Numerical Modeling of Conjugate Heat Transfer During Free Liquid Jet Impingement

Abstract

Abstract The paper presents the results of numerical simulation of a free jet of high Prandtl number fluid impinging perpendicularly on a solid substrate of finite thickness containing electronics on the opposite surface. The numerical model was developed considering both solid and fluid regions and solved as a conjugate problem. Equations for the conservation of mass, momentum, and energy were solved in the liquid region taking into account the transport processes at the inlet and exit boundaries as well as at the solid-liquid and liquid-gas interfaces. In the solid region, only heat conduction equation was solved. The shape and location of the free surface (liquid-gas interface) was determined iteratively as a part of the solution process by satisfying the kinematic condition as well as the balance of normal and shear forces at this interface. The number of elements in the fluid and solid regions were determined from a systematic grid-independence study. A non-uniform grid distribution was used to adequately capture large variations near the solid-fluid interface. Computed results included the velocity, temperature, and pressure distributions in the fluid, and the local and average heat transfer coefficients at the solid-fluid interface. Computations were carried out to investigate the influence of different operating parameters such as jet velocity, heat flux, plate thickness, and plate material. Numerical results were validated with available experimental data. It was found that the local heat transfer coefficient is maximum at the center of the disk and decreases gradually with radius as the flow moves downstream. The average heat transfer coefficient and the maximum temperature occurring in the solid decreased with increase of disk thickness and increase of thermal conductivity of the disk material.