Automatic oil return device of carbon dioxide cascade refrigeration system

Abstract

The invention discloses an automatic oil return device of a carbon dioxide cascade refrigeration system. The automatic oil return device comprises a shell-and-tube heat exchanger, adjusting valves, electromagnetic valves, a pressure-differential adjusting valve connected with the top of the shell side of the shell-and-tube heat exchanger, a liquid level meter connected with the shell side of the shell-and-tube heat exchanger, and two liquid level switches, wherein one adjusting valve and one electromagnetic valve are connected with the middle part of the shell side of the shell-and-tube heat exchanger; and the other adjusting valve and the other electromagnetic valve are connected with the bottom of the shell side of the shell-and-tube heat exchanger. The whole oil return device comprises 5 ports connected with external devices, namely port 1 connected with a condenser or a liquid reservoir, port 2 connected with an expansion valve, port 3 connected with a carbon dioxide pump outlet pipeline, port 4 connected with a circulatory barrel, and port 5 connected with an air suction port of a compressor. Through the adoption of the automatic oil return device disclosed by the invention, during the operation of the refrigeration system, refrigerant oil dissolved in carbon dioxide in the low-pressure circulatory barrel can be automatically extracted and returned to the compressor, so that the heat exchange efficiency of refrigeration equipment is improved; and the refrigerating capacity of the refrigeration system is not lost during operation, and the operation of the compressor is not influenced, so that the practicability is high.

Description

technical field [0001] The invention relates to a refrigeration device, in particular to an automatic oil return device for a carbon dioxide cascade refrigeration system, which is used to extract the frozen oil at the low-pressure side of the refrigeration system and automatically transport it back to a compressor. Background technique [0002] In recent years, people have paid more and more attention to environmental problems such as the destructive effect of Freon-like synthetic refrigerants on the atmospheric ozone layer and the greenhouse effect that are widely used in the refrigeration industry, and relevant personnel are also actively researching alternative technologies for Freon refrigerants. Environmentally friendly refrigerants with low ODP (ozone layer depletion potential) and low GWP (greenhouse effect potential) are receiving more and more attention. CO2 is a natural working fluid with stable chemical properties, ODP of 0, GWP of 1, non-flammable, non-toxic, and...

AI Technical Summary

Problems solved by technology

[0003] In the large-scale carbon dioxide cascade refrigeration system, the carbon dioxide compressor mostly adopts the oil-injected screw type. Due to the needs of operation, some refrigerated oil will be mixed into it during the process of compressing carbon dioxide gas. However, there is still a small amount of refrigerated oil that will enter other equipment in the system. This small amount of refrigerated oil will not automatically return to the compressor. Over time, there will be two problems: one is the oil in the oil-gas separator Second, the refrigerant oil content of liquid carbon dioxide in the low-pressure circulation barrel is getting higher and higher, which will seriously hinder the evaporation of carbon dioxide in the air cooler and reduce the efficiency of the air cooler

[0004] Most of the refrigerated oil in the carbon dioxide system is a synthetic oil that can be miscible with carbon dioxide. There is no stratification in the low-pressure circulation barrel, and the refrigerated oil cannot be released directly

The commonly used method is to lead a path of liquid from the carbon dioxide circulating pump, and directly return to the suction port of the compressor after passing through the throttle valve. The disadvantage of this method is that most of the liquid led back to the suction port of the compressor is carbon dioxide. Contains a small amount of refrigeration oil, the oil return efficiency is low, and the cooling capacity of the compressor is lost, and too much liquid returns, which brings a wet stroke to the compressor and affects the normal operation of the compressor

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