JPH0745980B2 - Refrigeration cycle controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle control device using a non-azeotropic mixed refrigerant.

2. Description of the Related Art A conventional refrigeration cycle using a non-azeotropic mixed refrigerant has been proposed as shown in FIG. 4 in which capacity control and performance improvement are performed by changing the composition of the refrigerant circulating in the refrigeration cycle.

FIG. 4 shows a refrigeration cycle using a non-azeotropic mixed refrigerant,
In the figure, 1 is a compressor, 2 is a condenser, 3 is a first capillary tube, 4 is a rectification column, 5 is an overhead cooler, 6 is a reservoir,
7 is a second capillary tube, 8 is an evaporator,
A non-azeotropic mixed refrigerant is enclosed in the refrigeration cycle. Here, the compressor 1, the condenser 2, the first capillary tube 3, the second capillary tube 7, and the evaporator 8
The circuit configured by is called a main cycle.

Regarding the refrigeration cycle configured as described above,
The operation will be described.

First, the refrigerant circulates through the compressor 1, the condenser 2, the first capillary tube 3, the rectification column 4, the second capillary tube 7 and the evaporator 8, and the condenser 2 radiates heat and the evaporator 8
To absorb heat.

The refrigerant circulating in the cycle is a gas-liquid two-phase refrigerant due to adiabatic expansion when it exits the first capillary tube 3. Of these, the gas phase component rich in low-boiling components rises in the rectification column 4, is cooled and liquefied by the overhead condenser 5, and is stored in the reservoir 6. The liquid overflowing from the reservoir 6 flows down in the rectification tower 4 and comes into contact with the refrigerant vapor rising in the rectification tower 4 to enhance the rectification effect.

In this way, the rectification separation is performed, and the refrigerant rich in low boiling point components can be stored in the reservoir 6.

By the action as described above, the refrigerating cycle is controlled so that the refrigerant concentration of the main cycle is varied and high capacity is obtained when the main cycle is rich in low boiling point components, and low capacity is obtained when the main cycle is rich in high boiling point components. It is a thing.

Problems to be Solved by the Invention In the heat pump device as in the above-mentioned conventional example, although the composition of the refrigerant can be basically changed, it is necessary to determine the amount of the refrigerant vapor to be fed into the rectification column 4. Intermediate pressure (rectification tower 4
Since the resistance values of the first capillary tube 3 and the second capillary tube 7 that set the pressure) were fixed, the amount of refrigerant vapor necessary for rectification separation could not be obtained. That is, if the intermediate pressure (pressure in the rectification column 4) is too high, the refrigerant is not sufficiently decompressed even at the outlet of the first expansion device and does not become a gas-liquid two-phase refrigerant. In some cases, the refrigerant vapor for performing the process cannot be obtained, the refrigerant composition cannot be changed, and the refrigeration cycle capacity cannot be controlled.

Means for Solving Problems The first capillary tube and the second capillary tube that determine the pressure of the rectification column are used as a first electric expansion valve and a second electric expansion valve, respectively, and a first electric expansion valve The valve opening degree of the second electric expansion valve is controlled by the pressure detection means of the rectification tower, the tower bottom temperature detection means, the dew point temperature calculation means, the temperature comparison means, the valve opening calculation means of the electric expansion valve, and the valve opening degree output means. It is provided with a control device for controlling.

Action The present invention has the above-described structure, and the dew point temperature of the non-azeotropic mixed refrigerant at the bottom of the rectification column is obtained by the pressure detection means and the dew point temperature calculation means of the rectification column, and the rectification column is detected by the bottom temperature detection means. The first electric expansion valve and the second electric motor are compared with the bottom temperature by the temperature comparison means and the valve opening calculation means of the electric expansion valve is used in accordance with the output of the temperature comparison means so that the tower bottom temperature does not fall below the dew point temperature. By obtaining the valve opening of the expansion valve and changing the valve opening of the first electric expansion valve and the second electric expansion valve by the output from the valve opening output means, rectification separation is always performed at the bottom of the rectification column. The required refrigerant vapor can be secured.

Embodiment A control apparatus for a refrigeration cycle according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows the structure of the refrigeration cycle. In the figure, 1 is a compressor, 2 is a condenser, 16 is a first electric expansion valve, 4 is a rectification tower, 5 is a top cooler, 6 is a reservoir, 17 is a second electric expansion valve, 8 is an evaporator, 9 is column bottom temperature detecting means,
Reference numeral 10 is a pressure detecting means, and 11 is a control device. The main cycle comprises a compressor 1, a condenser 2, a first electric expansion valve 16, a bottom portion of the rectification column 4, a second electric expansion valve 17, and an evaporator 8 which are sequentially connected in an annular shape. Further, the separation cycle is configured by connecting the rectification tower 4, the overhead condenser 5, and the reservoir 6 in a ring shape.

FIG. 1 is a block diagram of a refrigeration cycle control device 11. In the figure, 10 is pressure detecting means, 9 is temperature detecting means, 12 is dew point temperature calculating means, 13 is temperature comparing means, 14 is valve opening calculating means of the electric expansion valve, and 15 is valve opening outputting means. .

The rectification action of the refrigeration cycle having the above configuration will be described.

First, the high-pressure liquid refrigerant discharged from the condenser 2 is decompressed by the first electric expansion valve 16, becomes a gas-liquid two-phase refrigerant, and flows into the lower part of the rectification column 4. The gas component of the gas-liquid two-phase refrigerant rises in the rectification tower 4, is cooled in the tower top cooler 5 and liquefied, and is stored in the reservoir 6. The liquid overflowing from the reservoir 6 flows back to the upper part of the rectification column 4 and descends in the rectification column 4, and ascends gas and substances, heat exchanges to perform rectification, and the reservoir 6 becomes a low boiling point component. The rich refrigerant is stored, and the refrigerant rich in high-boiling components flows into the main cycle from the lower part of the rectification column 4 through the second electric expansion valve 17.

Next, the operation of the control device 11 will be described with reference to the flowchart of FIG. First, the pressure detecting means 10 detects the pressure in the rectification column 4. In the dew point temperature calculation means 12,
The relationship between the pressure of the non-azeotropic mixed refrigerant used and the temperature of the dew point is set in advance. From the pressure of the rectification column 4,
Get dew point temperature. Next, the tower bottom temperature detecting means 9 detects the temperature at the bottom of the tower, and the temperature comparing means 13 compares the temperature at the bottom of the tower with the dew point temperature. As a result of comparison, when the temperature at the bottom of the tower is less than or equal to the dew point temperature, the valve opening calculation means 14 of the electric expansion valve decreases the valve opening of the first electric expansion valve 16 by ΔP pulses (makes the resistance large). , The opening degree of the second electric expansion valve 17 by Δ
Increase P pulse (reduce resistance). When the temperature at the bottom of the tower is higher than the dew point temperature, the first electric expansion valve 16
The opening degree of the electric expansion valve 17 is not changed.

EFFECTS OF THE INVENTION As described above, according to the present invention, a non-azeotropic mixed refrigerant is enclosed in a circuit in which a compressor, a condenser, a first electric expansion valve, a rectification column, a second electric expansion valve, and an evaporator are annularly connected. In the refrigeration cycle, the dew point temperature of the non-azeotropic mixed refrigerant at the bottom of the rectification column is calculated by the pressure detection means for detecting the pressure of the rectification column and the dew point temperature calculation means, and the rectification column is detected by the column bottom temperature detection means. The bottom opening temperature is compared with the temperature comparison means, and the valve opening calculation means of the electric expansion valve determines the valve opening degrees of the first electric expansion valve and the second electric expansion valve according to the output of the temperature comparison means. By providing a control device of the refrigeration cycle that changes the valve opening of the first electric expansion valve and the second electric expansion valve by the output from the opening output means, the pressure of the rectification tower can be controlled at the bottom of the rectification tower. A reliable refrigerant that can be controlled to always obtain the refrigerant vapor required for rectification separation. The composition can be changed, and the capacity control of the refrigeration cycle can be reliably performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a refrigeration cycle controller in one embodiment of the present invention, FIG. 2 is a flowchart of the refrigeration cycle controller, FIG. 3 is the same refrigeration cycle diagram, and FIG. 4 is a conventional refrigeration cycle. It is a figure. 1 ... Compressor, 2 ... Condenser, 4 ... Fractionation tower, 5 ... Top condenser, 6 ... Reservoir, 8 ... Evaporator, 9 ... Tower bottom temperature detecting means, 10 ... ... Pressure detection means, 12 ... Dew point temperature calculation output means, 13 ... Temperature comparison means, 14 ... Electric expansion valve valve opening calculation means, 15 ... Valve opening output means, 16 ... First electric Expansion valve, 17 …… Second electric expansion valve.

Claims (1)

[Claims] 1. A circuit in which a compressor, a condenser, a first electric expansion valve, a rectification column in which a cooler and a reservoir are annularly connected to the top of a tower, a second electric expansion valve, and an evaporator are annularly connected. A non-azeotropic mixed refrigerant is sealed in the pressure detecting means for detecting the pressure of the rectification column, and the dew point temperature of the non-azeotropic mixed refrigerant at the bottom of the rectification column is determined by the pressure detected by the pressure detecting means. Dew point temperature calculation means, temperature detection means for detecting the temperature of the tower low, temperature comparison for comparing the temperature of the bottom of the rectification column detected by the temperature detection means and the temperature calculated by the dew point temperature calculation means Means, a valve opening degree calculating means for calculating valve opening degrees of the first electric expansion valve and the second electric expansion valve according to the output of the temperature comparing means, and a signal from the valve opening degree calculating means. Of the first electric expansion valve and the second electric expansion valve based on Control apparatus for a refrigeration cycle having a valve opening degree outputting means for outputting a signal for changing the opening.