Experimental study on flow characteristics of falling film over horizontal tubes under countercurrent gas flow

Abstract

Open-absorption heat pump serves as an important means of industrial waste heat recovery, and the overall performance of the heat pump system depends on the absorber’s performance. Horizontal-tube–falling-film absorption refers to a complex process involving the coupling of fluid flow, heat transfer, and mass transfer. For the complete understanding of the intertube flow characteristics of horizontal-tube falling film under countercurrent gas flow (We), Visual experimental studies on falling-film flow were conducted using high-speed photography. The critical Reynolds number (Re) was quantitatively characterized to represent the transition of different flow patterns between tubes. The experiment was conducted to investigate the variation in the critical Re under the coupling effects of various factors and establish an experimental prediction correlation formula for the critical Re and solution properties, We, s, and d with an error margin of less than 10%.The influence of single factors was characterized qualitatively and then subjected to sensitivity analysis. The factors affecting the critical Re in descending order of magnitude were as follows: solution mass fraction > s > d > countercurrent gas flow (We). A reduction of approximately 50% in the critical Re for every 10% increase in the solution mass fraction.