JPH07190506A - Saturated vapor temperature detector of refrigeration cycle - Google Patents

Abstract

PURPOSE:To detect saturated vapor temperature of a compressor suction refrigerant in a refrigeration cycle using a non azeotropic mixture refrigerant without complicating the construction of the refrigeration cycle. CONSTITUTION:There is disposed a bypass circuit 5, one end of which is connected with a line extending from an outlet of a condenser 2 to a motor driven expansion valve 3 and the other end of which is connected with a line extending from an outlet of an evaporator 4 to an inlet of a compressor 1. On the bypass circuit 5 there are provided in order from the upstream side an auxiliary drawing 6, a temperature sensor 7, and saturated vapor temperature correction means for detecting refrigerant temperature using the temperature sensor 7 and adding a predetermined value to the refrigerant temperature in response to the kind of the used refrigerant and a composition ratio of the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a saturated vapor temperature detector for a refrigeration cycle using a non-azeotropic mixed refrigerant in which two or more kinds of refrigerants having different boiling points are mixed at a predetermined ratio.

[0002]

2. Description of the Related Art In recent years, from the standpoint of protecting the global environment, regulations on CFCs that destroy the ozone layer have been strengthened, and it has been decided to abolish CFC (chlorofluorocarbon), which has a particularly high destructive power, at the end of 1995. Also, regarding the FCFC (hydrochlorofluorocarbon), which has a relatively small destructive power, the total amount regulation was started in 1996, and it has been decided that it will be completely abolished in the future. Therefore, for devices that use CFCs as refrigerants, alternative refrigerants are being developed, and HFCs (hydrofluorocarbons) that do not destroy the ozone layer are being studied, but HCFCs used in refrigerators and air conditioners are being investigated. No substitute refrigerant that can be used alone as a substitute refrigerant is found in HFC, and therefore, a non-azeotropic mixed refrigerant obtained by mixing two or more kinds of HFC refrigerants is considered promising.

Conventionally, a refrigeration cycle such as a refrigerator or an air conditioner using a single refrigerant such as CFC or HCFC has a COP
In order to improve the (coefficient of performance) and ensure the reliability of the compressor, superheat control was performed, and for that purpose, a saturated steam temperature detection circuit was provided.

A conventional saturated vapor temperature detecting circuit will be described below with reference to the drawings. FIG. 5 is a refrigeration cycle diagram of a conventional refrigerator, air conditioner, or the like. In the figure, 1 is a compressor, 2 is a condenser, 3 is an electric expansion valve whose valve opening can be pulse-controlled by using a stepping motor, 4
Are evaporators, which are in turn connected in a ring.
Reference numeral 5 denotes a bypass circuit having one end connected to a pipe line connecting the condenser 2 and the electric expansion valve 3 and the other end connected to a pipe line connecting the evaporator 4 and the compressor 1. Is provided with an auxiliary aperture 6. Furthermore, the temperature sensor 7 is provided on the bypass circuit 5 and the suction side pipe of the compressor 1, respectively.
8 is provided, and the valve opening calculation circuit 10 uses the temperature detected by the temperature sensors 7 and 8 to drive the electric expansion valve 3
The valve opening signal of the electric expansion valve 3 is controlled by the expansion valve drive circuit 11 in response to the valve opening signal.

FIG. 6 shows this refrigeration cycle on the P-h (Moriel) diagram.
The points indicated by the symbols B and C indicate the states of the refrigerant at the positions A, B and C in FIG. As is clear from the figure, since the point C is in the gas-liquid two-phase state, the temperature of the refrigerant is the saturated vapor temperature TS of the refrigerant at the point B. Therefore, the difference (T2-TS) between the temperature TS detected by the temperature sensor 7 and the temperature T2 detected by the temperature sensor 8 represents the superheat amount ΔT of the refrigerant sucked into the compressor 1.

Next, the control of this refrigeration cycle will be described. FIG. 7 is a diagram showing the relationship between the superheat amount and the valve opening change amount of the electric expansion valve 3, which is based on the temperature signals TS and T2 detected by the temperature sensors 7 and 8 and which is used for calculating the valve opening calculation circuit at predetermined intervals. 10, ΔT is calculated, and according to the relationship shown in FIG. 7 (when the superheat amount is larger than the set value, the valve opening is increased, and when it is smaller than the set value, the valve opening is decreased),
The valve opening signal of the electric expansion valve 3 is sent to the expansion valve driving circuit 11, and the expansion valve driving circuit 11 controls the valve opening of the electric expansion valve 3 to keep the superheat amount at a set value.

[0007]

However, the conventional saturated vapor temperature detection circuit for the refrigeration cycle has the following problems.

FIG. 8 shows a refrigeration cycle in the case of using a non-azeotropic mixed refrigerant as a refrigerant on the P-h (Mollier) diagram, and the points of symbols A, B and C in FIG. 5 shows states of the refrigerant at positions A, B and C in FIG.
Here, the amount of superheat at the point B can be obtained by the difference between the temperature at the point B and the saturated steam temperature (point E). Here, in the case of a single refrigerant, FIG.
As shown in FIG. 8, the temperature at point C is the same as the saturated vapor temperature, but in the case of a non-azeotropic mixed refrigerant, as shown in FIG.
Since the isotherm in the phase region is a line descending to the right, the temperature at point C is lower than the temperature at the saturated steam temperature (point E). Therefore, ΔT calculated from the temperature signals TS and T2 detected by the temperature sensors 8 and 9 becomes a value larger than the true amount of superheat, and the refrigerant for controlling to keep the set value in this state is It is sucked into the compressor when the actual amount of superheat is lower than the set value or in the state of wet steam.

Therefore, there is a possibility that the reliability of the compressor may be lowered and the COP may be lowered due to the liquid compression.

In view of the above problems, the saturated vapor temperature detection circuit of the refrigeration cycle of the present invention, in a refrigeration cycle using a non-azeotropic mixed refrigerant, does not complicate the structure of the refrigeration cycle, but the saturated vapor temperature of the compressor suction refrigerant The purpose of this is to easily detect and to realize the optimal refrigeration cycle control.

[0011]

In order to solve the above problems, a saturated vapor temperature detection circuit of a refrigerating cycle according to the present invention is a non-azeotropic mixture in which two or more kinds of refrigerants having different boiling points are mixed at a predetermined ratio as refrigerants. Using a refrigerant, a compressor, a condenser, a decompressor, and an evaporator are sequentially connected by a pipe in a ring shape to form a refrigerant circuit, and one end is connected to a conduit from the condenser outlet to the decompressor outlet, and the other end. A bypass circuit connected to the pipeline from the evaporator outlet to the compressor inlet is provided, and an auxiliary decompressor and refrigerant temperature detecting means are provided in this bypass circuit in order from the upstream side, and the refrigerant temperature is detected by the refrigerant temperature detecting means. It has a saturated vapor temperature correction means for detecting and adding a predetermined value according to the type of refrigerant used and its composition ratio to the refrigerant temperature.

A saturated vapor temperature detection circuit of another refrigeration cycle of the present invention uses a non-azeotropic mixed refrigerant in which two or more kinds of refrigerants having different boiling points are mixed at a predetermined ratio as the refrigerant.
A compressor, a condenser, a pressure reducer, and an evaporator are sequentially connected in an annular shape by a pipe to form a refrigerant circuit, and a plurality of refrigerant temperature detecting means are provided in a pipeline from the evaporator inlet to the outlet, and the refrigerant temperature is set. It has a saturated vapor temperature calculation means for calculating the saturated vapor temperature of the refrigerant sucked into the compressor using the plurality of refrigerant temperatures detected by the detection means.

A saturated vapor temperature detecting circuit of another refrigeration cycle of the present invention uses a non-azeotropic mixed refrigerant in which two or more kinds of refrigerants having different boiling points are mixed at a predetermined ratio as the refrigerant.
A compressor, a condenser, a pressure reducer, and an evaporator are sequentially connected in an annular shape by a pipe to form a refrigerant circuit, and a plurality of refrigerant temperature detecting means are provided in a pipeline from the evaporator inlet to the outlet, and the refrigerant temperature is set. Saturated steam temperature calculation means for calculating the saturated steam temperature of the refrigerant sucked into the compressor using the plurality of refrigerant temperatures detected by the detection means and the saturated steam temperature calculated by the saturated steam temperature calculation means It has a saturated vapor temperature correction means.

[0014]

The present invention has the following actions due to the above means.

That is, a bypass circuit having one end connected to a conduit from the condenser outlet to the decompressor outlet and the other end connected to a conduit from the evaporator outlet to the compressor inlet is provided. Auxiliary decompressor and refrigerant temperature detecting means are provided in order from the upstream side, the refrigerant temperature is detected by the refrigerant temperature detecting means, and a saturated vapor temperature is added to the refrigerant temperature to a predetermined value according to the type of refrigerant used and its composition ratio. By including the correction means, in the refrigeration cycle using the non-azeotropic mixed refrigerant, the saturated vapor temperature of the compressor suction refrigerant can be easily obtained without complicating the structure of the refrigeration cycle, and thereby the optimum refrigeration cycle can be obtained. It is possible to realize cycle control.

Further, a plurality of refrigerant temperature detecting means are provided in a pipe line from the evaporator inlet to the outlet, and the saturated vapor of the refrigerant sucked into the compressor by using the plurality of refrigerant temperatures detected by the refrigerant temperature detecting means. By having the saturated vapor temperature calculating means for calculating the temperature, in the refrigeration cycle using the non-azeotropic mixed refrigerant, the saturated vapor temperature of the compressor suction refrigerant can be easily obtained without providing a bypass circuit. It is possible to realize optimal refrigeration cycle control.

Further, a plurality of refrigerant temperature detecting means are provided in a pipeline extending from the evaporator inlet to the outlet, and the refrigerant sucked into the compressor is saturated using the plurality of refrigerant temperatures detected by the refrigerant temperature detecting means. By having a saturated vapor temperature calculating means for calculating the vapor temperature and a saturated vapor temperature correcting means for correcting the saturated vapor temperature calculated by the saturated vapor temperature calculating means, in the refrigeration cycle using the non-azeotropic mixed refrigerant, the bypass The saturated vapor temperature of the refrigerant sucked into the compressor can be easily and accurately obtained without providing a circuit, and thus optimal refrigeration cycle control can be realized.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that components having the same functions as those described in the section of the related art are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 1 is a refrigeration cycle diagram in the first embodiment of the present invention. In the figure, 1 is a compressor, 2 is a condenser, 3 is an electric expansion valve, and 4 is an evaporator, which are sequentially connected in an annular shape and use a non-azeotropic mixed refrigerant as a refrigerant. Reference numeral 5 denotes a bypass circuit having one end connected to a pipe line connecting the condenser 2 and the electric expansion valve 3 and the other end connected to a pipe line connecting the evaporator 4 and the compressor 1. Is provided with an auxiliary aperture 6. In addition, temperature sensors 7 and 8 are provided on the pipeline on the downstream side of the auxiliary throttle 6 and the pipeline on the suction side of the compressor 1, respectively. Also,
Reference numeral 9 denotes a saturated steam temperature correction circuit that receives and corrects the temperature TS detected by the temperature sensor 7. Reference numeral 10 denotes a value TS1 corrected by the saturated steam temperature correction circuit 9 and value T detected by the temperature sensor 8.
2 is a valve opening calculation circuit that calculates the opening of the electric expansion valve 3 and sends a valve opening signal. The expansion valve drive circuit 11 receives the valve opening signal and the electric expansion valve 3 Control the valve opening degree of.

Further, the refrigerant lines A, B and C in FIG.
The state of the refrigerant at the position of is the points A, B in FIG.
Represented by C.

The control of the refrigeration cycle will be described. First, the temperature sensor 7 detects the temperature TS and the temperature sensor 8 detects the temperature T2 at predetermined intervals, and the temperature T2 is sent to the valve opening calculation circuit 10 as it is. The temperature TS is sent to the saturated steam temperature correction circuit 9. TS is the position of point C in FIG. 8, and has a value smaller than the temperature of point E, which is the saturated vapor temperature of the refrigerant at point B, as described in the section of the related art. The temperature difference between points E and C is
This value can be calculated by the known mixed refrigerant thermophysical property estimation method from the type of refrigerant used and its composition ratio.
When the value is 1, the saturated steam temperature correction circuit 9 calculates the correction value TS1 of the saturated steam temperature by the formula (TS1 = TS + TR1),
This value is sent to the valve opening calculation circuit 10. In the valve opening calculation circuit 10, ΔT is calculated from the temperatures TS1 and T2 at every predetermined cycle (ΔT = T2-TS1), and according to the relationship shown in FIG. 7 (when the superheat amount is larger than the set value, The valve opening degree of the electric expansion valve 3 is sent to the expansion valve drive circuit 11, and the expansion valve drive circuit 11 causes the electric expansion valve 3 to increase.
Controls the valve opening of to keep the superheat amount at the set value.
Thus, even when using a non-azeotropic mixed refrigerant as the refrigerant, it is possible to accurately detect the saturated vapor temperature of the compressor suction refrigerant without complicating the configuration of the refrigeration cycle,
This makes it possible to realize optimum refrigeration cycle control.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a refrigeration cycle diagram in the second embodiment of the present invention. In the figure, 1
Reference numerals 2 and 13 denote temperature sensors that detect the temperature of the refrigerant near the inlet and intermediate portions of the pipes that form the evaporator 4, and 14 is saturated from the temperature T3 detected by the temperature sensor 12 and the temperature T4 detected by the temperature sensor 13. It is a saturated steam temperature calculation circuit that calculates the steam temperature.

The control of the refrigeration cycle will be described. First, the temperature T is measured by the temperature sensors 12 and 13 every predetermined period.
3 and T4 are detected and these values are sent to the saturated steam temperature calculation circuit 14, and the saturated steam temperature calculation circuit 14 detects the temperature T
Calculate saturated vapor temperature using 3 and T4. This calculation method will be described with reference to the drawings. FIG. 3 shows changes in the refrigerant temperature in the refrigerant pipe line in the evaporator 4. As is clear from the figure, as a phenomenon unique to the non-azeotropic mixed refrigerant,
The temperature rises in the evaporator as the refrigerant evaporates, and the rate of increase is linear. Then, in the vicinity of the evaporator outlet, it enters the overheated region and the temperature rises rapidly.
Therefore, the saturated steam temperature TS is calculated by the formula (TS = T3 + (T4
When calculated by −T3) × 2), a value close to the true saturated steam temperature can be obtained. The temperature TS calculated in this way is sent to the valve opening calculation circuit 10. In the valve opening calculation circuit 10, ΔT is calculated from the temperatures TS and T2 at predetermined intervals.
Is calculated (ΔT = T2-TS) and according to the relationship shown in FIG. 7 (when the superheat amount is larger than the set value, the valve opening is increased, and when the superheat amount is smaller than the set value, the valve opening is decreased). The valve opening signal of the electric expansion valve 3 is sent to the expansion valve drive circuit 11
And the expansion valve drive circuit 11 controls the valve opening of the electric expansion valve 3 to maintain the superheat amount at a set value.

As described above, even when the non-azeotropic mixed refrigerant is used as the refrigerant, it is possible to easily detect the saturated vapor temperature of the compressor suction refrigerant without newly providing a bypass circuit. It is possible to realize cycle control.

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a refrigeration cycle diagram in the third embodiment of the present invention. In the figure, the difference from the second embodiment shown in FIG. 2 is that a saturated steam temperature correction circuit 15 is provided between the saturated steam temperature calculation circuit 14 and the valve opening calculation circuit 10. The saturated steam temperature correction circuit 15 corrects by subtracting a predetermined value TR2 from the saturated steam temperature detected by the saturated steam temperature calculation circuit 14.
As a result, even when the refrigerant pipe from the evaporator 4 to the compressor 1 is long, the pressure loss is large, and the saturated vapor temperature of the refrigerant sucked into the compressor 1 is different from the saturated vapor temperature in the evaporator 4, the superconductivity is accurately measured. It becomes possible to control by calculating the heat amount.

The control of the refrigeration cycle will be described. First, the temperature T is measured by the temperature sensors 12 and 13 every predetermined period.
3 and T4 are detected and these values are sent to the saturated steam temperature calculation circuit 14, and the saturated steam temperature calculation circuit 14 detects the temperature T
3 and T4, the saturated steam temperature TS is calculated in the same manner as in the second embodiment, and the calculated temperature TS is sent to the saturated steam temperature correction circuit 15 to correct the saturated steam temperature TS2.
Is calculated by the equation (TS2 = TS−TR2) and sent to the valve opening calculation circuit 10. In the valve opening calculation circuit 10, ΔT is calculated from the temperatures TS2 and T2 at predetermined intervals (ΔT = T
2-TS2), according to the relationship shown in FIG. 7 (if the superheat amount is larger than the set value, the valve opening is increased, and if it is smaller than the set value, the valve opening is decreased). To the expansion valve drive circuit 11, and the expansion valve drive circuit 11 controls the valve opening degree of the electric expansion valve 3 to maintain the superheat amount at the set value.

As described above, even when the non-azeotropic mixed refrigerant is used as the refrigerant, the saturated vapor temperature of the compressor suction refrigerant can be accurately detected without newly providing a bypass circuit. It is possible to realize cycle control.

In the above first to third embodiments, the case where the saturated steam temperature detected by the saturated steam temperature detecting circuit of the present invention is used for superheat control has been described, but the present invention is not limited to this. , For example, the freezing of the evaporator is estimated from the detected saturated vapor temperature, a conversion formula to the saturated pressure is created, and the compressor suction pressure is calculated from the detected saturated vapor temperature and used for protection control. It can also be used for other controls.

In the first embodiment, one end of the bypass circuit 5 is connected to the condenser 2 and the pressure reducer (electric expansion valve 3).
Although it is connected to a part of the pipe line connecting to and, the present invention is not limited to this, and it is sufficient if the ratio of the liquid refrigerant is large and the pressure becomes higher than the suction side of the compressor 1. For example, when the decompressor is divided into two, it may be connected between the two decompressors, and when the decompressor is a capillary tube, it may be connected to any position on the pipeline of the capillary tube. Good.

In the second and third embodiments, two temperature sensors 1 are used to calculate the saturated steam temperature.
Although 2 and 13 are provided, the number is not limited to this, and the number of sensors may be increased, and the calculation formula is not limited to this.

Further, the saturated vapor temperature detection circuit of the present invention is
Not only the CFC-based refrigerant but also a non-azeotropic mixed refrigerant can be applied to other refrigerants.

[0032]

As is apparent from the above embodiment, the saturated vapor temperature detection circuit of the refrigeration cycle of the present invention has one end connected to the conduit from the condenser outlet to the pressure reducer outlet, and the other end from the evaporator outlet. A bypass circuit connected to the pipeline leading to the compressor inlet was provided, and an auxiliary decompressor and refrigerant temperature detecting means were provided in this bypass circuit in order from the upstream side, and the refrigerant temperature was detected by the refrigerant temperature detecting means and used. By having a saturated vapor temperature correction means for adding a predetermined value depending on the type of refrigerant and its composition ratio to the refrigerant temperature, in a refrigeration cycle using a non-azeotropic mixed refrigerant, without complicating the structure of the refrigeration cycle. The saturated vapor temperature of the refrigerant sucked into the compressor can be easily obtained, and thus optimal refrigeration cycle control can be realized.

Further, a plurality of refrigerant temperature detecting means is provided in a pipeline extending from the evaporator inlet to the outlet, and the saturated vapor of the refrigerant sucked into the compressor by using the plurality of refrigerant temperatures detected by the refrigerant temperature detecting means. By having the saturated vapor temperature calculating means for calculating the temperature, in the refrigeration cycle using the non-azeotropic mixed refrigerant, the saturated vapor temperature of the compressor suction refrigerant can be easily obtained without providing a bypass circuit. It is possible to realize optimal refrigeration cycle control.

Further, a plurality of refrigerant temperature detecting means are provided in the pipeline extending from the evaporator inlet to the outlet, and the refrigerant sucked into the compressor is saturated using the plurality of refrigerant temperatures detected by the refrigerant temperature detecting means. By having a saturated vapor temperature calculating means for calculating the vapor temperature and a saturated vapor temperature correcting means for correcting the saturated vapor temperature calculated by the saturated vapor temperature calculating means, in the refrigeration cycle using the non-azeotropic mixed refrigerant, the bypass The saturated vapor temperature of the refrigerant sucked into the compressor can be easily and accurately obtained without providing a circuit, and thus optimal refrigeration cycle control can be realized.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle diagram in a first embodiment of a saturated vapor temperature detection circuit of the present invention.

FIG. 2 is a refrigeration cycle diagram in a second embodiment of the saturated vapor temperature detection circuit of the present invention.

FIG. 3 is a characteristic diagram showing a change in refrigerant temperature in the evaporator in the example.

FIG. 4 is a refrigeration cycle diagram in a third embodiment of the saturated vapor temperature detection circuit of the present invention.

FIG. 5 is a refrigeration cycle diagram of a conventional saturated vapor temperature detection circuit.

FIG. 6 is a refrigeration cycle diagram on the Ph diagram in the saturated vapor temperature detection circuit.

FIG. 7 is a relationship diagram between the superheat amount and the valve opening change amount of the electric expansion valve.

FIG. 8 is a refrigeration cycle diagram on the Ph diagram when a non-azeotropic mixed refrigerant is used in a conventional saturated vapor temperature detection circuit.

[Explanation of symbols]

 1 Compressor 2 Condenser 3 Electric expansion valve (pressure reducer) 4 Evaporator 5 Bypass circuit 6 Auxiliary throttle (auxiliary pressure reducer) 7 Temperature sensor (refrigerant temperature detecting means) 9 Saturated steam temperature correction circuit (saturated steam temperature correction means) 12 temperature sensor (first refrigerant temperature detecting means) 13 temperature sensor (second refrigerant temperature detecting means) 14 saturated steam temperature calculation circuit (saturated steam temperature calculation means) 15 saturated steam temperature correction circuit (saturated steam temperature correction means)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshinori Kobayashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A non-azeotropic mixed refrigerant in which two or more kinds of refrigerants having different boiling points are mixed at a predetermined ratio is used as a refrigerant, and a compressor, a condenser, a pressure reducer, and an evaporator are sequentially connected in an annular shape by pipes. A refrigerant circuit is constructed by connecting one end to the pipeline from the condenser outlet to the decompressor outlet, and the other end is connected to the pipeline from the evaporator outlet to the compressor inlet. Auxiliary pressure reducer and refrigerant temperature detection means are provided in order from the upstream side in the circuit, the refrigerant temperature is detected by the refrigerant temperature detection means, and a predetermined value according to the type of refrigerant used and its composition ratio is added to the refrigerant temperature. A saturated steam temperature detecting device for a refrigeration cycle, which has a steam temperature correcting means. 2. A non-azeotropic mixed refrigerant in which two or more kinds of refrigerants having different boiling points are mixed at a predetermined ratio is used as a refrigerant, and a compressor, a condenser, a decompressor, and an evaporator are sequentially connected in an annular shape by pipes. A refrigerant circuit, and a plurality of refrigerant temperature detecting means are provided in a pipeline from the evaporator inlet to the outlet, and the refrigerant is sucked into the compressor using the plurality of refrigerant temperatures detected by the refrigerant temperature detecting means. A saturated vapor temperature detection device for a refrigeration cycle, comprising saturated vapor temperature calculation means for calculating the saturated vapor temperature of a refrigerant. 3. A non-azeotropic mixed refrigerant in which two or more kinds of refrigerants having different boiling points are mixed at a predetermined ratio is used as a refrigerant, and a compressor, a condenser, a decompressor, and an evaporator are sequentially connected by a pipe in an annular shape. A refrigerant circuit, and a plurality of refrigerant temperature detecting means are provided in a pipeline from the evaporator inlet to the outlet, and the refrigerant is sucked into the compressor using the plurality of refrigerant temperatures detected by the refrigerant temperature detecting means. A saturated steam temperature detecting device for a refrigeration cycle, which has a saturated steam temperature calculating means for calculating a saturated steam temperature of a refrigerant and a saturated steam temperature correcting means for correcting the saturated steam temperature calculated by the saturated steam temperature calculating means. 4. A first refrigerant temperature detecting means is provided near an inlet of a pipeline extending from an inlet of the evaporator to an outlet thereof, and a second refrigerant temperature detecting means is provided near an intermediate portion of the evaporator, and the following equation is used in the saturated vapor temperature calculating means. The saturated vapor temperature detection device of the refrigeration cycle according to claim 2 or 3, wherein the saturated vapor temperature is calculated using the saturated vapor temperature. TS = T3 + (T4−T3) × 2 where T3 represents the temperature detected by the first refrigerant temperature detecting means, T4 represents the temperature detected by the second refrigerant temperature detecting means, and TS represents the saturated vapor temperature. 5. The saturated steam temperature detecting device for a refrigeration cycle according to claim 3, wherein the saturated steam temperature correcting means corrects the saturated steam temperature calculated by the saturated steam temperature calculating means by subtracting a predetermined value from the saturated steam temperature.