A falling-film water-cooled screw low-temperature solution unit

Abstract

The invention discloses a falling-film water-cooled screw low-temperature solution unit. The screw compressor communicates with the air inlet of a built-in oil condenser, and the oil outlet valve of the built-in oil condenser communicates with the suction pipeline of the screw compressor. One way of the liquid outlet of the condenser is connected with the energy-saving gas supply port of the screw compressor through the second channel of the economizer, and the other way is through the first channel of the oil return heat exchanger, the second channel of the economizer, the electronic expansion valve and the double-stage falling film evaporator The liquid inlet is connected, the gas outlet of the double-stage falling film evaporator is connected with the inlet of the screw compressor; the oil outlet valve of the double-stage falling film evaporator is connected with the second channel of the oil return heat exchanger and the middle inlet of the ejector , The outlet of the ejector communicates with the suction passage of the screw compressor. The invention creatively applies the falling film evaporator to the water-cooled screw low-temperature solution unit, which improves the heat exchange efficiency of the evaporator, saves the space of the unit with a built-in oil condenser, and the design of the oil circuit makes the oil return of the screw compressor safer and more efficient. more reliable.

Description

technical field [0001] The invention relates to the field of refrigeration, more specifically, to a falling-film water-cooled screw low-temperature solution unit. Background technique [0002] At present, in the field of refrigeration, a brine (NaCl or CaCl 2 ) or ethylene glycol solution as the refrigerant and the refrigeration unit using the screw compressor, and the heat exchanger adopts the dry shell-and-tube evaporator and the water-cooled shell-and-tube condenser. This type of unit is generally called dry water-cooled screw low temperature Saline (ethylene glycol) solution unit. Since the refrigeration system using the dry shell-and-tube evaporator relies on the evaporator itself to return air and carry oil, there is no oil in the evaporator, and no additional oil return system is required, so the system design and control are simple. However, the heat exchange of the dry evaporator is heat exchange for boiling in the tube. As the refrigerant continues to evaporate, ...

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Problems solved by technology

However, the heat exchange of the dry evaporator is heat exchange for boiling in the tube. As the refrigerant continues to evaporate, the gas refrigerant must occupy a part of the heat exchange area. At the same time, the refrigerant distribution at the end of the dry evaporator is difficult to achieve uniformity. Affects the overall heat transfer efficiency of the heat exchanger. The heat transfer temperature difference between the refrigerant and the brine is generally above 5°C, and the improvement of the heat transfer efficiency is limited, making it difficult to improve the operating efficiency of the entire refrigeration unit.

Flooded evaporators are generally used in chillers in the field of air conditioning. The refrigerant in the flooded evaporator boils and exchanges heat in the liquid pool outside the tube, which can achieve a small heat transfer temperature difference, generally within 2°C, so that the refrigeration unit can run The efficiency is greatly improved; since there is a large amount of liquid refrigerant in the flooded evaporator, a certain amount of refrigerated oil will dissolve in the refrigerant, and the return air cannot take away this part of the refrigerated oil, so the flooded evaporator Generally, the liquid in the evaporator is ejected through the Venturi ejector using high-pressure gas as the power to realize the oil return. However, the evaporation temperature of the refrigeration unit in the air-conditioning condition is above 0°C, and the fluidity of the refrigerating oil is good. The flooded type The oil return effect in the evaporator is better, but when the flooded evaporator is used in the medium and low temperature below -15°C, the oil return in the evaporator will not be smooth, resulting in a large amount of oil in the evaporator. This will greatly reduce the heat transfer efficiency of the heat exchanger, thereby affecting the operating efficiency and safety of the entire refrigeration unit; moreover, the refrigerant charge of the refrigeration unit using the flooded evaporator is much larger than that of the dry unit, which also makes the full-liquid evaporator The economy and environmental protection of liquid refrigeration units are greatly reduced, so flooded evaporators are hardly used in water-cooled screw low-temperature brine / ethylene glycol solution units with evaporation temperatures below -15°C in the prior art

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