Flow Structure and Heat Transfer During Free Liquid Jet Impingement Over a Rotating Disk

The aim of this computational study was to characterize the flow structure and convective heat transfer for a free liquid jet impinging on a rotating and uniformly heated solid wafer of finite thickness and radius. The main focus considered was the effect of cooling by adding a secondary rotational flow with jet impingement. The model covers the entire fluid region (impinging jet and flow spreading out over the rotating surface) and the solid disk as a conjugate problem. Calculations were done for various standard microelectronics materials, namely aluminum, copper, silver, Constantan, and silicon; at Reynolds number ranging from 445 to 1800, under a broad rotational rate range from 125 to 6000 rpm, and range of wafer thickness from 0.2 to 2 mm, respectively. The working fluids used for this simulation included water (H₂O), ammonia (NH₃), flouroinert (FC-77), and (MIL-7808) oil. In the present work only laminar liquid flow was considered for Ekman number range from 5.52 × 10⁻⁶ to 2.65 × 10⁻⁴. The nozzle to disk radius ratio (r_d/d_n) of 6.333 was kept constant for this study. Plate materials with higher thermal conductivity maintained a more uniform temperature distribution at the solid-fluid interface. Higher Reynolds numbers increased the Nusselt number and local heat transfer coefficient distributions reducing the wall to fluid temperature difference over the entire interface. In general, the rotational rate increases the local Nusselt number values over the entire solid-fluid interface. However, at high rate of rotation, the local Nusselt number decreases because the fluid tends to separate from the rotating disk surface. It was also found that wafer thickness beyond 1 mm did not change significantly the average solid-fluid dimensionless interface temperature and Nusselt number distributions.