[TECHNICAL FIELD]
[0001] The present invention relates to a refrigeration cycle device and a liquid heating
device having the same.
[BACKGROUND TECHNIQUE]
[0002] Patent document 1 discloses a supercritical steam compression type refrigeration
cycle including a compressor which compresses refrigerant in two stages, and two expanding
devices which expand refrigerant in two stages. Carbon dioxide is used as refrigerant.
[0003] The supercritical steam compression type refrigeration cycle of patent document 1
includes a gas-liquid separator. Refrigerant having gas phase in the gas-liquid separator
as main component is intermediately injected into a refrigerant mixer located on the
way to an intermediate connection circuit of the compressor from the injection circuit.
The refrigerant is mixed into refrigerant discharged from a low-stage side rotation
compression rotating element, and the mixed refrigerant is sucked into a high-stage
side rotation compression rotating element.
[0004] In patent document 1, a ratio (displacement capacity ratio) of displacement capacity
of the high-stage side rotation compression rotating element in comparison with displacement
capacity of the low-stage side rotation compression rotating element is equal to or
higher than isentropic index root of quotient obtained by dividing suction pressure
of the compressor by refrigerant saturated liquid pressure in a first expanding device.
According to this, discharge pressure of the low-stage side rotation compression rotating
element is set equal to or lower than critical pressure of the refrigerant.
[0005] Further, as refrigerant, patent document 2 uses refrigerant other than carbon dioxide.
Patent document 2 discloses a refrigeration device including a compressor which compresses
refrigerant in two stages, and two expanding devices which expand refrigerant in two
stages.
[0006] The refrigeration device of patent document 2 includes a supercooling heat exchanger
and an injection circuit. The injection circuit decompresses a portion of refrigerant
discharged from the compressor by a bypass expansion valve, and the decompressed refrigerant
is heated by the supercooling heat exchanger. Thereafter, the heated decompressed
refrigerant is injected into the intermediate port which is in communication with
a low-stage side and a high-stage side of the compressor. Refrigerant from the injection
circuit and refrigerant discharged from the low stage are mixed with each other in
the intermediate port. The mixed refrigerant is sucked into the high-stage side rotating
element. An opening degree of the bypass expansion valve is adjusted in accordance
with a degree of superheat of the sucked refrigerant, thereby preventing liquid from
returning to the compressor.
[PRIOR ART DOCUMENTS]
[PATENT DOCUMENTS]
[SUMMARY OF THE INVENTION]
[PROBLEM TO BE SOLVED BY THE INVENTION]
[0008] However, according to the above-described conventional configuration, the intermediate
port is connected directly to a compression chamber of the compressor, and refrigerant
which passes through the supercooling heat exchanger (intermediate heat exchanger)
is injected into the compression chamber. In the case of the compressor having such
a configuration that injected refrigerant and refrigerant which is on the way to be
compressed are mixed in the compression chamber and again compressed in this way,
if the injected refrigerant is liquid refrigerant, there is a problem that liquid
back is generated, and reliability of the compressor is deteriorated. Further, it
is difficult to directly measure a degree of superheat of refrigerant which is obtained
after refrigerant injected in the compression chamber and refrigerant which is on
the way to be compressed are mixed with each other.
[0009] The present invention is for solving the above problem, and it is an object of the
invention to provide a reliable refrigeration cycle device which prevents liquid back
by bringing, equal to or higher than a predetermined value, a degree of superheat
of refrigerant after it passes through an intermediate heat exchanger. It is another
object of the invention to provide a liquid heating device having the above-described
refrigeration cycle device.
[MEANS FOR SOLVING THE PROBLEM]
[0010] To solve the conventional problem, a refrigeration cycle device of the present invention
including: a main refrigerant circuit formed by sequentially connecting, to one another
through a pipe, a compression mechanism composed of a compression rotating element,
a use-side heat exchanger for heating use-side heat medium by refrigerant discharged
from the compression rotating element, an intermediate heat exchanger, a first expanding
device and a heat source-side heat exchanger; a bypass refrigerant circuit which branches
off from the pipe between the use-side heat exchanger and the first expanding device,
in which after the refrigerant which is branched is decompressed by a second expanding
device, the branched refrigerant exchanges heat, in the intermediate heat exchanger,
with the refrigerant flowing through the main refrigerant circuit, and merges with
refrigerant which is on the way of compression of the compression rotating element;
a pre-cooling temperature sensor for detecting temperature of the refrigerant flowing
through the bypass refrigerant circuit located upstream of the intermediate heat exchanger;
a post-cooling temperature sensor for detecting temperature of the refrigerant flowing
through the bypass refrigerant circuit located downstream of the intermediate heat
exchanger; and a control device, wherein the control device calculates a degree of
superheat of the refrigerant which merges with the compression rotating element based
on temperature data acquired from the pre-cooling temperature sensor and from the
post-cooling temperature sensor, and when the calculated degree of superheat is lower
than a predetermined value, the control device operates to reduce a valve opening
degree of the second expanding device.
[0011] According to this, it is possible to prevent the liquid back which is generated when
liquid refrigerant is mixed into the compression chamber of the compression rotating
element.
[EFFECT OF THE INVENTION]
[0012] According to the present invention, it is possible to prevent the increase of the
vibration of a compression mechanism which is caused by generation of the liquid back,
and it is possible to secure the reliability of the compression mechanism. Especially,
when the second expansion valve is opened to a predetermined position at the time
of actuation, it is possible to prevent refrigerant from being gasified and from being
injected while keeping its liquid state. Hence, it is possible to provide a reliable
refrigeration cycle device and a liquid heating device having the same.
[BRIEF DESCRIPTION OF THE DRAWINGS]
[0013]
Fig. 1 is a block diagram of a liquid heating device according to an embodiment of
the present invention;
Figs. 2(a) and (b) are pressure-enthalpy diagrams (P-h diagrams) under an ideal condition
concerning a refrigeration cycle device; and
Fig. 3 is a flowchart of control of a bypass expansion valve in the embodiment.
[MODE FOR CARRYING OUT THE INVENTION]
(Knowledge and the like which become a foundation of present disclosure)
[0014] In a refrigeration cycle in which refrigerant heated by an inter-cooler is injected
into a compression chamber, an optimum injection amount differs depending upon outside
temperature and water temperature at the time of operation. Hence, it is a general
control method to adjust the injection amount of refrigerant by a pressure reducing
valve. However, when the injection amount is adjusted, the injection amount of refrigerant
becomes too much, intermediate pressure-side refrigerant cannot entirely evaporate
and flows into the compressor in its liquid state. Therefore, liquid compression is
generated, and reliability of the compressor is deteriorated in some cases. Generally,
to secure the reliability of the compressor, control is performed to prevent the liquid
compression on the suction side. Not only that, in the case of a refrigeration cycle
in which injection is carried out, it is necessary to also take the liquid compression
in the injection. To solve this problem, the subject matter of the present disclosure
is configured.
[0015] The present disclosure provides a reliable refrigeration cycle device which prevents
liquid back of refrigerant which is injected after it passes through an intermediate
heat exchanger, and also provides a liquid heating device having the same.
[0016] An embodiment will be described in detail below with reference to the drawings. However,
description which is detail more than necessary will be omitted in some cases. For
example, detailed description of already well known matters, or redundant description
of substantially the same configuration will be omitted in some cases. This is for
preventing the following description from becoming redundant more than necessary,
and for making it easy for a person skilled in the art to understand the present disclosure.
[0017] The accompanying drawing and the following description are provided so that a person
skilled in the art can sufficiently understand the present disclosure, and it is not
intended that they limit the subject matter described in claims.
(Embodiment)
[1-1. Configuration]
[0018] Fig. 1 is a block diagram of a liquid heating device according to an embodiment.
The liquid heating device is composed of a use-side heat medium circuit 30, and a
refrigeration cycle device which is a supercritical steam compression type refrigeration
cycle. The refrigeration cycle device is composed of a main refrigerant circuit 10
and a bypass refrigerant circuit 20.
[0019] The main refrigerant circuit 10 is formed by sequentially connecting, to one another
through a pipe 16, a compression mechanism 11 which compresses refrigerant, a radiator
12 which is a use-side heat exchanger, an economizer 13 which is an intermediate heat
exchanger, a main expansion valve 14 which is a first expanding device, and an evaporator
15 which is a heat source-side heat exchanger. Carbon dioxide (CO
2) is used as the refrigerant.
[0020] As the refrigerant, it is optimal to carbon dioxide, but it is also possible to use
zeotropic refrigerant mixture such as R407C, pseudo azeotropic refrigerant mixture
such as R410A, single refrigerant such as R32, and flammable refrigerant such as propane.
[0021] The compression mechanism 11 injects refrigerant from the bypass refrigerant circuit
20 on the way of compression of refrigerant by the rotating element, the compression
mechanism 11 makes the refrigerant from the bypass refrigerant circuit 20 and the
refrigerant which is on the way of compression merge with each other, and the compression
mechanism 11 again compresses them. The radiator 12 heats the use-side heat medium
by the refrigerant discharged from the compression mechanism 11.
[0022] The bypass refrigerant circuit 20 branches off from the pipe 16 located between the
radiator 12 and the main expansion valve 14, and the bypass refrigerant circuit 20
is connected to the compression chamber which is on the way of compression of the
compression mechanism 11.
[0023] The bypass refrigerant circuit 20 is provided with a bypass expansion valve 21 which
is a second expanding device. A portion of high pressure refrigerant after it passes
through the radiator 12 or a portion of high pressure refrigerant after it passes
through the economizer 13 is decompressed by the bypass expansion valve 21 and becomes
intermediate pressure refrigerant. Thereafter, the intermediate pressure refrigerant
exchanges, in the economizer 13, heat with high pressure refrigerant which flows through
the main refrigerant circuit 10, the intermediate pressure refrigerant is injected
into the rotating element of the compression mechanism 11, and the intermediate pressure
refrigerant merges with refrigerant which is on the way of compression of the main
refrigerant circuit 10.
[0024] The use-side heat medium circuit 30 is formed by sequentially connecting the radiator
12, a transfer pump 31 which is a transfer device and heating terminal 32a to one
another through a heat medium pipe 33. Water or antifreeze liquid is used as the use-side
heat medium.
[0025] The use-side heat medium circuit 30 in the embodiment includes a heating terminal
32a and a hot water tank 32b located in parallel thereto. By switching between a first
switching valve 34 and a second switching valve 35, the use-side heat medium is circulated
through the heating terminal 32a or the hot water tank 32b. It is only necessary that
the use-side heat medium circuit 30 includes any one of the heating terminal 32a and
the hot water tank 32b.
[0026] High temperature water produced by the radiator 12 radiates heat in the heating terminal
32a, the heat is used for heating homes, and low temperature water which radiates
heat in the heating terminal 32a is again heated by the radiator 12.
[0027] The high temperature water produced by the radiator 12 in introduced into the hot
water tank 32b from an upper portion of the hot water tank 32b, low temperature water
is derived from a lower portion of the hot water tank 32b and is heated by the radiator
12.
[0028] A hot water supply-heat exchanger 42 is placed in the hot water tank 32b, and exchanges
heat between water supplied from the water supply pipe 43 and high temperature water
in the hot water tank 32b. That is, if the hot water tap 41 is opened, water is supplied
from the water supply pipe 43 into the hot water supply-heat exchanger 42. The water
is heated by the hot water supply-heat exchanger 42, temperature of the water is adjusted
to a predetermined value by the hot water tap 41, and hot water is supplied from the
hot water tap 41. Water is supplied from the water supply pipe 43 and is heated by
the hot water supply-heat exchanger 42. Hot water supplied from the hot water tap
41 and high temperature water in the hot water tank 32b are not mixed with each other
and they are heated indirectly.
[0029] The hot water supply-heat exchanger 42 is a water heat exchanger using a copper pipe
or a stainless pipe as a heattransfer pipe. As shown in Fig. 1, the hot water supply-heat
exchanger 42 is connected to the water supply pipe 43 and the hot water tap 41 extending
from a water-supply source (waterline). The water supply pipe 43 introduces ordinary
temperature water to a lower end of the hot water supply-heat exchanger 42, i.e.,
to a lower portion in the hot water tank 32b. The ordinary temperature water introduced
from the water supply pipe 43 into the hot water supply-heat exchanger 42 takes heat
from high temperature water in the hot water tank 32b while moving upward from a lower
portion in the hot water tank 32b. The ordinary temperature water becomes high temperature
heated water and is supplied from the hot water tap 41.
[0030] In the hot water tank 32b, a plurality of hot water tank temperature thermistors
measure temperature of hot water at a plurality of different height positions. For
example, a first hot water tank temperature thermistor 55a, a second hot water tank
temperature thermistor 55b and a third hot water tank temperature thermistor 55c are
provided. The ordinary temperature Water which enters the hot water supply-heat exchanger
42 from the water supply pipe 43 takes heat from high temperature water in the hot
water tank 32b while moving upward from a lower portion in the hot water tank 32b.
Hence, temperature of the hot water in the hot water tank 32b naturally becomes high
in its upper portion and lower in its lower portion.
[0031] The main refrigerant circuit 10 is provided with a high pressure-side pressure detecting
device 51 in the pipe 16 on a discharge-side of the compression mechanism 11. The
high pressure-side pressure detecting device 51 is provided in the main refrigerant
circuit 10 from a discharge-side of the compression mechanism 11 to an upstream-side
of the main expansion valve 14. It is only necessary that the high pressure-side pressure
detecting device 51 can detect the pressure of the high pressure refrigerant of the
main refrigerant circuit 10.
[0032] An intermediate heat exchanger main refrigerant inlet thermistor 57 is provided in
the pipe 16 on a downstream-side of the use-side heat exchanger 12 of the main refrigerant
circuit 10, i.e., on an upstream-side of the economizer 13. The intermediate heat
exchanger main refrigerant inlet thermistor 57 detects temperature of refrigerant
which flows out from the use-side heat exchanger 12. Further, the bypass refrigerant
circuit 20 is provided with an intermediate heat exchanger bypass inlet thermistor
56. The intermediate heat exchanger bypass inlet thermistor 56 detects temperature
of refrigerant which flows out from a second expanding device 21 on a downstream-side
of the second expanding device 21, i.e., on the upstream side of the economizer 13.
[0033] The use-side heat medium circuit 30 includes a heat medium outlet temperature thermistor
53 and a heat medium inlet temperature thermistor 54. The heat medium outlet temperature
thermistor 53 detects temperature of use-side heat medium which flows out from the
use-side heat exchanger 12. The heat medium inlet temperature thermistor 54 detects
temperature of use-side heat medium which flows into the use-side heat exchanger 12.
[0034] Further, the bypass refrigerant circuit 20 includes the intermediate heat exchanger
bypass inlet thermistor 56, an intermediate heat exchanger bypass outlet thermistor
58 and an intermediate pressure-side pressure detecting device 52. The intermediate
heat exchanger bypass inlet thermistor 56 detects refrigerant temperature on the upstream
side of the economizer 13. The intermediate heat exchanger bypass outlet thermistor
58 detects refrigerant temperature on the downstream-side of the economizer 13. The
intermediate pressure-side pressure detecting device 52 directly or indirectly detects
pressure on the downstream side of the second expanding device 21.
[0035] When the intermediate pressure-side pressure detecting device 52 directly detects
the pressure, this pressure detecting device 52 directly, i.e., mechanically detects
pressure of refrigerant.
[0036] When the intermediate pressure-side pressure detecting device 52 indirectly detects
the pressure, a control device 60 calculates a value of pressure (intermediate pressure)
of refrigerant after this pressure is reduced by the second expanding device 21 based
on detection pressure detected by the high pressure-side pressure detecting device
51 and detection pressure detected by the intermediate heat exchanger main refrigerant
inlet thermistor 57. Further, the control device 60 calculates a value of intermediate
pressure based on detection temperature detected by the heat medium inlet temperature
thermistor 54 and detection temperature detected by the intermediate heat exchanger
bypass inlet thermistor 56. The control device 60 has arithmetic processing function.
[0037] That is, the control device 60 memorizes a pressure-enthalpy diagram (P-h diagram)
as shown in Fig. 2.
[0038] The high pressure-side pressure detecting device 51 detects, every predetermined
time, high pressure-side pressure (discharge pressure of high-stage side compression
rotating element 11b), the intermediate heat exchanger main refrigerant inlet thermistor
57 detects, every predetermined time, outlet temperature (point A) of the use-side
heat exchanger 12, and the intermediate heat exchanger bypass inlet thermistor 56
detects, every predetermined time, inlet temperature (point e) of refrigerant of the
bypass refrigerant circuit 20 of the intermediate heat exchanger 13.
[0039] Based on an ideal condition that enthalpies at the point A and the point e are substantially
the same, the control device 60 calculates pressure and the enthalpy at the point
e. According to this, it is possible to calculate a value of pressure (intermediate
pressure) of refrigerant after the pressure is reduced by the second expanding device
21, and it is possible to determine whether the pressure is equal to or higher than
critical pressure by the calculated value.
[0040] It is possible to use detection temperature which is detected by the heat medium
inlet temperature thermistor 54 instead of using the detection value detected by the
intermediate heat exchanger main refrigerant inlet thermistor 57 because these values
are substantially the same.
[0041] That is, it is possible to determine that pressure (intermediate pressure) of refrigerant
after this pressure is reduced by the second expanding device 21 is equal to or higher
than the critical pressure based on the discharge pressure of the compression mechanism
11, based on the outlet temperature (point A) of refrigerant of the use-side heat
exchanger 12, and based on the inlet temperature (point e) of refrigerant of the bypass
refrigerant circuit 20 of the intermediate heat exchanger 13, or based on temperature
of the use-side heat medium which flows into the use-side heat exchanger 12.
[0042] It is only necessary that the intermediate pressure-side pressure detecting device
52 includes any one of the pressure detecting devices which directly or indirectly
detect pressure.
[0043] The control device 60 controls operating frequency of the compression mechanism 11,
opening degrees of the main expansion valve 14 and the bypass expansion valve 21,
and the transfer pump 31 based on detection pressures detected by the high pressure-side
pressure detecting device 51 and the intermediate pressure-side pressure detecting
device 52, and based on detection temperatures detected by the heat medium outlet
temperature thermistor 53 and the heat medium inlet temperature thermistor 54.
[1-2. Action]
[0044] Figs. 2 are pressure-enthalpy diagrams (P-h diagrams) under an ideal condition concerning
a refrigeration cycle device, wherein Fig. 2(a) shows a case in which high pressure
is lower than predetermined pressure, and Fig. 2(b) shows a case in which high pressure
is equal to or higher than the predetermined pressure. Points a to e and point A to
B in Fig. 2 correspond to respective points of the liquid heating device shown in
Fig. 1.
[0045] Action of the refrigeration cycle device will be described using Figs. 2.
[0046] First, high pressure refrigerant (point a) discharged from the compression mechanism
11 radiates heat in the radiator 12 and then, the high pressure refrigerant branches
off from the main refrigerant circuit 10 at a refrigerant branch point A. The high
pressure refrigerant is reduced in pressure to intermediate pressure by the bypass
expansion valve 21, the pressure becomes equal to the intermediate pressure refrigerant
(point e), and the intermediate pressure refrigerant exchanges heat in the economizer
13.
[0047] The high pressure refrigerant which flows through the main refrigerant circuit 10
after it radiates heat in the radiator 12 is cooled by the intermediate pressure refrigerant
(point e) which flows through the bypass refrigerant circuit 20, and the refrigerant
is reduced in pressure by the main expansion valve 14 in a state where its enthalpy
is reduced (point b).
[0048] According to this, after the pressure is reduced by the main expansion valve 14,
refrigerant enthalpy of the refrigerant (point c) which flows into the evaporator
15 is also reduced. Dryness of the refrigerant when it flows into the evaporator 15
is lowered, and liquid component of the refrigerant is increased. Hence, this fact
contributes to evaporation in the evaporator 15, a ratio of the refrigerant is increased,
heat absorption from the outside air is increased, and the refrigerant returns to
the suction side (point d) of the compression mechanism 11. The dryness of the refrigerant
is a ratio of weight occupied by gas phase component with respect to the entire refrigerant.
[0049] On the other hand, refrigerant of an amount corresponding to an amount of gas phase
component which does not contribute to evaporation in the evaporator 15 bypasses to
the bypass refrigerant circuit 20 and becomes low temperature intermediate pressure
refrigerant (point e). The intermediate pressure refrigerant is heated by high pressure
refrigerant which flows through the main refrigerant circuit 10 in the economizer
13. In a state where refrigerant enthalpy becomes high, the intermediate pressure
refrigerant reaches a merging point B of refrigerant which is on the way of compression
of the compression mechanism 11.
[0050] Therefore, at the merging point (point B) of the compression mechanism 11, since
the refrigerant pressure is higher than that on the suction side (point d) of the
compression mechanism 11, refrigerant density is higher. At the same time, refrigerant
which merges with refrigerant which is on the way of compression of the compression
mechanism 11 is further compressed by the compression mechanism 11 and discharged.
Hence, a flow rate of the refrigerant which flows into the radiator 12 is largely
increased, and ability for heating water which is the use-side heat medium is largely
enhanced.
[0051] Discharge pressure of the compression mechanism 11 rises and exceeds a predetermined
value, the control device 60 starts controlling a vale opening degree of the bypass
expansion valve 21 such that pressure of refrigerant after it is reduced by the bypass
expansion valve 21 exceeds the critical pressure as shown in Fig. 2(b).
[0052] More specifically, when it is determined that the detection pressure detected by
the high pressure-side pressure detecting device 51 rises and exceeds a first predetermined
high pressure value, if detection pressure detected by the intermediate pressure-side
pressure detecting device 52 is equal to or lower than the critical pressure, the
control device 60 starts the operation to increase the valve opening degree of the
bypass expansion valve 21.
[0053] Then, the control device 60 operates to increase the valve opening degree of the
bypass expansion valve 21 as shown in Fig. 2(b). At the same time, the control device
60 increases operating frequency of the compression mechanism 11, and increases a
circulation amount of refrigerant which flows through the bypass refrigerant circuit
20. According to this, the control device 60 controls such that detection pressure
detected by the high pressure-side pressure detecting device 51 becomes equal to a
second predetermined high pressure value which is a target high pressure value. The
second predetermined high pressure value is higher than the first predetermined high
pressure value.
[0054] At the same time, as shown in Fig. 2(a), when pressure (intermediate pressure) of
refrigerant after it is reduced by the second expanding device 21 is lower than the
critical pressure, the control device 60 controls the valve opening degree of the
bypass expansion valve 21 as shown in a control flow in Fig. 3. On the downstream
side of the economizer 13 of the bypass refrigerant circuit 20, degrees of superheat
SHm of refrigerant which is on the way of compression of the compression mechanism
11 and refrigerant before merging are acquired (S1). When it is determined that the
degrees of superheat SHm are lower than a predetermined value SHt (YES in S2), the
control device 60 operates to reduce the valve opening degree of the bypass expansion
valve 21 and a flow rate of refrigerant is reduced (S3). According to this, a temperature
rising width of refrigerant caused by heat exchange with the main refrigerant circuit
10 is increased and on the downstream side of the economizer 13, the degrees of superheat
SHm of the refrigerant which is on the way of compression of the compression mechanism
11 and the refrigerant before merging rise. Hence, refrigerant which is injected to
the compression mechanism 11 becomes gas. When it is determined that the acquired
degree of superheat SHm of refrigerant on the downstream side of the economizer 13
exceeds the predetermined value SHt (NO in S2), the control device 60 operates to
increase the valve opening degree of the bypass expansion valve 21, and the flow rate
of refrigerant is increased (S4). According to this, the temperature rising width
of refrigerant caused by heat exchange with the main refrigerant circuit 10 becomes
small and on the downstream side of the economizer 13, the degrees of superheat SHm
of the refrigerant which is on the way of compression of the compression mechanism
11 and the refrigerant before the merging are reduced. Further, temperature of refrigerant
which merges with the main refrigerant circuit 10 on the way of compression of the
compression mechanism 11 is lowered, and discharge temperature which is temperature
of refrigerant discharged from the compression mechanism 11 is lowered.
[0055] At that time, the degree of superheat SHm of refrigerant injected into the compression
mechanism 11 can be calculated from a difference between temperature obtained from
the intermediate heat exchanger bypass inlet thermistor 56 and temperature obtained
from the intermediate heat exchanger bypass outlet thermistor 58 while taking pressure
loss of the economizer 13 into account. This is because that when pressure (intermediate
pressure) of refrigerant after it is reduced by the second expanding device 21 is
lower than the critical pressure, temperature detected by the intermediate heat exchanger
bypass inlet thermistor 56 becomes saturated temperature. The degree of superheat
SHm can also be calculated from pressure information detected by the intermediate
pressure-side pressure detecting device 52 and temperature information detected by
the intermediate heat exchanger bypass outlet thermistor 58.
[0056] Action when the hot water tank 32b is used in the use-side heat medium circuit 30
will be described below.
[0057] Of the plurality of hot water tank temperature thermistors, the first hot water tank
temperature thermistor 55a is positioned at the highest position in the hot water
tank 32b. For example, when detection temperature detected by the first hot water
tank temperature thermistor 55a is lower than the predetermined value, the control
device 60 determines that high temperature water is insufficient in the hot water
tank 32b.
[0058] Thus, the control device 60 operates the compression mechanism 11 and heats low temperature
water by the radiator 12. According to this, the transfer pump 31 is operated such
that detection temperature detected by the heat medium outlet temperature thermistor
53 which is heated produced temperature becomes equal to target temperature.
[0059] According to this, low temperature water derived from the lower portion in the hot
water tank 32b is heated by the radiator 12. According to this, high temperature water
is produced, and the produced high temperature water is introduced into the hot water
tank 32b from the upper portion in the hot water tank 32b. At that time, since the
detection temperature detected by the heat medium inlet temperature thermistor 54
is equal to or lower than third predetermined temperature, the transfer pump 31 is
operated in the state shown in Fig. 2(a).
[0060] Since high temperature water is gradually stored in the hot water tank 32b from above,
detection temperature detected by the heat medium inlet temperature thermistor 54
is gradually rising. Thereafter, when the detection temperature detected by the heat
medium inlet temperature thermistor 54 exceeds the third predetermined temperature,
the transfer pump 31 is operated in the state shown in Fig. 2(b).
[0061] That is, the control device 60 controls such that the valve opening degree of the
bypass expansion valve 21 is increased, and the operating frequency of the compression
mechanism 11 is increased, thus the circulation amount of refrigerant flowing through
the bypass refrigerant circuit 20 is increased, and detection pressure detected by
the high pressure-side pressure detecting device 51 becomes equal to the second predetermined
high pressure which is the target high pressure value. At the same time, the control
device 60 operates such that detection pressure detected by the intermediate pressure-side
pressure detecting device 52 becomes equal to predetermined intermediate pressure
which is the target intermediate pressure value.
[0062] According to this, inlet temperature of heat medium entering the radiator 12 becomes
high, and an enthalpy difference (a-A) of refrigerant in the radiator 12 becomes small.
To compensate this reduced enthalpy difference, heating ability of refrigerant in
the radiator 12 is enhanced. According to this, it is possible to keep supplying the
high temperature water to the hot water tank 32b.
[0063] When the detection temperature detected by the heat medium inlet temperature thermistor
54 exceeds the first predetermined temperature which is higher than the third predetermined
temperature, the control device 60 reduces the operating frequency of the compression
mechanism 11. According to this, it is possible to store the high temperature water
in the hot water tank 32b such that pressure of high pressure refrigerant in the radiator
12 does not exceeds the second predetermined high pressure value which is the target
high pressure value while suppressing the pressure rise of the high pressure refrigerant
in the radiator 12.
[0064] The same operating action may be executed respectively using the first predetermined
high pressure value and the second predetermined high pressure value which are detection
pressures detected by the high pressure-side pressure detecting device 51 as the threshold
values instead of using the third predetermined temperature and the first predetermined
temperature which are detection temperatures detected by the heat medium inlet temperature
thermistor 54.
[0065] A case where the heating terminal 32a is used in the use-side heat medium circuit
30 will be described.
[0066] The control device 60 operates the compression mechanism 11 and heats circulating
water by the radiator 12. The control device 60 operates the transfer pump 31 such
that a temperature difference between the detection temperature detected by the heat
medium outlet temperature thermistor 53 and the detection temperature detected by
the heat medium inlet temperature thermistor 54 becomes equal to the target temperature
difference.
[0067] According to this, high temperature water produced by the radiator 12 radiates heat
in the heating terminal 32a, and the heat is used for heating homes, and low temperature
water which radiates heat in the heating terminal 32a is again heated by the radiator
12. At that time, control is performed such that the temperature difference between
the detection temperature detected by the heat medium outlet temperature thermistor
53 and the detection temperature detected by the heat medium inlet temperature thermistor
54 becomes equal to the target temperature difference. At the same time, since the
detection temperature detected by the heat medium outlet temperature thermistor 53
is equal to or lower than fourth predetermined temperature, the transfer pump 31 is
operated in the state shown in Fig. 2(a).
[0068] The home-heating load gradually becomes small. Therefore, since the control is performed
such that the temperature difference between the detection temperature detected by
the heat medium outlet temperature thermistor 53 and the detection temperature detected
by the heat medium inlet temperature thermistor 54 becomes equal to the target temperature
difference, the detection temperature detected by the heat medium outlet temperature
thermistor 53 and the detection temperature detected by the heat medium inlet temperature
thermistor 54 are gradually rising. Thereafter, when the detection temperature detected
by the heat medium outlet temperature thermistor 53 exceeds the fourth predetermined
temperature, the transfer pump 31 is operated in the state shown in Fig. 2(b).
[0069] That is, the control device 60 controls such that the valve opening degree of the
bypass expansion valve 21 is increased, and the operating frequency of the compression
mechanism 11 is increased, thus the circulation amount of refrigerant flowing through
the bypass refrigerant circuit 20 is increased, and the detection pressure detected
by the high pressure-side pressure detecting device 51 becomes equal to the second
predetermined high pressure value which is the target high pressure value.
[0070] At the same time, when pressure (intermediate pressure) of refrigerant after it is
reduced by the second expanding device 21 is lower than the critical pressure, the
control device 60 controls the valve opening degree of the bypass expansion valve
21 as shown in the control flowchart shown in Fig. 3. On the downstream side of the
economizer 13 of the bypass refrigerant circuit 20, the degrees of superheat SHm of
the refrigerant on the way of compression of the compression mechanism 11 and refrigerant
before merging are acquired (S1). When it is determined that the degree of superheat
SHm becomes lower than the predetermined value SHt (YES in S2), the control device
60 operates to reduce the valve opening degree of the bypass expansion valve 21, and
the flow rate of refrigerant is reduced (S3). According to this, the temperature rising
width of refrigerant caused by heat exchange with the main refrigerant circuit 10
becomes large, and the degrees of superheat SHm of refrigerant on the way of compression
of the compression mechanism 11 and the refrigerant before merging rise on the downstream
side of the economizer 13. Therefore, refrigerant injected into the compression mechanism
11 becomes gas. When it is determined that the acquired degree of superheat SHm of
refrigerant on the downstream side of the economizer 13 exceeds the predetermined
value SHt (NO in S2), the control device 60 operates to increase the valve opening
degree of the bypass expansion valve 21, and the flow rate of refrigerant is increased
(S4). According to this, the temperature rising width of the refrigerant caused by
the heat exchange with the main refrigerant circuit 10 becomes small, the degrees
of superheat SHm of the refrigerant on the way of compression of the compression mechanism
11 and the refrigerant before merging are lowered, temperature of refrigerant which
merges with the main refrigerant circuit 10 on the way of compression of the compression
mechanism 11 is lowered, and discharge temperature which is temperature of refrigerant
discharged from the compression mechanism 11 is lowered.
[0071] At that time, the degree of superheat SHm of refrigerant injected into the compression
mechanism 11 can be calculated from a difference between temperature obtained by the
intermediate heat exchanger bypass inlet thermistor 56 and temperature obtained by
the intermediate heat exchanger bypass outlet thermistor 58 while taking the pressure
loss of the economizer 13 into account. This is because that when pressure (intermediate
pressure) of refrigerant after it is reduced by the second expanding device 21 is
lower than the critical pressure, temperature detected by the intermediate heat exchanger
bypass inlet thermistor 56 becomes the saturated temperature. The degree of superheat
SHm of refrigerant injected into the compression mechanism 11 can also be calculated
from pressure information detected by the intermediate pressure-side pressure detecting
device 52 and temperature information detected by the intermediate heat exchanger
bypass outlet thermistor 58.
[0072] According to this, the home-heating load becomes small, and the enthalpy difference
(a-A) of refrigerant in the radiator 12 becomes small. To compensate this reduced
enthalpy difference, the heating ability of refrigerant in the radiator 12 is enhanced.
According to this, it is possible to keep supplying high temperature water to the
heating terminal 32a.
[0073] When detection temperature detected by the heat medium outlet temperature thermistor
53 exceeds the second predetermined temperature which is higher than the fourth predetermined
temperature, the control device 60 reduces the operating frequency of the compression
mechanism 11. According to this, it is possible to utilize the liquid heating device
as a home-heating device using high temperature water while suppressing the pressure
rise of high pressure refrigerant in the radiator 12 such that pressure of the high
pressure refrigerant in the radiator 12 does not exceed the second predetermined high
pressure value which is the target high pressure value.
[1-3. Effect and the like]
[0074] When the degrees of superheat SHm of the refrigerant on the way of compression of
the compression mechanism 11 and the refrigerant before merging become lower than
the predetermined value SHt on the downstream side of the economizer 13 of the bypass
refrigerant circuit 20, operation is carried out such that the valve opening degree
of the bypass expansion valve 21 becomes small. According to this, the degrees of
superheat SHm of the refrigerant on the way of compression of the compression mechanism
11 and the refrigerant before merging rise on the downstream side of the economizer
13. Hence, it is possible to prevent refrigerant injected into the compression mechanism
11 from being compressed in a liquid state.
[0075] When the degrees of superheat SHm of the refrigerant on the way of compression of
the compression mechanism 11 and the refrigerant before merging exceed the predetermined
value SHt on the downstream side of the economizer 13, operation is carried out such
that the valve opening degree of the bypass expansion valve 21 becomes large. According
to this, the degrees of superheat SHm of the refrigerant on the way of compression
of the compression mechanism 11 and the refrigerant before merging are lowered on
the downstream side of the economizer 13, and the discharge temperature which is temperature
of refrigerant discharged from the compression mechanism 11 can also be lowered. Hence,
excessive rise of discharge temperature exceeding a range of use can be suppressed.
[0076] From these facts, by controlling the degrees of superheat SHm of the refrigerant
on the way of compression of the compression mechanism 11 and the refrigerant before
merging on the downstream side of the economizer 13 using the bypass expansion valve
21, it is possible to secure the reliability of the compression mechanism 11. The
predetermined value SHt which operates to increase the valve opening degree of the
bypass expansion valve 21 and the predetermined value SHt which operates to reduce
the valve opening degree of the bypass expansion valve 21 may be the same or different
from each other. That is, the predetermined value SHt which operates to increase the
valve opening degree of the bypass expansion valve 21 may be higher than the predetermined
value SHt which operates to reduce the valve opening degree of the bypass expansion
valve 21.
[0077] The same operating action may be executed using the first predetermined high pressure
value and the second predetermined high pressure value which are detection pressures
detected by the high pressure-side pressure detecting device 51 as the threshold values
instead of using the fourth predetermined temperature and the second predetermined
temperature which are detection temperatures detected by the heat medium outlet temperature
thermistor 53.
[0078] It is preferable that in the refrigeration cycle device of the embodiment, carbon
dioxide is used as the refrigerant. This is because that temperature of the use-side
heat medium can be made high in the radiator 12 when the use-side heat medium is heated
by the carbon dioxide which is the refrigerant.
[0079] If water or antifreeze liquid is used as the use-side heat medium, high temperature
water can be used the heating terminal 32a or can be stored in the hot water tank
32b.
[INDUSTRIAL APPLICABILITY]
[0080] As described above, the refrigeration cycle device of the present invention includes
the main refrigerant circuit having the intermediate heat exchanger and the bypass
refrigerant circuit. By making the degree of superheat of refrigerant injected from
the bypass refrigerant circuit into the compression mechanism equal to or higher than
the predetermined value, it is possible to prevent liquid compression from being generated
in the compression mechanism. Hence, the present invention is useful for a liquid
heating device of a refrigerator, an air conditioner, hot water supply system and
a home-heating device using the refrigeration cycle device.
[EXPLANATION OF SYMBOLS]
[0081]
10 main refrigerant circuit
11 compression mechanism
12 radiator (use-side heat exchanger)
13 economizer (intermediate heat exchanger)
14 main expansion valve (first expanding device)
15 evaporator (heat source-side heat exchanger)
16 pipe
20 bypass refrigerant circuit
21 bypass expansion valve (second expanding device)
30 use-side heat medium circuit
31 transfer pump (transfer device)
32a heating terminal
32b hot water tank
33 heat medium pipe
34 first switching valve
35 second switching valve
41 hot water tap
42 hot water supply-heat exchanger
43 water supply pipe
51 high pressure-side pressure detecting device
52 intermediate pressure-side pressure detecting device
53 heat medium outlet temperature thermistor
54 heat medium inlet temperature thermistor
55a first hot water tank temperature thermistor
55b second hot water tank temperature thermistor
55c third hot water tank temperature thermistor
56 intermediate heat exchanger bypass inlet thermistor (pre-cooling temperature sensor)
57 intermediate heat exchanger main refrigerant inlet thermistor
58 intermediate heat exchanger bypass outlet thermistor (post-cooling temperature
sensor)
60 control device
1. A refrigeration cycle device comprising:
a main refrigerant circuit (10) formed by sequentially connecting, to one another
through a pipe (16), a compression mechanism (11) composed of a compression rotating
element, a use-side heat exchanger (12) for heating use-side heat medium by refrigerant
discharged from the compression rotating element, an intermediate heat exchanger (13),
a first expanding device (14) and a heat source-side heat exchanger (15);
a bypass refrigerant circuit (20) which branches off from the pipe (16) between the
use-side heat exchanger (12) and the first expanding device (14), in which after the
refrigerant which is branched is decompressed by a second expanding device (21), the
branched refrigerant exchanges heat, in the intermediate heat exchanger (13), with
the refrigerant flowing through the main refrigerant circuit (10), and merges with
the refrigerant which is on the way of compression of the compression rotating element;
a pre-cooling temperature sensor (56) for detecting temperature of the refrigerant
flowing through the bypass refrigerant circuit (20) located upstream of the intermediate
heat exchanger (13);
a post-cooling temperature sensor (58) for detecting temperature of the refrigerant
flowing through the bypass refrigerant circuit (20) located downstream of the intermediate
heat exchanger (13); and
a control device (60), wherein
the control device (60) calculates a degree of superheat of the refrigerant which
merges with the compression rotating element based on temperature data acquired from
the pre-cooling temperature sensor (56) and from the post-cooling temperature sensor
(58), and when the calculated degree of superheat is lower than a predetermined value,
the control device (60) operates to reduce a valve opening degree of the second expanding
device (21).
2. The refrigeration cycle device according to claim 1, wherein
the control device (60) calculates the degree of superheat of the refrigerant which
merges with the compression rotating element based on the temperature data acquired
from the pre-cooling temperature sensor (56) and from the post-cooling temperature
sensor (58), and when the calculated degree of superheat is equal to or higher than
the predetermined value, the control device (60) operates to increase the valve opening
degree of the second expanding device (21).
3. The refrigeration cycle device according to claim 2, further comprising an intermediate
pressure-side pressure detecting device (52) for detecting pressure of the refrigerant
flowing through the bypass refrigerant circuit (20) located downstream of the second
expanding device (21), wherein
when detection pressure detected by the intermediate pressure-side pressure detecting
device (52) is equal to or lower than a critical pressure, the control device (60)
operates to increase the valve opening degree of the second expanding device (21).
4. The refrigeration cycle device according to claim 3, wherein
the control device (60) increases operating frequency of the compression rotating
element.
5. The refrigeration cycle device according to claim 4, further comprising a high pressure-side
pressure detecting device (51) for detecting high pressure-side pressure of the main
refrigerant circuit (10), wherein
when detection pressure detected by the high pressure-side pressure detecting device
(51) exceeds a predetermined value, the control device (60) reduces the operating
frequency of the compression rotating element.
6. The refrigeration cycle device according to any one of claims 1 to 5, wherein
the refrigerant is carbon dioxide.
7. A liquid heating device comprising the refrigeration cycle device according to any
one of claims 1 to 5, and a use-side heat medium circuit (30) for circulating the
use-side heat medium by a transfer device (31).
8. The liquid heating device according to claim 7, comprising
a heat medium outlet temperature thermistor (53) for detecting temperature of the
use-side heat medium which flows out from the use-side heat exchanger (12), and
a heat medium inlet temperature thermistor (54) for detecting temperature of the use-side
heat medium which flows into the use-side heat exchanger (12), wherein
the control device (60) operates the transfer device (31) such that detection temperature
detected by the heat medium outlet temperature thermistor (53) becomes equal to a
target temperature, and when the detection temperature detected by the heat medium
inlet temperature thermistor (54) exceeds first predetermined temperature, the control
device (60) reduces operating frequency of the compression rotating element.
9. The liquid heating device according to claim 7, comprising
a heat medium outlet temperature thermistor (53) for detecting temperature of the
use-side heat medium which flows out from the use-side heat exchanger (12), and
a heat medium inlet temperature thermistor (54) for detecting temperature of the use-side
heat medium which flows into the use-side heat exchanger (12), wherein
the control device (60) operates the transfer device (31) such that a temperature
difference between detection temperature detected by the heat medium outlet temperature
thermistor (53) and detection temperature detected by the heat medium inlet temperature
thermistor (54) becomes equal to a target temperature difference, and when the detection
temperature of the heat medium outlet temperature thermistor (53) exceeds second predetermined
temperature, the control device (60) reduces operating frequency of the compression
rotating element.
10. The liquid heating device according to any one of claims 7 to 9, wherein
the use-side heat medium is water or antifreeze liquid.