Forced convection of the brass-beads packed bed situated in a vertical oncoming flow

This study experimentally investigated the convective heat transfer and pressure drop of a vertical oncoming airflow onto the brass-beads packed bed. The 120 mm-length (L) brass-beads packed bed was fully filled in a horizontal rectangular channel having a cross section of 60 mm width (W) and variable height (H). The flow entry, with variable width (wj), was located at the center of the upper wall of the test channel. Besides, three kinds of packed beds with various bead diameters (d) were used herein. The ranges of relevant parameters were wj/L = 0.212–1, H/L = 0.083–0.25 and d = 2–6 mm. Experimental results reveal that, at wj/L = 0.212, the local Nusselt number (Nu) at the stagnation point (x/L = 0) right under the flow entry was maximal and then monotonically decreased along the transverse flow direction. However, when wj/L = 0.583 and 1, the Nu firstly decreased from x/L = 0 to x/L   = 0.1, then rose along the transverse flow direction. Additionally, under the same pumping power, the largest average Nusselt number (Nu¯) appeared on wj/L = 0.212, H/L = 0.083 and d   = 6 mm, and the smallest Nu¯ happened at wj/L = 1, H/L = 0.25 and d   = 2 mm. The largest Nu¯ was around 3 times of the smallest Nu¯. This work systemically completed the parametric studies on heat transfer and pressure drop. The relevant correlations of experimental results were also presented.