Investigation of thermal performance of a ribbed solar air heater for sustainable built environment

Solar air heater plays a crucial role for development of sustainable built environment, which can fulfil the need of heating load of building by harnessing solar energy. A solar air heater (SAH) to warm a building has poor thermal performance due to the lack of a sufficiently coherent heat transfer rate. Utilizing a roughened surface is one of the most effective means for enhancing heat transfer of a SAH to the creation of a sustainable built environment. The impact of a discrete double-arc roughness was investigated in order to test the effects of current rib roughness on the characteristics on the thermohydraulic performance (THP) of rectangular SAH ducts. Reynolds number (Re) is varied from 3010 to 13935 with the relative roughness pitch was considered in the range of 6.67-8.33 while the angle of attack (alpha) varying from 30 degrees- 75 degrees. As a result of using discrete double arc ribs, Nusselt number (Nu) values increased as the Re increased, and friction factor (f) values decreased as Re increased. The Nu and f have been shown to increase by a maximum of 217% and 207% respectively. It was determined that THP reached the maximum level of 2.82. Correlations for Nu and f were also developed.