Thermal Performance Characteristics of Three Sides Artificially Roughened Solar Air Heaters With and Without Booster Mirrors

This paper represents the results on data collected under actual outdoor conditions for three sides artificially roughened and smooth solar air heaters with and without booster mirrors. The results show that the effect of boosting of solar radiation is appreciable and consequently, the thermal efficiency of the roughened collectors with booster mirrors increases further over the roughened ones without any further increase in the pressure drop over that in the roughened ones. The values of the collector heat removal factor and collector efficiency factor of roughened solar air heaters with booster mirrors have been found to increase by 12.6% and 11.9% respectively over the roughened ones without booster mirrors and 45.6% and 46.5% respectively over the smooth ones with booster mirrors and 144.1% and 141% respectively over the smooth ones. For a given value of relative roughness height of 0.022 and relative roughness pitch of 15,the value of thermal performance of roughened collector with booster mirror and without booster mirror have been found out to be about 54% and 46% respectively. A maximum of 1.865% of uncertainty in the value of thermal performance have been found. Such solar air heaters are thermally useful quantitatively and qualitatively both.