Numerical study of heat transfer of laminar air flow in perforated trapezoidal corrugated plate-fin ducts

A novel trapezoidal corrugated perforated fin core is proposed in this study. The porosity of the fin surface, or perforations, is indicated to promote the unusual behavior of increasing the heat transfer coefficient, while reducing the friction factor with respect to its non-perforated counterpart, primarily due to surface transpiration, which leads to better flow mixing and successive boundary layer disturbances. This allows the heat exchanger to be built much more compact with a smaller volume and a front area. To highlight this, the results of the computational simulations for velocity and temperature fields in typical trapezoidal corrugated perforated plate-fin ducts are presented. Constant property, fully or periodically developed laminar airflow P r = 0.71 with Reynolds number 10 <= R e <= 1000 passing through inter-fin passages, with fins at constant wall temperature T, in which the fin walls have perforations equally spaced along the length of the duct, is considered and a parametric study of the effects of the duct geometry, including the variation of the inclination angle phi of the diverging plane, the aspect ratio of the channel or period length and fin density effects lambda = L / D h and the converging-diverging ratio of the plate epsilon , is performed. The results of the Fanning friction factor and the Nusselt number over the wide range of the Reynolds number, which was treated in this study, show the improved performance. The improvement is assessed quantitatively by the area goodness factor (j/f) relative to Re, comparison with simple flat channels. It is seen that increasing phi to 45 degrees improves the core performance; As phi increases beyond 45 degrees , performance starts to decrease. j/f increases with increasing lambda; and lambda = 3.6 acts as an inflection point. It is better to have a large lambda value for lower Re range and vice versa. As epsilon increases, the performance increases; so, the highest area goodness factor value occurs at epsilon = 0.36 . In case 11, with lambda = 3.6 , phi = 45 degrees , and epsilon = 0.36 at Re = 200, compared to the non-perforated channel, the friction factor decreases about 11%, and the area goodness factor increases about 72%. Thus, the area goodness factor of the perforated case reaches 0.37.