Pressure Drop and Heat Transfer Characteristics for Partially-Confined Heat Sinks in Ducted Flow

The pressure drop and heat transfer characteristics for partially-confined heat sinks with different fin types, including plain-plate fin, pin-fin array and strip-fin array, in ducted flow are investigated. The main focus of the experimental results is on pressure drop and heat transfer characteristics of generalized heat sink in ducted flow with considering the flow top- and side-bypass effects. The parameters controlled in the study are the heating load (Q_t), inlet flow velocity (U_i), the ratio of heat sink height to duct height (H_s/H_c), and the ratio of heat sink width to duct width (W_s/W_c). The ranges of parameters studied are U_i=2~12m/s, Q_t=10~30W, W_s/W_c = 0.6~1, and H_s/H_c = 0.5~1. In the present study, an effective friction factor related to the overall pressure drop is defined; and a new experimental correlation for the effective friction factor for generalized heat sinks in ducted flow with top- and side-bypass effects is presented. A satisfactory agreement between the experimental data and the theoretical predictions is achieved with the maximum and average deviations of 17.2% and 9.6%, respectively. As for convective heat transfer performance, the average Nusselt number is not significantly affected by Grashof number; while, it increases significantly with increasing Reynolds number. Furthermore, the thermal performance increases with increasing top or side confinement ratio (H_s/H_c or W_s/W_c). The best thermal performance occurred at the fully-confined condition, i.e., H_s/H_c=1, W_s/W_c = 1. Based on all the experimental data for three types of partially-confined heat sinks, a generalized correlation of average Nusselt number for partially-confined heat sinks in ducted flow in terms of Re, H_s/H_c and W_s/W_c is presented. The maximum and average deviations of the results obtained by the experimental data from the theoretical prediction are 12.4% and 7.5%, respectively.