Publication date: April 2019
Source: Renewable Energy, Volume 133
Author(s): Piyush Kumar Jain, Atul Lanjewar
Artificial roughness in solar air heater is useful technique to enhance the heat transfer rate. Investigators have always strived to improve the performance of V-rib geometry. This paper presents overview of V-rib roughness geometries used in solar air heater and also evaluates performance of a new V-rib with symmetrical gap and staggered rib geometry. Proposed roughness has fixed relative staggered rib pitch (P’/P) as 0.65, relative gap width (g/e) as 4, relative staggered rib size (w/e) as 4 and angle of attack (α) as 60°. Number of gaps on each side of V-rib was kept as 3. Relative roughness pitch (P/e) and Reynolds number (Re) were varied from 10 to 16 and 3000 to 14,000 respectively. Four rib roughened plates having V-rib with the symmetrical gap and staggered rib geometry with relative roughness pitch (P/e) of 10, 12, 14, and 16 were tested. Maximum enhancement in Nusselt number and friction factor were found to be 2.30 and 3.18 times respectively for relative roughness pitch of 12. Thermo-hydraulic performance parameter is maximum for relative roughness pitch of 12. Thermo-hydraulic comparison indicates that the present roughness geometry has better performance for Reynolds number range of 3000–14,000 than existing V-rib geometries.