Heat transfer in the hydraulic jump region of circular free-surface liquid jets

Because of its high heat transfer potential, liquid jet impingement is broadly used in cooling applications. As a free-surface jet spreads radially after impinging on a flat surface, a hydraulic jump can occur that severely affects the heat transfer. This study numerically scrutinizes the effects of different flow structures within the jump on the local heat transfer of the impinged plate subjected to a uniform heat flux. For the numerical simulations, a modified version of the interFoam solver of OpenFOAM is used, in which the interface compression scheme is amended implementing the continuum surface stress method. To create different flow structures in the jump region, an obstacle with a varying height is placed at the edge of the impinged plate. Jump structures and the transitions between them are distinguished by virtue of the appearance of a separation bubble on the bottom surface and/or a roller underneath the interface in the jump region. The results show that the hydraulic jump in itself reduces the local Nusselt number, whereas the roller underneath the free surface slightly improves the heat transfer. The minimum heat transfer rate occurs right before the separation bubble (at the separation point); however, the local stagnation point ahead of the separation bubble increases the Nusselt number.