Second law analysis of a solar air heater having 60° inclined discrete rib roughness on absorber plate

Artificially roughened solar air heaters perform better than the smooth ones under the same operating conditions. However, artificial roughness leads to even more fluid pressure thereby increasing the pumping power. The entropy generation in the duct of solar air heater having 60° inclined discrete rib roughness on one broad wall is studied numerically. The effect of system parameters such as relative roughness height (e/D), relative roughness pitch (P/e) and relative gap position (d/W) have been studied on the heat transfer and entropy generation as well as fluid friction with relative gap width (g/e) 1 and temperature rise parameter (ΔT/I) varied from 0.002 to 0.02. For the range of parameters considers in this study, it is seen that for optimum conditions, the entropy and entropy generation number are minimum with maximum effective efficiency. Key words: Solar air heater, 60° inclined discrete roughness, entropy generation, effective efficiency.

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