Investigations of Performance of Mini-Channel Condensers and Evaporators for Propane

This paper provides the results of experimental investigations of the exemplary mini-channel heat exchanger in its application as a condenser and an evaporator in a compressor refrigeration system with propane as a working fluid. The aim of the investigations was to identify the mean heat transfer coefficient of the refrigerant side for the entire operating range of the tested heat exchanger. The experiments covered a mass velocity range from 50 to 160 kg/(m 2 × s). The experiments covered a range of liquid subcooling in the condenser from 3 to 15 K and a range of vapour superheating at the outlet of the evaporator from 3 up to 15 K. The experiments on the condenser were conducted at the saturation temperature of 34 °C, and in the case of the evaporator, at the saturation temperature of 8 °C. The average heat transfer coefficients as well as pressure drops in the case of the operation of the tested heat exchanger as an evaporator and condenser were calculated. The heat transfer coefficient was calculated by means of the separated thermal resistance method with the application of the Wilson plot technique. The experiments confirmed the increase in the heat transfer coefficient with the increase in the refrigerant mass flow rate for the tested mini-channel heat exchanger. A dimensionless correlation was proposed for the pressure drop based on the modified Müller-Steinhagen correlation in the case of the operation of the mini-channel heat exchanger as a condenser and as an evaporator.