Résumé:
This thesis presents a numerical simulation of the forced convection in a horizontal channel contained identical heated blocks with uniform and pulsation flow in the entrance of the channel. We examined two applications: horizontal channel contains heated blocks with and without deflectors. Theses configurations simulate the cooling applications of the electronic components generating heat by the Joule effect during the electrical current flow.
The principal objective of the thesis is the amplification of instabilities to produce the thermal resonance phenomenon in order to improve the convective heat transfer of the heated blocks mounted in the package and printed circuit board. The flow field is governed by the Navier–Stokes equations in the fluid region, and the thermal field by the energy equation. The finite volume method and the SIMPLER algorithm have been used to solve these equations.
The first part of the thesis has been focused on the heat transfer in the channel contained nine identical heated blocks mounted on the bottom wall. The air pulsation is introduced in the channel inlet. The natural frequencies of the flow are obtained for various Reynolds numbers. The bands of thermal resonance which ensure a better heat transfer of the heated blocks are obtained. The analysis of the flow with pulsation and its effect on the heat transfer gain of each block are discussed in detail. The results show that the enhanced heat transfer coefficient achieve 25 to 55% compared with uniform flow without pulsation. Good agreement between numerical simulations and experimental results available from the literature is obtained.
The second part of this thesis is focused to study the effect of the air pulsation in the entrance of the channel contains heated blocks with various kinds of deflectors (rectangular and triangular shapes).The results show that the integration of the deflectors improves the heat transfer of the heated blocks significantly, up to 34% in the uniform flow case. The exploiting natural instabilities require: the creation of the system with flow separation through the deflectors and the tandem blocks, the determination of the resonance frequency and then the excitation with appropriate modulation. This part showed that the combination of the passive and active techniques of the cooling ensures an enhancement of heat transfer of the electronic components in the channel.
