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Effect of PAG oil circulation rate on the heat transfer performance of an air-cooled heat exchanger in carbon dioxide heat pump systems.

Author(s) : YOSHIOKA S., KIM H., KASAI K.

Summary

In carbon dioxide (R744) heat pump systems, PAG oil is commonly used for lubrication of the compressor, while it is reported that the presence of oil is greatly influential on heat transfer performance due to its immiscibility against R744. This paper deals with an experimental study on the heat transfer performance of fin and tube heat exchangers working with R744 while taking the effect of PAG oil into account. The experimental apparatus was designed to enable control the oil circulation rate (OCR) independently by using an independent oil circulation line from the refrigerant circuit. Two types of heat exchangers with different tubes, smooth tube and internally grooved tube, have been tested while varying the OCR in the range from nearly zero to 5 wt%. It was found that the OCR change affects significantly in the heat transfer performance at the low range of OCR in both evaporation and gas cooling. The effect of the OCR, however, is different between the smooth tube and grooved tube. For understanding of these phenomena, the oil retention rate in each heat exchanger was measured.

Details

  • Original title: Effect of PAG oil circulation rate on the heat transfer performance of an air-cooled heat exchanger in carbon dioxide heat pump systems.
  • Record ID : 2009-0819
  • Languages: English
  • Source: 9th IEA Heat Pump Conference 2008: advances and prospects in technology, applications and markets. Conference proceedings [CD-ROM + abstracts].
  • Publication date: 2008/05/20

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