A homogeneous model of one dimension for pure refrigerants flowing through adiabatic capillary tubes according to pressure drop in adiabatic capillary tubes was provided in this paper. The model can be used to calculate length of capillary tubes and change of thermodynamic characteristics along the tubes. In the model, the flow of the refrigerant in a capillary tube is divided into two regions: single-phase subcooled liquid and two-phase liquid-vapor regions. On the base of this model, the flow characteristics of conventional refrigerants R12, R22 and alternative refrigerants R134a, R152a in capillary tubes arc given detailed calculation. And the model is validated by comparing with the data of references. Then, the thermodynamic characteristics of refrigerants and their alternatives in several flow conditions are compared and analyzed.
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