DEVELOPMENT OF A CONTINUOUS EMPIRICAL CORRELATION FOR NON-ADIABATIC CAPILLARY TUBE USING R-600A AND R-134A AS REFRIGERANTS

A capillary tube-suction line heat exchanger (CT-SLHX) is widely used as a refrigerant expansion device in small sized refrigeration and air-conditioning systems, which enhances the refrigeration capacity and ensures that a superheated vapor of refrigerant enters the compressor. To calculate mass flow rate in a capillary tube, it is necessary to develop an accurate non-adiabatic capillary tube model. In the present study, conservation laws in a one dimension was used to generate reference data. An empirical model which is continuous at saturated liquid point is developed for both subcooled and two-phase capillary tube inlet conditions with introduction of new dimensionless pi parameters. Wide ranges of capillary tube inner diameter, capillary total length, capillary inlet quality or subcooling temperature, heat exchanger length, suction line diameter, capillary inlet pressure, evaporator inlet temperature, superheating temperature and refrigerant type are used in the process of data generation. The new model shows a good agreement with experimental data.