Experimental study on effects of surfactant and spray inclination on heat transfer performance in nonboiling regime

Abstract

ABSTRACT The present research emphasizes the optimization of surfactant concentration and examines its effect on spray cooling heat transfer using a pressure swirl nozzle with a 0.51 mm orifice size. Three distinct surfactants, namely, polyvinyl pyrrolidone (polymer surfactant), Sodium lauryl Sulfate (an anionic surfactant), and Tween20 (a nonionic surfactant) have been mixed in distilled water at different volume fractions. The optimum concentration levels of these surfactants have been identified experimentally and result analyzed for surfactant systems revealed that nonionic and anionic surfactants provided higher cooling compared to polymer surfactant that diminished the heat transfer capacity of distilled water. It was also observed that temperature nonuniformity did not improve with any of the surfactants and a maximum heat transfer coefficient of 32⨯103 W/m2K was attained with Tween20 at optimum concentration. The heat transfer performance degraded beyond the optimal concentration due to bubble formation. In addition, the effect of spray inclination of 30º to lessen the effect of foaming and bubble accumulation at high concentrations has been examined. The heat transfer coefficient increased by almost 13% when compared to horizontal spray, reaching a maximum heat transfer coefficient of 36.1×103 W/m2K with Tween20, and the optimum concentration back shift phenomenon was observed. Experiments performed in the present study will not only give insights into the understanding of the spray cooling enhancement, but also facilitate the designing of models for industrial applications.