JPH0828975A - Turbo refrigerator - Google Patents

Abstract

PURPOSE:To execute an operation with a minimum bypass quantity of hot gas and to conduct the operation at optimum thermal efficiency by detecting the ratio between a condensation pressure and an evaporation pressure and also by controlling the respective openings of an inlet vane and a hot gas bypass control valve on the basis of the result of the detection. CONSTITUTION:Refrigerant vapor generated in an evaporator 1 is compressed to be superheated vapor of high pressure by a turbo compressor 2 and this vapor is cooled down to be a liquid by a condenser 3. The liquid of high pressure is subjected to pressure reduction in an expansion valve 4, the temperature is lowered and the refrigerant of low pressure and low temperature is evaporated to be vapor of low pressure in the evaporator 1 and returned to the turbo compressor 2 again. When the inlet temperature of cooling water in the condenser 3 changes, a condensation pressure changes and also a compression ratio of the turbo compressor 2 changes. In this case, pressure transmitters 9A and 9B are attached to the condenser 3 and the evaporator 1 respectively and the respective pressure transmission signals thereof are made compression ratio signals by an arithmetic unit 10, while an inlet vane 12 and a bypass control valve 6 are controlled when a detected temperature of a temperature sensor 13 lowers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo refrigerator in which a minimum amount of hot bypass operation is performed according to cooling water conditions and refrigerator load.

[0002]

2. Description of the Related Art FIG. 3 is a system diagram of a conventional turbo refrigerator. In the figure, 1 is an evaporator, 2 is a turbo compressor, 3 is a condenser, 4 is an expansion valve, and these are connected by a refrigerant pipe. Reference numeral 12 is a suction vane of the turbo compressor 2. Reference numeral 7 is a cooling target place, where a refrigerating load is generated. A brine circulation circuit is provided between the cooling target location 7 and the evaporator 1. Reference numeral 8 is a brine pump provided on the circulation circuit. Reference numeral 5 is a hot gas bypass pipe that connects the condenser 3 and the evaporator 1 to each other, and 6 is a bypass control valve provided on the bypass pipe. Reference numeral 13 is a temperature sensor provided on the outlet side of the evaporator 1 in the brine circulation circuit, and 14 is a controller connected to the temperature sensor, for controlling the suction vane 12 and the bypass control valve 6 of the turbo compressor. belongs to.

In the above system, the refrigerant vapor generated from the evaporator 1 is compressed by the turbo compressor 2 to become high-pressure superheated vapor, and the condenser 3 removes heat from the cooling water to become a liquid. When the pressure of this high-pressure liquid is reduced by the expansion valve 4, the temperature drops. When this low-pressure low-temperature refrigerant is evaporated in the evaporator 1, the heat of evaporation is taken from the surroundings to form low-pressure vapor, which returns to the turbo compressor 2.

The capacity of the turbo compressor 2 is controlled by adjusting the opening degree of the suction vane 12 attached to the compressor. During low load operation of the refrigerator, the amount of evaporative gas in the evaporator is small, and therefore the amount of suction gas in the compressor is naturally small. When the temperature detected by the temperature sensor 13 provided on the brine outlet side of the evaporator 1 is equal to or higher than a predetermined value, the suction vane 12 of the turbo compressor 2 is operated at an opening of 100%. Then, the opening degree of the suction vane 12 is sequentially decreased from 100% via the controller 14, the capacity of the turbo compressor is decreased, and the brine outlet temperature is kept at a predetermined temperature.

The turbo compressor has a peculiar phenomenon called a surging phenomenon, and when the amount of suction gas is less than a certain flow rate, it causes a backflow phenomenon of fluid, which hinders continuous operation. In order to avoid this surging phenomenon and continue the low load operation, a hot gas bypass pipe for bypassing the refrigerant from the condenser to the evaporator is provided. The temperature detected by the temperature sensor further decreases, and the suction vane 1 of the turbo compressor
When the opening degree of 2 becomes equal to or smaller than the predetermined opening degree, the bypass control valve 6 of the hot gas bypass pipe starts to open. The opening degree of the bypass control valve is increased via the controller 14 in conjunction with the decrease in the opening degree of the suction vane 12.

FIG. 4 is a diagram showing the relationship between the conventional intake vane opening and the bypass control valve opening in the above operation. When the detected value of the temperature sensor 13 becomes lower than a predetermined value, the suction vane opening moves from the point A to the point B on the line in FIG. When the suction vane opening reaches the point B and the detected value of the temperature sensor 13 further decreases, the bypass control valve 6 is opened while maintaining the relationship of the line B-C in the figure. When the detected value of the temperature sensor 13 rises, control in the opposite direction is performed. The control for interlocking the two valves is the controller 14
Done by

[0007]

The relationship between the opening degree of the bypass control valve and the opening degree of the suction vane shown in FIG. 4 is that the inlet temperature of the cooling water flowing into the condenser 3 is constant throughout the year.
For example, it was set based on the assumption of 32 ° C.
That is, the relationship in Figure 4 was fixed throughout the year.

However, in reality, the inlet temperature of the cooling water changes depending on the season and load changes. As a result, the operable range of the turbo compressor 2 also changes. FIG. 5 shows the operating characteristics, and shows the relationship between the suction gas amount of the turbo compressor and the compression ratio (= condensing pressure / evaporating pressure) corresponding to various vane openings, and the cooling water in the condenser is shown. The inlet temperature (CW) is listed as a parameter. The surging area is also shown.

Looking at FIG. 5 for each cooling water inlet temperature, (1) At CW = 32 ° C., the amount of suction gas is only Q, and operation cannot be performed due to surging. Therefore, by increasing the suction gas amount by the X amount of hot gas bypass, surging can be avoided and operation can be performed, but the hot gas bypass amount causes a refrigerator loss and the operating efficiency decreases. (2) Also, at CW = 28 ° C, the X ′ amount is CW32 ° C.
Although the amount is smaller than that of, the loss is similar and the operating efficiency is reduced. (3) At CW = 24 ° C., the hot gas bypass is not necessary because it is in the operable range on the right side of the surging range.

Conventionally, the cooling water temperature is assumed to be constant at, for example, CW = 32 ° C. throughout the year, but FIG. 5 shows that such an assumption is unreasonable. The present invention is based on the premise that the cooling water temperature is variable,
Provided is an efficient turbo chiller that controls the valve opening that minimizes the hot gas bypass amount by utilizing the fact that the condensation pressure changes and the compression ratio changes when the cooling water inlet temperature of the condenser changes. Is what you are trying to do.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and is a turbo refrigerating system in which a capacity control operation is performed by controlling an opening of a suction vane of a turbo compressor and an opening of a hot gas bypass control valve. The present invention relates to a turbo refrigerator having the following features. (1) A means for detecting the ratio of the condensation pressure and the evaporation pressure, and a control means for controlling the suction vane opening and the hot gas bypass control valve opening by the output signal from the detection means are provided. (2) In the turbo refrigerator according to the above item (1), the compression ratio detecting means has a condensation pressure detector provided in the condenser, an evaporation pressure detector provided in the evaporator, and a pressure detected by both detectors. Comprising a computing unit that computes and calculates the ratio.

[0012]

[Operation] The cooling water inlet temperature changes depending on the season and load changes. Since the condensing pressure of the condenser changes with the change of the cooling water inlet temperature, the compression ratio, which is the ratio of the condensing pressure to the evaporating pressure, changes. By controlling the opening of the refrigerator suction vane and the opening of the hot gas bypass control valve by this change in the compression ratio, the hot gas bypass amount that matches the cooling water conditions and the refrigeration load, that is, always operates with the minimum hot gas bypass amount. It is possible to continue. Therefore, the most efficient energy-saving operation is achieved.

[0013]

1 is a system diagram of a turbo refrigerator according to an embodiment of the present invention. In the figure, 9A is a pressure transmitter provided in the condenser 3, 9B is a pressure transmitter provided in the evaporator 1, 10 is an arithmetic unit for receiving signals from both pressure transmitters, and calculating a compression ratio, 11 Is a controller that receives the temperature detection signal of the temperature sensor 13 and the compression ratio signal from the arithmetic unit 10 and controls the opening degree of the suction vane 12 of the turbo compressor and the bypass control valve 6 of the hot gas bypass pipe. . The configuration other than the above is the same as the conventional technique. Further, the refrigerating action by the circulation of the refrigerant and the circulation of the brine is the same as that of the conventional technique.

When the inlet temperature of the cooling water sent to the condenser 3 changes due to changes in season and load, the condensing pressure changes.
When the condensing pressure changes, the compression ratio of the turbo compressor 2 changes. In the turbo chiller of the present embodiment, the pressure transmitters 9 are attached to the condenser 3 and the evaporator 1, and the signals of both transmitters are applied to the arithmetic unit 10 to obtain a compression ratio signal, which is input to the controller 11 for control. The output signal of the container 11 causes the suction vane 1 to operate in a low load range, that is, when the temperature detected by the temperature sensor 13 decreases.
2 and the bypass control valve 6 are controlled to continue the operation with the minimum amount of hot gas bypass.

FIG. 2 is a diagram showing the relationship between the opening degrees of the both valves in the low load range. When the temperature detected by the temperature sensor 13 falls below a predetermined value, the suction vane opening is changed from point A to point B in the figure.
The point of decreasing toward the point is the same as in the prior art. When the detected temperature further decreases and the suction vane opening becomes smaller than point B, the correlation between the bypass control valve opening and the suction vane opening is conventionally constant as shown in FIG. In the present invention, as shown in FIG. 2, the relationship between the suction vane opening and the bypass control valve opening changes depending on the condenser inlet cooling water temperature. That is, when the opening of the intake vane is less than the point B, the opening of the bypass control valve is line B-C, line B-
It is designed to be controlled by either the D line, the B-E line, or the like, and which one of the bypass control valve openings is controlled on the selected line is determined by the temperature sensor 13 described above. Determined by the suction vane opening, which is determined by the detected temperature. Therefore, the amount of hot gas bypass can be minimized for efficient operation.

[0016]

In the turbo refrigerator according to the present invention, the suction vane opening and the hot gas bypass control valve opening are controlled by means for detecting the ratio between the condensation pressure and the evaporation pressure, and the output signal from the detection means. Since the control means for controlling is provided, the operation can be performed with the minimum hot gas bypass amount. Therefore, optimal thermal efficiency operation can be performed.

[Brief description of drawings]

FIG. 1 is a system diagram of a turbo refrigerator according to an embodiment of the present invention.

FIG. 2 is a relationship diagram between the intake vane opening and the bypass control valve opening according to the above embodiment.

FIG. 3 is a system diagram of a conventional turbo refrigerator.

FIG. 4 is a relational diagram of a conventional suction vane opening and a bypass control valve opening.

FIG. 5 is a relationship diagram of a suction gas amount and a compression ratio of a turbo compressor.

[Explanation of symbols]

 1 Evaporator 2 Turbo Compressor 3 Condenser 4 Expansion Valve 5 Hot Gas Bypass Pipe 6 Bypass Control Valve 7 Cooling Target Place 8 Brine Pump 9A Pressure Transmitter 9B Pressure Transmitter 10 Computing Unit 11 Controller 12 Suction Vane 13 Temperature Sensor 14 Controller

Claims (2)

[Claims] 1. A turbo chiller which controls a suction vane opening and a hot gas bypass control valve opening of a turbo compressor to perform a capacity control operation, and means for detecting a ratio between a condensation pressure and an evaporation pressure, and A turbo chiller comprising control means for controlling the opening of the suction vane and the opening of the hot gas bypass control valve according to an output signal from the detection means. 2. The calculating means calculates the ratio by calculating the pressures detected by the condensation pressure detector provided in the condenser, the evaporation pressure detector provided in the evaporator, and both detectors. The turbo chiller according to claim 1, wherein the turbo chiller is configured with a refrigerator.