Experimental research on falling film flow and heat transfer characteristics outside the vertical tube

Abstract

• Flow and heat transfer characteristics of falling film are studied experimentally. • The experimental data show large differences with values of existing correlations. • Correlations of heat transfer coefficient and dry burning condition are developed. • The study provides a reference for the research on evaporator of MVR. The falling film flow has attracted much attention recently due to its advantages of low temperature difference, low flow rate, high heat transfer coefficient and high heat flux density. In this paper, a series of experiments were carried out to investigate the falling film flow and heat transfer characteristics outside the vertical tube based on the established experimental system. Flow patterns, the trend of heat transfer coefficients along the tube as well as the falling film breakdown phenomenon were described. Two new correlations were obtained to predict the heat transfer coefficient and falling film dry burning based on experimental data, and the maximum deviation between the experimental data and predicted values were −13.36% and 16.81%, respectively. The new correlations can provide a reference for the design of the heater in the Mechanical vapor recompression systems.