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Experimental heat-transfer coefficients of CO2 in a microchannel evaporator.

Author(s) : ZHAO Y., OHADI M. M., FRANÇA F. H. R.

Summary

An experimental study was conducted to characterize the performance of a CO2 evaporator over a range of operating conditions encountered in typical residential heat pumps. The heat exchanger evaporator involved internal flow boiling of CO2 refrigerant in a microchannel heat exchanger, which was heated by an external airflow. The experiments were conducted to evaluate the evaporator capacity (heat transfer rate) for various airflow rates, refrigerant inlet qualities, saturation temperatures, and mass flow rates. The microchannels used in the present study had a hydraulic diameter of approximately 1 mm. For the range of parameters reported in the paper, CO2 operated under subcritical flow boiling conditions. Utilizing the experimental results, a semi-empirical model was also developed to predict the capacities of CO2 microchannel evaporators. The model takes into account the effects of airside moisture condensation and refrigerant outlet superheat. All experiments were successfully conducted with an energy balance of plus or minus 3%.

Details

  • Original title: Experimental heat-transfer coefficients of CO2 in a microchannel evaporator.
  • Record ID : 2005-1134
  • Languages: English
  • Source: ASHRAE Transactions. 2003 Winter Meeting, Chicago, Illinois. Volume 109, part 1 + CD-ROM.
  • Publication date: 2003

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