Experimental investigation on radiation heat transfer property degradation of aluminium solar receiver tube material

Abstract

ABSTRACTThe study of surface heat transfer property degradation is mandatory as the solar water heater receiver tubes operating temperature increases. In this study, investigation is carried out on the radiation heat transfer property degradation of aluminium material. The emissivity () and absorptivity (α) of aluminium surface has been measured before and after exposing to sunlight in four interval between 240 and 960 h. Moreover, these properties’ variations are also temperature dependent; hence temperature dependency of the above-said properties are measured at 10 equal intervals. Unlike those of stainless steel [Mageshwaran, G., S. Ramachandran, G. Iyappan, and R. B. Durairaj. 2016. Experimental Investigation on Surface Radiation Properties’ Degradation of Solar Collector Receiver Tube Material. International Journal of Ambient Energy doi:10.1080/01430750.2016.1202139], both the properties increases for aluminium, and temperature dependency is strong after 150°C. The absorptivity increases at lower rate than the emissivity; hence the net effect is reduction in aS/E ratio, which in turn increases the radiation heat loss of exposed surfaces than the unexposed surfaces.