Assessment of Convective Heat Transfer Characteristics for Elliptical-Shaped Pin-Roughened Surface for the Jet Impingement Cooling

Abstract

In a jet impingement cooling (JIC) system, the layout of the target surface and length of the jet holes can change both the flow field and the heat transfer characteristics. Elliptical-shaped pins (ESPs) with different heights and layouts on the target surface of the extended jet hole configurations were examined numerically in a jet impingement system. The ESPs were arranged in a staggered and circular form. Normalized nozzle length (Gj/Dj = 1.0, 2.0, 6.0) and normalized pin height (Hp/Dj = 0, 0.167, 0.417, 0.667) were investigated as geometric parameters. Also, the effect of different pin layouts (R1, R2, R3) on heat transfer dissipation was studied by changing the number of pin rows in particular configurations. A numerical model was developed and verified with experimental and numerical data from the literature. Numerical analyses were conducted with the shear stress transport (SST) k–ω turbulence model taking the boundary conditions into account under turbulent flow conditions (16,250 ≤ Re ≤ 32,500). Nusselt (Nu) numbers, pressure drop, and the thermo-hydraulic performance of the physical model were quantitatively researched to elucidate the underlying mechanisms of enhanced heat transfer by the ESPs. Results were compared with the orifice surface (Hp/Dj = 0 and Gj/Dj = 6.0). Results showed that area-averaged Nu number on the target wall increased up to 35.82% for Re = 16,250 by R2_Gj/Dj = 1.0 and Hp/Dj = 0.167 compared to the conventional JIC system. The performance evaluation criterion (PEC) was used to analyze the thermo-hydraulic performance of the examined physical models. According to the PEC values, the most feasible parameters for all Re numbers were R3_Gj/Dj = 1.0 and Hp/Dj = 0.167. Furthermore, increasing the number of pin rows in the channel also increased the uniformity of the local heat transfer distribution according to Nu contours.