Experimental Study of the Performance of LPG as Refrigerant in Adiabatic Capillary Tube used in Split-Type Air-Conditioner

This paper presents experimental results and also develops a non-dimensional correlation based on the test results of the adiabatic capillary tube for LPG and R22 refrigerants. Also, for the purpose of comparison, an experimental data for R-22 refrigerant, a conventional refrigerant used in split-type air-conditioner, was obtained. Capillary tube of several lengths and inner diameters were selected for the test. The mass flow rate for several condensing temperatures and different inlet degree of subcooling of capillary tube were obtained. The chosen condensing temperature for the test were at 34, 36, 38, 40 and 42°C and the degree of subcooling were adjusted to 1.5, 4.5, 7.5 and 13.5°C. In order to reduce the number of experiment to be performed, central composite method, a statistical experimental design approach was employed. A new correlation to predict the mass flow rate of refrigerant based on Buckingham Pi theorem was developed. Considering the effect of the capillary tube geometry and inlet condition of the tube, dimensionless parameters were chosen. The new correlation predicts the experimental data within relative deviation of -10% to +10% for all the test condition of the LPG and R-22 refrigerants. The predictions by this correlation are also in good agreement with results in published literature.