Friction factor effect and heat transfer enhancement in combined dimple geometry arrange in different angle to flow direction

Abstract

One of the most effective passive techniques for heat transfer enhancement in heat exchanger devices is the surface roughness flow augmentation model. In this study, the surface pressure and heat transfer are measured using experimental and computational methods in a rectangular channel. Three aspect ratios, AR, 0.05, 0.035, and 0.025, dimple channel with pitch to depth ratios, P/δ = 6 are tested in this study. The angled dimple surface comprises of two cases; case 1 0 °Circular - 45°Oval dimple (0 °C – 45°O) and Case2 45° Oval - 0° Circular dimple (45° O – 0 °C). The computational study is conducted for Reynolds number, Re 600–11000. The data from the compound-dimple channel is normalized with the smooth channel data of heat transfer and friction factor parameters. It is revealed that friction factors, f, friction factors ratio, f/fo, average Nusselt number, Nuavg, Nusselt number ratios, Nu/Nuo, are dependent on Re. The performance index on the compound dimple surface using the ratio of Nusselt numbers, Nu/Nuo, to friction factors, f/fo. The arrangement and location of the dimple have momentous consequences for the pressure drop parameters f and f/fo. The surface pressure and temperature show that the flow is uniformly distributed in the channel. The performance index improves and Re has strong influence on it. The compound dimple geometry does indicate a strong model for application in heat exchanger devices. Optimum performance of 49% for case 1 and 23% for case 2 are observed.

Keywords

• Angled compound dimple
• Aspect ratio
• Friction factor
• Heat transfer enhancement
• Passive technique and Nusselt number