|dc.description.abstract||Spray cooling is a promising and predominant heat transfer mechanism for many industrial applications, including cooling of microelectronic devices. However, there are numerous parameters that influence the physical mechanisms in spray cooling. It is a cumbersome process to characterize the entire spray cooling process due to the associated complexities including the non-uniformity in droplet sizes, velocities, droplet collision and breakup, among others. In order to better understand the underlying physical mechanisms of spray cooling, an experimentally-validated well-controlled droplet train impingement cooling process was simulated using Computational Fluid Dynamics (CFD). The well-controlled multiple droplet impingements consisted of simulating mono-dispersed droplets with controlled velocities in line with the experimental conditions.
Literature review reveals that the previous droplet train impingement numerical studies have mainly focused on single droplet, single stream and few double droplet train impingement cases. In the present study, hydrodynamics and heat transfer characteristics of single, double and triple droplet train impingement arrays have been investigated numerically in conjunction with the available experimental results.
Numerically, ANSYS-Fluent was employed to simulate the droplet impingement process using the Volume of Fluid approach coupled with the Level Set method (CLSVOF). A structured 2D axisymmetric and 3D quarter symmetric meshes were created for simulating single stream of droplets under spreading and splashing conditions, respectively. A 3D half symmetric mesh was generated for double and triple stream impingement (triangular pattern) cases. The Dynamic Mesh Adaption technique (DMA) was also used in the simulations, which was capable of capturing the propagation of the droplet-induced crown with time dependent spatial and temporal resolutions. A good agreement was reached between experimental and numerical data in terms of droplet-induced crown diameter, number of cusps emanating from the moving crown rim, adjacent hump height and impact crater diameter. In single stream cases, the effect of Weber number on spreading to splashing transition has been characterized. The effect of spreading-splashing hydrodynamics on surface heat transfer for single stream impingement has also been investigated numerically.
In double stream and triple stream cases, the influence of horizontal droplet stream spacing on adjacent hump height and impact crater hydrodynamics has been studied. In double and triple stream cases, horizontal impact spacing plays a crucial role in terms of hump formation and crater interactions. In summary, the effects of droplet Weber number, impact spacing and impingement pattern on heat transfer and hydrodynamics during droplet train impingement have been explored and elucidated.||en