JPH0745981B2 - 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. 6 in which capacity control and performance improvement are performed by varying the composition of the refrigerant circulating in the refrigeration cycle.

FIG. 6 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 absorbs heat. Do.

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 refrigeration cycle as in the above-mentioned conventional example, although the refrigerant composition can be basically changed, it is necessary to determine the amount of refrigerant vapor to be fed into the rectification column 4. First to set intermediate pressure
Since the resistance values of the capillary tube 3 and the second capillary tube 7 were fixed, it was difficult to obtain the optimum amount of the refrigerant vapor for the rectification separation when the state of the refrigeration cycle changed. That is, if the amount of the refrigerant vapor is too small, the rectification separation action in the rectification column 4 is deteriorated, and if the amount of the refrigerant vapor is too large, the cooling capacity of the top cooler 5 is insufficient and the inside of the reservoir 6 As a result, the refrigerant could not be stored as a liquid refrigerant, the refrigerant composition could not be changed sufficiently, and the control range of the refrigeration cycle was also narrowed.

Means for Solving the Problems In order to solve the above problems, the present invention provides a control device in which the first capillary tube and the second capillary tube are a first electric expansion valve and a second electric expansion valve, respectively. As the column bottom temperature detecting means, the tower top temperature detecting means, the temperature difference calculating means, the temperature difference setting means, the temperature difference comparing means, the valve opening calculating means of the electric expansion valve, and the valve opening output means.

Operation According to the present invention, with the above-described configuration, the tower bottom temperature detecting means and the tower top temperature detecting means detect the tower bottom temperature and the tower top temperature, and the temperature difference comparing means obtains the temperature difference between the tower bottom temperature and the tower top temperature.
This temperature difference can be divided into three cases depending on the state of the rectification column. If the temperature difference is small, the refrigerant vapor rising in the rectification tower is too large for the cooling amount of the overhead condenser, and the liquid refrigerant cannot be stored in the reservoir, and composition separation cannot be performed. Is rapidly increased, there is no refrigerant vapor rising in the rectification tower and the refrigerant at the tower top is cooled in the tower cooler to become a supercooled liquid and composition separation is not possible, and the temperature difference is When gradually increasing, there is an appropriate refrigerant vapor in the rectification column, and the rectification action is performed, and the tower top temperature and the tower bottom temperature are respectively changed by the change of the refrigerant composition in the rectification tower. It is a state where the saturation temperature of the refrigerant composition at the tower top and the tower bottom is reached. The first temperature difference and the second temperature difference are set by the temperature difference setting means in order to discriminate the states in the above three rectification columns, and the first temperature difference, the second temperature difference and the tower top temperature are set. The temperature difference of the tower bottom temperature is compared by the temperature difference comparison means, the valve opening degree is calculated by the electric expansion valve opening degree calculation means according to the result, and the valve opening degree output means outputs the valve opening degree to the first electric expansion valve. By controlling the second electric expansion valve, the temperature difference between the tower top temperature and the tower bottom temperature can be stabilized between the first temperature difference and the second temperature difference set by the temperature difference setting means. In addition, a proper amount of refrigerant vapor can be always obtained for rectification separation, and good separation performance can be obtained.

Embodiment An embodiment of the control device for the refrigeration cycle according to the present invention will be described with reference to the drawings. FIG. 5 shows a refrigeration cycle. In the figure, 1 is a compressor, 2 is a condenser, 17 is a first electric expansion valve, 4 is a rectification tower, 5 is a top cooler, 6 is a reservoir, 18 is a second electric expansion valve, 8 Is an evaporator, 9 is a bottom temperature detecting means, 10 is a top temperature detecting means, 11
Is a control device. The main cycle comprises a compressor 1, a condenser 2, a first electric expansion valve 17, a bottom portion of the rectification column 4, a second electric expansion valve 18, and an evaporator 8 which are sequentially connected in an annular shape. The separation cycle is constituted by connecting the rectification tower 4, the top cooler 5, and the reservoir 6 in a ring shape.

FIG. 1 is a block diagram of the control device 11. In the figure, 9 is a tower bottom temperature detecting means, 10 is a tower top temperature detecting means, 12 is a temperature difference calculating means, 13 is a temperature difference setting means, 14 is a temperature difference comparing means, and 15 is a valve opening degree calculation of the electric expansion valve. Means, 16 is a valve opening output 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 17, 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 from the lower part of the rectification column 4 into the main cycle through the second electric expansion valve 18.

Next, the operation of the control device 11 will be described.

FIG. 4 shows the state of the refrigeration cycle shown on the Mollier diagram. The pressure of the rectification column 4 is in the range of a, b, or c.

FIG. 3 shows the relationship between the operating time t and the tower top temperature Tt for the pressure ranges a, b and c of the rectification tower 4. When the pressure of the rectification column 4 is in the range of a, the amount of the refrigerant vapor is too large and the cooling amount of the top condenser 5 is insufficient, so that the liquid refrigerant cannot be stored in the reservoir 6 and the composition separation is performed. Since the rectification column 4 is in the gas-liquid two-phase state with the same refrigerant composition, the temperature difference between the column bottom and the column top is small. When the pressure of the rectification column 4 is in the range of b, the amount of the refrigerant vapor is appropriate, the rectification action is performed, and the temperature difference between the bottom and the top of the column is the refrigerant composition of the bottom and the top of the column. The saturation temperature is reached. When the pressure of the rectification column 4 is in the range of c, there is no refrigerant vapor in the rectification column 4 and the whole region becomes liquid refrigerant, and the top of the column is rapidly cooled by the top cooler 5 and becomes supercooled liquid. No rectification is performed. In order to determine the above three cases, the temperature difference setting means 13
The temperature difference ΔT ₁ and the second temperature difference ΔT ₂ are set.

FIG. 2 is a flowchart of the control device 11. First, the tower bottom temperature T _B is detected by the tower bottom temperature detection means 9, the tower top temperature Tt is detected by the tower top temperature detection means 10, and the temperature difference calculation means 12 (T _B −Tt).
Ask for. Next, the temperature difference setting means 13 causes the temperature differences ΔT ₁ and ΔT ₂
(However, ΔT ₁ <ΔT ₂ ) is set and the temperature difference comparison means 14 sets (T _B
-Tt) is compared with ΔT ₁ and ΔT ₂ in magnitude. (T _B −Tt)
When ≦ ΔT ₁ , it is determined that the pressure of the rectification column 4 is in the range a, and the valve opening of the first electric expansion valve 17 is increased by ΔP pulses,
The valve opening degree of the second electric expansion valve 18 is decreased by ΔP pulses.

When ΔT ₁ <(T _B −Tt) <ΔT ₂ , the pressure in the rectification column 4 is b
Therefore, the valve opening degree of both the first electric expansion valve 17 and the second electric expansion valve 18 is not changed. (T _B −Tt)
When ≧ ΔT ₂ , it is determined that the pressure of the rectification column 4 is in the range of c, the valve opening degree of the first electric expansion valve 17 is decreased by ΔP pulses, and the valve opening degree of the second electric expansion valve 18 is decreased. Is increased by ΔP pulses. By the above control, the pressure of the rectification column 4 can be always stabilized within the range of b.

EFFECTS OF THE INVENTION The refrigeration cycle control device according to the present invention is a non-azeotropic mixture 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. Enclose the refrigerant,
The difference between the temperatures detected by the tower top temperature detection means and the tower top temperature detection means is obtained by the temperature difference calculation means, and the output of the temperature calculation means and the first temperature difference preset by the temperature difference setting means, the second
Of the first electric expansion valve and the second electric expansion valve of the electric expansion valve by the output of the temperature difference comparison means. Calculate,
Output from the valve opening output means to control the pressure in the rectification column within a range where rectification can be performed, thereby realizing a refrigeration cycle that always performs a rectification even if the state of the refrigeration cycle changes. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram of a refrigeration cycle control device according to an embodiment of the present invention, FIG. 2 is a flowchart of the refrigeration cycle control device, and FIG. 3 is a time change characteristic diagram of the top temperature of the refrigeration cycle, FIG. 4 is a state diagram on the Mollier diagram of the refrigeration cycle, FIG. 5 is the refrigeration cycle diagram, and FIG. 6 is a refrigeration cycle diagram of a conventional example. 1 ... Compressor, 2 ... Condenser, 4 ... Fractionation tower, 5 ... Tower cooler, 6 ... Reservoir, 8 ... Evaporator, 12 ... Temperature difference calculation means, 13 ... ... Temperature difference setting means, 14 ... Temperature difference comparison means, 15 ... Electric expansion valve valve opening calculation means, 16 ... valve opening output means, 17 ... first electric expansion valve, 18 ... first 2 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 filled in the temperature difference calculating means for obtaining a difference between the temperature detected by the tower low temperature detecting means and the tower top temperature detecting means, and the output of the temperature difference calculating means and the temperature difference setting means are preset. The temperature difference comparing means for comparing the magnitude of the first temperature difference and the second temperature difference, and the output of the temperature difference comparing means between the first electric expansion valve and the second electric expansion valve. A refrigeration cycle control device comprising valve opening calculation means for calculating a valve opening and valve opening output means for outputting a signal from the valve opening calculation means to each electric expansion valve.