JP2008106987A - Refrigerating cycle apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency while keeping the balance of a refrigerating cycle regardless of operating conditions in a refrigerating cycle apparatus subjected to constraint that the density ratio is uniform. <P>SOLUTION: This refrigerating cycle apparatus 1 includes a refrigerant circuit 10 in which a compressor 2, a radiator 3, an expander 4, and an evaporator 5 are sequentially connected. A bypass passage 1 is put in the parallel-connecting state between the radiator 3 and the expander 4 of the refrigerating circuit 10. A part of the refrigerating circuit 10 to which the bypass passage 11 is parallel connected is provided with an opening and closing valve 12. An internal heat exchanger 15 for making heat exchange between a refrigerant flowing through a high temperature side passage 13 and a refrigerant flowing through a low temperature side passage 14 is provided on the downstream side of the radiator 3 of the refrigerating cycle apparatus 1. The refrigerating cycle apparatus 1 includes a flow control device 20, wherein the flow control device 20 controls opening and closing of the opening and closing valve 12 based on the detection value of a pressure sensor 31 so that the pressure of a refrigerant delivered from the compressor 2 is within a predetermined range. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus, and more particularly to a refrigeration cycle apparatus in which a rotation speed ratio between a compressor and an expander is constant.

In recent years, a refrigeration cycle apparatus using a carbon dioxide refrigerant (CO ₂ ) suitable for the natural environment has attracted attention from the viewpoint of ozone layer destruction and prevention of global warming. CO ₂ refrigerant has a critical temperature as low as about 31 ° C. Therefore, the COP of the refrigeration cycle apparatus is lower than that of a conventional refrigerant. Therefore, in a refrigeration cycle apparatus using a CO ₂ refrigerant, means for improving COP is important.

  Therefore, a refrigeration cycle apparatus in which the rotational speed ratio between the compressor and the expander is always constant, for example, an expander-integrated compressor in which the compressor and the expander are mechanically connected by a rotating shaft has been provided. A refrigeration cycle apparatus is used. In the expander-integrated compressor, the expansion energy generated in the expander is recovered and used for compressing the refrigerant in the compressor. Thereby, since the motive power of the electric motor etc. which rotationally drive a compressor is reduced, COP can be improved.

  In the refrigeration cycle apparatus provided with the above-described compressor integrated with an expander, when the rotational speed of the rotary shaft is N, the cylinder volume of the compressor is Vc, and the cylinder volume of the expander is Ve, the volume circulation amount of the compressor is (Vc × N), the volume circulation amount of the expander is (Ve × N). Moreover, the mass circulation amount G of the refrigerant | coolant which flows through each of a compressor and an expander is equal. Therefore, the density Dc of the refrigerant sucked into the compressor (compressor sucked refrigerant) is (G / (Vc × N)), and the density De of the refrigerant sucked into the expander (expander sucked refrigerant) is (G / (Ve × N)). In addition, the density ratio (De / Dc) is (G / (Ve × N)) / (G / (Vc × N)) = Vc / Ve. Vc / Ve (design volume ratio) is a constant determined when the device is designed. As described above, the refrigeration cycle apparatus is operated so that the density ratio De / Dc between the compressor intake refrigerant and the expander intake refrigerant is always a constant value (Vc / Ve). This is called “constant density ratio”.)

  However, the operating conditions of the refrigeration cycle apparatus are not always constant. Therefore, in a refrigeration cycle apparatus designed to be optimal at a predetermined density ratio, if the operating conditions change from what was assumed at the time of design, for example, if the heat of the refrigerant cannot be sufficiently dissipated in the radiator, the density ratio The cycle tries to balance by increasing the high-pressure side pressure (the pressure of the refrigerant discharged from the compressor and sucked into the expander) from a certain constraint. For this reason, the pressure and temperature of the refrigerant discharged from the compressor increase, and the efficiency of the refrigeration cycle decreases. As a result, the balance of the refrigeration cycle is lost, making it difficult to maintain an optimal COP. In order to maintain the optimum COP, it is necessary to set the operation state (refrigerant pressure, temperature) optimum for the operation condition according to the operation condition.

Therefore, in such a case, a refrigeration cycle apparatus has been proposed that cools the refrigerant sucked into the expander by exchanging heat with the refrigerant sucked into the compressor (for example, see Patent Document 1). In the refrigeration cycle apparatus, when the heat of the refrigerant cannot be sufficiently dissipated in the radiator, the refrigerant sucked into the expander is increased by cooling the refrigerant sucked into the expander. As a result, the restriction of a constant density ratio is avoided and the refrigeration cycle is balanced.
JP 2004-108683 A

  However, the refrigerant sucked into the compressor is not a gas-liquid two-phase refrigerant but a gas. Therefore, the temperature of the refrigerant sucked into the compressor rises with heat exchange with the high-temperature refrigerant sucked into the expander. Therefore, the refrigerant sucked into the compressor has a problem that the refrigerant sucked into the expander cannot be sufficiently cooled.

  The present invention has been made in view of the above points, and the object of the present invention is to improve efficiency while maintaining the balance of the refrigeration cycle regardless of the operating conditions in the refrigeration cycle apparatus subject to a constant density ratio constraint. Is to plan.

  A refrigeration cycle apparatus according to the present invention includes a compressor that compresses a refrigerant, a radiator that dissipates heat from the refrigerant compressed by the compressor, an expander that expands the refrigerant, and evaporates the refrigerant expanded by the expander. An evaporator, sequentially connected, a refrigerant circuit in which a ratio between the rotation speed of the compressor and the rotation speed of the expander is constant, a high-temperature side flow path into which the refrigerant flowing out of the radiator flows, An internal heat exchanger for exchanging heat between the refrigerant in the high-temperature side channel and the refrigerant in the low-temperature side channel, and a low-temperature side channel into which the refrigerant discharged from the expander flows. And a control device that controls the amount of heat exchange by the exchanger.

  The refrigeration cycle apparatus includes an internal heat exchanger that exchanges heat between the refrigerant flowing out of the radiator (refrigerant sucked into the expander) and the refrigerant discharged from the expander. Therefore, when the operating conditions change from what was assumed at the time of design, for example, even when the heat of the refrigerant cannot be sufficiently dissipated in the radiator, the refrigerant sucked into the expander is expanded in the internal heat exchanger. It is cooled by the refrigerant discharged from. Thereby, since the density of the refrigerant sucked into the expander increases, an increase in the high-pressure side pressure due to insufficient cooling of the refrigerant sucked into the expander can be prevented. Accordingly, it is possible to prevent a decrease in the efficiency of the compressor due to an increase in the high-pressure side pressure.

  In the refrigeration cycle apparatus, since the refrigerant discharged from the expander is in a gas-liquid two-phase state, heat exchange at a constant temperature (heat exchange due to changes in latent heat) is performed in the internal heat exchanger. Therefore, unlike the refrigerant (gaseous refrigerant) sucked into the compressor, the refrigerant discharged from the expander can exchange heat while maintaining a high temperature difference from the refrigerant sucked into the expander. Therefore, according to the refrigeration cycle apparatus, the refrigerant sucked into the expander (expander intake refrigerant) can be sufficiently cooled.

  Furthermore, the refrigeration cycle apparatus includes a control device that controls the amount of heat exchange by the internal heat exchanger. Therefore, the heat exchange amount can be appropriately changed according to the operation state. Therefore, according to the refrigeration cycle apparatus, the refrigeration cycle can be balanced regardless of operating conditions.

  The control device includes: a bypass flow path connected in parallel to the high temperature side flow path of the internal heat exchanger; an open / close valve provided in a portion where the bypass flow path of the refrigerant circuit is connected in parallel; It is preferable to have a flow rate control device that controls opening and closing of the valve.

  According to the control device described above, the flow rate of the refrigerant flowing through the high temperature side passage of the internal heat exchanger (the refrigerant flowing out of the radiator) can be controlled by opening and closing the on-off valve. Thereby, the heat exchange amount by the internal heat exchanger can be controlled. Therefore, according to the refrigeration cycle apparatus, the heat exchange amount between the expander intake refrigerant and the expander discharge refrigerant can be appropriately changed by simple flow rate control.

  The control device includes a bypass flow channel connected in parallel to the high temperature side flow channel of the internal heat exchanger, an open / close valve provided in the bypass flow channel, and a flow rate control device that controls the open / close valve. It is preferable to have.

  According to the above control device, the flow rate of the refrigerant flowing through the high-temperature side channel of the internal heat exchanger (the refrigerant flowing out of the radiator) is controlled by opening and closing the on-off valve and controlling the flow rate of the refrigerant flowing into the bypass channel. Can be controlled. Thereby, the heat exchange amount by the internal heat exchanger can be controlled. Therefore, according to the refrigeration cycle apparatus, the heat exchange amount between the expander intake refrigerant and the expander discharge refrigerant can be appropriately changed by simple flow rate control.

  The control device includes: a bypass channel connected in parallel to the low temperature side channel of the internal heat exchanger; an on-off valve provided in a portion where the bypass channel of the refrigerant circuit is connected in parallel; It is preferable to have a flow rate control device that controls opening and closing of the valve.

  According to the control device described above, the flow rate of the refrigerant (refrigerant discharged from the expander) flowing through the low-temperature channel of the internal heat exchanger can be controlled by opening and closing the on-off valve. Thereby, the heat exchange amount by the internal heat exchanger can be controlled. Therefore, according to the refrigeration cycle apparatus, the heat exchange amount between the expander intake refrigerant and the expander discharge refrigerant can be appropriately changed by simple flow rate control.

  The control device includes a bypass flow channel connected in parallel to the low temperature flow channel of the internal heat exchanger, an open / close valve provided in the bypass flow channel, and a flow control device that controls the open / close valve. It is preferable to have.

  According to the control device, the flow rate of the refrigerant (refrigerant discharged from the expander) flowing in the low-temperature side flow path of the internal heat exchanger by controlling the flow rate of the refrigerant flowing into the bypass flow path by opening and closing the on-off valve. Can be controlled. Thereby, the heat exchange amount by the internal heat exchanger can be controlled. Therefore, according to the refrigeration cycle apparatus, the heat exchange amount between the expander intake refrigerant and the expander discharge refrigerant can be appropriately changed by simple flow rate control.

  The control device includes a high-pressure side bypass passage connected in parallel to the high-temperature side passage of the internal heat exchanger, and a low-pressure side bypass passage connected in parallel to the low-temperature side passage of the internal heat exchanger. A high-pressure side opening / closing valve provided in a portion where the high-pressure side bypass flow path of the refrigerant circuit is connected in parallel; and a low-pressure side opening / closing valve provided in a portion where the low-pressure side bypass flow path of the refrigerant circuit is connected in parallel It is preferable to have a valve and a flow rate control device that controls opening / closing of one or both of the high-pressure side on-off valve and the low-pressure side on-off valve.

  According to the above control device, the flow rate of the refrigerant flowing through the high-temperature side flow path or the low-temperature side flow path of the internal heat exchanger is controlled by opening or closing one or both of the high-pressure side on-off valve and the low-pressure side on-off valve. can do. Thereby, the heat exchange amount by the internal heat exchanger can be controlled. Therefore, according to the refrigeration cycle apparatus, the heat exchange amount between the expander intake refrigerant and the expander discharge refrigerant can be appropriately changed by simple flow rate control.

  The control device includes a high-pressure side bypass passage connected in parallel to the high-temperature side passage of the internal heat exchanger, and a low-pressure side bypass passage connected in parallel to the low-temperature side passage of the internal heat exchanger. A high pressure side on / off valve provided in the high pressure side bypass flow path, a low pressure side on / off valve provided in the low pressure side bypass flow path, one or both of the high pressure side on / off valve and the low pressure side on / off valve It is preferable to have a flow rate control device that controls opening and closing.

  According to the above flow rate control device, by controlling the flow rate of the refrigerant flowing into the high pressure side bypass flow path or the low pressure side bypass flow path by opening / closing either one or both of the high pressure side open / close valve and the low pressure side open / close valve, It is possible to control the flow rate of the refrigerant flowing through the high temperature side channel or the low temperature side channel of the internal heat exchanger. Thereby, the heat exchange amount by the internal heat exchanger can be controlled. Therefore, according to the refrigeration cycle apparatus, the heat exchange amount between the expander intake refrigerant and the expander discharge refrigerant can be appropriately changed by simple flow rate control.

  The refrigeration cycle apparatus includes a pressure sensor that detects a pressure of the refrigerant discharged from the compressor, and the flow rate control device is configured such that a detection value of the pressure sensor is a predetermined value based on a detection value of the pressure sensor. Thus, it is preferable to change the opening degree of the on-off valve.

  The flow control device of the refrigeration cycle apparatus changes the opening degree of the on-off valve so that the pressure of the refrigerant discharged from the compressor becomes a predetermined value. Thereby, the heat exchange amount in the internal heat exchanger is appropriately adjusted according to the pressure of the refrigerant discharged from the compressor. Therefore, according to the refrigeration cycle apparatus, the high-pressure side pressure is automatically and suitably adjusted regardless of the operating conditions, and the cycle can be stabilized.

  The refrigeration cycle apparatus includes a pressure sensor that detects a pressure of a refrigerant sucked into the expander, and the flow rate control device is configured such that a detection value of the pressure sensor is a predetermined value based on a detection value of the pressure sensor. Thus, it is preferable to change the opening degree of the on-off valve.

  The flow rate control device of the refrigeration cycle device changes the opening degree of the on-off valve so that the pressure of the expander suction refrigerant becomes a predetermined value. Thereby, the heat exchange amount in the internal heat exchanger is appropriately adjusted according to the pressure of the refrigerant sucked into the expander. Therefore, according to the refrigeration cycle apparatus, the high-pressure side pressure is automatically and suitably adjusted regardless of the operating conditions, and the cycle can be stabilized.

  The refrigeration cycle apparatus includes a pressure sensor that detects a pressure of a refrigerant sucked into the compressor, and the flow rate control device is configured such that a detection value of the pressure sensor is a predetermined value based on a detection value of the pressure sensor. Thus, it is preferable to change the opening degree of the on-off valve.

  The flow rate control device of the refrigeration cycle device changes the opening degree of the on-off valve so that the pressure of the refrigerant sucked into the compressor becomes a predetermined value. Thereby, the heat exchange amount in the internal heat exchanger is appropriately adjusted according to the pressure of the refrigerant sucked into the compressor. Therefore, according to the refrigeration cycle apparatus, the low pressure side pressure (the pressure of the refrigerant discharged from the expander and sucked into the compressor) is automatically and suitably adjusted, and the cycle can be stabilized.

  The refrigeration cycle apparatus includes a pressure sensor that detects a pressure of the refrigerant discharged from the expander, and the flow rate control device has a detection value of the pressure sensor that is a predetermined value based on a detection value of the pressure sensor. Thus, it is preferable to change the opening degree of the on-off valve.

  The flow rate control device of the refrigeration cycle device changes the opening degree of the on-off valve so that the pressure of the refrigerant discharged from the expander becomes a predetermined value. Thereby, the heat exchange amount in the internal heat exchanger is appropriately adjusted according to the pressure of the refrigerant discharged from the expander. Therefore, according to the refrigeration cycle apparatus, the low-pressure side pressure is automatically and suitably adjusted, and the cycle can be stabilized.

  The refrigeration cycle apparatus includes a temperature sensor that detects a temperature of the refrigerant discharged from the compressor, and the flow rate control device is configured such that a detection value of the temperature sensor is a predetermined value based on a detection value of the temperature sensor. Thus, it is preferable to change the opening degree of the on-off valve.

  The flow rate control device of the refrigeration cycle device changes the opening degree of the on-off valve so that the temperature of the refrigerant discharged from the compressor becomes a predetermined value. Thereby, the heat exchange amount in the internal heat exchanger is appropriately adjusted according to the temperature of the refrigerant discharged from the compressor. Therefore, according to the refrigeration cycle apparatus, since the temperature of the refrigerant discharged from the compressor is automatically and suitably adjusted, the cycle can be stabilized.

  The refrigeration cycle apparatus includes a temperature sensor that detects a temperature of a refrigerant sucked into the expander, and the flow rate control device is configured such that a detection value of the temperature sensor is a predetermined value based on a detection value of the temperature sensor. Thus, it is preferable to change the opening degree of the on-off valve.

  The flow control device of the refrigeration cycle apparatus changes the opening degree of the on-off valve so that the temperature of the refrigerant sucked into the expander becomes a predetermined value. Thereby, the heat exchange amount in the internal heat exchanger is appropriately adjusted according to the temperature of the refrigerant sucked into the expander. Therefore, according to the refrigeration cycle apparatus, since the temperature of the refrigerant sucked into the expander is automatically and suitably adjusted, the cycle can be stabilized.

  The refrigeration cycle device includes a temperature sensor that detects a temperature of the refrigerant discharged from the expander, and the flow rate control device is configured such that a detection value of the temperature sensor is a predetermined value based on a detection value of the temperature sensor. Thus, it is preferable to change the opening degree of the on-off valve.

  The flow rate control device of the refrigeration cycle device changes the opening degree of the on-off valve so that the temperature of the refrigerant discharged from the expander becomes a predetermined value. Thereby, the heat exchange amount in the internal heat exchanger is appropriately adjusted according to the temperature of the refrigerant discharged from the expander. Therefore, according to the refrigeration cycle apparatus, since the temperature of the refrigerant discharged from the expander is automatically and suitably adjusted, the cycle can be stabilized.

  A refrigeration cycle apparatus according to the present invention includes a compressor that compresses a refrigerant, a radiator that dissipates heat from the refrigerant compressed by the compressor, an expander that expands the refrigerant, and evaporates the refrigerant expanded by the expander. An evaporator, sequentially connected, a refrigerant circuit in which a ratio between the rotation speed of the compressor and the rotation speed of the expander is constant, a high-temperature side flow path into which the refrigerant flowing out of the radiator flows, An internal heat exchanger for exchanging heat between the refrigerant in the high-temperature side channel and the refrigerant in the low-temperature side channel, and a low-temperature side channel into which the refrigerant discharged from the expander flows. A first bypass channel connected in parallel to the high temperature channel of the exchanger; a second bypass channel connected in parallel to the radiator in the refrigerant circuit; and the first bypass of the refrigerant circuit. 1st opening and closing provided in the part where the flow path was connected in parallel When, those comprising a second on-off valve provided in the second bypass passage, and a flow control device which controls the opening and closing of the said first on-off valve and the second on-off valve.

  The refrigeration cycle apparatus is connected in parallel to an internal heat exchanger that exchanges heat between a part of the refrigerant flowing out of the radiator (refrigerant sucked into the expander) and the refrigerant discharged from the expander, and the radiator. And a second bypass flow path. Therefore, even if the operating conditions are changed from those assumed at the time of design, the refrigeration cycle can be balanced. For example, when the heat of the refrigerant cannot be sufficiently dissipated in the radiator, the refrigerant sucked into the expander is cooled by the refrigerant discharged from the expander in the internal heat exchanger. Thereby, the density of the refrigerant | coolant suck | inhaled by an expander can be raised and the balance of a refrigerating cycle can be aimed at. On the other hand, for example, since heat is dissipated excessively in the radiator, a part of the refrigerant flowing into the radiator is caused to flow into the second bypass channel when the balance of the refrigeration cycle is lost. Thereby, the balance of a refrigerating cycle can be aimed at by controlling the amount of heat radiation and reducing the density of the refrigerant sucked into the expander.

  A refrigeration cycle apparatus according to the present invention includes a compressor that compresses a refrigerant, a radiator that dissipates heat from the refrigerant compressed by the compressor, an expander that expands the refrigerant, and evaporates the refrigerant expanded by the expander. An evaporator, sequentially connected, a refrigerant circuit in which a ratio between the rotation speed of the compressor and the rotation speed of the expander is constant, a high-temperature side flow path into which the refrigerant flowing out of the radiator flows, An internal heat exchanger for exchanging heat between the refrigerant in the high-temperature side channel and the refrigerant in the low-temperature side channel, and a low-temperature side channel into which the refrigerant discharged from the expander flows. A first bypass passage connected in parallel to the low temperature side passage of the exchanger; a second bypass passage connected in parallel to the radiator in the refrigerant circuit; and the first bypass of the refrigerant circuit. 1st opening and closing provided in the part where the flow path was connected in parallel When, those comprising a second on-off valve provided in the second bypass passage, and a flow control device which controls the opening and closing of the said first on-off valve and the second on-off valve.

  The refrigeration cycle apparatus is connected in parallel to an internal heat exchanger that exchanges heat between the refrigerant flowing out of the radiator (refrigerant sucked into the expander) and a part of the refrigerant discharged from the expander, and the radiator. And a second bypass flow path. Therefore, even if the operating conditions have changed from what was assumed at the time of design (for example, when the heat of the refrigerant cannot be sufficiently dissipated in the radiator or when the radiator dissipates excessive heat), the balance of the refrigeration cycle Can be achieved.

  It is preferable that the compressor and the expander are connected by a coaxial rotating shaft.

  Thereby, compared with the case where the rotating shaft of a compressor and the rotating shaft of an expander are connected via a power transmission mechanism, a compressor and an expander can be arrange | positioned compactly. In addition, the rotating shaft may be a single body, or a plurality of members coupled in a coaxial manner.

  The refrigerant may be carbon dioxide.

  In general, when carbon dioxide is used as the refrigerant of the refrigeration cycle apparatus, the COP is lower than that using chlorofluorocarbon as a refrigerant. Therefore, for example, it is necessary to improve the COP by using a power recovery type expander such as an expander-integrated compressor. However, in a refrigeration cycle apparatus using an expander in which the rotational speed ratio between the compressor and the expander, such as an expander-integrated compressor, is always constant, the density ratio is constant. Therefore, in the refrigeration cycle apparatus, the balance of the cycle is likely to be lost, and there is a risk that the COP may decrease instead. However, according to the refrigeration cycle apparatus of the present invention, COP can be improved while balancing the refrigeration cycle as described above. Therefore, even when carbon dioxide is used as the refrigerant, the above-described problems can be solved and COP can be improved.

  As described above, according to the present invention, in a refrigeration cycle apparatus that receives a constant density ratio constraint, efficiency can be improved while maintaining the balance of the refrigeration cycle regardless of operating conditions.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, although the refrigerating-cycle apparatus of this embodiment can be used for a refrigerating device, an air conditioning apparatus, a hot water heater, etc., the case where it uses for a hot water heater is demonstrated below.

(First embodiment)
-Configuration of refrigeration cycle equipment-
As shown in FIG. 1, the refrigeration cycle apparatus 1 according to the present embodiment includes a refrigerant circuit 10 in which a compressor 2, a radiator 3, an expander 4, and an evaporator 5 are sequentially connected. . Further, a bypass passage 11 is connected in parallel between the radiator 3 and the expander 4 of the refrigerant circuit 10.

  The compressor 2 and the expander 4 of the refrigeration cycle apparatus 1 are connected by a coaxial rotating shaft 6. An electric motor 7 is provided between the compressor 2 and the expander 4 of the rotary shaft 6, and the compressor 2, the expander 4, and the electric motor 7 are integrated by the rotary shaft 6 and operate in synchronization. The compressor 2, the expander 4, and the electric motor 7 are housed in the same casing 8 a and are incorporated in the refrigerant circuit 10 as the expander-integrated compressor 8.

  The radiator 3 is a heat exchanger having a high temperature side channel 3a and a low temperature side channel 3b. The high temperature side flow path 3a of the radiator 3 is connected to the refrigerant circuit 10, and the low temperature side flow path 3b is connected to a water supply tank, a water supply pump, etc. (not shown). Moreover, the water in a water supply tank is supplied to the low temperature side flow path 3b by a water supply pump. The radiator 3 exchanges heat between the high-temperature and high-pressure refrigerant flowing through the high-temperature side flow path 3a and the water flowing through the low-temperature side flow path 3b to heat the water and cool the refrigerant flowing through the high-temperature side flow path 3a.

  An internal heat exchanger 15 is provided on the downstream side of the radiator 3 of the refrigeration cycle apparatus 1. The internal heat exchanger 15 has a high temperature side channel 13 for circulating a high temperature and high pressure refrigerant, and a low temperature side channel 14 for circulating a low temperature and low pressure refrigerant. Heat is exchanged with the refrigerant flowing through the side flow path 14. The high temperature side channel 13 of the internal heat exchanger 15 is connected between the radiator 3 and the expander 4 of the refrigerant circuit 10, and the low temperature side channel 14 is connected between the expander 4 and the evaporator 5 of the refrigerant circuit 10. Connected between. The bypass flow path 11 described above is provided so as to bypass the high temperature side flow path 13 of the internal heat exchanger 15.

  An opening / closing valve 12 for controlling the amount of refrigerant flowing to the high temperature side flow path 13 of the internal heat exchanger 15 is provided at a portion connected in parallel with the bypass flow path 11 of the refrigerant circuit 10.

  The refrigeration cycle apparatus 1 includes a flow rate control device 20 that controls opening and closing of the on-off valve 12. A pressure sensor 31 that detects the pressure of the refrigerant discharged from the compressor 2 is provided between the compressor 2 and the radiator 3 of the refrigerant circuit 10. The pressure sensor 31 is connected to the flow control device 20. The flow control device 20 controls the opening / closing valve 12 based on the detection value of the pressure sensor 31 so that the pressure of the refrigerant discharged from the compressor 2 falls within a predetermined range. A specific control method of the flow control device 20 will be described in detail later.

The refrigerant circuit 10 is filled with a refrigerant that is in a supercritical state (a state that exceeds the critical temperature and critical pressure) in the high-pressure portion (the portion that reaches the expander 4 from the compressor 2 through the radiator 3). In the present embodiment, carbon dioxide (CO ₂ ) is filled as such a refrigerant. However, the type of refrigerant is not particularly limited.

  The above is the configuration of the refrigeration cycle apparatus 1 according to the present embodiment.

-Operation of refrigeration cycle equipment-
Next, the operation during operation of the refrigeration cycle apparatus 1 will be described. The state of the refrigerant as well as the operation will be described with reference to the Mollier diagram of FIG. Hereinafter, the cylinder volume of the compressor 2 is Vc, the cylinder volume of the expander 4 is Ve, the density of refrigerant sucked into the compressor 2 (compressor sucked refrigerant) is Dc, and the density of refrigerant sucked into the expander 4 ( The expansion machine suction refrigerant density) will be described as De. In FIG. 2, the alternate long and short dash line indicates a saturation line S, and below the saturation line S, the refrigerant is in a gas-liquid two-phase state. Also, the straight lines rising to the right indicate isodensity lines D1 (850 kg / m ² ) and D2 (750 kg / m ² ), and the broken lines rising to the left indicate isothermal lines t1 (35 ° C.) and t2 (20 ° C.). Yes.

  First, the case where the density ratio (De / Dc) in the actual operation state is substantially equal to the design volume ratio (Vc / Ve) assumed at the time of design will be described. At this time, the on-off valve 12 is controlled to be fully closed by the flow control device 20.

  The refrigerant in the low-pressure gas state (point A) flowing through the refrigeration circuit 10 is compressed in the compressor 2 and becomes a high-temperature and high-pressure supercritical state (point B ′). Thereafter, the high-temperature and high-pressure refrigerant discharged from the compressor 2 flows into the high-temperature channel 3 a of the radiator 3. In the radiator 3, the refrigerant that has flowed into the high temperature side flow path 3 a is cooled by exchanging heat with water supplied to the low temperature side flow path 3 b, and becomes a low temperature (t 2) liquid state (point E). On the other hand, the water supplied to the low temperature side channel 3b absorbs heat from the refrigerant flowing into the high temperature side channel 3a and is heated.

  The refrigerant cooled in the high temperature side flow path 3a does not flow to the internal heat exchanger 15 side but flows into the bypass flow path 11 because the on-off valve 12 is in a fully closed state. Thereafter, the refrigerant in the liquid state (point E) is sucked into the expander 4 and depressurized, and enters a gas-liquid two-phase state (point F) through the saturated liquid. In the expander 4, the pressure energy of the refrigerant is converted into power, and the power is transmitted to the rotating shaft 6. The input of the electric motor 7 is reduced by the power transmitted to the rotating shaft 6.

  The refrigerant in the gas-liquid two-phase state after decompression (point F) discharged from the expander 4 flows into the evaporator 5. The refrigerant is heated by the air in the vicinity of the evaporator 5 and enters a gas state with evaporation (point A). Thereafter, the refrigerant is again sucked into the compressor 2 and the same cycle is repeated.

  Next, a case where the density ratio (De / Dc) in the actual operation state is different from the design volume ratio (Vc / Ve) assumed at the time of design will be described.

  For example, when the refrigerant is not sufficiently cooled in the radiator 3, the density De of the refrigerant actually sucked into the expander 4 becomes small. That is, the density ratio (De / Dc) is smaller than the design volume ratio (Vc / Ve) assumed at the time of design. In such a case, the cycle of the refrigeration cycle apparatus 1 is out of the design range, and the refrigeration cycle apparatus 1 cannot operate normally. For example, since the temperature of the water supplied to the radiator 3 is 30 ° C. or higher, when the refrigerant is cooled only to the temperature t1 (35 ° C.), the cycle becomes a closed loop ABCD.

  In such a case, if the on-off valve 12 is left in the fully closed state, the refrigerant can be cooled only to the temperature t1 (35 ° C.) in the radiator 3, and the density (De) of the refrigerant sucked into the expander 4 However, it will fall compared with the case where it can cool to temperature t2 (20 degreeC). However, in the refrigeration cycle apparatus 1 using the expander-integrated compressor 8 in which the compressor 2 and the expander 4 operate in synchronization, the density ratio (De / Dc) must be always constant (constant density ratio). Restraint). Therefore, in the cycle of the refrigeration cycle apparatus 1, the density ratio is kept constant by increasing the high-pressure side pressure (pressure in the portion from the compressor 2 through the radiator 3 to the expander 4), and the cycle is stabilized. And Thereby, the refrigerant discharged from the compressor 2 has a pressure (point B) higher than the pressure assumed at the time of design (point B ').

  However, when the high-pressure side pressure rises above the desired pressure (point B ′) (point B), the discharge temperature and pressure of the compressor 2 rise and the amount of compression work increases, thereby increasing the input to the motor 7. Resulting in. Thereby, the operating efficiency of the refrigerating cycle apparatus 1 falls. In addition, the operation is out of the allowable range, and the reliability is lowered.

  Therefore, in such a refrigeration cycle apparatus 1 according to the present invention, in such a case, the on-off valve 12 is opened so that the refrigerant flows not only into the bypass channel 11 but also into the high temperature channel 13 side. Specifically, the pressure P 1 of the refrigerant discharged from the compressor 2 detected by the pressure sensor 31 is input to the flow control device 20. Then, the flow control device 20 opens the on-off valve 12 by a predetermined amount according to the detection value P1 of the pressure sensor 31. When the on-off valve 12 is opened, the refrigerant discharged from the expander 4 flows not only into the bypass channel 11 but also into the high-temperature channel 13 side.

  The refrigerant that has flowed into the portion where the bypass flow path 11 of the refrigerant circuit 10 is connected in parallel (point C ′) eventually flows into the high temperature side flow path 13 of the internal heat exchanger 15 and flows through the low temperature side flow path 14 at a temperature t3. The refrigerant is sufficiently cooled to the temperature t2 (20 ° C.) by the (5 ° C.) refrigerant (point E). As a result, the density of the refrigerant sucked into the expander 4 increases, the density ratio (De / Dc) approaches the design volume ratio (Vc / Ve) assumed at the time of design, and the cycle is stabilized. Then, the pressure of the refrigerant discharged from the compressor 2 does not increase and becomes a desirable pressure set at the time of design (point B ′).

  Thereafter, the refrigerant flows into the expander 4 and is depressurized, passes through the saturated liquid from the liquid phase (point E), and drops the pressure to a gas-liquid two-phase state at a temperature t3 (5 ° C.) (point F). Then, the refrigerant flows into the low temperature side flow path 14 of the internal heat exchanger 15 and is heated by the refrigerant flowing through the high temperature side flow path 13 to increase the temperature (point D '). Thereafter, the refrigerant flows into the evaporator 5 and is heated in the evaporator 5 to change from a gas-liquid two-phase state (point D ′) to a gas phase (point A) with evaporation.

  Note that the flow rate of the refrigerant flowing through the high temperature side flow path 13 of the internal heat exchanger 15 varies depending on the opening degree of the on-off valve 12. Therefore, by controlling the opening degree of the on-off valve 12, the flow rate of the refrigerant cooled in the internal heat exchanger 15 also changes. Therefore, the amount of heat exchange is changed by the flow control device 20 changing the opening degree of the on-off valve 12, and the temperature of the refrigerant sucked into the expander 4 can be adjusted. Thus, the temperature of the point E is changed from the temperature t3 (5 ° C.) near the downstream end (point D ′) of the low temperature side flow path 14 of the internal heat exchanger 15 by the opening degree of the on-off valve 12. Can be arbitrarily set in the range up to the temperature t1 (35 ° C.) near the upstream end of the point (point C ′). Further, the refrigerant flowing through the low-temperature side flow path 14 of the internal heat exchanger 15 is in a decompressed gas-liquid two-phase state. Therefore, it is possible to maintain the constant low temperature t3 (5 ° C.) and sufficiently cool the refrigerant flowing through the high temperature side flow path 13.

-Control of on-off valve-
Next, a control method of the on-off valve 12 by the flow control device 20 will be described with reference to the flowchart of FIG.

  First, in step S <b> 1, a lower limit value (Pmin) and an upper limit value (Pmax) of the pressure P <b> 1 of the refrigerant discharged from the compressor 2 are input to the flow control device 20. When the above value is input, the process proceeds to step S2, the pressure P1 of the refrigerant discharged from the compressor 2 is detected by the pressure sensor 31, and the detected value is input to the flow control device 20.

  When the pressure P1 is input, the process proceeds to step S3, and the flow control device 20 determines whether or not the pressure P1 is a value greater than the lower limit value (Pmin). When the pressure P1 is equal to or lower than the lower limit (Pmin), the process proceeds to step S4. In step S4, the opening degree of the on-off valve 12 is decreased, and the amount of refrigerant flowing through the high temperature side flow path 13 of the internal heat exchanger 15 is decreased. That is, the amount of heat exchange in the internal heat exchanger 15 is reduced. The opening change amount of the on-off valve 12 is adjusted according to the difference between P1 and Pmin.

  On the other hand, when the pressure P1 is larger than the lower limit (Pmin), the process proceeds to step S5. In step S5, it is determined whether or not the pressure P1 is smaller than an upper limit value (Pmax). If the pressure P1 is greater than or equal to the upper limit (Pmax), the process proceeds to step S6. In step S <b> 6, the opening degree of the on-off valve 12 is increased and the amount of refrigerant flowing through the high temperature side flow path 13 of the internal heat exchanger 15 is increased. That is, the amount of heat exchange in the internal heat exchanger 15 is increased. The opening change amount of the on-off valve 12 is adjusted according to the difference between P1 and Pmax.

  On the other hand, when the pressure P1 is smaller than the upper limit (Pmax), the process proceeds to step S7. In step S7, the opening degree of the on-off valve 12 is maintained without being changed. However, here, a slight change in the opening degree of the on-off valve 12 is included without changing the opening degree of the on-off valve 12.

  After step S4, step S6 or step S7, the process returns to step S2. Then, the above steps are repeated.

  As described above, the refrigeration cycle apparatus 1 according to this embodiment includes the internal heat exchanger 15 that exchanges heat between the refrigerant sucked into the expander 4 and the refrigerant discharged from the expander 4. Therefore, when the operating conditions change from what is assumed at the time of design, for example, even when the temperature of the cooling water supplied to the radiator 3 is high and the refrigerant is not sufficiently cooled, the internal heat exchanger 15 The refrigerant sucked in the expander 4 can be cooled to a suitable temperature. Thereby, since the density of the refrigerant | coolant sucked in the expander 4 can be raised, the raise of the high voltage | pressure side pressure resulting from insufficient cooling of the refrigerant | coolant sucked in the expander 4 can be prevented. Therefore, it is possible to prevent a decrease in the reliability of the compressor 2 due to an increase in the high-pressure side pressure. In addition, an increase in input to the electric motor 7 due to an increase in the work of compression can be prevented, and COP can be improved.

  In the refrigeration cycle apparatus 1, the refrigerant sucked into the expander 4 is cooled by the refrigerant discharged from the expander 4. Since the refrigerant discharged from the expander 4 is decompressed by the expander 4 and is in a gas-liquid two-phase state, heat exchange at a constant temperature (heat exchange due to changes in latent heat) is performed. Therefore, the refrigerant discharged from the expander 4 can exchange heat while maintaining a high temperature difference from the refrigerant sucked into the expander 4. Therefore, according to the refrigeration cycle apparatus 1, the intake refrigerant of the expander 4 can be sufficiently cooled by the discharge refrigerant of the expander 4.

  Further, the refrigeration cycle apparatus 1 includes a bypass flow path 11 that bypasses the high temperature side flow path 13 of the internal heat exchanger 15 and an on-off valve 12 for adjusting the flow rate of the refrigerant flowing through the high temperature side flow path 13. ing. Therefore, the amount of heat exchange in the internal heat exchanger 15 can be suitably adjusted by adjusting the flow rate of the refrigerant to the high temperature side flow path 13. Therefore, according to the present refrigeration cycle apparatus 1, the cooling of the refrigerant sucked into the expander 4 can be supplemented using the internal heat exchanger 15 according to the operating conditions and the like. Further, when heat exchange in the internal heat exchanger 15 is unnecessary, it is possible to cool the refrigerant only by the radiator 3 by closing the on-off valve 12, and such a change can be performed by simple flow control. It can be carried out. Thereby, according to this refrigeration cycle apparatus 1, the balance of a refrigeration cycle can be aimed at regardless of an operating condition.

  Further, the refrigeration cycle apparatus 1 includes a flow rate control device 20 that automatically adjusts the flow rate of the refrigerant flowing in the high temperature side flow path 13 of the internal heat exchanger 15, and a pressure sensor that detects the pressure of the refrigerant discharged from the compressor 2. 31. As described above, the flow control device 20 automatically opens the opening / closing valve 12 according to the difference between the pressure P1 of the refrigerant discharged from the compressor 2 and the preset upper limit value Pmax or lower limit value Pmin of P1. Adjust. Thereby, the pressure P1 of the refrigerant discharged from the compressor 2 is controlled so as to be within a predetermined range. Therefore, according to the refrigeration cycle apparatus 1, the flow rate of the refrigerant flowing through the internal heat exchanger 15 is automatically adjusted even when the operating conditions change, and the refrigerant sucked into the expander 4 is compressed. Cooling is performed by a necessary amount according to the pressure P1 of the refrigerant discharged from the machine 2. Therefore, in the present refrigeration cycle apparatus 1, the high-pressure side pressure of the cycle is suitably adjusted regardless of the operating conditions, so that the cycle can be stabilized.

(Modification 1)
As shown in FIG. 4A, the refrigeration cycle apparatus 1 according to Modification 1 includes an expander between the high temperature side flow path 13 of the internal heat exchanger 15 and the expander 4 instead of the pressure sensor 31. 4 is provided with a pressure sensor 32 for detecting the pressure P2 of the suction refrigerant 4.

  The flow control device 20 of the first modification changes the opening degree of the on-off valve 12 based on the pressure P2 of the refrigerant sucked by the expander 4 detected by the pressure sensor 32. Further, as in the first embodiment, the flow control device 20 is automatically operated according to the difference between the suction refrigerant pressure P2 of the expander 4 and the preset upper limit value Pmax or lower limit value Pmin of P2. The opening degree of the on-off valve 12 is adjusted. Thereby, the pressure P2 of the suction refrigerant of the expander 4 is controlled to be within a predetermined range.

  Therefore, even with the present refrigeration cycle apparatus 1, even when the operating conditions change, the flow rate of the refrigerant flowing through the internal heat exchanger 15 is automatically adjusted, and the refrigerant sucked into the expander 4 is the expander 4. The required amount of refrigerant is cooled according to the pressure P2 of the refrigerant. Therefore, also in the present refrigeration cycle apparatus 1, the high-pressure side pressure of the cycle is suitably adjusted regardless of the operating conditions, so that the operating efficiency can be improved and the cycle can be stabilized.

(Modification 2)
As shown in FIG. 4B, the refrigeration cycle apparatus 1 according to the modified example 2 sets the pressure P3 of the refrigerant sucked in the compressor 2 between the evaporator 5 and the compressor 2 instead of the pressure sensor 31. A pressure sensor 33 for detection is provided.

  The flow control device 20 of Modification 2 changes the opening degree of the on-off valve 12 based on the pressure P3 of the refrigerant sucked in the compressor 2 detected by the pressure sensor 33. Further, as in the first embodiment, the flow rate control device 20 automatically changes according to the difference between the suction refrigerant pressure P3 of the compressor 2 and the preset upper limit value Pmax or lower limit value Pmin of P3. The opening degree of the on-off valve 12 is adjusted. Thereby, the pressure P3 of the suction refrigerant of the compressor 2 is controlled to be within a predetermined range. For example, when the low-pressure side pressure is high, the opening degree of the on-off valve 12 is controlled to be large. As a result, the amount of heat exchange in the internal heat exchanger 15 increases, and as a result, the temperature of the refrigerant sucked in the compressor 2 rises and the refrigerant density decreases. As a result, the amount of refrigerant sucked into the compressor decreases, and the low-pressure side pressure decreases. Therefore, the present refrigeration cycle apparatus 1 can improve the operation efficiency and stabilize the cycle regardless of the operation conditions.

(Modification 3)
As shown in FIG. 4C, the refrigeration cycle apparatus 1 according to the modification 3 is arranged between the expander 4 and the low temperature side flow path 14 of the internal heat exchanger 15 instead of the pressure sensor 33 of the modification 2. Further, a pressure sensor 34 for detecting the pressure P4 of the refrigerant discharged from the expander 4 is provided.

  The flow control device 20 of Modification 3 changes the opening degree of the on-off valve 12 based on the pressure P4 of the refrigerant discharged from the expander 4 detected by the pressure sensor 34. Further, the flow control device 20 automatically adjusts the opening degree of the on-off valve 12 according to the difference between the pressure P4 of the refrigerant discharged from the expander 4 and the preset upper limit value Pmax or lower limit value Pmin of P4. . Thereby, the pressure P4 of the refrigerant discharged from the expander 4 is controlled so as to be within a predetermined range. That is, the low pressure side pressure is controlled to be within a predetermined range. Therefore, the present refrigeration cycle apparatus 1 can improve the operation efficiency and stabilize the cycle regardless of the operation conditions.

(Modification 4)
As shown in FIG. 5A, the refrigeration cycle apparatus 1 according to Modification 4 includes a compressor 2 and a radiator instead of the pressure sensor 31 used in the refrigeration cycle apparatus 1 according to the first embodiment. 3, a temperature sensor 35 for detecting the temperature T1 of the refrigerant discharged from the compressor 2 is provided. In such a case, the opening / closing control of the opening / closing valve 12 by the flow control device 20 is as shown in the flowchart of FIG. Hereinafter, opening / closing control of the opening / closing valve 12 will be described with reference to FIG.

  First, in step S11, a lower limit value (Tmin) and an upper limit value (Tmax) of the temperature T1 of the refrigerant discharged from the compressor 2 are input to the flow control device 20. When the above value is input, the process proceeds to step S12, the temperature sensor 35 detects the temperature T1 of the refrigerant discharged from the compressor 2, and the detected value is input to the flow control device 20.

  When the temperature T1 is input, the process proceeds to step S13, and the flow control device 20 determines whether or not the temperature T1 is higher than the lower limit value (Tmin). When temperature T1 is below a lower limit (Tmin), it progresses to Step S14. In step S <b> 14, the opening degree of the on-off valve 12 is reduced, and the amount of refrigerant flowing through the high temperature side passage 13 of the internal heat exchanger 15 is reduced. That is, the amount of heat exchange in the internal heat exchanger 15 is reduced. The opening change amount of the on-off valve 12 is adjusted according to the difference between T1 and Tmin.

  On the other hand, when temperature T1 is a value larger than a lower limit (Pmin), it progresses to step S15. In step S15, it is determined whether or not the temperature T1 is lower than an upper limit value (Tmax). If the temperature T1 is equal to or higher than the upper limit (Tmax), the process proceeds to step S16. In step S <b> 16, the opening degree of the on-off valve 12 is increased, and the amount of refrigerant flowing through the high temperature side passage 13 of the internal heat exchanger 15 is increased. That is, the amount of heat exchange in the internal heat exchanger 15 is increased. The opening change amount of the on-off valve 12 is adjusted according to the difference between T1 and Tmax.

  On the other hand, when the temperature T1 is lower than the upper limit (Tmax), the process proceeds to step S17. In step S17, the opening degree of the on-off valve 12 is maintained without being changed. However, here, a slight change in the opening degree of the on-off valve 12 is included without changing the opening degree of the on-off valve 12.

  After step S14, step S16 or step S17, the process returns to step S12. Then, the above steps are repeated.

  In this manner, the flow control device 20 of the modification 4 changes the opening degree of the on-off valve 12 based on the temperature T1 of the refrigerant discharged from the compressor 2 detected by the temperature sensor 35. Further, as in the first embodiment, the flow rate control device 20 automatically changes according to the difference between the temperature T1 of the refrigerant discharged from the compressor 2 and the preset upper limit value Tmax or lower limit value Tmin of T1. The opening degree of the on-off valve 12 is adjusted. Thereby, the temperature T1 of the refrigerant discharged from the compressor 2 is controlled to be within a predetermined range.

  Here, when the temperature of the refrigerant discharged from the compressor 2 is controlled to be within a predetermined range, the pressure of the refrigerant is also maintained within the predetermined range. That is, in the refrigeration cycle apparatus 1, the pressure of the refrigerant discharged from the compressor 2 can be controlled by controlling the temperature of the refrigerant discharged from the compressor 2. Thereby, also in the present refrigeration cycle apparatus 1, when the operating condition changes, the flow rate of the refrigerant flowing through the internal heat exchanger 15 is automatically adjusted, and the refrigerant sucked into the expander 4 is discharged from the compressor 2. The required amount of cooling is performed according to the temperature T1. Therefore, in the present refrigeration cycle apparatus 1 as well, the high-pressure side pressure of the cycle is suitably adjusted regardless of the operating conditions, so that the operating efficiency can be improved and the cycle can be stabilized.

(Modification 5)
As shown in FIG. 5B, the refrigeration cycle apparatus 1 according to the modified example 5 is provided between the high temperature side flow path 13 of the internal heat exchanger 15 and the expander 4 instead of the temperature sensor 35 in the modified example 4. Further, a temperature sensor 36 for detecting the temperature T2 of the refrigerant sucked in the expander 4 is provided.

  The flow control device 20 of the modification 5 changes the opening degree of the on-off valve 12 based on the temperature T2 of the refrigerant sucked by the expander 4 detected by the temperature sensor 36. Further, the flow control device 20 automatically adjusts the opening degree of the on-off valve 12 in accordance with the difference between the refrigerant refrigerant temperature T2 of the expander 4 and a preset upper limit value Tmax or lower limit value Tmin of T2. . Thereby, the temperature T2 of the suction refrigerant of the expander 4 is controlled to be within a predetermined range. That is, the temperature of the high-pressure side refrigerant is controlled to be within a predetermined range. Therefore, the present refrigeration cycle apparatus 1 can improve the operation efficiency and stabilize the cycle regardless of the operation conditions.

(Modification 6)
As shown in FIG. 5C, the refrigeration cycle apparatus 1 according to the modified example 6 is arranged between the expander 4 and the low temperature side flow path 14 of the internal heat exchanger 15 instead of the temperature sensor 35 in the modified example 4. Further, a temperature sensor 37 for detecting the temperature T3 of the refrigerant discharged from the expander 4 is provided.

  The flow control device 20 of the modification 6 changes the opening degree of the on-off valve 12 based on the temperature T3 of the refrigerant discharged from the expander 4 detected by the temperature sensor 37. Further, the flow control device 20 automatically adjusts the opening degree of the on-off valve 12 according to the difference between the temperature T3 of the refrigerant discharged from the expander 4 and a preset upper limit value Tmax or lower limit value Tmin of T3. . Thereby, the temperature T3 of the refrigerant discharged from the expander 4 is controlled to be within a predetermined range. For example, when the temperature of the refrigerant on the low-pressure side is high, the opening degree of the on-off valve 12 is controlled to be small, and the heat exchange amount in the internal heat exchanger 15 is reduced. Thereby, the temperature of the intake refrigerant of the expander 4 increases and the density decreases. Along with this, the amount of refrigerant discharged from the expander 4 increases, and the pressure of the discharged refrigerant rises. In this way, the temperature of the refrigerant discharged from the expander 4 that is in the gas-liquid two-phase state is lowered. Therefore, the present refrigeration cycle apparatus 1 can improve the operation efficiency and stabilize the cycle regardless of the operation conditions.

(Modification 7)
As shown in FIG. 7A, the refrigeration cycle apparatus 1 of Modification 7 includes an on-off valve 12 provided in a portion connected in parallel with the bypass flow path 11 of the refrigerant circuit 10 in the first embodiment. This is provided in the middle of the bypass flow path 11. The on-off valve 12 is for controlling the amount of refrigerant flowing into the high-temperature side flow path 13 of the internal heat exchanger 15 as in the first embodiment, and is controlled to be opened and closed by the flow rate control device 20. Since the other configuration is the same as that of the refrigeration cycle apparatus 1 according to the first embodiment, the description thereof is omitted.

  Note that the opening / closing control of the opening / closing valve 12 by the flow rate control device 20 is opposite to that of the first embodiment. As shown in the flowchart of FIG. 8, steps S1 to S3, S5, and S7 are the same as those in the first embodiment. Only steps S24 and S26 different from the flowchart of the first embodiment (see FIG. 3) will be described below.

  In step S3, when the pressure P1 is equal to or lower than the lower limit (Pmin) of the pressure of the discharged refrigerant, the process proceeds to step S24. In step S24, the opening degree of the on-off valve 12 is increased, and the amount of refrigerant flowing through the bypass flow path 11 is increased. That is, the amount of heat exchange in the internal heat exchanger 15 is reduced by decreasing the amount of refrigerant flowing through the high temperature side flow path 13 of the internal heat exchanger 15. The opening change amount of the on-off valve 12 is adjusted according to the difference between P1 and Pmin.

  On the other hand, when the pressure P1 is larger than the lower limit (Pmin), the process proceeds to step S5. In step S5, it is determined whether or not the pressure P1 is smaller than an upper limit value (Pmax). If the pressure P1 is equal to or higher than the upper limit (Pmax), the process proceeds to step S26. In step S <b> 26, the opening degree of the on-off valve 12 is reduced, and the amount of refrigerant flowing through the bypass passage 11 is reduced. That is, the amount of heat exchange in the internal heat exchanger 15 is increased by increasing the amount of refrigerant flowing through the high temperature side flow path 13 of the internal heat exchanger 15. The opening change amount of the on-off valve 12 is adjusted according to the difference between P1 and Pmax.

  On the other hand, when the pressure P1 is smaller than the upper limit (Pmax), the process proceeds to step S7. In step S7, the opening degree of the on-off valve 12 is maintained without being changed. However, here, a slight change in the opening degree of the on-off valve 12 is included without changing the opening degree of the on-off valve 12.

  After step S7, step S26 or step S24, the process returns to step S2. Then, the above steps are repeated.

  As described above, even when the on-off valve 12 is provided in the middle of the bypass flow path 11, the heat exchange amount control similar to that of the first embodiment can be performed in the internal heat exchanger 15. There is an effect.

(Modification 8)
As shown in FIG. 7B, the refrigeration cycle apparatus 1 of Modification 8 includes a portion connected in parallel with the bypass flow path 11 of the refrigerant circuit 10 and the internal heat exchanger 15 in the first embodiment. The on-off valve 12 provided on the upstream side of the high temperature side passage 13 is provided on the downstream side of the high temperature side passage 13 of the internal heat exchanger 15. The on-off valve 12 is for controlling the amount of refrigerant flowing into the high-temperature side flow path 13 of the internal heat exchanger 15 as in the first embodiment, and is controlled to be opened and closed by the flow rate control device 20. Since the other configuration is the same as that of the refrigeration cycle apparatus 1 according to the first embodiment, the description thereof is omitted. Even in such a form, the same effect as in the first embodiment can be obtained.

(Second Embodiment)
As shown in FIG. 9, the refrigeration cycle apparatus 1 according to the second embodiment replaces the bypass flow path 11 that bypasses the high temperature side flow path 13 of the internal heat exchanger 15 in the first embodiment with internal heat. A bypass channel 21 that bypasses the low temperature side channel 14 of the exchanger 15 is provided.

  The bypass flow path 21 is connected in parallel with the low temperature side flow path 14 of the internal heat exchanger 15 between the expander 4 and the evaporator 5 of the refrigerant circuit 10. In addition, an opening / closing valve 22 for controlling the amount of refrigerant flowing to the low temperature side flow path 14 of the internal heat exchanger 15 is provided in a portion connected in parallel with the bypass flow path 21 of the refrigerant circuit 10. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Note that the flow control device 20 of the present embodiment controls the opening / closing of the opening / closing valve 22 instead of the opening / closing valve 12. Since the specific method of the on / off control is the same as that of the on / off valve 12 of the first embodiment, the description thereof is omitted. In the present embodiment, when the on-off valve 22 is opened, the refrigerant discharged from the expander 4 flows not only in the bypass channel 21 but also in the low temperature side channel 14 of the internal heat exchanger 15. Thereby, in the internal heat exchanger 15, heat exchange between the suction refrigerant and the discharge refrigerant of the expander 4 is performed, and the suction refrigerant of the expander 4 is cooled by the discharge refrigerant.

  As described above, also in the refrigeration cycle apparatus 1 according to the present embodiment, similarly to the refrigeration cycle apparatus 1 according to the first embodiment, an increase in the high-pressure side pressure due to insufficient cooling of the refrigerant sucked in the expander 4 is prevented. And the fall of the reliability of the compressor 2 can be prevented. Further, other effects can be similarly achieved.

(Modification 1)
As shown in FIG. 10A, the refrigeration cycle apparatus 1 of Modification 1 includes an on-off valve 22 provided in a portion connected in parallel with the bypass flow path 21 of the refrigerant circuit 10 in the second embodiment. This is provided in the middle of the bypass flow path 21. The on-off valve 22 is for controlling the amount of refrigerant flowing into the low temperature side flow path 14 of the internal heat exchanger 15 as in the second embodiment, and is controlled to be opened and closed by the flow control device 20. Other configurations are the same as those of the refrigeration cycle apparatus 1 according to the second embodiment, and the opening / closing control of the on-off valve 12 by the flow rate control device 20 is the same as that of the modification 7 of the first embodiment (see FIG. 8). ). Even in such a form, the internal heat exchanger 15 can perform the same heat exchange amount control as in the second embodiment, and can achieve the same effects.

(Modification 2)
The refrigeration cycle apparatus 1 of Modification 2 includes a portion connected in parallel to the bypass flow path 21 of the refrigerant circuit 10 and the internal heat exchanger 15 in the second embodiment, as shown in FIG. The on-off valve 22 provided on the upstream side of the low temperature side channel 14 is provided on the downstream side of the low temperature side channel 14 of the internal heat exchanger 15. The on-off valve 22 is for controlling the amount of refrigerant flowing into the low temperature side flow path 14 of the internal heat exchanger 15 as in the second embodiment, and is controlled to be opened and closed by the flow control device 20. Since the other configuration is the same as that of the refrigeration cycle apparatus 1 according to the second embodiment, the description thereof is omitted. Even in such a form, the same effect as in the second embodiment can be obtained.

(Third embodiment)
The refrigeration cycle apparatus 1 according to the third embodiment is provided with the bypass channel 21 and the on-off valve 22 in the second embodiment in addition to the bypass channel 11 and the on-off valve 12 in the first embodiment. .

  As shown in FIG. 11A, a bypass flow path 11 is connected in parallel between the radiator 3 and the expander 4 of the refrigerant circuit 10, and between the expander 4 and the evaporator 5 of the refrigerant circuit 10. The bypass channel 21 is connected in parallel. The bypass channel 11 is provided so as to bypass the high temperature side channel 13 of the internal heat exchanger 15, and the bypass channel 21 is provided so as to bypass the low temperature side channel 14 of the internal heat exchanger 15. Yes. An opening / closing valve 12 is provided in a portion of the refrigerant circuit 10 connected in parallel with the bypass flow path 11, and an opening / closing valve 22 is provided in a portion of the refrigerant circuit 10 connected in parallel with the bypass flow path 21. Yes. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  As described above, also in the refrigeration cycle apparatus 1 according to the present embodiment, the high pressure side caused by insufficient cooling of the refrigerant sucked in the expander 4 as in the refrigeration cycle apparatus 1 according to the first embodiment or the second embodiment. An increase in pressure can be prevented, and a decrease in reliability of the compressor 2 can be prevented. Further, other effects can be similarly achieved.

  In the third embodiment, the opening / closing valve 12 is provided in a portion connected in parallel with the bypass flow path 11 of the refrigerant circuit 10, and the opening / closing valve 22 is connected in parallel with the bypass flow path 21 of the refrigerant circuit 10. Although provided in the part, as shown in FIG.11 (b), it is good also as providing the on-off valves 12 and 22 in the middle part of the bypass flow paths 11 and 21, respectively. Even in such a form, the internal heat exchanger 15 can perform the same heat exchange amount control as in the third embodiment, and can achieve the same effects.

(Fourth embodiment)
As shown to Fig.12 (a), the refrigeration cycle apparatus 1 which concerns on 4th Embodiment has the bypass flow path 41 which bypasses the heat radiator 3 to the refrigeration cycle apparatus 1 of 1st Embodiment, and the bypass flow path 41. And an on-off valve 42 for controlling the amount of refrigerant flowing into the vehicle. The on-off valve 42 is provided in the middle of the bypass channel 41. In the present embodiment, the flow control device 20 controls opening / closing of the opening / closing valve 12 and controlling opening / closing of the opening / closing valve 42 according to the detection value P <b> 1 of the pressure sensor 31.

  Specifically, as in the first embodiment, when the density ratio (De / Dc) in the actual operation state is smaller than the design volume ratio (Vc / Ve) assumed at the time of design, for example, the radiator 3 When the refrigerant is not sufficiently cooled in FIG. 2, the on-off valve 12 is opened by the flow control device 20. At this time, the on-off valve 42 remains closed. When the on-off valve 12 is opened, the refrigerant that has flowed out of the radiator 3 flows not only into the bypass channel 11 but also into the refrigerant circuit 10 side. As a result, the refrigerant flows into the high-temperature side flow path 13 of the internal heat exchanger 15, and the intake refrigerant of the expander 4 is cooled.

  On the other hand, when the density ratio (De / Dc) in the actual operation state is larger than the design volume ratio (Vc / Ve) assumed at the time of design, for example, the radiator 3 excessively dissipates the refrigerant. The density De of the refrigerant actually sucked into the expander 4 increases. Thereby, the density ratio (De / Dc) becomes larger than the design volume ratio (Vc / Ve) assumed at the time of design. In such a case, the cycle of the refrigeration cycle apparatus 1 is out of the design range, and the refrigeration cycle apparatus 1 cannot operate normally.

  In such a case, the flow control device 20 according to the present embodiment closes the on-off valve 12 and opens the on-off valve 42. When the on-off valve 42 is opened, a part of the refrigerant discharged from the compressor 2 flows into the bypass channel 41. Thereby, since the refrigerant | coolant amount which flows in into the radiator 3 reduces, the thermal radiation amount of the refrigerant | coolant in the radiator 3 is reduced.

  As described above, in the refrigeration cycle apparatus 1 according to the present embodiment, similarly to the refrigeration cycle apparatus 1 according to the first embodiment, an increase in the high-pressure side pressure due to insufficient cooling of the refrigerant sucked in the expander 4 is prevented. A decrease in the reliability of the compressor 2 can be prevented. Conversely, even when the refrigerant sucked into the expander 4 is excessively cooled, the amount of heat released in the radiator 3 can be reduced by opening the on-off valve 42, so that the cycle is brought into a normal state. Can be maintained. Therefore, according to the refrigeration cycle apparatus 1 according to the present embodiment, the refrigeration cycle can be more reliably stabilized regardless of operating conditions.

  In addition, as shown in FIG.12 (b), the opening and closing for controlling the bypass flow path 41 which bypasses the heat radiator 3 to the refrigeration cycle apparatus 1 which concerns on 2nd Embodiment, and the refrigerant | coolant amount which flows into the bypass flow path 41 Even in the refrigeration cycle apparatus 1 provided with the valve 42, the same effect can be obtained.

  In each of the above embodiments, the compressor 2 and the expander 4 are housed in the same casing 8a. However, the compressor 2 and the expander 4 are housed in their respective casings and formed separately. It may be. Moreover, although the compressor 2 and the expander 4 were connected by the coaxial rotating shaft 6, the rotating shaft of the compressor 2 and the rotating shaft of the expander 4 may be separate, and may not be coaxial. Good.

  As described above, the present invention is useful for a refrigeration cycle apparatus, particularly a refrigeration cycle apparatus (a refrigeration apparatus, an air conditioner, a water heater, or the like) in which the rotation speed ratio between a compressor and an expander is constant.

Refrigerant circuit diagram of the refrigeration cycle apparatus according to the first embodiment Mollier diagram of the refrigeration cycle apparatus according to the first embodiment The flowchart which shows the control method of the refrigerating-cycle apparatus which concerns on 1st Embodiment. (A), (b), (c) is the refrigerant circuit figure which concerns on the modification of 1st Embodiment. (A), (b), (c) is the refrigerant circuit figure which concerns on the modification of 1st Embodiment. The flowchart which shows the control method of the refrigerating-cycle apparatus which concerns on the modification of 1st Embodiment. (A), (b) is the refrigerant circuit figure which concerns on the modification of 1st Embodiment. The flowchart which shows the control method of the refrigerating-cycle apparatus which concerns on the modification of 1st Embodiment. Refrigerant circuit diagram of the refrigeration cycle apparatus according to the second embodiment (A), (b) is a refrigerant circuit figure of the refrigerating cycle device concerning the modification of a 2nd embodiment. (A) is a refrigerant circuit diagram of a refrigeration cycle apparatus according to the third embodiment, (b) is a refrigerant circuit diagram of a refrigeration cycle apparatus according to a modification of the third embodiment. (A) is a refrigerant circuit figure of the refrigerating cycle device concerning a 4th embodiment, (b) is a refrigerant circuit figure of a refrigerating cycle device concerning a modification of a 4th embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle apparatus 2 Compressor 3 Radiator 4 Expander 5 Evaporator 6 Rotating shaft 7 Electric motor 8 Expander-integrated compressor 10 Refrigerant circuit 11 Bypass channel (bypass channel, high-pressure side bypass channel, first bypass Flow path)
12 On-off valve (on-off valve, high-pressure side on-off valve, first on-off valve)
13 High-temperature side flow path 14 Low-temperature side flow path 15 Heat exchanger 20 Flow rate control device 21 Bypass flow path (bypass flow path, low-pressure side bypass flow path, first bypass flow path)
22 On-off valve (on-off valve, low-pressure side on-off valve, first on-off valve)
31 Pressure sensor 32 Pressure sensor 33 Pressure sensor 34 Pressure sensor 35 Temperature sensor 36 Temperature sensor 37 Temperature sensor 41 Bypass flow path (second bypass flow path)
42 On-off valve (second on-off valve)

Claims (18)

A compressor that compresses the refrigerant, a radiator that dissipates the refrigerant compressed by the compressor, an expander that expands the refrigerant, and an evaporator that evaporates the refrigerant expanded by the expander are sequentially connected, A refrigerant circuit in which the ratio of the rotation speed of the compressor and the rotation speed of the expander is constant;
It has a high temperature side channel into which the refrigerant that has flowed out of the radiator flows and a low temperature side channel into which the refrigerant discharged from the expander flows, and the refrigerant in the high temperature side channel and the low temperature side channel An internal heat exchanger for exchanging heat with the refrigerant inside,
A refrigeration cycle apparatus comprising: a control device that controls a heat exchange amount by the internal heat exchanger. The controller is
A bypass flow path connected in parallel to the high temperature flow path of the internal heat exchanger;
An on-off valve provided in a portion where the bypass flow path of the refrigerant circuit is connected in parallel;
A flow rate control device for opening and closing the on-off valve;
The refrigeration cycle apparatus according to claim 1, comprising: The controller is
A bypass flow path connected in parallel to the high temperature flow path of the internal heat exchanger;
An on-off valve provided in the bypass channel;
A flow rate control device for opening and closing the on-off valve;
The refrigeration cycle apparatus according to claim 1, comprising: The controller is
A bypass flow path connected in parallel to the low temperature flow path of the internal heat exchanger;
An on-off valve provided in a portion where the bypass flow path of the refrigerant circuit is connected in parallel;
A flow rate control device for opening and closing the on-off valve;
The refrigeration cycle apparatus according to claim 1, comprising: The controller is
A bypass flow path connected in parallel to the low temperature flow path of the internal heat exchanger;
An on-off valve provided in the bypass channel;
A flow rate control device for opening and closing the on-off valve;
The refrigeration cycle apparatus according to claim 1, comprising: The controller is
A high pressure side bypass flow path connected in parallel to the high temperature side flow path of the internal heat exchanger;
A low-pressure side bypass passage connected in parallel to the low-temperature side passage of the internal heat exchanger;
A high-pressure side on-off valve provided in a portion where the high-pressure side bypass flow path of the refrigerant circuit is connected in parallel;
A low-pressure side on-off valve provided in a portion where the low-pressure side bypass flow path of the refrigerant circuit is connected in parallel;
A flow rate control device that controls opening / closing one or both of the high-pressure side on-off valve and the low-pressure side on-off valve;
The refrigeration cycle apparatus according to claim 1, comprising: The controller is
A high pressure side bypass flow path connected in parallel to the high temperature side flow path of the internal heat exchanger;
A low-pressure side bypass passage connected in parallel to the low-temperature side passage of the internal heat exchanger;
A high-pressure side on-off valve provided in the high-pressure side bypass flow path;
A low-pressure side on-off valve provided in the low-pressure side bypass flow path;
A flow rate control device that controls opening / closing one or both of the high-pressure side on-off valve and the low-pressure side on-off valve;
The refrigeration cycle apparatus according to claim 1, comprising: A pressure sensor for detecting the pressure of the refrigerant discharged from the compressor;
The flow rate control device changes the opening degree of the on-off valve based on a detection value of the pressure sensor so that the detection value of the pressure sensor becomes a predetermined value. The refrigeration cycle apparatus described in 1. A pressure sensor for detecting the pressure of the refrigerant sucked into the expander;
The flow rate control device changes the opening degree of the on-off valve based on a detection value of the pressure sensor so that the detection value of the pressure sensor becomes a predetermined value. The refrigeration cycle apparatus described in 1. A pressure sensor for detecting the pressure of the refrigerant sucked into the compressor;
The flow rate control device changes the opening degree of the on-off valve based on a detection value of the pressure sensor so that the detection value of the pressure sensor becomes a predetermined value. The refrigeration cycle apparatus described in 1. A pressure sensor for detecting the pressure of the refrigerant discharged from the expander;
The flow rate control device changes the opening degree of the on-off valve based on a detection value of the pressure sensor so that the detection value of the pressure sensor becomes a predetermined value. The refrigeration cycle apparatus described in 1. A temperature sensor for detecting the temperature of the refrigerant discharged from the compressor;
The flow rate control device changes the opening degree of the on-off valve based on a detection value of the temperature sensor so that the detection value of the temperature sensor becomes a predetermined value. The refrigeration cycle apparatus described in 1. A temperature sensor for detecting the temperature of the refrigerant sucked into the expander;
The flow rate control device changes the opening degree of the on-off valve based on a detection value of the temperature sensor so that the detection value of the temperature sensor becomes a predetermined value. The refrigeration cycle apparatus described in 1. A temperature sensor for detecting the temperature of the refrigerant discharged from the expander;
The flow rate control device changes the opening degree of the on-off valve based on a detection value of the temperature sensor so that the detection value of the temperature sensor becomes a predetermined value. The refrigeration cycle apparatus described in 1. A compressor that compresses the refrigerant, a radiator that dissipates the refrigerant compressed by the compressor, an expander that expands the refrigerant, and an evaporator that evaporates the refrigerant expanded by the expander are sequentially connected, A refrigerant circuit in which the ratio of the rotation speed of the compressor and the rotation speed of the expander is constant;
It has a high temperature side channel into which the refrigerant that has flowed out of the radiator flows and a low temperature side channel into which the refrigerant discharged from the expander flows, and the refrigerant in the high temperature side channel and the low temperature side channel An internal heat exchanger for exchanging heat with the refrigerant inside,
A first bypass channel connected in parallel to the high temperature side channel of the internal heat exchanger;
A second bypass passage connected in parallel to the radiator in the refrigerant circuit;
A first on-off valve provided in a portion where the first bypass flow path of the refrigerant circuit is connected in parallel;
A second on-off valve provided in the second bypass flow path;
A flow control device for controlling opening and closing of the first on-off valve and the second on-off valve;
A refrigeration cycle apparatus comprising: A compressor that compresses the refrigerant, a radiator that dissipates the refrigerant compressed by the compressor, an expander that expands the refrigerant, and an evaporator that evaporates the refrigerant expanded by the expander are sequentially connected, A refrigerant circuit in which the ratio of the rotation speed of the compressor and the rotation speed of the expander is constant;
It has a high temperature side channel into which the refrigerant that has flowed out of the radiator flows and a low temperature side channel into which the refrigerant discharged from the expander flows, and the refrigerant in the high temperature side channel and the low temperature side channel An internal heat exchanger for exchanging heat with the refrigerant inside,
A first bypass channel connected in parallel to the low temperature side channel of the internal heat exchanger;
A second bypass passage connected in parallel to the radiator in the refrigerant circuit;
A first on-off valve provided in a portion where the first bypass flow path of the refrigerant circuit is connected in parallel;
A second on-off valve provided in the second bypass flow path;
A flow control device for controlling opening and closing of the first on-off valve and the second on-off valve;
A refrigeration cycle apparatus comprising:   The refrigeration cycle apparatus according to any one of claims 1 to 16, wherein the compressor and the expander are connected by a coaxial rotating shaft.   The refrigeration cycle apparatus according to any one of claims 1 to 17, wherein the refrigerant is carbon dioxide.

Images