The Effect of Weak Crossflow on the Heat Transfer Characteristics of Short-Distance Impinging Cooling

Abstract

T h e E ffect of W e a k C ro ssflo w on th e H e a t T ra n s fe r C h a ra c te ris tic s of S h o rt-D is ta n c e Im p in g in g C o o lin g This paper numerically and experimentally investigated the effect o f weak crossflow on the heat transfer characteristics o f a short-distance impinging jet. The Reynolds number o f the impinging je t ranged from 6000 to 15,000, and the mass velocity ratio (M) between the crossflow and the je t varied from 0 to 0.15. The separation distance (H) between the exit o f the je t nozzle and the impingement surface equals to the exit diameter (D) o f the impinging jet. In the experiments, the temperature distribution on the impingement target surface was measured using a transient liquid crystal method. In the numerical simula tion, a multiblock hexahedral mesh was applied to discrete the computational domain, and a commercial CFD package (ansys cfx-12.0) with a standard k-s turbulence model was used fo r computation. It was found that compared to the impinging cooling without crossflow, the heat transfer characteristics near the impinging stagnation point remained almost constant. At the same time, the presence o f crossflow decreased the heat transfer rate in the upstream region o f the impinging stagnation point, while increased that in the downstream o f the impinging stagnation point. Taken together, crossflow has a complex influence on the impinging cooling, which is highly dependent on the mass velocity ratio between the crossflow and the jet.