Experimental investigation on flow of R-600a inside a diabatic helically coiled capillary tube: Concentric configuration

This paper presents an experimental study of a diabatic flow of R-600a through a concentric configured helically coiled capillary tube suction line heat exchanger. The details of experimental facility for testing the diabatic capillary tube with different inlet sub-cooling degree and pressure are discussed. The effect of coil diameter, capillary length, capillary tube diameter, sub-cooling degree and inlet pressure on mass flow rate are presented. The degree of sub-cooling at the inlet of both straight and helical capillary tube is varied from 3-20 °C. In case of diabatic flow, the coiling reduces the mass flow rate of R-600a by 3-12 percent as compared to straight capillary tube. The refrigerant mass flow rate is scattered up with rise of pressure. A semi empirical correlation to predict the mass flow rate of R-600a flowing through a diabatic helical coiled capillary tube is proposed for sub-cooled inlet conditions. The proposed correlation predicts measured data with an error band of ± 20 percent.