JPH0566503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a refrigeration system using a non-azeotropic mixed refrigerant.

[Conventional technology]

A conventional refrigeration system using a non-azeotropic mixed refrigerant is disclosed in, for example, Japanese Patent Laid-Open No. 58-210447.

FIG. 7 is a block diagram of a refrigeration cycle when such a non-azeotropic mixed refrigerant is used in a refrigerator-freezer. In the same figure, 1 is a compressor, 2 is a depressor, and 3 is a compressor.
4 is a capillary, 4 is an evaporator for the freezer compartment, and 5 is an evaporator for the refrigerator compartment. These are connected in series through piping to constitute a refrigeration cycle of the refrigerator-freezer.

In the refrigerator-freezer configured as above,
The high-temperature, high-pressure refrigerant gas compressed by the compressor 1 is condensed in a high-pressure state by the condenser 2, and this high-pressure liquefied refrigerant is depressurized while passing through the capillary 3, and is then transferred to the next-stage freezing compartment evaporator 4 and refrigerator. It sequentially flows into the room evaporator 5. The refrigerant gas evaporated by the endothermic action in the two evaporators 4 and 5 returns to the compressor 1, where it is compressed again and sent to the condenser 1.

In such a refrigeration cycle, the refrigerant contains, for example, a low boiling point component of R22 (boiling point -40.75
℃), and the high boiling point component is R114 (boiling point 3.77℃). When a non-azeotropic mixed refrigerant with a boiling point difference of about 44℃ is used, the evaporation process is represented by the symbol 10, as shown in the Molière diagram in Figure 8. As shown in 11, first R22
Since the liquid refrigerant containing a large amount of R114 evaporates, its evaporation temperature is low, and then as the liquid refrigerant containing a large amount of R114 gradually evaporates, its evaporation temperature rises.

In the above evaporation process, the low temperature region 10 is used for the evaporator 4 for the freezer compartment, and the high temperature region 11 is used for the evaporator 5 for the refrigerator compartment. Since the indoor evaporator 4 can be used, and the refrigerator compartment evaporator 4 can be used in the refrigerator compartment at an evaporation temperature suitable for that temperature, the refrigeration effect is improved compared to systems that use a single refrigerant (for example, R12). can.

In the Molière diagram shown in FIG. 8, reference numeral 6 indicates an isothermal line, 7 indicates a compression region, 8 indicates a condensation region, and 9 indicates a reduced pressure region.

[Problem that the invention seeks to solve]

In the conventional refrigeration equipment described above, the above-mentioned effects may be obtained under optimal operating conditions, but in reality, changes in outside temperature and changes in the component ratio of the non-azeotropic refrigerant mixture Because the operating conditions such as these change, the refrigeration cycle cannot maintain optimal operation.

For example, in the refrigeration cycle as mentioned above,
When operating conditions change, if the liquid refrigerant is not completely evaporated in the evaporator and returns to the compressor, the compressor may be damaged. On the other hand, if the liquid refrigerant completely evaporates in the evaporator and returns to the compressor as a large amount of heated steam, the compression performance of the compressor may deteriorate, causing the problem that it will not be possible to maintain optimal operating conditions. Ta.

This invention was made to solve the above-mentioned problems, and allows the refrigeration cycle to always operate optimally even when operating conditions such as changes in the component ratio of the non-azeotropic mixed refrigerant and changes in outside temperature change. The purpose is to obtain a refrigeration system with

[Means for solving problems]

The refrigeration system according to the present invention includes a liquid receiver provided between a condenser and a pressure reducing device, detects the pressure and temperature in the liquid receiver to calculate a component ratio of a non-azeotropic mixed refrigerant, and calculates the component ratio of a non-azeotropic mixed refrigerant. It is equipped with arithmetic control means that calculates the degree of heating of the refrigerant sucked into the compressor based on the pressure and temperature at the outlet of the evaporator, and controls the degree of heating by the degree of opening and closing of the pressure reducing device. .

[Effect]

In this invention, the calculation control means controls the degree of opening and closing of the pressure reducing device so that the degree of heating of the refrigerant to the compressor, which is calculated from the component ratio of the non-azeotropic refrigerant mixture and the pressure and temperature at the outlet of the evaporator, becomes an optimum value. This enables optimal operation of the refrigeration cycle without being affected by changes in operating conditions.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a refrigeration system according to the present invention, in which 1 is a compressor, 2 is a condenser connected to the discharge side of the compressor 1, and 12 is a receiver connected to the outlet side of the condenser 2. 13 is a pressure reducing device connected to the outlet side of the liquid receiver 12 and is capable of adjusting the opening/closing degree; 14 is an evaporator in which the pressure reducing device 13 is connected between the suction side of the compressor 1, and these are connected in series by piping. A refrigeration cycle is constructed by connecting the refrigerant to the refrigeration cycle, and a non-azeotropic mixed refrigerant consisting of a high boiling point component R114 and a boiling point component R22, for example, is sealed in the refrigeration cycle.

The liquid receiver 12 has a saturation pressure of its internal refrigerant.
Pressure detector 15 that detects P ₁ and its saturation temperature
Temperature detectors 16 for detecting T ₁ are each provided, and detection signals from these detectors 15 and 16 are input to an arithmetic control circuit 17 .

Further, at the outlet of the evaporator 14, there is a pressure sensor 1 for detecting the pressure _P2 of the refrigerant sucked into the compressor.
8 and a temperature detector 19 for detecting temperature T ₂ are provided, and detection signals from these detectors 18 and 19 are input to an arithmetic control circuit 17 .

The arithmetic control circuit 17 has a function of calculating the component ratio η of the non-azeotropic mixed refrigerant based on the saturation pressure P ₁ and saturation temperature T ₁ from the detectors 15 and 16, and the function of calculating the component ratio η of the non-azeotropic mixed refrigerant and the refrigerant component ratio η and the detector 18. , 19 and the function of calculating the heating degree S/H of the refrigerant sucked into the compressor 1 based on the pressure P ₂ and temperature T ₂ from the compressor 1, and opening and closing of the pressure reducing device 13 so that the calculated heating degree becomes the optimum value. and an arithmetic control circuit 17
A control output signal from the pressure reducing device 13 is supplied to a driver 20 for adjusting the opening/closing degree of the pressure reducing device 13.

Next, the operation of this embodiment configured as described above will be explained.

The high-temperature, high-pressure refrigerant gas compressed by the compressor 1 is condensed in a high-pressure state by the condenser 2, and this high-pressure liquefied refrigerant flows into the receiver 12. The refrigerant flowing into the liquid receiver 12 is further reduced in pressure by a pressure reducing device 13, and then enters the evaporator 14, and the refrigerant gas evaporated due to its endothermic action returns to the compressor 1, completing the cycle.

Next, the operation of the arithmetic control circuit 17 will be explained based on the flowchart shown in FIG.

In the above cycle, the refrigerant in the liquid receiver 12 becomes a saturated liquid due to the action of the liquid receiver 12, so that the pressure P ₁ and the temperature T ₁ in the liquid receiver 12 become the saturated pressure and the saturated temperature, respectively.

When the operation of the arithmetic control circuit 17 is started, first, in step _S1 , the respective detectors 15, 1
The saturation pressure of the refrigerant in the liquid receiver 12 detected at 6
P ₁ and saturation temperature T ₁ are input into the arithmetic control circuit 17, and based on the detected pressure P ₁ and detected temperature T ₁ , the component ratio η (weight fraction of low boiling point component or high boiling point component) of the non-azeotropic mixed refrigerant is determined. is calculated from equation (1) (step S2).

η=F(P ₁ · T ₁ ) ...(1) However, F: Constant In the next step S3, the pressure P ₂ and temperature T ₂ of the refrigerant at the evaporator outlet detected by the detectors 18 and 19 are determined.
is taken into the arithmetic control circuit 17 and the next step
Proceeding to S4, the saturation temperature T _E is calculated using η and P ₂ . That is, in the arithmetic control circuit 17, the above
By executing equation (2) based on the component ratio η calculated using equation (1) and pressure P ₂ , the saturation temperature T _E of the non-azeotropic mixed refrigerant at pressure P ₂ is calculated.

T _E = G (P ₂ · η) ...(2) However, G: Constant Then, in the next step S5, T _E obtained from the above equation (2) and the evaporator outlet detected by the detector 19 are The heating degree S·H (difference between T ₂ and T _E ) of the non-azeotropic mixed refrigerant sucked into the compressor 1 is calculated using the temperature T ₂ .

Generally, there is a relationship shown in Figure 3 between the refrigeration capacity and COP (coefficient of performance) of the refrigeration cycle and the suction refrigerant heating degree S/H of the compressor 1, and at a certain heating degree,
Refrigeration capacity and COP are maximized.

Therefore, it is determined in step S6 whether the heating degree determined by the above equation (2) is the optimum value that maximizes the refrigeration capacity and COP of the refrigeration cycle. If it is determined that the value is the optimum value, the process moves to the end step, and if it is determined that the value is not the optimum value, the process proceeds to step S7.
Then, processing for changing the opening/closing degree of the pressure reducing device 13 is executed.

That is, a control command is sent from the arithmetic control circuit 17 to the driver 20, and the driver 20 is operated to adjust the opening/closing degree of the pressure reducing device 13 so that the heating degrees S and H become optimum values.

By repeating the above operations, the refrigeration cycle can be operated optimally even if the operating conditions change.

Note that FIG. 4 is a characteristic diagram showing the relationship between the refrigerant saturation temperature and the low boiling point component weight fraction η, and
The figure is a characteristic diagram showing the relationship between refrigerant saturation temperature and R22 weight fraction in steam.

FIG. 6 shows another embodiment of the refrigeration system of the present invention.

In the figure, the same symbols as in Fig. 1 represent the same parts, and the points that differ from Fig. 1 are the condenser 2 and the liquid receiver 1.
2, where a capillary 21 is provided.

The reason for providing the capillary 21 is to prevent the pressure P ₁ and temperature T ₁ in the liquid receiver 12 from reaching the saturated pressure and saturated temperature, respectively, when the refrigerant at the outlet of the condenser 2 becomes a complete liquid due to supercooling. By reducing the pressure of the liquid refrigerant from the condenser 2 in the capillary 21, saturated liquid flows into the liquid receiver 12. Therefore, even if the refrigerant is a complete liquid that has been supercooled in the condenser 2, the pressure inside the liquid receiver 12
P ₁ and temperature T ₁ become the saturation pressure and saturation temperature, respectively, and the optimal operation of the refrigeration cycle becomes possible as in FIG. 1.

〔Effect of the invention〕

As described above, according to the present invention, the opening/closing degree of the pressure reducing device is controlled so that the degree of suction heating of the compressor becomes an optimal value. There is an effect that the refrigeration cycle can always be operated optimally even if operating conditions change due to changes in outside air temperature, etc.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a refrigeration system according to the present invention, Fig. 2 is a flowchart for explaining the operation of the invention, Fig. 3 is a diagram showing the relationship between heating degree, refrigerating capacity, and COP. Figures 4 and 5 are diagrams showing the relationship between refrigerant saturation temperature and component weight percentage, Figure 6 is a circuit diagram showing another embodiment of the refrigeration system of the present invention, and Figure 7 is a circuit diagram of a conventional refrigeration system. figure,
FIG. 8 is a Moliere diagram of a non-azeotropic refrigerant mixture. 1... Compressor, 2... Condenser, 12... Liquid receiver, 13... Pressure reducing device, 14... Evaporator, 15,
18...pressure detector, 16, 19...temperature detector, 17...arithmetic control circuit, 21...capillary. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected in sequence, and a non-azeotropic mixed refrigerant consisting of a low-boiling point component and a high-boiling point component is used as a refrigerant,
A liquid receiver is provided between the condenser and the pressure reducing device, and a detector is provided to detect the saturation pressure and the saturation temperature in the liquid receiver, respectively, and the refrigerant pressure and temperature at the outlet of the evaporator are respectively detected. A detector is provided, and the component ratio of the non-azeotropic mixed refrigerant is calculated based on the saturation pressure and saturation temperature in the receiver detected by the detector, and the component ratio and the evaporation detected by the detector are calculated. A refrigeration system comprising arithmetic control means for calculating the degree of heating of the refrigerant sucked into the compressor based on the pressure and temperature at the outlet of the compressor, and controlling the magnitude of the degree of superheating by the opening/closing degree of the pressure reducing device. 2. The refrigeration system according to claim 1, wherein the refrigerant inlet of the liquid receiver is equipped with a capillary.