Evaporation heat transfer of falling films on horizontal tube - Part 2, Experimental study

Abstract

Evaporation heat transfer of a saturated falling film on a horizontal tube was studied experimentally. Experiments were performed on a vertical row of horizontal tubes, 25 mm in diameter and 50 mm in vertical pitch with saturated R11 at a pressure of 0.2 MPa in the range of film Reynolds number from 10 to 2,000. The influence of the liquid feeding system and method on an instrumented evaporation tube, and the effect of dummy tubes between a liquid feeder and the test tube were also investigated. The data were then compared with existing correlations in the literature and with the analytical results developed in a previous paper. The analytical results were found to underestimate the data by about 20% for all Reynolds numbers over 50. An empirical correlation to reproduce the present data with sufficient accuracy was developed as Nu{sub m} = (Re{sub f}{sup {minus}2/3} + Re{sub f}{sup 0.3} Pr{sup 0.25}/100){sup 1/2}.