Performance study of solar air heater having v-down discrete ribs on absorber plate

•The paper presents results of an outdoor experimental study on performance of smooth and roughened duct solar air heaters.•Study shows thermal performance enhancement due to the use of v-down discrete rib roughness on the absorber plate.•Experimental data has been utilized to validate mathematical models for both smooth and roughened duct solar air heaters.•The presented model can be utilized for performance prediction of smooth or roughened duct solar air heaters.•The paper has been revised as per the comments of the reviewers.

The paper presents results of an experimental study of thermo-hydraulic performance of a solar air heater with 60° v-down discrete rib roughness on the airflow side of the absorber plate along with that for a smooth duct air heater. The enhancement in the thermal efficiency due to the roughness on the absorber plate is found to be 12.5–20% depending on the airflow rate; higher enhancement is at the lower flow rate. The experimental data have been generated and utilized to validate a mathematical model, which can be utilized for design and prediction of performance of both smooth and roughened air heaters under different operating conditions. The results of a detailed thermo-hydraulic performance study of solar air heater with v-down discrete rib roughness using the mathematical model are also presented along with the effect of variation of various parameters on the performance.