ES2611980T3 - Refrigerant cycle device - Google Patents

Abstract

A refrigerant cycle apparatus comprising: at least one compressor (1), a radiator (2), decompression means (3) that can change an opening degree, a heat absorber (4), an internal heat exchanger (5) that performs heat exchange between a refrigerant at an outlet of the radiator (2) and the refrigerant at an outlet of the heat absorber (4), in which first temperature sensing means (30) are provided to detect a coolant temperature between a compressor outlet (1) and a radiator inlet (2) and second temperature sensing means (31) for detecting the temperature of the coolant between the radiator outlet (2) and a high pressure side inlet of the internal heat exchanger (5), third temperature detection means (41) to detect an inlet temperature of a medium to be heated and fourth temperature detection means (42) to detect an outlet temperature of the medium to be heated,characterized in that a degree of opening of the decompression means (3) is controlled so that a difference (ΔT1 - ΔT2) between a second temperature difference (ΔT1) between a detection temperature by means of the first temperature detection means ( 30) and the detection temperature by the fourth temperature detection means (42) and a third temperature difference (ΔT2) between the detection temperature by the second temperature detection means (31) and the detection temperature by the third temperature sensing means (41) is converted to a target value.

Description

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DESCRIPTION

Refrigerant cycle device Technical field

The present invention relates to a refrigerant cycle apparatus using an internal heat exchanger, more particularly to a refrigerant control to stably ensure performance.

Background of the technique

Descriptions of the prior art will be given as follows.

Conventionally, a hot water supply apparatus is proposed as a built-in refrigerant cycle apparatus, such as:

a hot water supply apparatus comprising a refrigerant cycle that includes a compressor, a hot water supply heat exchanger, an electronic expansion valve, and a side heat exchanger of the heat source from which the source of heat is an outside air, and a hot water supply cycle that includes a hot water supply heat exchanger and a hot water supply tank,

in which since a capacity control means using a variable capacity type compressor and controls the capacity of the compressor in response to changes in external environmental conditions of the heat exchanger side heat exchanger is fixed, control means of opening degree of expansion valve to control an opening degree of an electronic expansion valve in order to make a compressor discharge temperature an objective value in response to changes in external environmental conditions (an external temperature, for example ) of the side heat exchanger of the heat source and rotation speed control means to control a rotation speed of the compressor to be an objective value in response to changes in the external environmental conditions of the side heat exchanger of the heat source are fixed, an opening of the electronic expansion valve is controlled in order to make The compressor discharge temperature becomes an objective value in response to changes in the external environmental conditions (an external temperature, for example) of the heat exchanger side of the heat source; and the speed of rotation of the compressor is controlled to be an objective value in response to changes in the external environmental conditions of the heat exchanger side of the heat source, an optimum operating condition can be obtained in which a supply capacity of hot water and a load of hot water supply also agree, and a coefficient of performance (COP) can be improved and the reduction in size of elements such as a heat exchanger becomes possible. (For example, refer to patent document 1 or US2003 / 0061827)

A water heater is also proposed such as: a water heater for heating a hot water supply fluid in a supercritical heat pump cycle where a refrigerant pressure on a high pressure side becomes equal to or greater than the critical pressure of the refrigerant comprising:

a compressor,

a radiator that exchanges heat between a refrigerant discharged from the compressor and a hot water supply fluid and is configured so that a flow of refrigerant and a flow of hot water supply fluid are opposite,

a decompressor to decompress the refrigerant flowing out of the radiator, and

an evaporator that causes the refrigerant flowing out of the compressor to evaporate, causes the refrigerant to absorb heat to discharge it on a suction side of the compressor,

wherein a coolant pressure from a high pressure side is controlled so that a temperature difference (At) between the coolant flowing out of the radiator and the hot water supply fluid flowing therein becomes a predetermined temperature difference (ATo). (For example, refer to patent document 2). In this example of the prior art, a radiator heat exchange efficiency can be improved to improve the efficiency of a heat pump.

[Patent Document 1] Japanese Patent Gazette No. 3601369 (p. 6; Fig. 1)

[Patent Document 2] Japanese Patent Gazette No. 3227651 (pp. 1-3; Fig. 2).

Summary of the invention

Problem to be solved by the invention

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Both of the previous examples of the prior art control the conditions of the refrigerant so that a compressor discharge temperature or a temperature difference (AT) between the refrigerant flowing out of the radiator and the hot water supply fluid flowing in It becomes an objective value to achieve efficient operation. However, there is a problem that in the immediate vicinity where an efficiency (COP) of the refrigerant cycle becomes maximum, a control based only on an inlet side (the previous discharge temperature) of the radiator or an outlet side (the temperature difference At previous) it is difficult to achieve stable and efficient operating conditions because the changes in the discharge temperature or the temperature difference AT are small. In addition, since an operation with an internal heat exchanger in the refrigerant circuit is not being considered, the problem is that it was very difficult to control and achieve stable and efficient operating conditions.

The present invention aims to solve the prior problems of the prior art. The objective is to obtain a refrigerant cycle apparatus that can stably achieve efficient operating conditions by controlling the operating values based on the standard radiator conditions and the radiator outlet conditions so that they are an objective value.

Means to solve the problem

In order to solve the above problems, the refrigerant cycle apparatus according to the present invention includes at least one compressor, a radiator, decompression means that can change an open degree, a heat absorber, an internal heat exchanger which performs the heat exchange between a refrigerant at an outlet of the radiator and the refrigerant at the outlet of the heat absorber. The refrigerant cycle apparatus is characterized in that at least first means of detecting the conditions of the refrigerant are provided to detect the standard conditions of the radiator and second means of detection of the conditions of the refrigerant to detect the conditions of the refrigerant between an outlet of the radiator and a high pressure side inlet of an internal heat exchanger, and a degree of opening of decompression means is controlled so that a calculation value calculated based on the first means of detecting the conditions of the refrigerant and the outlet of the second means of detecting the conditions of the refrigerant becomes an objective value.

Effect of the invention

In accordance with the present invention, the degree of opening of the expansion valve is controlled so that the GOP becomes maximum based on standard conditions of the radiator conditions and the coolant conditions of the radiator outlet part, whereby a refrigerant cycle apparatus can be obtained which can stably achieve efficient operation.

Brief description of the drawings

[Fig. 1] Fig. 1 is a diagram showing a configuration of a refrigerant cycle apparatus according to the present invention;

[Fig. 2] Fig. 2 is a diagram showing an operating behavior in a P-h diagram of the present invention.

[Fig. 3] Fig. 3 is a diagram showing a temperature distribution of a refrigerant and water in a water heat exchanger of the present invention.

[Fig. 4] Fig. 4 is a diagram showing the conditions of the cycle versus an opening degree of the expansion valve of the present invention.

[Fig. 5] Fig. 5 is a diagram showing the changes in each calculation value, the heating capacity, and the gOp versus an opening degree of the expansion valve of the present invention.

[Fig. 6] Fig. 6 is a diagram showing the changes in another calculation value, the heating capacity, the arid COP versus an opening degree of the expansion valve of the present invention.

[Fig. 7] Fig. 7 is a flow chart of the control of the present invention.

Descriptions of codes and symbols

1 compressor

2 Radiator (water heat exchanger)

3 Expansion valve

4 Heat absorber (evaporator)

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5 Internal heat exchanger

20 Side pump for hot water supply

21 Hot water storage tank

22 Side use pump

23, 24, 25 On-off valve 29 Fan

30, 31, 32, 33, 41,42, 52 Temperature detection means

35, 51 Pressure sensing means

40 Controller

50 Heat source device

60 Hot water storage device

Best way to carry out the invention

Fig. 1 shows a configuration diagram of the refrigerant cycle apparatus according to the INVENTION. In the figure, the refrigerant cycle apparatus according to the present embodiment is a hot water supply apparatus that uses carbon dioxide (hereinafter CO2) as a refrigerant, composed of a heat source apparatus 50 , a hot water storage apparatus 60, and a controller 40 to control these. It shows an example of the hot water supply apparatus, however, it is not limited thereto. The apparatus can be an air conditioner. In the same way, the refrigerant is not limited to carbon dioxide, but an HFC refrigerant can also be used.

The heat source apparatus 50 is composed of a compressor 1 for compressing the refrigerant, a radiator 2 (hereinafter "water heat exchanger") for removing heat from a compressed refrigerant at high pressure and high temperature, in the compressor 1, an internal heat exchanger 5 to further cool the refrigerant outlet from the water heat exchanger 2, a decompressor 3 (hereinafter "expansion valve") that decompresses the refrigerant and whose degree of opening can be changed , a heat absorber 4 (hereinafter "evaporator") to evaporate the decompressed refrigerant in the expansion valve 3, and an internal heat exchanger 5 to further heat the refrigerant flowing out of the evaporator 4. That is, the Internal heat exchanger 5 is a heat exchanger that exchanges the refrigerant according to the heat at an outlet of the water heat exchanger 2 with the refrigerant at the outlet of the evaporator 4. It is provided a fan 29 is pressed to send air on an outer surface of the evaporator 4. First temperature detection means 30 are also provided to detect a discharge temperature of the compressor 1, second temperature detection means 31 to detect an outlet temperature of the exchanger of water heat 2, fifth temperature detection means 32 to detect a temperature of the evaporant inlet refrigerant 4, and sixth temperature detection means 33 to detect a compressor suction temperature 1. In addition, the first detection means of temperature 30 and the second means of temperature detection 31 correspond to first means of detection of conditions of the refrigerant and second means of detection of the conditions of the refrigerant, respectively, in a control example in Fig. 7 to be described later.

A hot water storage device 60 is connected to the water heat exchanger 2, which is a radiator, through pipes, which is composed of a side pump of the heat source 20, a hot water storage tank 21, a side-use pump 22, and on-off valves 23, 24, 25. Here, the on-off valves 23, 24, 25 can be a simple valve for changing the operation or a variable valve of opening. When the water level of the hot water storage tank 21 falls, the on-off valves 24, 25 close, the on-off valve 23 opens, and the operation for the storage of hot water is performed in a manner that the water supplied is heated to a predetermined temperature. When a loss of heat dissipation is large and the temperature in the hot water storage tank 21 decreases, such as in winter, the on-off valves 23, 25 are closed, the on-off valve 24 is opened, and the circulation heating operation is performed so that the hot water at low temperature in the hot water storage tank 21 is boiled again. At the time of using the hot water supply, the on-off valves 23, 24 are closed, the on-off valve 25 is opened, and the side use pump 22 starts operating to transfer the stored hot water to the side in use. On one inlet side of the water heat exchanger 2, the third temperature sensing means 41 is set to detect an inlet temperature of a medium (water) to be heated. On an outlet side of the water heat exchanger 2, the fourth temperature sensing means 42 is set to detect an outlet temperature of a medium (water) to be heated.

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A controller 40 performs calculations using values detected from the first temperature detection means 30, second temperature detection means 31, fifth temperature detection means 32, sixth temperature detection means 33, third temperature detection means 41 and fourth temperature sensing means 42 for controlling an opening degree of the expansion valve 3, a rotation speed of the compressor 1, and the rotation speed of the side hot water supply pump 20, respectively.

Fig. 2 is a Ph diagram describing cycle conditions during the hot water storage operation in the refrigerant cycle apparatus shown in Fig. 1. In Fig. 2, the continuous lines denote refrigerant conditions in a a certain degree of opening of the expansion valve and A, B, C, D, and E denote coolant conditions in the operation of hot water storage. At the time of operation of the hot water storage, a high pressure high temperature refrigerant (A) discharged from the compressor 1 flows to enter the water heat exchanger 2. In the water heat exchanger 2, the Coolant heats the water supplied while dissipating heat to the water circulating in the hot water storage circuit to lower the temperature itself. A refrigerant (B) that flows out of the water heat exchanger 2 dissipates the heat in the internal heat exchanger 5 to further decrease (C) the temperature, being decompressed (D) by the expansion valve 3 to become a Low temperature and low pressure refrigerant. The low temperature and low pressure refrigerant absorbs heat from the air in the evaporator 4 to evaporate it (E). The refrigerant flowing out of the evaporator 4 is heated in the internal heat exchanger 5 to become a gas (F) and is sucked out by the compressor 1 to form a refrigerant cycle.

Here, the expansion valve 3 is controlled so that a degree of superheat of the compressor 1 is converted to an objective value (for example, from 5 to 10 ° C). Specifically, based on a detection value of the fifth temperature sensing means 32 that detect a temperature of the evaporator inlet refrigerant 4, an amount of temperature decrease is corrected due to a loss of pressure in the evaporator 4 and the Internal heat exchanger 5, a suction temperature (ET) is estimated, a degree of suction superheating SHs is calculated by the following formula using a detection value (Ts) of the sixth temperature detection means 33 that detect a temperature of compressor suction 1.

SHs = Ts - ET

Using the above formula, an opening degree of the expansion valve 3 is controlled so that SHs becomes an objective value. An example is given in which an evaporation temperature (ET) is estimated based on the detection value of the fifth temperature detection means 32, however, it is not limited thereto. A pressure sensing means (second pressure sensing means) 51 (refer to Fig. 1) is installed between a low pressure side outlet of the internal heat exchanger 5 and the inlet of the compressor 1, and of the detection value , a saturation temperature of the refrigerant can be obtained. A control of the degree of superheating of suction precedes another control of high efficiency operation, since a function to prevent the return of liquid from the compressor 1 precedes a function to efficiently operate the water heat exchanger 2 for the purpose to ensure the reliability of the equipment.

Next, the operation in the Ph diagram, when the opening degree of the expansion valve 3 becomes smaller, is represented by broken lines in Fig. 2. When the opening degree of the expansion valve 3 is made smaller, the amount of refrigerant flow flowing from the expansion valve 3 to the evaporator 4 decreases and the degree of superheat suction of the compressor 1 temporarily increases. In addition, since the high pressure side coolant changes, the pressure on the high pressure side increases and a discharge temperature becomes high. At the same time, an outlet temperature of the water heat exchanger decreases so that a temperature difference in it becomes constant. When the outlet temperature of the water heat exchanger decreases, an amount of heat exchange in the internal heat exchanger 5 decreases, and as a result, the degree of suction overheating becomes almost the same state as before. what degree of opening of expansion valve 3 would be made smaller to indicate a constant value. That is, a change in the degree of opening of the expansion valve 3 is absorbed by the heat exchange amount of the internal heat exchanger 5 (the amount of heat exchange varies in response to the degree of opening of the expansion valve 3) to make the change in the degree of suction overheating small. Accordingly, the control of the degree of superheating of the compressor 1 by itself cannot ensure the heating capacity in the water heat exchanger 2 and the efficiency decreases. Therefore, a new control is required in order to ensure heating capacity and improve operating efficiency.

Next, descriptions will be given as to why a maximum local value is produced in yield (COP) using a temperature distribution in the water heat exchanger shown in Fig. 3.

Fig. 3 shows a distribution of the temperature of the refrigerant and the water in the water heat exchanger 2. In the figure, the thick continuous lines show a change in the temperature of the refrigerant, and the thin continuous lines denote a change in the water's temperature. AT1 denotes a temperature difference between the inlet temperature of the water heat exchanger and the outlet temperature of water, and AT2 denotes a

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temperature difference between the outlet temperature of the water heat exchanger and the inlet water temperature. A Tp is a temperature difference at a peak point, where the temperature difference between a coolant and the water in the water heat exchanger 2 becomes minimal. A T denotes a temperature difference between the inlet temperature of the water heat exchanger and the outlet temperature of the water heat exchanger. As shown by a cycle state versus the degree of opening of the expansion valve in Fig. 4, when a discharge temperature is increased by decreasing the degree of opening of the expansion valve 3, as long as the heating capacity in the water heat exchanger 2 is almost constant, the outlet temperature of the water heat exchanger 2 decreases so that an average temperature difference of the refrigerant and water can be maintained in the water heat exchanger 2, and the temperature difference A Tp at the peak point also decreases. In addition, as the amount of refrigerant moves to a high pressure side, a discharge pressure is raised to increase an input and the COP is reduced. On the contrary, when the opening degree of the expansion valve 3 becomes large and the discharge temperature is lowered, the outlet temperature of the water heat exchanger 2 increases so that an average temperature difference is maintained between the coolant and water in the water heat exchanger 2. The temperature difference ATp at the peak point also increases, however, the heating capacity ratio becomes smaller and the COP is reduced. Consequently, as shown by the dashed lines in the figure, there is an adequate degree of expansion opening that causes the COP to reach its maximum value.

Next, Fig. 5 shows the changes in the operating values obtained from the temperature of each part, when the degree of opening of the expansion valve 3 changes. In Fig. 5; the horizontal axis represents the degree of opening (%) of the expansion valve 3, and the vertical axis represents the degree of suction overheating, the discharge temperature, temperature difference A T2 between the outlet temperature of the heat exchanger of water and the water inlet temperature, the heating capacity ratio and the COP ratio. The heating capacity ratio and the COP ratio show a ratio when a maximum value is set against the degree of opening of the expansion valve as 100%, respectively. In the face of changes in the degree of opening of the expansion valve 3, changes in the degree of suction overheating can be considered as practically a constant value, so that it is understood that changes in the proportion of heating capacity and The proportion of POPs cannot be judged by the degree of suction overheating. When controlling the COP to be maximum based on the difference in temperature AT2 between the discharge temperature and the outlet temperature of the water heat exchanger and the temperature of the water inlet, the changes in the discharge temperature and the Temperature differences AT2 are small in the vicinity of the degree of opening of the expansion valve when the cOp reaches the maximum as shown by a broken line in the figure, so that it was found that a high precision temperature measurement is required to control the COP to be maximum.

Next, Fig. 6 shows changes in other operating values obtained from the temperatures of each part when the degree of opening of the expansion valve 3 is changed. In Fig. 6, the horizontal axis represents the degree of opening (%) of the expansion valve 3. The vertical axis represents a temperature difference A Thx of the internal heat exchanger outlet / inlet, a temperature difference AT between a discharge temperature and an outlet temperature of the heat exchanger Water heat, a total temperature difference £ AT from the previous AT1 and AT2, the heating capacity, and the proportion of COP, respectively. The characteristics of Fig. 6 show that the operation can be carried out in the immediate vicinity where the COP becomes maximum, either by controlling a heat exchange amount of the internal heat exchanger 5 based on the Thx A temperature difference between the output and inlet of the internal heat exchanger or by controlling the amount of heat exchange of the water heat exchanger 2 based on the total temperature difference £ AT of AT1 and AT2 of the water heat exchanger 2. In addition, the AT temperature difference between the discharge temperature and the outlet temperature of the water heat exchanger changes significantly in the immediate vicinity of the opening degree of the expansion valve at which the COP becomes maximum, so it is understood that a deviation from the maximum value of the COP could be controlled to be small based on the temperature difference A T. Only the case of the difference is shown here However, the same effect can be expected by controlling the difference in temperature AT1 and AT2 based on the difference (AT1 - AT2).

Therefore, it is possible to achieve an operation in the immediate vicinity of maximum efficiency by adopting a high pressure side outlet temperature of the internal heat exchanger 5 for A Thx, the discharge temperature for AT, and the discharge temperature and temperatures of water side exit / inlet for £ AT.

As understood from Fig. 6, a total temperature difference of £ AT from the temperature difference AT1 between the inlet temperature of the water heat exchanger and the outlet temperature of water and the difference in temperature AT2 between the outlet temperature of the water heat exchanger and the inlet water temperature becomes a minimum. Control based on such an Index has a physical meaning and is reasonable. However, a high precision temperature detection is required, because the change in temperature is small in the vicinity where the COP becomes a maximum compared to the temperature difference A T. In addition, in Fig. 3, It is considered that when the COP becomes a maximum value, a temperature difference A Tp at a peak is almost the same as that of AT2 between the temperature

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Water heat exchanger outlet and water inlet temperature. This is because maximum performance is shown when two temperature differences that become minimums in the water heat exchanger 2 become equal without being partial to any of them when considering the characteristics of the heat exchanger. Consequently, it is permissible to control the expansion valve 3 in order to make A Tp and A T2 equal.

Next, descriptions of an example of a control operation of the refrigerant cycle apparatus of Fig. 1 will be given in which an opening degree of the expansion valve is controlled in order to achieve a degree of superheating of suction and that the previous AT temperature difference converges in target values.

Fig. 7 is a flow chart showing a control operation of the refrigerant cycle apparatus. With the present invention, in order to give priority to the reliability of the products, the control of the degree of suction overheating (SHs) of the compressor 1 precedes the control of the temperature difference AT to ensure the heating capacity.

First, when the degree of suction overheating (SHS) is less than an objective value (SHM) by a preset ASH convergence range or less (S101), the opening degree of the expansion valve is reduced until the degree of superheat suction (SHS) converges. Therefore, when the degree of suction overheating (SHs) is ensured, the temperature difference AT is converged to the target value. Specifically, when the temperature difference AT is less than an objective value (ATm) by a preset convergence range 8 T or less (S102), the degree of expansion opening is lowered and AT is converged. Therefore, the lower limit values of the degree of suction overheating (SHs) and the temperature difference AT can be suppressed.

Then, when the degree of suction overheating (SHs) is greater than the target value (SHm) by a preset convergence range A SH or more (S103), the opening degree of the expansion valve is increased until the degree of suction overheating (SHs) converges. Therefore, when the degree of suction overheating (SHs) is converged, the temperature difference T A is converged to the target value. Therefore, when the degree of suction overheating (SHs) is converged, the temperature difference AT is converged to the target value. Specifically, when the temperature difference A T is greater than the target value (ATm) by a preset convergence range 8 T or more (S104), the degree of expansion opening is increased and AT is converged. Therefore, the upper limit values of the degree of suction overheating (SHs) and the temperature difference AT can be suppressed. An example is shown in which a priority is given to control the degree of suction overheating, however, it is not limited thereto when using a compressor that is resistant to liquid return. The same effect can be expected even when the order of priority is changed. Through the previous control, the degree of suction overheating (SHs) and the temperature difference AT are converged in the target values.

In the above, descriptions are given for an example in which the degree of suction overheating (SHs) and the temperature difference AT are controlled to converge on the target values (SHm, A Tm), however, it is permissible that, instead of the temperature difference AT, a total temperature difference £ AT of AT1 and AT2, a difference between AT1 and AT2 (AT1 - A T2), or AThx can be used to control them and converge on an objective value, respectively . When using Z AT and (AT1 - A T2), these are obtained by calculating the temperatures in the first temperature detection means 30, second temperature detection means 31, third temperature detection means 41, and fourth means of detection of temperature 42. When using Thx A, a temperature sensing means is coupled to the output of the internal heat exchanger 52 (see Fig. 1) between a high pressure side outlet of the internal heat exchanger 5 and an input of the expansion valve 3, the temperature difference AThx is obtained from a detection temperature in the second temperature detection means 31 and the output temperature detection means of the internal heat exchanger 52.

Since, in the INVENTION, in addition to the control of the degree of superheating of the compressor suction, the degree of opening of the expansion valve is made to be controlled so that the COP becomes maximum based on a temperature difference AT1 - AT2 between the discharge temperature and the outlet temperature of the water heat exchanger, and a high efficiency refrigerant cycle apparatus can be obtained.

A coolant saturation temperature (ET) is obtained based on an output of the fifth temperature detection means 32 or pressure detection means, the degree of suction superheat (SHs) is obtained by the detection temperature (Ts ) of the sixth means of detecting the temperature and the saturation temperature of the refrigerant (ET), and the degree of opening of the expansion valve is controlled so that the degree of suction overheating (SHs) becomes an objective value , so that the degree of overheating of the suction part of the compressor 1 is ensured, the return of liquid to the compressor 1 is prevented and reliability can be ensured. In the example of Fig. 1, descriptions are given for an example in which the fifth temperature sensing means 32 is disposed between the expansion valve 3 and the evaporator 4, can be arranged in any position between the evaporator inlet 4 and a low pressure side inlet of the internal heat exchanger 5.

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In the present invention, when controlling the degree of overheating and the previous temperature difference ATI-AT2, the control of the degree of overheating precedes the control of the previous temperature differences. From this point, the reliability of the compressor 1 is assured.

In the present invention, the radiator is composed of the water heat exchanger, so that a high efficiency hot water supply apparatus can be obtained.

In said refrigerant cycle apparatus mentioned above, sixth temperature detection means can be provided to detect the temperature of the refrigerant between a low-pressure side outlet of said internal heat exchanger and an inlet of said compressor;

The degree of superheating of a suction part of the compressor can be calculated from a saturation temperature of the refrigerant at a detection point of said sixth temperature detection means and a detection temperature by means of said sixth temperature detection means, Y

The degree of opening of said decompression means can be controlled so that said degree of overheating becomes the target value.

In said refrigerant cycle apparatus mentioned previously

second pressure sensing means can be provided between the low pressure side outlet of said inner heat exchanger and the inlet of said compressor and

said coolant saturation temperature can be calculated based on a detection value of said second pressure detection means.

In said refrigerant cycle apparatus fifth temperature sensing means may be arranged between the inlet of said heat absorber and the low pressure side inlet of said internal heat exchanger and

said coolant saturation temperature can be calculated based on the detection temperature of said fifth temperature detection means.

In said refrigerant cycle apparatus, priority can be given to controlling said degree of overheating over said temperature difference.

In any of said refrigerant cycle devices the mentioned radiator can be a heat exchanger that exchanges heat with water.

In any of the refrigerant cycle devices mentioned above, carbon dioxide can be used as a refrigerant.

Claims (7)

5 10 fifteen twenty 25 30 35 40 1. A refrigerant cycle apparatus comprising: at least one compressor (1), a radiator (2), decompression means (3) that can change an opening degree, a heat absorber (4), an internal heat exchanger (5) that performs heat exchange between a coolant at a radiator outlet (2) and the coolant at a heat absorber outlet (4), in which first temperature sensing means (30) are provided to detect a coolant temperature between a compressor outlet ( 1) and a radiator inlet (2) and second temperature detection means (31) to detect the coolant temperature between the radiator outlet (2) and a high pressure side inlet of the internal heat exchanger (5), third temperature detection means (41) to detect an inlet temperature of a medium to be heated and fourth temperature detection means (42) to detect an outlet temperature of the medium to be heated, characterized in that an opening degree of the decompression means (3) is controlled so that a difference (AT1-AT2) between a second temperature difference (AT1) between a detection temperature by the first temperature detection means (30) and the detection temperature by means of the fourth temperature detection means (42) and a third temperature difference (AT2) between the detection temperature by means of the second temperature detection means (31) and the detection temperature by the third means of detection Temperature detection (41) becomes an objective value. 2. The refrigerant cycle apparatus of claim 1, wherein: a sixth temperature sensing means (33) is provided to detect the coolant temperature between a low pressure side outlet of the internal heat exchanger (5) and a compressor inlet (1), a degree of superheating of a suction part of the compressor is calculated from a saturation temperature of the refrigerant at a detection point of the sixth temperature detection means (33) and a detection temperature by the sixth means of detection of temperature (33), and the degree of opening of the decompression means (3) is controlled so that the degree of overheating becomes the target value. 3. The refrigerant cycle apparatus of claim 2, wherein a second pressure sensing means (51) is disposed between the low pressure side outlet of the internal heat exchanger (5) and the compressor inlet (1 ) and the coolant saturation temperature is calculated based on a detection value of the second pressure sensing means (51). 4. The refrigerant cycle apparatus of claim 2, wherein the fifth temperature sensing means (32) is disposed between the heat absorber inlet (4) and the low pressure side inlet of the internal heat exchanger (5) and the coolant saturation temperature is calculated based on the detection temperature of the fifth temperature detection means (32). 5. The refrigerant cycle apparatus of any one of claims 2 to 4, wherein priority is given to controlling the degree of overheating against the temperature difference. 6. The refrigerant cycle apparatus of any one of claims 1 to 5, wherein the radiator (2) is a heat exchanger that exchanges heat with water. 7. The refrigerant cycle apparatus of any one of claims 1 to 6, wherein carbon dioxide is used as a refrigerant.