JPH0524417B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a refrigeration system using a refrigeration cycle using a non-azeotropic mixed refrigerant, and more particularly to an improvement of a refrigeration system that can improve the cycle efficiency.

[Conventional technology]

Fig. 4 shows the refrigerant circuit configuration of the conventional refrigeration cycle shown in Japanese Patent Application No. 60-39368. 3 is a pressure reducing device (expansion valve) that reduces the pressure of the refrigerant gas from the condenser 2; 4 is an evaporator that evaporates the refrigerant gas reduced in pressure by the pressure reducing device 3; It is.

By using a non-azeotropic refrigerant mixture tailored to the purpose as the refrigerant gas in such refrigeration equipment, it is possible to achieve lower evaporation temperatures or higher condensation temperatures that could not be obtained with a single refrigerant, as well as improved cycle efficiency. It has been known for a long time that advantages such as reduction can be obtained. In addition, Fig. 5 shows the state changes of the non-azeotropic mixed refrigerant used as a refrigerant in a refrigeration system using the above-mentioned refrigeration cycle on a Mollier diagram. B is the outlet of the compressor 1 and the inlet of the condenser 2, C is the outlet of the condenser 2 and the inlet of the pressure reducing device 3, and D is the outlet of the pressure reducing device 3 and the inlet of the evaporator 4. The azeotropic mixed refrigerant state is shown, and corresponding parts in FIG. 4 are given the same reference numerals. Also, a ₁ −b ₁ , a ₂ −b ₂ , a ₃ −b ₃ , a ₄
−b ₄ indicates the same temperature point in the two-phase region on the Mollier diagram.

[Problem that the invention seeks to solve]

Since the conventional refrigeration system using a non-azeotropic mixed refrigerant is constructed as described above, if the operating conditions of the refrigeration system are constant, an efficient refrigeration cycle as shown in Fig. 5 can be constructed. When the load conditions change, the refrigerant pressure changes and the amount of refrigerant in the condenser and evaporator changes. Therefore, the actual circulation mixture ratio circulating in the refrigeration cycle relative to the charged mixture ratio of the non-azeotropic refrigerant mixture changes. The amount of heat exchanged in the condenser and evaporator also changes, so it is necessary to adjust the refrigerant flow rate from time to time according to each state change, and to do this, it is necessary to adjust the opening of the pressure reducing device. However, since it is a non-azeotropic mixed refrigerant, it is difficult to adjust it as it is, which is a problem.

This invention was made to solve the above problems, and automatically adjusts the opening degree of the pressure reducing device according to changes in the load conditions of the refrigeration equipment to determine the optimal value of the refrigerant flow rate. The purpose is to obtain a refrigeration system using a non-azeotropic mixed refrigerant that can be operated efficiently.

[Means for solving problems]

In the refrigeration system according to the present invention, as a first means, a liquid reservoir is provided in the middle of the piping constituting the refrigeration cycle, and the pressure and temperature of the refrigerant in this liquid reservoir are detected, and the evaporator outlet and the compressor are connected. Detect the pressure and temperature of the refrigerant in the refrigerant piping, determine the circulation mixing ratio from the temperature and pressure in the liquid reservoir, and adjust the temperature at the evaporator outlet to the optimum temperature and pressure at the evaporator outlet determined from this circulation mixing ratio. and the opening degree of the pressure reducing device is adjusted so that the pressures match.

A second method is to detect the temperature of the refrigerant in the refrigerant piping at the inlet, center, and outlet of the evaporator, and detect the temperature difference between the inlet and center of the evaporator and the temperature difference between the center and outlet. The opening degree of the pressure reducing device is adjusted so that the difference between the two is always constant.

[Effect]

In the first means of the present invention, the circulation mixing ratio in the refrigeration cycle is obtained based on the pressure and temperature of the refrigerant in the liquid reservoir, and the refrigerant at the evaporator outlet is determined based on this circulation mixing ratio, which can configure the most efficient refrigeration cycle. The pressure and temperature are calculated, and when the pressure and temperature of the refrigerant at the evaporator outlet differ from the calculated values, the opening degree of the pressure reducing device is adjusted to obtain the optimal refrigerant flow rate. In the second method, the opening degree of the pressure reducing device is adjusted by a controller so that the difference in temperature between the inlet and the center of the evaporator and the difference in temperature between the center and the outlet of the evaporator are always constant. Ru.

〔Example〕

An embodiment of this invention will be described below.
The same parts as in the conventional example are indicated by the same reference numerals, and in FIG. 1, 5 is a liquid reservoir for the non-azeotropic mixed refrigerant used, 6 is a temperature detection element for detecting the temperature of the refrigerant in this liquid reservoir 5, 7 is a pressure detection element for detecting the pressure of the refrigerant in the liquid reservoir 5; 8 is a temperature detection element for detecting the temperature of the refrigerant at the outlet of the evaporator 4; 9 is a pressure detection element for detecting the pressure of the refrigerant at the outlet of the evaporator 4. The detection element 10 is a controller.

Next, the operation of this invention will be explained.
First, in the system shown in FIG. 1, a liquid reservoir 5 is filled with liquid refrigerant of a non-azeotropic mixed refrigerant liquefied in a condenser 2, which flows into a pressure reducing device 3. By the way, the pressure and temperature of the refrigerant in this liquid reservoir 5 are determined by the circulation mixing ratio of the non-azeotropic refrigerant mixture flowing through the refrigeration cycle. That is, according to Raoult's law, for example, the pressure P of a mixed refrigerant of refrigerants R22 and R114 at a certain temperature T°C is the molar fraction ζ ₂₂ of R22, the pure refrigerant pressure P ₂₂ of R22, and the molar ratio of R114. fraction (1-ζ ₂₂ ),
From the pure refrigerant pressure P ₁₁₄ of R114, there is a relationship such that P = ζ ₂₂ P ₂₂ + (1-ζ ₂₂ ) P ₁₁₄ . Therefore, the circulation mixing ratio can be determined by detecting the pressure and temperature of the refrigerant in the liquid reservoir, and for this purpose, the outputs obtained by the temperature detection element 6 and the pressure detection element 7 are sent to the controller 10. send.

On the other hand, the third step is to operate the refrigeration cycle efficiently.
It is necessary to keep the temperature difference between points A and ₃ points b in the figure constant, and when this is large, it means that the evaporation pressure is too low, and the efficiency of the compressor 1 decreases. Furthermore, when the amount is small, the liquid refrigerant in the evaporator 4 does not completely evaporate and flows into the compressor 1, which also reduces efficiency.

When a non-azeotropic refrigerant mixture is used as the refrigerant, the optimum temperature difference between _{the three} points A and b is determined by the circulation mixing ratio (usually 0 to 5°C), and this is the difference between the temperature detection element 6 and the temperature detection element 6. This is obtained by the pressure detection element 7. Therefore, the optimum temperature difference state obtained here is confirmed by the above-mentioned temperature detection element 8 and pressure detection element 9 attached to the outlet of the evaporator 4. When the temperature difference obtained by the temperature detection element 8 and the pressure detection element 9 is small compared to the optimum temperature difference between the _three points A and B, it means that the opening degree of the pressure reducing device 3 is too large. A signal of the optimum throttling amount calculated in the device 10 is sent to the pressure reducing device 3 to reduce the flow rate of refrigerant flowing in the refrigeration cycle.

Furthermore, when the temperature difference is large, a signal opposite to the above case is sent to increase the refrigerant flow rate. Through the control described above, an optimal refrigeration cycle is constructed by adjusting the opening degree of the pressure reducing device 3 in accordance with changes in load.

In the above embodiment, the circulating mixing ratio of the non-azeotropic refrigerant mixture in the refrigeration cycle, which changes depending on the load conditions applied to the refrigeration system, is determined by the pressure of the refrigerant in the liquid reservoir 5 provided upstream of the pressure reducing device 3. The temperature is detected and the opening degree of the pressure reducing device 3 is adjusted by the controller 10 so that the temperature and pressure of the refrigerant at the outlet of the evaporator 4 are appropriate. By detecting the temperature of the refrigerant at three points at the outlet, it is also possible to appropriately adjust the pressure and temperature of the refrigerant at the evaporator outlet.

That is, FIG. 2 shows an example thereof, and in this figure, 11 is a temperature detection element that detects the temperature of the refrigerant at the inlet of the evaporator 4, and 12 is a temperature detection element that detects the temperature of the refrigerant at the inlet of the evaporator 4.
This is a temperature detection element that detects the temperature of the refrigerant at the center of the refrigerant. And T ₈ in Figure 3 is A
T11 is the temperature measured by the temperature detection element 8 at the point D, and _T11 is the temperature measured by the temperature detection element 11 at the point D.
T ₁₂ is the temperature measured by the temperature detection element 12 at the center of the evaporator 4 . Temperature difference between T12 and T11 and temperature at _three points b
Since the temperature difference with T12 is almost equal, the difference between the temperature difference between T8 and T12 and the temperature difference between T12 and T11 is the difference between point A and
b is equal to the temperature difference between _{the three} points.

Therefore, from these measured temperatures (T ₈ −T ₁₂ ) −
By adjusting the opening degree of the pressure reducing device 3 using the controller 10 so that (T ₁₂ −T ₁₁ ) becomes constant,
The temperature difference between points A and _B becomes constant, allowing efficient operation of the refrigeration cycle.

〔Effect of the invention〕

The first aspect of the present invention is configured so that conditions such as the temperature of the refrigerant at the outlet of the evaporator are adjusted by controlling the pressure reducing device based on the circulation mixture ratio, so that the refrigeration cycle can be controlled with high accuracy. This has the effect of enabling efficient operation in response to changes in load conditions. Further, according to the second invention, there is no need to use an expensive pressure detection element, and only an inexpensive temperature detection element can be used, so that the cost of the apparatus can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant circuit diagram showing one embodiment of the refrigeration system of the present invention, FIG. 2 is a similar refrigerant circuit diagram showing another embodiment of the invention, and FIG. FIG. 4 is a refrigerant circuit diagram showing a conventional refrigerant device, and FIG. 5 is a curve diagram showing the state of the refrigerant in the refrigeration device on the Mollier diagram. In the figure, 1 is a compressor, 2 is a condenser, 3 is a pressure reducing device, 4 is an evaporator, 5 is a liquid reservoir, 6, 8, 11 and 12 are temperature detection elements, 7 and 9 are pressure detection elements, 10 indicates a controller. In other figures, the same reference numerals indicate the same parts.

Claims (1)

[Scope of Claims] 1. A refrigeration circuit in which a compressor, a condenser, a pressure reducing device, and an evaporator are sequentially connected by refrigerant piping, in which a non-azeotropic mixed refrigerant is used as a refrigerant, and the above-mentioned condenser and pressure reducing device are used. A liquid reservoir is provided between the refrigerant pipes, and this liquid reservoir is equipped with a temperature detection element and a pressure detection element for detecting the temperature and pressure of the refrigerant inside, and also at the evaporator outlet. A temperature detection element and a pressure detection element are provided to detect the temperature and pressure detection elements, and the values measured by the temperature and pressure detection elements are used to determine the non-azeotropic mixture from the measurement values by the temperature detection element and pressure detection element in the liquid reservoir. Find the refrigerant circulation mixing ratio,
The controller controls the opening degree of the pressure reducing device so that the values measured by the temperature detection element and pressure detection element at the evaporator outlet match the optimal temperature and pressure of the refrigerant at the evaporator outlet determined from this circulation mixing ratio. A refrigeration system characterized in that the opening degree of a pressure reducing device is controlled using the determined output. 2. In a refrigeration circuit in which a compressor, a condenser, a pressure reducing device, and an evaporator are sequentially connected by refrigerant piping, a non-azeotropic mixed refrigerant is used as the refrigerant, and refrigerant piping is provided at the inlet, center, and outlet of the evaporator. Each temperature detection element is provided to detect the temperature of the refrigerant in the evaporator, and the temperature difference between the inlet and center of the evaporator and the temperature difference between the center and outlet are determined from the temperature measurement values obtained by these temperature detection elements. A refrigeration system characterized in that the opening degree of the pressure reducing device is determined by a controller so that the difference in temperature is always constant, and the opening degree of the pressure reducing device is controlled by the output of the controller.