Experimental investigation on radiation heat transfer properties degradation of (black nickel-coated aluminium) solar receiver tube material

ABSTRACTIn our previous research, we have studied the surface property degradation of the uncoated receiver tubes of solar water heater at elevated temperatures Logesh et al. [2017. “Experimental Investigation on Radiation Heat Transfer Properties Degradation of Aluminium Solar Receiver Tube Material.” International Journal of Ambient Energy1–6]. In this study, the investigation is extended to property degradation of selective surface, black nickel-coated aluminium material. The selective surface has been investigated for its absorptivity (α) and emissivity (ϵ) changes due to its exposure to sunlight at elevated temperatures. The duration of exposure ranges from 240 to 960 h; the properties are measured at four intervals in the selected range of exposure. The investigation is also carried out to find the temperature dependence nature of the heat transfer properties. The properties are measured at 10 temperature intervals for every period of exposure. The absorptivity (α) is found to be increased for the coated surface than the uncoated, whereas the emissivity (ϵ) gets decreased for the same period of exposure.