Numerical Study of Convective Heat Transfer for Flat Unglazed Transpired Solar Collectors

摘要

Convective heat transfer coefficients (CHTC) for flat unglazed transpired solar collectors have been computed using high-resolution 3-dimensional steady RANS CFD simulations. The Standard k-ε, Renormalization Normal Group k- ε (RNG k-ε), Realizable k-ε and Shear Stress Transport k-ω (SST k-ω) turbulence closure models were used and the results were compared with experimental data from the literature. The validation study showed that both the Standard k-ε and the RNG k-ε model performed better in terms of matching the experimental data and showing consistently faster convergence. Local CHTC along the plate were evaluated with the validated model for different suction flow rates (0.0448 to 0.0688 m/s) and free stream turbulence intensity (0.8% and 20%) at 6 m/s approaching flow velocity with the results showing that the turbulence intensity has a more profound impact on the overall convective heat transfer process. The local CHTC in the solid surface region of the collector remains constant after a certain length for the cases considered; however, the starting length was found to be longer compared to the values reported in previous analytical studies.