Flow Pattern of Pure Refrigerant HFC134a Evaporating in a Horizontal Capillary Tube

In the present study, the characteristics of flow pattern are investigated experimentally for evaporation of pure refrigerant HFC134a in a capillary tube of 1.2mm I.D. The capillary tube consists of a heating-copper tube section and a glass-tube section, which is located at the right after the outlet of the heating section. The flow pattern is observed through the glass tube section in the ranges of mass velocity of G=80～1260kg/(m^2 s) and vapor quality of x=0.008～0.975 at a constant pressure of 920 kPa. The flow patterns observed are the bubble flow, the plug flow, the slug flow, the wavy annular flow and the annular flow. These flow patterns are typical for a relatively large diameter tube used as the heat transfer tube in commercial refrigeration and air-conditioning systems. However the transition points between each flow pattern are different from the modified Baker map and the Taitel-Dukler map, which are proposed for a relatively large diameter tube