Effect of shot peening on enhancing the heat transfer performance of a tubular heat exchanger

Abstract

The present work is an experimental investigation on heat transfer and pressure drop characteristics and the determination of figure of merit in a tubular heat exchanger in which the inner tube is treated using shot peening. The outer surface of the copper inner tube was shot peened by means of pressurized shot peening mechanism. Experimental data regarding convective heat transfer coefficient and pressure drop in water flow inside a tubular heat exchanger with a rough surface was measured and compared with a smooth surfaced tube. Cold water (inner tube) and hot water (annulus) inlet temperatures were maintained at 30 °C and 60 °C respectively. The Reynolds number during the experiments were in the range of 4000–22,000 for tubular heat exchanger based on the hydraulic diameter of the annular space between two heat exchange tubes. Cold water Reynolds number was kept constant at 5500. Experimental results showed that the shot peening in tube surfaces has an appreciable effect on the performance of flow behavior and heat transfer. Experimental results revealed that increase in Nusselt number, friction factor and figure of merit existed as the effect of shot peening. Nusselt number augmented with increasing Reynolds number whereas opposite tendencies were found for the case of friction factor and figure of merit. The predicted data are in good agreement in the range of 0.96 and 0.97 for the Nusselt number and friction factor correspondingly.