Cooling techniques for electronic equipment

Mixed convection from an isolated heat source in a rectangular enclosure

Abstract: The mixed convection transport from an isolated thermal source, with a uniform surface heat flux input and located in a rectangular enclosure, is studied numerically. The enclosure simulates a practical system such as an oven or an air-cooled electronic device, where an airstream flows through the openings on the two vertical walls. The heat source represents a heater or an electronic component located in such an enclosure. The interaction of the cooling stream with the buoyancy-induced flow from the heat source is of interest in this work. Laminar, two-dimensional flow is assumed, and the problem lies in the mixed convection regime, governed by the buoyancy parameter GrIRe1 and the Reynolds number Re. Other significant variables include the locations of the heat source and the outflow opening. The inflow is kept at a fixed position. The mathematical model is developed with vorticity and stream function, along with temperature, as the dependent variables. The unsteady terms are retained in the vo...

Numerical investigation of laminar heat transfer performance of various cooling channel designs

Abstract: This study addresses the heat transfer performance of various cooling channel designs e.g., parallel, serpentine, wavy, coiled and novel hybrid channels. The cooling channel is designed to be placed on top of an electronic chip which dissipates heat at a constant flux. Laminar flow of a Newtonian fluid in a square cross-section channel is investigated using a three-dimensional computational fluid dynamic approach. Five channels Reynolds number are investigated to quantify the effect of Reynolds number on the performance of the cooling channel designs. Advantages and limitations of each design are discussed in the light of numerical results. Figures of merit, viz. heat transferred per unit pumping power are compared for the wide variety of channels examined.

Conjugate natural convection combined with surface thermal radiation in a three-dimensional enclosure with a heat source

Abstract: Numerical analysis of natural convection and surface thermal radiation in a cubical cavity having heat-conducting solid walls of finite thickness with a heat source located at the bottom of the cavity in conditions of convective heat exchange with an environment has been carried out. Mathematical study has been based on a numerical solution of the three-dimensional Boussinesq equations in the dimensionless variables such as vector potential functions, vorticity vector and temperature by finite difference method. Main attention was paid to the effects of the Rayleigh number 103 ⩽ Ra ⩽ 105, an emissivity of internal surfaces of the solid walls 0 ⩽ ɛ

Optimization of pin-fin heat sinks using anisotropic local thermal nonequilibrium porous model in a jet impinging channel

Abstract: A numerical study has been carried out to optimize the thermal performance of a pin-fin heat sink. A pin-fin heat sink, which is placed horizontally in a channel, is modeled as a hydraulically and thermally anisotropic porous medium. A uniform heat flux is prescribed at the bottom of the heat sink. Cool air is supplied from the top opening of the channel and exhausts to the channel outlet. Comprehensive numerical solutions are derived from the governing Navier-Stokes and energy equations using the Brinkman-Forchheimer extended Darcy model and the local thermal nonequilibrium (LTNE) porous model for the region occupied by the heat sink. Results from this study indicate that the anisotropy in permeability and solid-phase effective thermal conductivity changes substantially with the variation of porosity. Optimum porosity for maximum heat dissipation depends on the pin-fin thickness, the pin-fin height, and the Reynolds number. A correlation for predicting the optimum porosity for a pin-fin heat sink is prop...

Thermal fatigue reliability enhancement of plastic ball grid array (PBGA) packages

Abstract: A combined design of experiment and numerical analysis approach is used to determine the effect of four design parameters on the thermal fatigue life of solder joints. The four parameters considered were: substrate thickness, array configuration, ball pitch, acid pad size. A full factorial experiment was designed which was conducted numerically. A validated life prediction model was then used to determine the fatigue lives for each combination. Up to a factor of five improvement in fatigue life is predicted when these parameters were changed from one level to another.