Numerical simulation of drop array impingement onto a superheated wall

Spray cooling is a very efficient method for thermal management of high-performance electronics. The performance of spray cooling is determined by the fluid dynamics and the heat transport when a single drop or multiple drops hit the superheated wall. To understand this process, we numerically study the generic situation of simultaneous impingement of periodic drop arrays onto a superheated wall. We study three different cases in which the distance between the drops varies. The refrigerant used is perfluorohexane (FC-72) in a pure vapor atmosphere under saturation conditions. Drops impinge at moderate Reynolds and Weber numbers, where no splashing occurs during single drop impingement. The wall temperature is above the saturation temperature of the fluid but below the onset of nucleate boiling. Simulations are performed using the OpenFOAM software library, taking into account a dynamic contact angle, evaporation and conjugate heat transfer. We show that the coalescence of more than two drops results in the formation of a liquid jet. A small distance between the drops results in the formation of a thin liquid film while a large distance results in small drops sitting on the wall. In the latter case, the largest amount of heat is transferred, but the occurrence of dry spots is undesirable for cooling applications. The results contribute to a better understanding of spray cooling and provide a perspective for efficient spray cooling.