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Transient oil-refrigerant mixture flow change after compressor shutdown at suction and discharge.

Number: 1347

Author(s) : WANG X., MILJKOVIC N., ELBEL S.

Summary

The compressor oil is retained at different locations of the vapor compression system during operation. After shutdown, the retained oil absorbs the vapor refrigerant and mixes with the liquid refrigerant with temperature and pressure changes. In this paper, the liquid mixture behaviors after shutdown at the compressor suction and discharge are observed by flow visualization. The liquid mixture property variations are estimated with existing models according to the temperature and pressure variations. The refrigerant concentration in the liquid phase increases rapidly at suction after shutdown. The viscosity of the liquid decreases quickly with temperature and refrigerant mass fraction change. Flow visualization shows that the mixture film breaks from the top of the tube wall and flows down. Transient vapor condensation and re-evaporation occur with a sudden pressure increase. The oil-refrigerant mixture liquid level increases and decreases within seconds. At the discharge, the refrigerant solubility fluctuates within a small range. Viscosity increases because of temperature decrease then decreases because of refrigerant mass fraction increase. After shutdown, the oil flow in contact with the inner wall of the discharge stops immediately while oil droplets in the vapor core flow slow down gradually. Flow behaviors and property variations are compared after three different operation conditions. The results show that larger flow property changes and more severe vapor condensation happen at the suction with the higher outdoor temperature. The vapor refrigerant, liquid refrigerant, and oil relationship is investigated and estimated after shutdown to better understand oil retention.

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  • Original title: Transient oil-refrigerant mixture flow change after compressor shutdown at suction and discharge.
  • Record ID : 30033604
  • Languages: English
  • Subject: Technology
  • Source: 2024 Purdue Conferences. 27th International Compressor Engineering Conference at Purdue.
  • Publication date: 2024/07/18

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