Investigation on the effect of different coated absorber plates on the thermal efficiency of the flat-plate solar collector

The aim of the present work is to compare thermal efficiency of three flat-plate collectors, which are different in the type of coatings used in the absorber plate. The thermal efficiency of the collector was investigated using three types of absorber plate: the black painted, the black chrome coating, and the carbon coating. The thermal performance of the collectors was considered based on American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 93 (2010). The volume flow rate varied from 0.5 to 1.5 L min(-1). The field emission scanning electron microscope images demonstrated that the carbon coating had high absorption due to trapping the light and avoiding the reflection of the light. The collector with the carbon-coated absorber plate at the flow rate of 1.5 L min(-1) has the maximum thermal efficiency of approximately 69.4%. Furthermore, the thermal efficiency of the carbon-coated absorber plate and black chrome-coated absorber plate is averagely 13% and 11.3% higher than the black-painted absorber plate, respectively. Additionally, the removed energy parameter (FRULat the flow rate of 1.5 L min(-1) decreases approximately 35.4% for the collector with the carbon-coated absorber plate and 28.4% for the collector with the black chrome-coated absorber plate compared to the black-painted absorber plate.