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.