side heat
exchanger, 26b use side heat exchanger, 26c use side heat
exchanger, 26d use side heat exchanger, 27 bypass, 27a bypass, 27b
bypass, 27c bypass, 27d bypass, 31 first temperature sensor, 31a
first temperature sensor, 31b first temperature sensor, 32 second
temperature sensor, 32a second temperature sensor, 32b second
temperature sensor, 33 third temperature sensor, 33a third
temperature sensor, 33b third temperature sensor, 33c third
temperature sensor, 33d third temperature sensor, 34 fourth
temperature sensor, 34a fourth temperature sensor, 34b fourth
temperature sensor, 34c fourth temperature sensor, 34d fourth
temperature sensor, 35 fifth temperature sensor, 36 pressure
sensor, 37 sixth temperature sensor, 38 seventh temperature sensor,
39 pressure sensor, 40 pressure sensor, 50 non-living space, 60
controller, 71a discharge valve, 71b discharge valve, 100
air-conditioning apparatus
* * * * *