Numerical Simulations and Experimental Characterization of Heat Transfer From a Periodic Impingement of Droplets

Abstract

In this combined experimental and simulation investigation, a stream of HFE-7100 droplets striking a prewetted surface under constant heat flux was studied. An implicit free surface capturing technique based on the Volume-of-Fluid (VOF) approach was employed to simulate this process numerically. Experimentally, an infrared thermography technique was used to measure the temperature distribution of the surface consisting of a 100 nm ITO layer on a ZnSe substrate. The heat flux was varied to investigate the heat transfer behavior of periodic droplet impingement at the solid–liquid interface. In both experiments and simulations, the morphology of the impact zone was characterized by a quasi-stationary liquid impact crater. Comparison of the radial temperature profiles on the impinging surface between the experiments and numerical simulations yielded reasonable agreement. Due to the strong radial flow emanating from successive droplet impacts, the temperature distribution inside the crater region was found to be significantly reduced from its saturated value. In effect, the heat transfer mode in this region was governed by single phase convective and conductive heat transfer, and was mostly affected by the HFE-7100 mass flow rates or the number of droplets. At higher heat fluxes, the minimum temperature, and its gradient with respect to the radial coordinate, increased considerably. Numerical comparison between average and instantaneous temperature profiles within the droplet impact region showed the effect of thermal mixing produced by the liquid crowns formed during successive droplet impact events.

Validation of the S‐CLSVOF method with the density‐scaled balanced continuum surface force model in multiphase systems coupled with thermocapillary flows

“…The surface tension terms are calculated as the surface fluxes. Equation (36) is discretized as follows: [77] In OpenFOAM, the surface tension term is calculated within this equation. Finally, one can transform the equation into…”

Computation of effective free surfaces in two phase flows

“…We remark that the obtained expressions (31) and (32) for the fluctuating quantities depend only on the model parameters {T, r, V d } and the position of the effective (sharp) interfaceΓ LG . We are thus in the position to calculate the averaged products of fluctuations appearing as components of tensors A and B in (23a) and (23b).…”

“…In the inner region |x| < r 0 , using (31) and (32), we can write after employing some straightforward properties of pulse function (28)…”

“…In the transitional region r 0 < |x| < r, again using (31) and (32), and following the steps involved in obtaining (39) and (40), we can express F v and F v v as…”

“…Harlow & Shannon 28 were the first to simulate this phenomenon and several other authors have applied the Volume-of-Fluid (VoF) based approaches such as RIPPLE 29 and SOLA-VOF 30 to understand droplet impingement phenomena. Trujillo et al 31 also performed a numerical investigation and experimental characterization of the heat transfer from a periodic impingement of droplets.…”