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Impact of lubricant in the evaporator as a function of oil circulation rate in variable speed heat pumps working with R290.

Number: 2215

Author(s) : OSSORIO R., NAVARRO-PERIS E., BARTA R. B., LOPEZ A.

Summary

Modulating the speed of the compressors and adapting its capacity to the required load has led to a decrease in the annual energy consumption in many applications. However, in the compressor, having adequate lubrication at low speeds usually implies discharging too much lubricant at higher speeds. Although necessary for compressor operation, lubricating oil acts as a contaminant in the rest of the system. Consequently, manufacturers have to consider the oil circulation rate (OCR), as it limits the speed range of the compressor.
In a previous study, a compressor was tested over its speed range (30 to 110Hz), working with R290 and POE68 as a lubricant. Experimental data confirm the increase of OCR with speed and suggests that working with R290-POE68 could imply higher OCR values compared to other refrigerant-oil mixtures.
In this study, the impact of the OCR in the performance of a R290 heat pump evaporator was theoretically assessed. Two contributions were studied: The heat transfer coefficient (HTC) reduction in the evaporator and the effect of refrigerant being solved in oil. It was found that OCR values of 5% could decrease the coefficient of performance (COP) by 6%.

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  • Original title: Impact of lubricant in the evaporator as a function of oil circulation rate in variable speed heat pumps working with R290.
  • Record ID : 30030610
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022

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