An experimental evaluation of capillary tube-suction line heat exchanger performance with refrigerant HFC-134A
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abstract
Capillary tube-suction line heat exchanger performance with refrigerant HFC-134a was experimentally evaluated for a range of heat exchanger geometries and operating conditions typically found in household refrigerators. Due to the number of variables that could potentially influence heat exchanger performance, statistical methods were employed in designing the experimental test plan and in reducing the data. Key variables and their respective ranges tested included; capillary tube inner diameter (0.66 to 0.79 mm), capillary tube length (2440 to 3300 mm), heat exchanger length (1000 mm to 1780 mm), condensing temperature (29.4 to 55.6C, which corresponds to a condensing pressure of 758 kPa and 1516 kPa), evaporator pressure (131 to 165 kPa), capillary tube inlet condition (2.8 to 5.6C subcool), and oil concentration level (0 to 3%). For these experiments, the measured HFC-134a mass flow rates ranged between 2.7 and 9.5 kg/hr, and measured effective subcooling level ranged between 13 and 33C. Based on the resulting performance database, design correlations predicting mass flow rate and the heat exchanger effectiveness were developed and verified. The HFC-134a results were also compared to measured heat exchanger performance with refrigerants HFC-152a and CFC-12.
