JP2765613B2 - heat pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pump provided with a liquid-filled evaporator (hereinafter, referred to as a heat pump including a refrigerator).

[0002]

2. Description of the Related Art Conventionally, a heat pump shown in FIGS. 7 and 8 has been known (related invention: Japanese Patent Application Laid-Open No. 5-187378). Among them, the heat pump shown in FIG.
1, a condenser (including one integrated with a receiver and one separated from a receiver in this specification) 12, an expansion valve 13,
The compressor 11 is provided with a closed refrigerant flow path 16 including a liquid-filled evaporator 14 and a manual flow rate control valve 15, and a slide valve 17 for capacity adjustment. The condenser 12 has a high-temperature side passage 18 through which a liquid to be heated flows inside and outside the condenser 12.
The evaporator 14 is connected to a low-temperature side flow path 19 through which the liquid to be cooled flows inside and outside the evaporator 14.

Further, a temperature detector 20 for detecting the temperature in the low-temperature side flow path 19 is provided in a flow path on the side from which the liquid to be cooled flows out. The temperature signal indicating the detected temperature is output to the temperature controller 2.
1 is input. At the time of automatic operation after the flow control valve 15 is fully opened, based on the temperature signal, the compressor 11 is set to have a capacity where the difference between the refrigerant temperature in the evaporator 14 and the temperature of the liquid to be cooled is the set temperature. Next, the position of the slide valve 17 is controlled by the temperature controller 20.

At the time of start-up, the flow control valve 15 is fully closed and the evaporator 1 is closed in order to prevent the refrigerant liquid from the evaporator 14 from being sucked into the compressor 11 (so-called liquid back).
4 and the temperature controller 2
0 is set to the manual operation mode. After startup, flow control valve 1
The temperature of the liquid to be cooled is lowered by increasing the opening degree of 5 and cooling the refrigerant liquid in the evaporator 14. When the temperature of the liquid to be cooled falls to the design point, the temperature controller 20 is switched to the automatic operation mode, and the automatic operation described above is started.

During this time, the flow control valve 15 is opened as slowly as possible to cool the refrigerant liquid while applying a minimum load to the compressor 11 so as to prevent the refrigerant liquid from being bumped in the evaporator 14. This is very important. During startup, the difference between the evaporation temperature of the refrigerant liquid in the evaporator 14 and the temperature of the liquid to be cooled becomes particularly large. Since the volume of the refrigerant in the evaporator 14 is limited, the temperature immediately decreases, but the temperature of the liquid to be cooled does not immediately decrease if it is warm. The difference between these two temperatures causes bumping.

The heat pump shown in FIG. 8 is different from the heat pump shown in FIG.
A pressure detector 22 for detecting the suction pressure of the compressor 11 between the pressure control valve 15 and the flow control valve 15;
Are substantially the same except that a pressure regulator 23 is provided in place of, and the corresponding parts are denoted by the same reference numerals and description thereof is omitted. In this heat pump, a pressure signal indicating the detected pressure is input from the pressure detector 22 to the pressure regulator 23. During the automatic operation after the flow control valve 15 is fully opened, the pressure regulator 23
Based on the pressure signal, the temperature of the refrigerant in the evaporator 14 is calculated, so that the compressor 11 has a capacity to set the difference between the refrigerant temperature in the evaporator 14 and the temperature of the liquid to be cooled to a set temperature. The position of the slide valve 17 is controlled. The temperature of the refrigerant in the evaporator 14 is uniquely obtained from the suction pressure as the saturation temperature at that time.

At the time of starting, the evaporator 1 is operated in the same manner as described above.
In order to prevent so-called liquid back, in which the refrigerant liquid from 4 is sucked into the compressor 11, the flow control valve 15 is fully closed,
And, while keeping the liquid level in the evaporator 14 at the lowest level,
The pressure regulator 23 is set to the manual operation mode. After starting,
By increasing the opening of the flow control valve 15 to cool the refrigerant liquid in the evaporator 14, the temperature of the liquid to be cooled is lowered and the suction pressure of the compressor 11 is lowered. When the suction pressure drops to the design point, the temperature controller 20 is switched to the automatic operation mode, and the automatic operation described above is started.

[0008]

In the case of the above-mentioned conventional heat pump, the temperature of the liquid to be cooled is reduced by cooling the refrigerant liquid in the evaporator 14 while manually gradually opening the opening of the flow control valve 15 at startup. To prevent the occurrence of the liquid back phenomenon. However, the speed of increasing the opening of the flow control valve 15 may not always be appropriate, and in this case, a liquid back phenomenon occurs. When the liquid back phenomenon occurs, there arises a problem that damage to the bearing due to a decrease in the viscosity of the lubricating oil and damage to the rotor in the compressor occur. The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a heat pump capable of preventing liquid back to a compressor.

[0009]

According to a first aspect of the present invention, a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator is formed in addition to a compressor having a capacity adjusting means. A temperature detector for detecting a temperature in a flow path on the side from which the liquid to be cooled flows out of the evaporator, in the low-temperature side flow path for flowing the liquid to be cooled in and out of the evaporator; A pressure detector for detecting the suction pressure of the compressor, and the temperature detector detects the detected temperature T when the compressor starts.
A temperature signal indicating, and from the pressure detector, receives a pressure signal indicating the detected suction pressure P _s, the calculation of the saturation pressure P _e of the refrigerant at the temperature T, the calculation of the pressure difference [Delta] P = P _e -P _s , And the difference between ΔP and a predetermined set pressure C _p (ΔP
−C _p ), and outputs a control signal to the capacity adjusting means. If the difference (ΔP−C _p ) is negative,
Reducing the capacity of the compressor, if the difference is zero, as well as increasing the capacity, by changing the set pressure C _p to a lower set pressure, when the difference is positive, the capacity And a pressure regulator that repeats the control after calculating the difference again.

A second invention provides a heat pump having a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator, in addition to a compressor with a capacity adjusting means, wherein a liquid to be cooled is provided inside and outside the evaporator. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out from the evaporator, a pressure detector for detecting the suction pressure of the compressor, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, receives a pressure signal indicating the detected suction pressure P _s, the refrigerant at a suction pressure P _s saturated calculation of the temperature T _s, the temperature difference Δ
Calculation of T = T−T _s and calculation of a difference (ΔT−C _t ) between ΔT and a predetermined set temperature C _t , outputting a control signal to the capacity adjusting means, and calculating the difference (ΔT −C _t ) is negative, the capacity of the compressor is reduced, and if the difference is zero, the capacity is increased and the set temperature C is increased.
_{When t} was changed to a lower set temperature, and when the difference was positive, the temperature was maintained, and a temperature controller for repeating the control after the calculation of the difference again was provided.

Further, the third invention provides a heat pump having a closed refrigerant flow path including at least a condenser, an expansion valve, an evaporator, and a suction pressure control valve in addition to the compressor. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out of the evaporator, and a pressure detector for detecting the suction pressure of the compressor, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, receives a pressure signal indicative of the detected suction pressure P _s, the saturation pressure of the refrigerant at the temperature T calculation of P _e, the pressure difference [Delta] P =
P _e -P _s calculations, and set pressure C _p determined in advance and ΔP
Performs calculation of the difference (ΔP-C _p) and outputs a control signal to said capacity adjusting means, when the difference (ΔP-C _p) is negative, the opening degree of the suction pressure regulating valve When the difference is 0, the opening is increased, and the set pressure C _p is changed to a smaller set pressure. When the difference is positive, the opening is maintained, A pressure regulator that repeats the control after calculating the difference is provided.

Further, a fourth aspect of the present invention is directed to a heat pump that forms a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator in addition to a compressor with a capacity adjusting means. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out from the evaporator, a pressure detector for detecting the suction pressure of the compressor, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, receives a pressure signal indicating the detected suction pressure P _s, the refrigerant at a suction pressure P _s saturated calculation of the temperature T _s, the temperature difference Δ
Calculation of T = T−T _s and calculation of a difference (ΔT−C _t ) between ΔT and a predetermined set temperature C _t , outputting a control signal to the capacity adjusting means, and calculating the difference (ΔT When −C _t ) is negative, the opening of the suction pressure control valve is reduced, and when the difference is 0, the opening is increased and the set temperature C _t is reduced to a lower set temperature. When the difference is positive, a temperature controller that maintains the opening and repeats the control after calculating the difference is provided.

[0013]

With the construction as described above, the difference between the temperature of the refrigerant in the evaporator and the temperature of the liquid to be cooled is maintained within a certain range in which the refrigerant does not bump. become.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a heat pump according to the first invention, and the same parts as those of the heat pump shown in FIG. In the present embodiment, the pressure detector 1 is provided between the evaporator 14 and the compressor 11, and a temperature signal indicating the detected temperature from the temperature detector 20 and a pressure signal indicating the detected pressure from the pressure detector 1 are output. The pressure is input to the pressure regulator 2, and the position of the slide valve 17 is controlled by the pressure regulator 2 to adjust the capacity of the compressor 11.

[0015] Specifically, as shown in FIG. 2, and detects the temperature T of the object to be cooled by the temperature detector 20, the pressure of the refrigerant by the pressure detector 1, i.e. the suction pressure P _s of the compressor 11 detecting, thereby calculating the saturation pressure P _e of the refrigerant at the temperature T in the pressure regulator 2. Further, the pressure regulator 2, the difference ΔP between the saturation pressure P _e and the suction pressure P _s
= P _e -P _s calculation and the difference Δ between ΔP and set pressure C _p
It is made to the calculation of _{P-C p.} The set pressure C _p is determined in a range that is small enough not to cause bumping of the refrigerant in the evaporator 14 and large enough that heat exchange between the refrigerant and the liquid to be cooled is efficiently performed in the evaporator 14. Experience.

When the difference ΔP−C _p is positive,
The capacity of the compressor 11 is reduced, if 0, the capacity of the compressor 11 is increased, and the set pressure _Cp is reduced. If negative, the current capacity of the compressor 11 is maintained. perform the calculation of the difference [Delta] p-C _p, is formed so as thereafter to repeat the same steps. In this manner, in the present embodiment, even at the time of start-up, while keeping the refrigerant pressure in the evaporator 14 within an appropriate range with respect to the saturation pressure, the refrigerant temperature is gradually lowered to reach the design temperature. It is formed so as to eliminate bumping of the refrigerant in the evaporator 14 and prevent occurrence of a liquid back phenomenon.

FIG. 3 shows a heat pump according to the second invention, which is substantially the same as the heat pump shown in FIG. 1 except that a temperature controller 3 is provided instead of the pressure controller 2. Therefore, common portions are denoted by the same reference numerals and description thereof is omitted. In this embodiment, as shown in FIG. 4, the saturation temperature T _s of the refrigerant at the suction pressure P _s in the temperature controller 3.
Calculations, the difference between the temperature T of the cooling liquid and the saturation temperature T _s [Delta] T =
Calculation of T−T _s and difference ΔT− between ΔT and set temperature C _t
Ct is calculated. This set temperature C _t is set in the evaporator 1
It is an empirical value that is low enough to prevent bumping of the refrigerant in the evaporator 4 and high enough to allow efficient heat exchange between the refrigerant and the liquid to be cooled in the evaporator 14.

When the difference ΔT− _Ct is positive,
The capacity of the compressor 11 is reduced, if 0, the capacity of the compressor 11 is increased, and the set pressure _Cp is reduced. If negative, the current capacity of the compressor 11 is maintained. The difference ΔT−C _t is calculated, and the same steps are repeated thereafter. In this manner, in the present embodiment, even at the time of startup, the refrigerant temperature is gradually decreased while maintaining the refrigerant temperature in the evaporator 14 within an appropriate range with respect to the saturation temperature to reach the design temperature. It is formed so as to eliminate bumping of the refrigerant in the evaporator 14 and prevent occurrence of a liquid back phenomenon.

FIG. 5 shows a heat pump according to a third invention. The heat pump shown in FIG. 1 is different from the heat pump shown in FIG. 1 in that a compressor 11a having no slide valve is provided instead of the compressor 11, and a new evaporator 14 and a compressor are provided. 11a, except that a flow control valve 4 is provided between them and a pressure regulator 5 are provided, and the other parts are substantially the same. I do. The pressure regulator 5 receives a temperature signal from the temperature detector 20 and a pressure signal from the pressure detector 1 as in the case of the pressure regulator 2, and basically has the same control flow as the control flow shown in FIG. The opening degree of the flow control valve 4 is adjusted in accordance with the following equation. However, in the case of this embodiment, when increasing the capacity of the compressor 11a,
To increase the opening of the flow control valve 4 and conversely reduce the capacity, the opening of the flow control valve 4 is reduced.

FIG. 6 shows a heat pump according to a fourth invention, which is substantially the same as the heat pump shown in FIG. 5 except that a temperature controller 6 is provided in place of the pressure controller 5. Common parts are denoted by the same reference numerals, and description thereof is omitted. The temperature controller 6 receives a temperature signal from the temperature detector 20 and a pressure signal from the pressure detector 1 as in the case of the pressure controller 5, and basically has the same control flow as the control flow shown in FIG. The opening degree of the flow control valve 4 is adjusted in accordance with the following equation. And, by constituting as in the third and fourth inventions, the same operation as in the case of the first and second inventions is produced.

The first to fourth aspects of the present invention are not limited to the above-described embodiment, and the capacity adjusting means may be an intake capacity adjusting device or a vane provided in the intake section of the compressor in addition to the above-described means. It may be a bypass flow path that bypasses the discharge part and the suction part of the compressor via the flow control valve. Also, the compressor is a screw type compressor when the slide valve 17 is provided, and a centrifugal type compressor when the vane is provided. However, in other cases, the type is not limited.

[0022]

As is apparent from the above description, according to the first invention, in addition to the compressor with the capacity adjusting means, a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator is formed. In the heat pump, a temperature detector for detecting a temperature in a flow path on a side where the liquid to be cooled flows out from the evaporator in a low-temperature side flow path for flowing the liquid to be cooled in and out of the evaporator; a pressure detector for detecting the suction pressure, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, receives a pressure signal indicating the detected suction pressure P _s , performs the computation of the saturation pressure P _e of the refrigerant at the temperature T, the calculation of the pressure difference [Delta] P = P _e -P _s, and the calculation of the difference ([Delta] P-C _p) between the set pressure C _p of predetermined and [Delta] P , A control signal is output to the capacity adjusting means, and the difference (ΔP− When C _p ) is negative, the capacity of the compressor is reduced, and when the difference is zero, the capacity is increased, and the set pressure C _p is changed to a lower set pressure to change the compressor capacity. Is positive, a pressure regulator is provided to maintain the above capacity and repeat the control after the calculation of the difference again.

According to the second aspect of the present invention, there is provided a heat pump which forms a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator, in addition to the compressor having a capacity adjusting means.
A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out of the evaporator in the low-temperature side flow path for flowing the liquid to be cooled in and out of the evaporator, and the suction pressure of the compressor. a pressure detector for detecting, when starting the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, receives a pressure signal indicating the detected suction pressure P _s, the suction pressure calculation of the saturation temperature T _s of the refrigerant at the time of P _s, performs calculation of the difference (ΔT-C _t) between the temperature difference [Delta] T = T-T _s calculations, and [Delta] T with a predetermined set temperature C _t, the A control signal is output to the capacity adjusting means, and the difference (ΔT−C
_{If t} ) is negative, the capacity of the compressor is reduced, and if the difference is 0, the capacity is increased and the set temperature C _t is changed to a lower set temperature to reduce the difference. In the case of a positive value, a temperature controller for maintaining the above capacity and repeating the control after the calculation of the difference is provided.

Further, according to the third invention, in a heat pump which forms a closed refrigerant flow path including at least a condenser, an expansion valve, an evaporator, and a suction pressure control valve in addition to the compressor, the heat pump is provided inside and outside the evaporator. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out of the evaporator, and a pressure detector for detecting the suction pressure of the compressor in the low-temperature side flow path through which the liquid to be cooled flows If, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, receives a pressure signal indicating the detected suction pressure P _s, the refrigerant at the temperature T calculation of saturation pressure P _e, performs calculation of difference ([Delta] P-C _p) between the set pressure C _p calculation of the pressure difference ΔP = P _e -P _s, and determined in advance and [Delta] P, with respect to the volume adjustment means A control signal is output and the difference (ΔP−
When C _p ) is negative, the opening of the suction pressure control valve is reduced, and when the difference is 0, the opening is increased and the set pressure C _p is reduced to a smaller set pressure. On the other hand, when the difference is positive, a pressure regulator that maintains the opening degree and repeats the control after calculating the difference is provided.

Further, according to the fourth invention, in addition to the compressor having the capacity adjusting means, in a heat pump having at least a condenser, an expansion valve, and a closed refrigerant flow path including an evaporator, the heat pump is provided inside and outside the evaporator. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out of the evaporator, and a pressure detector for detecting the suction pressure of the compressor, , at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, receives a pressure signal indicating the detected suction pressure P _s, the refrigerant at a suction pressure P _s Calculation of the saturation temperature T _s of
Calculation of temperature difference ΔT = T−T _s and calculation of difference (ΔT−C _t ) between ΔT and a predetermined set temperature C _t , outputting a control signal to the capacity adjusting means, (ΔT−
When C _t ) is negative, the opening of the suction pressure control valve is reduced, and when the difference is 0, the opening is increased and the set temperature C _t is reduced to a lower set temperature. change,
If the difference is positive, a temperature controller is provided to maintain the opening degree and repeat the control after the calculation of the difference again. For this reason, even at the time of startup, the difference between the temperature of the refrigerant in the evaporator and the temperature of the liquid to be cooled is kept within a certain range where bumping of the refrigerant does not occur. As a result, it is possible to avoid damage to the bearing due to a decrease in the viscosity of the lubricating oil due to mixing of the refrigerant into the lubricating oil, and also to avoid damage to the rotor in the compressor.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a heat pump according to a first invention.

FIG. 2 is a diagram showing a control flow for adjusting the capacity of a compressor in the heat pump shown in FIG.

FIG. 3 is a diagram showing an overall configuration of a heat pump according to a second invention.

4 is a diagram showing a control flow for adjusting the capacity of a compressor in the heat pump shown in FIG.

FIG. 5 is a diagram showing an overall configuration of a heat pump according to a third invention.

FIG. 6 is a diagram showing an overall configuration of a heat pump according to a fourth invention.

FIG. 7 is a diagram showing an entire configuration of a conventional heat pump.

FIG. 8 is a diagram showing an overall configuration of another conventional heat pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure detector 2 Pressure regulator 3 Temperature regulator 4 Pressure regulator 5 Temperature regulator 11, 11a Compressor 12 Condenser 13 Expansion valve 14 Evaporator 15 Flow control valve 16 Refrigerant flow path 17 Slide valve 19 Low temperature side flow path 20 Temperature detector

Claims (4)

(57) [Claims] In a heat pump that forms a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator in addition to a compressor with a capacity adjusting means, a low-temperature side flow for flowing a liquid to be cooled into and out of an evaporator. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out of the evaporator,
Shows the pressure detector for detecting the suction pressure of the compressor, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, the detected suction pressure P _s receives the pressure signals, the difference in the calculation of the saturation pressure P _e of the refrigerant, the calculation of the pressure difference [Delta] P = P _e -P _s, a and [Delta] P with a predetermined set pressure C _p at the temperature T ([Delta] P-C _p)
Is calculated, and a control signal is output to the capacity adjusting means. If the difference (ΔP−C _p ) is negative, the capacity of the compressor is reduced. When the capacity is increased, the set pressure C _p is changed to a lower set pressure, and when the difference is positive, a pressure regulator that maintains the capacity and repeats the control after calculation of the difference again is used. A heat pump characterized by being provided and formed. 2. In a heat pump that forms a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator, in addition to a compressor with a capacity adjusting means, a low-temperature side flow for flowing a liquid to be cooled into and out of the evaporator. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out of the evaporator,
Shows the pressure detector for detecting the suction pressure of the compressor, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, the detected suction pressure P _s receives the pressure signals, calculates the saturation temperature T _s of the refrigerant at a suction pressure P _s, the calculation of the temperature difference [Delta] T = T-T _s,
And the difference between ΔT and a predetermined set temperature C _t (ΔT−
_Ct ) is calculated, and a control signal is output to the capacity adjusting means. When the difference (ΔT− _Ct ) is negative, the capacity of the compressor is reduced, and when the difference is 0, In addition, while the capacity is increased, the set temperature C _t is changed to a lower set temperature, and when the difference is positive, the capacity is maintained and the control after the difference calculation is repeated again. A heat pump characterized in that it is formed by providing a heat pump. 3. In a heat pump that forms a closed refrigerant flow path including at least a condenser, an expansion valve, an evaporator, and a suction pressure control valve in addition to the compressor, a low-temperature side through which a liquid to be cooled flows inside and outside the evaporator. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out from the evaporator,
Shows the pressure detector for detecting the suction pressure of the compressor, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, the detected suction pressure P _s receives the pressure signals, the difference in the calculation of the saturation pressure P _e of the refrigerant, the calculation of the pressure difference [Delta] P = P _e -P _s, a and [Delta] P with a predetermined set pressure C _p at the temperature T ([Delta] P-C _p)
Is calculated, and a control signal is output to the capacity adjusting means. If the difference (ΔP−C _p ) is negative, the opening of the suction pressure adjusting valve is reduced, and the difference becomes zero. In this case, the opening is increased, and the set pressure C _p is changed to a smaller set pressure. If the difference is positive, the opening is maintained, and control after the difference calculation is performed again. A heat pump formed by providing a pressure regulator that is repeated. 4. A low-temperature side flow through which a liquid to be cooled flows inside and outside of an evaporator in a heat pump that forms a closed refrigerant flow path including at least a condenser, an expansion valve, and an evaporator, in addition to the compressor with capacity adjusting means. A temperature detector for detecting the temperature in the flow path on the side from which the liquid to be cooled flows out of the evaporator,
Shows the pressure detector for detecting the suction pressure of the compressor, at the start of the compressor, from the temperature detector, a temperature signal indicating the detected temperature T, and from the pressure detector, the detected suction pressure P _s receives the pressure signals, calculates the saturation temperature T _s of the refrigerant at a suction pressure P _s, the calculation of the temperature difference [Delta] T = T-T _s,
And the difference between ΔT and a predetermined set temperature C _t (ΔT−
_Ct ) is calculated and a control signal is output to the capacity adjusting means. If the difference (ΔT− _Ct ) is negative, the opening of the suction pressure adjusting valve is reduced, and the difference is calculated. Is 0, the opening is increased, and the set temperature _Ct is changed to a lower set temperature. If the difference is positive, the opening is maintained and the calculation of the difference is performed again. And a temperature controller that repeats the above control.