Experimental study of R134a condensation heat transfer inside the horizontal micro-fin tubes

Abstract

The condensation heat transfer for R134a in the two kinds of in-tube three-dimensional (3-D) micro-fin tubes with different geometries is experimentally investigated. Based on the flow pattern observations, the flow patterns in the Soliman flow regime map are divided into two-flow regimes; one with the vapor-shear-dominant annular regime and the other with the gravitational-force-dominant stratified-wavy regime. The flow regime transition criterion between the annular regime and the stratified-wavy regime is at Fr equal to 2. In the annular regime, the heat transfer coefficients h of the two kinds of in-tube 3-D micro-fin tubes decreases as the vapor quality x decreases. The regressed condensation heat transfer correlation from the experimental data of the annular flow region is obtained. The dispersibility of the experimental data is inside the limits of /spl plusmn/25%. In the stratified-wavy regime, the number of micro fins in the 3-D micro-fin tube is not the controlling factor for the performance of a condensation heat transfer and the average heat transfer coefficient h of the two kinds of in-tube 3-D micro fin tubes increases as the mass flux increases. The regressed condensation heat transfer correlation of the stratified-wavy flow regime is experimentally obtained. The dispersibility of the experimental data is inside the limits of /spl plusmn/22%.