EXPERIMENTAL INVESTIGATION ON PROPERTIES OF SURFACE RADIATION OF SOLAR COLLECTOR RECEIVER TUBE MATERIAL WITH BLACK NICKEL COATING

In this study, the characteristics of surface radiation heat transfer properties of stainless steel 304with Black Nickel coating is investigated with and without exposure of sunlight to measure the emissivity (€) and absorptivity (ὰ). Exposure of sunlight is carried out for various time internals (240, 480, 720 and 960 hrs). For every 10 equal intervals, the material is measured for temperature dependency property. The emissivity (€) and absorptivity (ὰ) is measured for various spray distance (30, 35 and 40mm) of coating. It is observed that emissivity of the material is decreasing and absorptivity of the material is increasing with exposure time. The combined effect of decrease in emissivity and increase in absorptivity leads to which the rate of radiation loss for exposed surface with compared to unexposed surface is decreasing with black nickel coating at an optimum spray distance of 35mm.