繁 小山

Experimental study on void fraction of two-phase flow inside a micro-fin tube

In this paper the void fraction and flow pattern of the two-phase flow in a micro-fin tube were investigated experimentally for a pure refrigerant HFC134a. The experiment was carried out at a pressure range of 0.6 and 1.2MPa with mass velocities of 90 and 180kg/m^2 s, in which the vapor quality varied from 0 to 1. The void fraction was measured by means of simultaneously closing valves of both sides of the test tube at adiabatic condition. Experimental results for the micro-fin tube were compared with previous correlations for smooth tube. It was found that experimental data of the micro-fin tube were lower than predicted results using correlations for smooth tube. As a trial, an empirical correlation was proposed, based on the present experimental results. The observation of the flow pattern through a sight glass was also carried out with a camera. The observation results were compared with modified Bakers map.

Prediction Method of In-tube Condensation of Multi-component Vapor Mixture

This paper deals with a prediction method for the condensation of multi-component refrigerant mixture inside a horizontal smooth tube. Based on some reliable assumptions, the governing equations for the local heat and mass transfer characteristics are derived, and the prediction calculation for the condensation of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a, including R407C, is carried out; the local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, mass flux etc. are obtained for a constant wall temperature and a constant wall heat flux conditions. The effects of the composition of HFC32/HFC125/HFC134a on the heat transfer characteristics are clarified, and the heat transfer characteristics of R407C are compared with those of R22.

多成分混合気の平板上での層流膜状凝縮熱伝達の代数的予測法 : 第1報 強制対流凝縮の場合

Laminar forced convection film condensation of multicomponent mixtures on a flat plate is theoretically treated on the basis of two-phase boundary layer theory. The governing equations for the vapour boundary layer, which are coupled complicatedly with respect to concentration terms, are orthogonally transfomed to uncoupled equations similar to those of binary mixtures. Then, generalized simultaneous algebraic equations for predicting the heat and mass transfer characteristics of condensation of multicomponent mixtures are derived by applying the correlation equations for the boundary values of similarity solutions for binary mixtures.