Thermal Transport During Liquid Jet Impingement from a Confined Spinning Nozzle

Abstract

Liquid jet impingement heat transfer from a uniformly heated solid disk of finite thickness and radius is considered in this investigation. The jet nozzle is fitted with a confinement disk that spins with a constant angular velocity about the axis of the nozzle. This arrangement is suitable for microgravity applications in which centrifugal force due to disk rotation can be used to force the fluid over the heated surface. The model covers the entire fluid region (impinging jet and flow spreading out under the confined spinning surface) and solid disk as a conjugate problem. The aim of this paper is to examine how the heat transfer is affected by adding a secondary rotational flow over the jet impingement region. Calculations were done for a range of jet Reynolds numbers (500-1500), rotational rates of 0-750 rpm or Ekman numbers (7.08 x 10 -5 - ∞), nozzle-to-target spacings (β = 0.25-5.0), and disk-thicknesses-to-nozzle-diameter ratios (b/d n = 0.25-1.67). Calculations were done for ammonia (NH 3 ), water (H 2 O), flouroinert (FC-77), and oil (MIL-7808), which were used as working fluids, and copper, silver, constantan, and silicon, which were used as solid disk materials. This provided a Prandtl number range of 1.29-124.44 and a solid-to-fluid thermal conductivity ratio of 36.91-2222. Plate materials with higher thermal conductivity maintained a more uniform and lower interface temperature distribution. A higher Reynolds number increased the local heat transfer coefficient over the entire interface. The rotational rate increased the local heat transfer coefficient under most conditions.