Low-temperature environment screw refrigerating unit and starting method thereof

Abstract

The invention provides a low-temperature environment screw refrigerating unit. The low-temperature environment screw refrigerating unit comprises a screw compressor, a pressure maintaining valve, an air cooling condenser, a liquid storage device, a liquid pipe stop valve, an electronic expansion valve and an evaporator which are sequentially connected to form a refrigerating circulation system, wherein the electronic expansion valve keeps a certain valve opening degree during standby; and an upper liquid level is arranged in the liquid storage device, and a pipeline between a liquid outlet ofthe liquid storage device and a refrigerant inlet of the evaporator is positioned below the upper liquid level. According to the screw refrigerating unit, the oil supply pressure difference of the screw compressor is maintained through the pressure maintaining valve; due to the fact that the pipeline between the liquid outlet of the liquid storage device and the refrigerant inlet of the evaporatoris positioned below the upper liquid level, the pipeline is filled with refrigerants, and power can be provided for flowing of the refrigerants; and the electronic expansion valve keeps a certain valve opening degree during standby, a certain amount of liquid refrigerants can rapidly pass through the electronic expansion valve after the unit is started so that the refrigerants can be provided forthe evaporator in time, and machine jamming caused by long-time continuous evacuation of the screw compressor is prevented.

Description

technical field [0001] The invention relates to the technical field of refrigeration devices, in particular to a low-temperature environment screw refrigeration unit and a starting method thereof. Background technique [0002] At present, some special occasions require the screw refrigeration unit to be able to refrigerate at an environment below -25°C to produce chilled water with a stable temperature and supply it to the terminal equipment of the plant to adjust the ambient temperature required in the production process. For example, the patent No. ZL201510103831.6 is an invention patent titled an air-cooled water chiller in a high and low temperature environment and its control method. The communication room mentioned in the background technology section, especially the large data center, needs to be refrigerated throughout the year, that is, whether it is Stable cooling operation is required in both hot summer and cold winter, and in some cold regions, the ambient temper...

AI Technical Summary

Problems solved by technology

When starting the unit under such working conditions, there will be the following defects: 1. The high and low pressure difference of the unit is low, resulting in a low oil supply pressure difference of the compressor; 2. Due to the low pressure inside the condenser, the condenser It is difficult for the internal liquid refrigerant to flow out of the condenser and cannot provide refrigerant for the evaporator; 3. In the prior art, the valve opening of the expansion valve is gradually opened from the closed state, and the change of the valve opening cannot meet the compressor's demand for refrigerant in time. needs

These defects will cause insufficient refrigerant supply in the refrigeration system, resulting in low-pressure tripping of the unit or compressor jam due to overheating, making the unit unable to start smoothly

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