Prediction of two-phase flow distribution in multipass tube by utilizing annular flow division model

摘要

In this paper, a new method of predicting two-phase flow distribution in a header type multipass tube is proposed. Meant to have universality, an existing flow model of T-junction is utilized in the method for the prediction basis. The data analyzed here is obtained in the authors' previous experiemntal researches conducted with a multipass evaporator tube which consisted of a vertical main pipe and five horizontal passes. All the tube had 6 mm in id.d. and refrigerant HCFC-123 was used as test fluid. In the analysis, dividing flow model of Hwang, et. al. (1988) which focused on annular flow regime is used. Further, taking into account of the effect of physical properties of test fluid, correlation of liquid film thickness derived by Taitel and Dukler (1976) and that of entrainment ratio by Ishii and Mishima (1982) are adopted. In order to achieve a more accurate prediction, the model is improved by considering entraiment division. By this model, fraction of mass taken off for liquid calculated against that for gas obtained by measurement, is well predicted for junction 1. For other junctions, difference between predicted data and measured data is adjusted by considering features of multipass tube, liquid film loss by upstream junction, unevenly applied pass heating load, and flow reversal at junction 4. Finally, the present model predicts the experimental data within 20 percent accuracy.