Turbulent flow heat transfer and friction factor characteristics of shrouded fin arrays with uninterrupted fins

Experiments were performed to study the fully developed turbulent flow heat transfer and friction factor characteristics of shrouded, rectangular cross-sectioned longitudinal fin arrays with uninterrupted fins subjected to a uniform heat flux boundary condition at the fin base. The inter-fin spacing was varied from 9.3 to 53 mm, the fin height from 0 to 40 mm, and the fin tip-to-shroud clearance from 0 to 20 mm. The overall height and width of the duct (flow passage) were held constant at 40 mm and 228.6 mm, respectively. The working fluid was air, and tests were conducted for Reynolds numbers ranging from 2000 to 50,000. The equivalent diameter, defined as four times the flow area divided by the wetted perimeter, was taken as the characteristic dimension. In all, seven different fin configurations and the rectangular duct configuration with no fins were investigated. The heat transfer tests showed that the Petukhov-Popov equation is applicable for the rectangular duct configuration with no fins and that the Dittus-Boelter equation is applicable for the configurations with no clearance. The Dittus-Boelter equation is also applicable for fin configurations with clearance if the clearance-to-spacing ratio is small or the spacing-to-fin height ratio is large. Lower values of the Nusselt number were obtained for the fin configuration that did not satisfy the above conditions. As expected, the pressure drop tests showed that the Prandtl equation for evaluating friction factor is applicable for the rectangular duct configuration with no fins as well as for the fin configurations with no clearance. The configurations with clearance yielded friction factor values different from the Prandtl equation. These values have been correlated.