Numerical Analysis of Solar Air Heater Roughened with B-Shape and D-Shape Roughness Geometry

A ۲-D computational analysis of heat transfer augmentation and fluid flow characteristics with B-shaped and D-shaped artificial roughness has been carried out under the Reynolds number (Re) range from ۴۰۰۰-۲۰۰۰۰. Comparing the predictions of different turbulence models with experimental results available in the literature, the renormalization group k-Ɛ (RNG) turbulence model is selected for the present study. A detailed analysis of heat transfer variation was done using various geometrical parameters such as four different pitch (P) values of ۱۰, ۱۵, ۲۰, and ۲۵ mm corresponding to pitch ratio (P/e) of ۱۱.۱۱۱, ۱۶.۶۶۶, ۲۲.۲۲۲, and ۲۷.۷۷۷ respectively, at constant height (e) of ۰.۹ mm. The highest value of Nusselt number (Nu) improvement reached up to ۲.۲۶۴ times and ۲۱.۹۱ times at P/e of ۱۱.۱۱۱ for B-shape and D-shape roughness respectively for Re of ۲۰۰۰۰ as compared to the smooth channel. A significant enhancement of heat transfer is predicted in the present simulation and the maximum Thermohydraulic Performance Parameter (THPP) attained up to ۱.۴۷ for B-shaped roughness. The novelty of the proposed model appears as present numerical findings offer better performance compared to existing research.

Keywords:

Solar air heater , B-shape roughness , D-shape roughness , Nusselt number , Friction factor. Thermohydraulic performance