Thermo-fluid analysis of a pentagonal ribbed triangular solar air heater duct (TSAHD): A three-dimensional numerical investigation

Providing roughness elements on the absorber plate appreciably improves the heat removal rate through the solar air heater ducts. The present numerical work elucidates the thermo-fluid behavior of a triangular solar air heater duct (TSAHD) with pentagonal ribs on the heated plate. For the ongoing analysis, the Relative roughness pitch (P/e) varies from 6 to 12, relative roughness height (e/Dh) changes from 0.03 to 0.05, and Reynolds number (Re) changes from 4 x 103 to 18 x 103 for a parametric study. The three-dimensional domain is simulated using the full Navier stokes equation with the RNG k-epsilon model and the energy equation. In the considered parametric range, the maximum improvement in the heat transfer is 101% more than the base model for P/e = 10 and e/Dh = 0.05 at Re=15 x 103, and the maximum frictional penalty is 2.97 times of the base model for P/e = 10 and e/ Dh = 0.05 at Re=4 x 103. The highest thermal enhancement ratio (TER) is 1.46 with P/e = 10 and e/Dh= 0.05. The data collected from the study in the form of NuR and fR have been used to formulate generalized correlation as a function of considered roughness and flow variables.

Automated summary

Providing roughness elements significantly improves the heat removal rate in solar air heater ducts. Numerical analysis shows that the maximum improvement in heat transfer is 101% compared to the base model, while the maximum frictional penalty is 2.97 times higher. The highest thermal enhancement ratio achieved is 1.46. The collected data has been used to formulate a generalized correlation for roughness and flow variables.