Flow of refrigerants through capillary tubes: A state-of-the-art

A review of the research carried out during past decade on flow of different refrigerants through adiabatic and diabatic capillary tubes of different geometries viz. straight and coiled has been discussed in this paper. The paper outlines the effective techniques revealed in literature to improve the overall performance of a capillary tube based refrigeration system. The studies on the flow of HCFC/HFC/CFC refrigerants, their mixtures and natural refrigerants inside capillary tubes has been discussed. The data for the flow of natural refrigerants inside a capillary tube are limited. Amongst all the natural refrigerants, most of the work has been carried out on R-744 during last 10 year literature. The transcritical R-744 cycle is effective with capillary tube in case of small scale heat pump or a refrigeration system.