JPS5935757A - Method and device for controlling flow rate of refrigerant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling the flow rate of a refrigerant, characterized in that the flow rate of the refrigerant is constantly adjusted in response to disturbances such as refrigerant load fluctuations and refrigerant pressure fluctuations.

Conventionally, thermostatic automatic expansion valves have been mainly used to control the flow rate of refrigerant in refrigeration systems that use dry evaporators. This temperature-type automatic expansion valve maintains the refrigerant gas temperature at the evaporator outlet at a superheat temperature of 3 to 7'C above the evaporation temperature, and detects this temperature with a thermosensor installed several times on the evaporation outlet side. , the pressure of the gas sealed inside the temperature-sensing cylinder fluctuates, and this gas pressure change is guided to the diaphragm surface of the valve body through the capillary tube, and the guiaphragm is distorted by the pressure change, opening and closing the valve, thereby supplying refrigerant to the evaporator. It is configured to control the flow rate of This temperature-type automatic expansion valve should be able to follow load fluctuations in terms of capacity and time if the refrigerant load fluctuations and evaporator capacity match, but in reality, refrigerant evaporation in the evaporator process, the mechanical (1i
Currently, there are various factors such as construction, compressor capacity control, etc. that cannot be achieved, and it is impossible to obtain a perfect one.
Due to the constraints of the mechanical structure of the IJ expansion valve, the capacity can only be controlled within ±30% of the set value, so it is difficult to respond to any load fluctuations on the evaporator, and it becomes a problem. . In addition, the pressure difference between the high pressure and the low pressure after the expansion valve 11 (I) affects the flow of the refrigerant liquid, and the control range of the expansion valve is limited as described above.
There is a drawback that the amount of refrigerant liquid supplied may be too large or too small beyond the control range. As a result, an excess supply of refrigerant will cause a liquid buildup in the compressor, which may cause a malfunction. An insufficient supply of refrigerant will lead to a lack of refrigeration capacity, consuming more power than necessary, and meeting the requirements for energy conservation. Doesn't match. For this reason, expansion valves for high temperature, medium temperature, and low temperature are inserted in parallel in the refrigeration cycle, and each expansion valve is artificially adjusted to A according to the outside temperature to cope with the limited capacity range. In ships, each expansion valve must be adjusted depending on the temperature of the seawater in the sea area in which it is sailing, and in land equipment, in summer and winter, etc., and IL control cannot be achieved by manual adjustment. Furthermore, since the valve is opened and closed depending on the strain rate of the diaphragm, the control amount becomes wave-like, and the range of ±0.25 to 0.25 is required for temperature control of fruits and vegetables.
Accurate control to obtain strict temperature accuracy such as 5℃ is impossible, and damage and permanent distortion of the Guiaflame occur.
There are various drawbacks such as capacity control not working properly.

In the present invention, the evaporation temperature and the suction superheat temperature are directly detected with a temperature measuring element, the detected values are input into an electronic circuit, converted into an electric signal, the difference is calculated, and the output and temperature controller are The flow rate control valve is operated so that the set values are the same, and the refrigerant flow rate is fully controlled, so it can always respond to disturbances such as load fluctuations and pressure fluctuations automatically in terms of capacity and time. This does not require any manual adjustment as in the past.

In this case, the flow rate control valve (which may be either electric or pneumatic) functions as an electronic thermostatic expansion valve.

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

2 is an evaporator, and 2 is a temperature measuring element such as a thermocouple, which is attached to the inlet side of the evaporator 10 to measure the evaporation temperature of the refrigerant liquid. Reference numeral 3 denotes a temperature measuring element similar to the above, which is attached to the outlet of the evaporator 1 to measure the superheating temperature of the refrigerant gas sucked into the compressor. Reference numeral 4 denotes a converter, which extracts the resistance change of the thermocouples, etc. of the temperature sensors 2 and 3 as an electrical signal.
The terminals are connected to converters 4a and 4b on each side, respectively. Reference numeral 5 denotes an arithmetic unit for calculating the difference between the output electric signals from the converters 4a and 4b, which utilizes the arithmetic function of a known adder/subtractor or computer. Reference numeral 6 denotes a known electronic temperature controller having PID (proportional, integral, differential) control operation, and the output of the difference between the evaporation temperature and the suction superheating temperature from the computing unit 5 is connected to an input terminal.

This is a 7 piece flow control valve that serves a purpose at the inlet of evaporator 1.
It may be either an electric type or a pneumatic type, and the operation output terminal of the temperature controller 6 is connected to the drive circuit 8.

Here, FIG. 2 shows an example of application when the resistance loss inside the evaporator 1 is small, and FIG. 3 shows an example of application when the resistance loss inside the evaporator 1 is large. In the figure, the refrigerant gas temperature at the outlet of the evaporator 1 is compared with the evaporation temperature, and in order to obtain a superheating temperature (6 to 8°C) similar to the embodiment shown in FIG. It is attached to the middle part between the outlet and the inlet.

When using the present invention, the temperature measuring element 2 measures the evaporation temperature.
The temperature measuring element 3 directly detects the suction overheating temperature, and each detected value is input to the converters 4a and 4b to convert it into an electric signal, and each output is added or subtracted. □Use the calculation function of a calculator or computer. The difference is calculated by the calculation unit 5, which takes out the value as an electric signal, and the operation signal from the temperature controller 6 is used to drive the refrigerant flow rate control valve 7 until the value matches the value set in advance by the temperature controller 6. Since the refrigerant flow rate is adjusted and controlled by the Katsura νJ circuit 8, the superheating temperature difference is constantly measured and calculated, so the capacity can be adjusted automatically in response to disturbances such as load fluctuations and pressure fluctuations without any manual adjustment. : It can be followed both in terms of target and time.

With the above, the conventional temperature type mortar! The characteristics of the present invention with respect to the performance standards of the IJ1 expansion valve are that (1) there is no mechanical component interposed between the valves, and since it is an electronic type, the temperature-sensing response speed is very fast; In the formula 71 taste controller, the proportional operation band can be changed freely, and the capacity (range ability) of the flow rate control valve can be controlled within the capacity range of 3 to 100, and the proportional operation band is wide. (3) In the conventional type, the diaphragm operated by gas pressure may be damaged or permanently deformed, and the capacity control 111 may not operate normally, but the flow control valve of the present invention is a direct acting type or pneumatic type and is powerful. (4) According to experiments, it operates perfectly in the range of +10'C to -70'C, and has a wide operating temperature range; (5) The present invention is an electronic Since it is operated using the arithmetic function of a computer, it is possible to achieve accuracy several steps higher than conventional methods, and the superheating temperature remains constant within the operating temperature range.

[Brief explanation of drawings]

The attached figures show an example of implementing the present invention, and Fig. 1 is a block diagram showing the wiring of the device of the present invention, and Fig. 2 is a schematic diagram showing an example of application when resistance loss in the evaporator is small. The explanatory diagram, FIG. 3, is a schematic explanatory diagram showing an example of application when the resistance loss within the evaporator is large. 1... Evaporator, 2, 3... Temperature measuring element, 4.4a, 4b
...Converter, 5...Arithmetic unit, 6...Temperature controller,
7...Flow control valve, 8...Drive circuit. Applicant: Nisshin Gyogyo Co., Ltd.

Claims (1)

[Claims] 1. Directly detect the evaporation temperature and suction superheating temperature of the refrigerant, convert the detected values into electrical signals, calculate them, and compare them with the set value of the temperature controller to control the flow rate control valve. A refrigerant flow rate control method characterized in that the refrigerant flow rate control method operates. 2. Temperature measuring elements are installed at the inlet and outlet of the evaporator to measure the evaporation temperature and suction superheating temperature, respectively, and a converter is installed in each temperature measuring element and converts the detected value from the temperature measuring element into an electrical signal. connecting each converter to a computing unit, the output of the computing unit to a temperature controller, and the operating output of the temperature controller to a flow control valve installed at the inlet of the evaporator; Refrigerant flow measurement 1 characterized in that a flow control valve is operated so that the output value of the computing unit and the set value of the temperature controller are equal.
ii11 device.