Thermohydraulic Analysis of Double Pass Solar Air Heater Duct with Perforated Blocks and Semicircular Tubes as Artificial Roughness

Solar air heaters (SAHs) convert solar energy into thermal energy for low-temperature applications. In this study, a three-dimensional computational method is used to examine the thermohydraulic performance of double-pass solar air heater (DPSAH) having perforated blocks and semicircular tubes as roughness elements. The analysis is conducted at Reynolds numbers (Re) of 3000 to 19000, relative roughness height ratio (e
b
/H) of 0.4 to 0.8, open area ratio (ϕ) of 13 to 30%, and tube amplitude ratio (a
t
/H) of 0.2 to 0.5. To validate the numerical results, the experiment was conducted for the range of Re from 3000 to 15000, e
b
/H of 0.4, ϕ of 30% and a
t
/H of 0.3. It was found that the results of the experiment were in close agreement with those of the simulation, with a mean absolute percentage error for Nusselt number of 1.82% and friction factor of 5.28%. Based on the comparison of the thermohydraulic performance parameter (THPP) with the smooth double pass duct, the maximum THPP value is reported as 3.07. This corresponding to a value of Re as 3000, ϕ of 30%, e
b
/H of 0.4, and a
t
/H of 0.3. In light of the research outputs presented, researchers and manufacturers can develop and design double-pass solar drying systems for various applications, including timber drying, poultry farming, solar drying, and space heating.