Abstract: Although the critical two-phase flow of refrigerant through adiabatic capillary tube is nonlinear, its mass flow characteristics under some typical operating conditions show good linearity. Application of the linear characteristics is helpful to modify or simplify the design and rating method of capillary tube. The linear characteristics are interpreted and extended by the approximate analytic method. Experimental data from the open literature and additional numerical data from an advanced distributed-parameter model for R22, R410A and R407C are used to illustrate the proposed theoretical relations and conform well to the theory.

Key words: Capillary tube, Refrigerant, Refrigeration