[Technical Field]
[0001] The present disclosure relates to a heat source device and a control method thereof
suitable for use in a heat pump chiller or the like, for example.
[Background Art]
[0002] Heat pump chillers are used as one of heat source devices for industrial use or the
like. When a heat pump chiller is used in a heating operation to supply hot water,
a lower ambient temperature particularly tends to cause a high pressure ratio and
a higher temperature of a refrigerant discharged from a compressor. When a low-boiling
refrigerant such as R32 is used as a low global warming potential (GWP) refrigerant,
the refrigerant discharge temperature will be much higher. Since a higher refrigerant
discharge temperature makes it difficult to use conventional components that have
been used for refrigerants which are not a low-boiling refrigerant, it is required
to reduce the refrigerant discharge temperature.
[0003] Patent Literature 1 discloses that a part of a refrigerant guided from an indoor
unit is expanded by a throttle device to a gas-liquid two-phase, this two-phase refrigerant
is supplied to the refrigerant intake side of a compressor, and thereby the refrigerant
discharge temperature is reduced.
[Citation List]
[Patent Literature]
[Summary of Invention]
[Technical Problem]
[0005] In Patent Literature 1, however, since a refrigerant in a gas-liquid two-phase is
used as a cooling refrigerant, the specific volume of the refrigerant becomes larger
than that of a liquid refrigerant, and this results in a larger diameter of a pipe.
This is an obstacle not only to improvement of piping arrangement but also to a cost
reduction.
[0006] When a cooling operation in addition to a heating operation is performed by a heat
pump, since a required amount of a refrigerant differs for each operation, there is
a problem of an excessive refrigerant in use.
[0007] In Patent Literature 1, a throttle device is provided in a pipe that guides a gas-liquid
two-phase refrigerant used for cooling, and the opening of the throttle device is
controlled. However, it is complicated to perform opening control of the throttle
device in addition to expansion valve control of the main refrigerant circuit.
[0008] The present disclosure has been made in view of such circumstances and intends to
provide a heat source device and a control method thereof that can reduce the diameter
of a pipe used for supplying a cooling refrigerant to be guided to the intake side
of a compressor.
[0009] Further, the present disclosure intends to provide a heat source device and a control
method thereof that can reduce the amount of a used refrigerant even with a heat source
device that performs a heating operation and a cooling operation.
[0010] Further, the present disclosure intends to provide a heat source device and a control
method thereof that can supply a cooling refrigerant to the intake side of a compressor
by using simple control.
[Solution to Problem]
[0011] A heat source device according to one aspect of the present disclosure includes:
a compressor configured to compress a refrigerant; a heat medium heat exchanger configured
to perform heat exchange between a refrigerant and a heat medium; an expansion valve
configured to expand a refrigerant; an air heat exchanger configured to perform heat
exchange between a refrigerant and air; and a liquid bypass pipe configured to guide
a liquid refrigerant to an intake side of the compressor, an upstream end of the liquid
bypass pipe being connected between the heat medium heat exchanger and the expansion
valve.
[0012] A control method of a heat source device according to one aspect of the present disclosure
is a control method of a heat source device including a compressor configured to compress
a refrigerant, a heat medium heat exchanger configured to perform heat exchange between
a refrigerant and a heat medium, an expansion valve configured to expand a refrigerant,
an air heat exchanger configured to perform heat exchange between a refrigerant and
air, a liquid bypass pipe configured to guide a liquid refrigerant to an intake side
of the compressor, a liquid bypass pipe configured to guide a liquid refrigerant to
an intake side of the compressor, an upstream end of the liquid bypass pipe being
connected between the heat medium heat exchanger and the expansion valve, a liquid
bypass valve provided in the liquid bypass pipe, and a selector valve configured to
guide a refrigerant discharged from the compressor to the heat medium heat exchanger
during a heating operation for heating the heat medium and guide a refrigerant discharged
from the compressor to the air heat exchanger during a cooling operation for cooling
the heat medium, and the control method includes: controlling the liquid bypass valve
from a closed position to an open position when the heating operation is performed
and when an air temperature around the air heat exchanger becomes a predetermined
value or lower.
[Advantageous Effects of Invention]
[0013] It is possible to reduce the diameter of a pipe used for supplying a cooling refrigerant
to be guided to the intake side of a compressor.
[0014] The amount of a used refrigerant can be reduced even with a heat source device that
performs a heating operation and a cooling operation.
[0015] A cooling refrigerant can be supplied to the intake side of a compressor by using
simple control.
[Brief Description of Drawings]
[0016]
[Fig. 1]
Fig. 1 is a schematic configuration diagram illustrating a refrigerant circuit during
a heating operation according to a first embodiment of the present disclosure.
[Fig. 2]
Fig. 2 is a schematic configuration diagram illustrating the refrigerant circuit during
a cooling operation according to the first embodiment of the present disclosure.
[Fig. 3]
Fig. 3 is a schematic configuration diagram illustrating a refrigerant circuit during
a heating operation according to a second embodiment of the present disclosure.
[Fig. 4]
Fig. 4 is a schematic configuration diagram illustrating the refrigerant circuit during
a cooling operation according to the second embodiment of the present disclosure.
[Fig. 5]
Fig. 5 is a graph illustrating a p-h diagram of a refrigerant circuit according to
a third embodiment of the present disclosure.
[Fig. 6]
Fig. 6 is a schematic configuration diagram illustrating a refrigerant circuit illustrating
a modified example of the third embodiment of the present disclosure.
[Description of Embodiments]
[0017] Each embodiment according to the present disclosure will be described below with
reference to the drawings.
[First Embodiment]
[0018] A first embodiment of the present disclosure will be described below with reference
to Fig. 1 and Fig. 2.
[0019] Fig. 1 and Fig. 2 illustrate a refrigerant circuit configuration of a chiller (heat
source device) 1 of the present embodiment. The chiller 1 can perform a heating operation
and a cooling operation by switching a four-way valve (selector valve) 4 provided
on the discharge side of the compressor 3. The heating operation is an operation to
heat water (heat medium) in a water heat exchanger (heat medium heat exchanger) 5,
and the cooling operation is an operation to cool water in the water heat exchanger
5. Fig. 1 illustrates a refrigerant circuit when the heating operation is performed,
and Fig. 2 illustrates the refrigerant circuit when the cooling operation is performed.
[0020] In the chiller 1, for example, R32 is used as a refrigerant. The R32 is a low-boiling
refrigerant, which is a low global warming potential (GWP) refrigerant. Other refrigerants
may be used instead of the R32.
[0021] The chiller 1 has the compressor 3 that compresses a refrigerant, the four-way valve
4, the water heat exchanger 5, a first expansion valve 6, a receiver 7, a second expansion
valve 8, an air heat exchanger 9, and an accumulator 10. The compressor 3, the four-way
valve 4, the water heat exchanger 5, the first expansion valve 6, the receiver 7,
the second expansion valve 8, the air heat exchanger 9, and the accumulator 10 are
connected to each other via refrigerant pipes, and thereby a refrigerant circuit that
performs a refrigeration cycle is formed.
[0022] The compressor 3 is a scroll compressor or a rotary compressor, for example, and
a compression mechanism 3b such as a scroll compression mechanism or a rotary compression
mechanism is provided inside a housing 3a of the compressor 3. A compression mechanism
3b is driven by an electric motor (not illustrated). The electric motor has an invertor
device, and the rotational rate thereof may be changed to any value in accordance
with an instruction from a control unit (not illustrated).
[0023] A discharge temperature sensor 14 that measures the discharge temperature of a refrigerant
is provided on the discharge side of the compressor 3. The output of the discharge
temperature sensor 14 is transmitted to the control unit.
[0024] The four-way valve 4 is switched so that a refrigerant discharged from the compressor
3 is guided to the water heat exchanger 5 during a heating operation (Fig. 1) and
is switched so that a refrigerant discharged from the compressor 3 is guided to the
air heat exchanger 9 during a cooling operation (Fig. 2). The control of the four-way
valve 4 is performed by a control unit (not illustrated).
[0025] The water heat exchanger 5 operates as a condenser during a heating operation (Fig.
1) and operates as an evaporator during a cooling operation (Fig. 2). A water pipe
16 that circulates water to and from an external load is connected to the water heat
exchanger 5. In the water heat exchanger 5, heat exchange is performed between water
guided from the water pipe 16 and a refrigerant.
[0026] The first expansion valve 6 expands a refrigerant condensed and liquified by the
water heat exchanger 5 when operating as a condenser as with Fig. 1. The opening of
the first expansion valve 6 is controlled by the control unit.
[0027] The second expansion valve 8 expands a refrigerant condensed and liquified by the
air heat exchanger 9 when operating as a condenser as with Fig. 2. The opening of
the second expansion valve 8 is controlled by the control unit.
[0028] The receiver 7 is a container provided between the first expansion valve 6 and the
second expansion valve 8 and configured to temporarily store a part of a refrigerant
expanded by the first expansion valve 6 or the second expansion valve 8. The capacity
(size) of the receiver 7 is determined in accordance with an amount of a refrigerant
circulating in the refrigerant circuit.
[0029] The air heat exchanger 9 operates as an evaporator during a heating operation (Fig.
1) and operates as a condenser during a cooling operation (Fig. 2). In the air heat
exchanger 9, heat exchange is performed between a refrigerant and air. Air is delivered
from a fan 12 to the air heat exchanger 9.
[0030] The accumulator 10 is a container provided in upstream of the compressor 3, that
is, on the refrigerant intake side and configured to temporarily store a refrigerant
evaporated by the air heat exchanger 9 or the water heat exchanger 5.
[0031] The upstream end of a liquid bypass pipe 20 is connected between the water heat exchanger
5 and the first expansion valve 6. The downstream end of the liquid bypass pipe 20
is connected to the intake side of the compression mechanism 3b of the compressor
3. A part of a liquid refrigerant guided from the water heat exchanger 5 operating
as a condenser during a heating operation is guided to the compression mechanism 3b
via a liquid bypass valve 22. That is, the liquid bypass valve 22 bypasses the first
expansion valve 6, the receiver 7, the second expansion valve 8, the air heat exchanger
9, and the accumulator 10.
[0032] The liquid bypass valve 22 is provided in an intermediate position of the liquid
bypass pipe 20. The liquid bypass valve 22 is an on-off valve such as an electromagnetic
valve, and the on-off operation thereof is performed by the control unit.
[0033] An ambient temperature sensor 18 is provided inside the casing of the chiller 1 or
near the chiller 1. The ambient temperature is measured by the ambient temperature
sensor. The ambient temperature measured by the ambient temperature sensor 18 represents
a temperature of air guided to the air heat exchanger 9 by the fan 12. The output
of the ambient temperature sensor 18 is transmitted to the control unit.
[0034] The control unit is formed of a central processing unit (CPU), a random access memory
(RAM), a read only memory (ROM), a computer readable storage medium, and the like,
for example. Further, a series of processes for implementing various functions are
stored in a storage medium or the like in a form of a program as an example, and various
functions are implemented when the CPU loads the program into the RAM or the like
and performs information processing and computation. For a program, a form of being
installed in advance in the ROM or other storage media, a form of being provided in
a state of being stored in a computer readable storage medium, a form of being delivered
via a wired or wireless communication connection, or the like may be applied to the
program. The computer readable storage medium may be a magnetic disk, a magneto-optical
disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.
[0035] Next, the operation of the chiller 1 configured as above will be described.
<Heating operation: Fig. 1>
[0036] When water is heated by the water heat exchanger 5, the four-way valve 4 is switched
as illustrated in Fig. 1, and thereby a high-pressure gas refrigerant discharged from
the compressor 3 is guided to the water heat exchanger 5. In the water heat exchanger
5, heat exchange with water guided from the water pipe 16 causes the refrigerant to
condense. Water is heated by latent heat occurring when the refrigerant condenses.
The heated water is guided to the external load via the water pipe 16.
[0037] The liquid refrigerant condensed by the water heat exchanger 5 is guided to the first
expansion valve 6 and expanded. The expanded refrigerant is guided to the receiver
7, and a part of the refrigerant is stored in the receiver 7 as an excessive refrigerant.
The refrigerant taken out of the receiver 7 is guided to the air heat exchanger 9
via the second expansion valve 8.
[0038] In the air heat exchanger 9, heat exchange with air guided by the fan 12 causes the
refrigerant to evaporate. The refrigerant evaporating from the air heat exchanger
9 is guided to the accumulator 10 through the four-way valve 4. The gas refrigerant
guided from the accumulator 10 is guided to the intake side of the compressor 3 and
is again compressed by the compression mechanism 3b.
[0039] The control unit controls the liquid bypass valve 22, which is provided in the liquid
bypass pipe 20, from a closed position to an open position when the ambient temperature
measured by the ambient temperature sensor 18 falls to a low ambient temperature that
is a predetermined value or lower (for example, 0 □ or lower or -5 □ or lower). Accordingly,
a part of a liquid refrigerant guided from the water heat exchanger 5 is guided to
the intake side of the compression mechanism 3b of the compressor 3 via the liquid
bypass pipe 20. The liquid refrigerant is supplied to the intake side of the compression
mechanism 3b in such a way, and thereby the discharge temperature of the refrigerant
discharged from the compressor 3 is reduced.
[0040] Closing and opening of the liquid bypass valve 22 may be controlled by using a temperature
measured by the discharge temperature sensor 14 or a pressure ratio of the compressor
3 in addition to a temperature measured by the ambient temperature sensor 18 or instead
of a temperature measured by the ambient temperature sensor 18. For example, when
the measurement value of the discharge temperature sensor 14 reaches a temperature
corresponding to a case where the temperature of water heated by the water heat exchanger
5 is 50 □ and/or when the pressure ratio of the compressor 3 rises to 4.5 or higher,
the liquid bypass valve 22 is controlled from a closed position to an open position.
<Cooling operation: Fig. 2>
[0041] When water is cooled by the water heat exchanger 5, the four-way valve 4 is switched
as illustrated in Fig. 2, and thereby a high-pressure gas refrigerant discharged from
the compressor 3 is guided to the air heat exchanger 9. In the air heat exchanger
9, heat exchange with air guided by the fan 12 causes the refrigerant to condense.
[0042] The liquid refrigerant condensed by the air heat exchanger 9 is guided to the second
expansion valve 8 and expanded. The expanded refrigerant is guided to the receiver
7, and a part of the refrigerant is stored in the receiver 7. The refrigerant taken
out of the receiver 7 is guided to the water heat exchanger 5 via the first expansion
valve 6.
[0043] In the water heat exchanger 5, heat exchange with water guided from the water pipe
16 causes the refrigerant to evaporate. The water cooled by the evaporation latent
heat of the refrigerant is guided to the external load via the water pipe 16.
[0044] The refrigerant evaporated by the water heat exchanger 5 is guided to the accumulator
10 through the four-way valve 4. The gas refrigerant guided from the accumulator 10
is guided to the intake side of the compressor 3 and again compressed by the compression
mechanism 3b.
[0045] The control unit leaves the liquid bypass valve 22 closed during a cooling operation.
That is, the liquid bypass pipe 20 is not used during the cooling operation.
[0046] According to the present embodiment, the following effects and advantages are achieved.
[0047] A liquid refrigerant is guided to the intake side of the compression mechanism 3b
through the liquid bypass pipe 20, and thereby the temperature of the refrigerant
discharged from the compressor 3 can be reduced. This enables an operation at a high
pressure ratio and an expanded range of use of the chiller 1.
[0048] Since a liquid refrigerant flows in the liquid bypass pipe 20, the opening diameter
(the pipe inner diameter) can be smaller than that for a two-phase refrigerant mixed
with a gas refrigerant. This can reduce the cost and facilitates piping arrangement
of the pipe.
[0049] The upstream end of the liquid bypass pipe 20 is provided between the water heat
exchanger 5 and the first expansion valve 6. Accordingly, a refrigerant before expanded
can be reliably guided as a liquid medium to the compressor 3.
[0050] Since a part of the liquid refrigerant is bypassed to the compressor 3 by the liquid
bypass pipe 20, this enables a reduced capacity (size) of the receiver 7 provided
between the first expansion valve 6 and the second expansion valve 8. This enables
space saving and cost reduction.
[0051] During a heating operation and at a low ambient temperature at which the ambient
temperature is a predetermined value or lower, the pressure ratio may be high (for
example, 4.5 or higher), and the temperature of the refrigerant discharged from the
compressor 3 may rise to a high temperature. Accordingly, in a case of such a condition,
the liquid bypass valve 22 is opened to guide the liquid refrigerant to the intake
side of the compression mechanism 3b.
[Second Embodiment]
[0052] Next, a second embodiment of the present disclosure will be described with reference
to Fig. 3 and Fig. 4. Since the present embodiment has the same basic configuration
as the first embodiment, only the configuration added to the first embodiment will
be described below.
[0053] As illustrated in Fig. 3 and Fig. 4, a parallel refrigerant pipe 30 branched from
a part between the upstream end of the liquid bypass pipe 20 and the first expansion
valve 6 and branched from a part between the second expansion valve 8 and the air
heat exchanger 9 is provided. The parallel refrigerant pipe 30 is provided in parallel
to the first expansion valve 6, the receiver 7, and the second expansion valve 8.
Accordingly, the parallel refrigerant pipe 30 connects the water heat exchanger 5
and the air heat exchanger 9 to each other while bypassing the first expansion valve
6, the receiver 7, and the second expansion valve 8.
[0054] A third expansion valve 32 is provided in the parallel refrigerant pipe 30. The opening
of the third expansion valve is controlled by the control unit.
[0055] Next, the operation of chiller 1 configured as above will be described.
<Heating operation: Fig. 3>
[0056] During a heating operation, the third expansion valve 32 is fully closed in accordance
with an instruction from the control unit. Therefore, since the parallel refrigerant
pipe 30 is not used during a heating operation, the same operation as that of Fig.
1 in the first embodiment takes place during the heating operation. At a low ambient
temperature, the liquid bypass valve 22 is opened in the same manner as in the first
embodiment to reduce the refrigerant discharge temperature by using a liquid refrigerant.
<Cooling operation: Fig. 4>
[0057] During a cooling operation, the first expansion valve 6 and the second expansion
valve 8 are fully closed in accordance with an instruction from the control unit so
that no refrigerant flows to the receiver 7. The liquid bypass valve 22 is also fully
closed, and the liquid bypass pipe 20 is not used. Therefore, all the liquid refrigerant
guided from the air heat exchanger 9 is guided to the parallel refrigerant pipe 30
and expanded by the third expansion valve 32 whose opening is controlled by the control
unit. The refrigerant expanded by the third expansion valve 32 is guided to the water
heat exchanger 5. Since the subsequent operation is the same as that of Fig. 2 in
the first embodiment, the description thereof will be omitted.
[0058] The chiller 1 of the present embodiment achieves the following effects and advantages.
[0059] The parallel refrigerant pipe 30 is provided in parallel to the first expansion valve
6, the receiver 7, and the second expansion valve 8. Further, during a heating operation,
the third expansion valve 32 is closed so that the refrigerant flows to the first
expansion valve 6 side. Accordingly, an excessive refrigerant can be stored in the
receiver 7 during the heating operation.
[0060] At a low ambient temperature, a part of the liquid refrigerant can be guided to the
compressor 3 to bypass the receiver 7 by using the liquid bypass pipe 20. This can
reduce the capacity of the receiver 7.
[0061] On the other hand, during a cooling operation, the third expansion valve 32 is opened
so that the refrigerant flows in the parallel refrigerant pipe 30 and no refrigerant
flows to the second expansion valve 8 side. This makes it possible to use a required
refrigerant neither too much nor too little without storing the refrigerant in the
receiver 7 during the cooling operation.
[0062] As set forth, a necessary and sufficient amount of a refrigerant can be selected
even with the chiller 1 that performs a heating operation and a cooling operation,
and the amount of a used refrigerant can thus be reduced.
[0063] When the parallel refrigerant pipe 30 is used during a cooling operation, a refrigerant
is expanded by the third expansion valve 32, and the expansion can be performed by
a single expansion valve. Therefore, with use of only the third expansion valve 32
in the parallel refrigerant pipe 30, an insufficient opening diameter of the expansion
valve can be avoided when the high-low differential pressure (the refrigerant differential
pressure between the water heat exchanger 5 and the air heat exchanger 9) is relatively
lower than a case where two of the first expansion valve 6 and the second expansion
valve 8 are used for expansion.
[Third Embodiment]
[0064] Next, a third embodiment of the present disclosure will be described.
[0065] In the chiller 1 of the present embodiment, since the configuration of the first
embodiment and the second embodiment illustrated in Fig. 1 to Fig. 4 can be used,
the description thereof will be omitted.
[0066] The control unit of the present embodiment controls the opening of the first expansion
valve 6 during the heating operation illustrated in Fig. 1 and Fig. 3 so that the
temperature of a refrigerant discharged from the compressor 3 becomes a predetermined
value or lower. Specifically, when the measurement value of the discharge temperature
sensor 14 exceeds a predetermined value, the opening of the first expansion valve
6 is reduced in the closing direction. Herein, the predetermined value means a measurement
temperature at the discharge temperature sensor 14 corresponding to a case where the
temperature of water heated by the water heat exchanger 5 is 50 □ or a temperature
lower by several degrees Celsius than the measurement temperature, for example.
[0067] The opening of the first expansion valve 6 is reduced, thereby, the amount of refrigerant
circulation is reduced, the condensing capacity of the water heat exchanger 5 is increased,
the liquid phase rate of the refrigerant is increased, and the amount of the liquid
refrigerant guided to the compressor 3 through the liquid bypass pipe 20 is increased.
The amount of the liquid refrigerant guided to the intake side of the compressor 3
then increases, and thereby the discharge gas temperature decreases.
[0068] The above process is illustrated in a p (pressure)-h (specific enthalpy) diagram
of Fig. 5. As illustrated in Fig. 5, the first expansion valve 6 is throttled, thereby,
the specific enthalpy moves from point C2 of HL2 to point C1 of HL1, and the degree
of excessive cooling increases. The refrigerant (point L1) having the increased degree
of excessive cooling and the increased amount of the liquid refrigerant reaches point
A (specific enthalpy HA) that is the intake position of the compressor 3 via the liquid
bypass pipe 20, merges at the intake side of the compression mechanism 3b with a refrigerant
expanded up to point D1 by the first expansion valve 6 and evaporated by the air heat
exchanger 9, and reaches point S1 (specific enthalpy HS1). The refrigerant compressed
by the compression mechanism 3b is then at a high temperature and a high pressure
and reaches point B1.
[0069] On the other hand, a refrigerant before the opening of the first expansion valve
6 is reduced moves from point C2 and merges at point S2 (specific enthalpy HS2) via
point D2 and point L2. The refrigerant compressed by the compression mechanism 3b
then reaches point B2.
[0070] As is clear from comparison between point B1 and point B2, it is found that point
B1 at which the opening of the first expansion valve 6 is reduced has a lower temperature
and a lower discharge temperature than point B2.
[0071] As described above, by reducing the opening of the first expansion valve 6, it is
possible to increase the degree of excessive cooling and reduce the discharge temperature
without controlling the opening of the liquid bypass valve 22.
[0072] The effects and advantages of the present embodiment are as follows.
[0073] The opening of the first expansion valve 6 is controlled, and thereby the temperature
of a refrigerant discharged from the compressor 3 is controlled to be a predetermined
value or lower. Accordingly, it is possible to employ an on-off valve (electromagnetic
valve) where only opening/closing of the valve takes place as the liquid bypass valve
22 rather than employing a regulator valve having a variable valve opening, and this
enables cost reduction. Further, since adjustment of the opening of the liquid bypass
valve 22 is unnecessary, the control can be simplified.
[0074] The present embodiment can be modified as with Fig. 6.
[0075] Fig. 6 corresponds to Fig. 1, however, the position of the upstream end of the liquid
bypass pipe 20 differs. The remaining configuration is the same as that of Fig. 1.
In the present modified example, the upstream end of the liquid bypass pipe 20 is
connected between the first expansion valve 6 and the receiver 7. Even with such a
configuration, the discharge refrigerant temperature can be controlled by the first
expansion valve 6 as with the present embodiment described above.
[0076] The heat source device and the control method thereof described above in each embodiment
are understood as follows, for example.
[0077] The heat source device (1) according to one aspect of the present disclosure includes:
a compressor (3) configured to compress a refrigerant; a heat medium heat exchanger
(5) configured to perform heat exchange between a refrigerant and a heat medium; an
expansion valve (6) configured to expand a refrigerant,; an air heat exchanger (9)
configured to perform heat exchange between a refrigerant and air; and a liquid bypass
pipe (20) configured to guide a liquid refrigerant to an intake side of the compressor,
an upstream end of the liquid bypass pipe being connected between the heat medium
heat exchanger and the expansion valve.
[0078] The liquid refrigerant is guided to the intake side of the compressor through the
liquid bypass pipe, and thereby the temperature of the refrigerant discharged from
the compressor can be reduced. This enables an operation at a high pressure ratio
and an expanded range of use of the heat source device.
[0079] Since a liquid refrigerant flows in the liquid bypass pipe, the opening diameter
(the pipe inner diameter) can be smaller than that for a two-phase refrigerant mixed
with a gas refrigerant. This can reduce the cost and facilitates piping arrangement
of the pipe.
[0080] Furthermore, in the heat source device according to one aspect of the present disclosure,
the expansion valve includes a first expansion valve provided on the heat medium heat
exchanger side and a second expansion valve (8) provided on the air heat exchanger
side, the upstream end of the liquid bypass pipe is connected between the heat medium
heat exchanger and the first expansion valve, and a receiver (7) configured to store
a refrigerant is provided between the first expansion valve and the second expansion
valve.
[0081] The upstream end of the liquid bypass pipe is provided between the heat medium heat
exchanger and the first expansion valve. Accordingly, the refrigerant before expanded
can be reliably guided as a liquid medium to the compressor.
[0082] Since a part of the liquid refrigerant is bypassed to the compressor by the liquid
bypass pipe, this enables a reduced capacity of the receiver provided between the
first expansion valve and the second expansion valve. This enables space saving and
cost reduction.
[0083] Furthermore, the heat source device according to one aspect of the present disclosure
includes: a selector valve configured to guide a refrigerant discharged from the compressor
to the heat medium heat exchanger during a heating operation for heating the heat
medium and guide a refrigerant discharged from the compressor to the air heat exchanger
during a cooling operation for cooling the heat medium; a liquid bypass valve (22)
provided in the liquid bypass pipe; and a control unit configured to control the liquid
bypass valve from a closed position to an open position when the heating operation
is performed and when an air temperature around the air heat exchanger becomes a predetermined
value or lower.
[0084] When a heating operation is performed and when the air temperature around the air
heat exchanger becomes a predetermined value (for example, 0 □) or lower, the pressure
ratio may be high (for example, 4.5 or higher), and the temperature of the refrigerant
discharged from the compressor may rise to a high temperature. Accordingly, in a case
of such a condition, the liquid bypass valve is opened to guide the liquid refrigerant
to the intake side of the compressor.
[0085] Furthermore, the heat source device according to one aspect of the present disclosure
includes: a selector valve configured to guide a refrigerant discharged from the compressor
to the heat medium heat exchanger during a heating operation for heating the heat
medium and guide a refrigerant discharged from the compressor to the air heat exchanger
during a cooling operation for cooling the heat medium; a parallel refrigerant pipe
(30) provided in parallel to the first expansion valve, the receiver, and the second
expansion valve and connecting the heat medium heat exchanger and the air heat exchanger
to each other; a third expansion valve (32) provided in the parallel refrigerant pipe;
and a control unit configured to close the third expansion valve and control an opening
of the first expansion valve and/or the second expansion valve so that a refrigerant
flows to the first expansion valve side during the heating operation and configured
to open the third expansion valve and control an opening of the first expansion valve
and/or the second expansion valve so that a refrigerant does not flow to the second
expansion valve side during the cooling operation.
[0086] The parallel refrigerant pipe is provided in parallel to the first expansion valve,
the receiver, and the second expansion valve. Further, during a heating operation,
the third expansion valve is closed so that the refrigerant flows to the first expansion
valve side. Accordingly, an excessive refrigerant can be stored in the receiver during
the heating operation. On the other hands, during a cooling operation, the third expansion
valve is opened so that the refrigerant flows in the parallel refrigerant pipe and
no refrigerant flows to the second expansion valve side. This makes it possible to
use a required refrigerant neither too much nor too little without storing the refrigerant
in the receiver during the cooling operation.
[0087] As set forth, a necessary and sufficient amount of a refrigerant can be selected
even with the heat source device that performs a heating operation and a cooling operation,
and the amount of a used refrigerant can be reduced.
[0088] When the parallel refrigerant pipe is used during a cooling operation, a refrigerant
is expanded by the third expansion valve, and the expansion can be performed by a
single expansion valve. Therefore, with use of only the third expansion valve in the
parallel refrigerant pipe, an insufficient opening diameter of the expansion valve
can be avoided when the high-low differential pressure (the refrigerant differential
pressure between the heat medium heat exchanger and the air heat exchanger) is relatively
lower than a case where two of the first expansion valve and the second expansion
valve are used for expansion.
[0089] Furthermore, the heat source device according to one aspect of the present disclosure
includes: a selector valve configured to guide a refrigerant discharged from the compressor
to the heat medium heat exchanger during a heating operation for heating the heat
medium and guide a refrigerant discharged from the compressor to the air heat exchanger
during a cooling operation for cooling the heat medium; a liquid bypass valve provided
in the liquid bypass pipe and being an on-off valve; and a control unit configured
to control an opening of the first expansion valve during the heating operation so
that a temperature of a refrigerant discharged from the compressor becomes a predetermined
value or lower.
[0090] The opening of the first expansion valve is controlled, and thereby the temperature
of a refrigerant discharged from the compressor is controlled to be a predetermined
value or lower. Accordingly, it is possible to employ an on-off valve where only opening/closing
of the valve takes place as the liquid bypass valve rather than employing a regulator
valve having a variable valve opening, and this enables cost reduction. Further, since
adjustment of the opening of the liquid bypass valve is unnecessary, the control can
be simplified.
[0091] A control method of a heat source device according to one aspect of the present disclosure
is a control method of a heat source device including a compressor configured to compress
a refrigerant, a heat medium heat exchanger configured to perform heat exchange between
a refrigerant and a heat medium, an expansion valve configured to expand a refrigerant,
an air heat exchanger configured to perform heat exchange between a refrigerant and
air, a liquid bypass pipe configured to guide a liquid refrigerant to an intake side
of the compressor, an upstream end of the liquid bypass pipe being connected between
the heat medium heat exchanger and the expansion valve, a liquid bypass valve provided
in the liquid bypass pipe and a selector valve configured to guide a refrigerant discharged
from the compressor to the heat medium heat exchanger during a heating operation for
heating the heat medium and guide a refrigerant discharged from the compressor to
the air heat exchanger during a cooling operation for cooling the heat medium, and
the control method includes: controlling the liquid bypass valve from a closed position
to an open position when the heating operation is performed and when an air temperature
around the air heat exchanger becomes a predetermined value or lower.
[0092] A control method of a heat source device according to one aspect of the present disclosure
is a control method of a heat source device including a compressor configured to compress
a refrigerant, a heat medium heat exchanger configured to perform heat exchange between
a refrigerant and a heat medium, an air heat exchanger configured to perform heat
exchange between a refrigerant and air, a first expansion valve provided on the heat
medium heat exchanger side, a second expansion valve provided on the air heat exchanger
side, a liquid bypass pipe configured to guide a liquid refrigerant to an intake side
of the compressor, an upstream end of the liquid bypass pipe being connected between
the heat medium heat exchanger and the first expansion valve, a liquid bypass valve
provided in the liquid bypass pipe, a receiver provided between the first expansion
valve and the second expansion valve and configured to store a refrigerant, a selector
valve configured to guide a refrigerant discharged from the compressor to the heat
medium heat exchanger during a heating operation for heating the heat medium and guide
a refrigerant discharged from the compressor to the air heat exchanger during a cooling
operation for cooling the heat medium, a parallel refrigerant pipe provided in parallel
to the first expansion valve, the receiver, and the second expansion valve and connecting
the heat medium heat exchanger and the air heat exchanger to each other, and a third
expansion valve provided in the parallel refrigerant pipe, and the control method
includes: during the heating operation, closing the third expansion valve and controlling
an opening of the first expansion valve and/or the second expansion valve so that
a refrigerant flows to the first expansion valve side; and during the cooling operation,
opening the third expansion valve and controlling an opening of the first expansion
valve and/or the second expansion valve so that a refrigerant does not flow to the
second expansion valve side.
[0093] A control method of a heat source device according to one aspect of the present disclosure
is a control method of a heat source device including a compressor configured to compress
a refrigerant, a heat medium heat exchanger configured to perform heat exchange between
a refrigerant and a heat medium, an air heat exchanger configured to perform heat
exchange between a refrigerant and air, a first expansion valve provided on the heat
medium heat exchanger side, a second expansion valve provided on the air heat exchanger
side, a liquid bypass pipe configured to guide a liquid refrigerant to an intake side
of the compressor, an upstream end of the liquid bypass pipe being connected between
the heat medium heat exchanger and the first expansion valve, a liquid bypass valve
provided in the liquid bypass pipe, a receiver provided between the first expansion
valve and the second expansion valve and configured to store a refrigerant, and a
selector valve configured to guide a refrigerant discharged from the compressor to
the heat medium heat exchanger during a heating operation for heating the heat medium
and guide a refrigerant discharged from the compressor to the air heat exchanger during
a cooling operation for cooling the heat medium, and the control method includes:
controlling an opening of the first expansion valve during the heating operation so
that a temperature of a refrigerant discharged from the compressor becomes a predetermined
value or lower.
[Reference Signs List]
[0094]
- 1
- chiller (heat source device)
- 3
- compressor
- 3a
- housing
- 3b
- compression mechanism
- 4
- four-way valve (selector valve)
- 5
- water heat exchanger (heat medium heat exchanger)
- 6
- first expansion valve
- 7
- receiver
- 8
- second expansion valve
- 9
- air heat exchanger
- 10
- accumulator
- 12
- fan
- 14
- discharge temperature sensor
- 16
- water pipe
- 18
- ambient temperature sensor
- 20
- liquid bypass pipe
- 22
- liquid bypass valve
- 30
- parallel refrigerant pipe
- 32
- third expansion valve