Numerical analysis of the effectiveness of a unique roughened surface solar air heater

Abstract

ABSTRACT The main goal of this study is to enhance the functionality of the solar air heater by adding unique roughened surfaces to the absorber section that disrupt the sluggish sub-layer. The roughened surfaces are created so that the depth of roughened surface’s dimension is constant for all the cases; there will not be any pressure difference lost. Initially, a square roughened surface is considered for the primary plain tube solar air heater. Later, the remaining roughened surfaces are created by removing some triangular portions from the basic square rib surfaces. The primary intention of creating surfaces like this is that the sharp edges facing the upwind stream disturb the viscous sub-layer at a greater level than the squared rib roughened surfaces. Using a computational fluid dynamics tool, this research problem has been investigated numerically by computing formula that controls the fluid flow with the RNG k-ε turbulence model. The functionality of solar-powered air heaters has been examined at different Reynolds numbers by studying temperature, turbulence, and the Nusselt number. Based on the overall comparison of the numerical results for the different roughened surfaces, Case 4 offers superior heat transmission performance compared to the simple tube solar air heater, which has 43.7% more turbulence. In the investigated range, the roughened surface solar air heater had a high Nusselt number 3.15 times more than the plain tube solar heater with a comparable roughness value of 7.14 at a Reynolds number (Re) of 15,000. Case-4 solar-powered air heater with roughened surfaces reached a maximum temperature of 406.4 K