Transient Thermal Management of Microelectronics Using Free Liquid Jet Impingement
The results of numerical simulation of a transient heat transfer process when a free jet of high Prandtl number fluid impinges perpendicularly on a solid substrate of finite thickness containing discrete electronics on the opposite surface are presented. 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 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 and plate material. It was found that the average heat transfer coefficient is maximum at early stages of the transient process and decreases gradually with time to the final steady state condition.