2010 Volume 23 Issue 5 Pages 597-604
In recently years, both the downsizing and the optimization of a heat exchanger with phase change have been requested, and a variety of working fluids have been utilized as refrigerants. Therefore, the clarification of gas-liquid two-phase flow in small diameter pipes is necessary for various liquids other than water. The purpose of this study is to clarify experimentally the effects of surface tension and liquid viscosity on the flow characteristics of two-phase slug flows in vertical small diameter pipes. In the experiment, flow structures such as void fractions in liquid slug and large gas bubble sections, ratio of large gas bubble length to slug unit length, and liquid film thickness around large gas bubbles were measured using 9 and 5 mm i.d. vertical circular pipes. As the test fluids, air and three kinds of test liquids in the property ranges of 0.042-0.071 N/m in surface tension and 0.797-19.6 mPa·s in liquid viscosity. New correlations of the above parameters were obtained from the present data, and compared with correlations in literatures and the present data.
