An entropy generation minimization, EGM, method is ap-plied to study the thermodynamic losses caused by heat trans-fer and pressure drop for the fluid in a cylindrical pin-fin heat sink and bypass flow regions. A general expression for the en-tropy generation rate is obtained by considering control volumes around heat sink and bypass regions. The conservation equa-tions for mass and energy with the entropy balance are applied in both regions. Inside the heat sink, analytical/empirical cor-relations are used for heat transfer coefficients and friction fac-tors, where the reference velocity used in Reynolds number and pressure drop is based on the minimum free area available for the fluid flow. In bypass regions theoretical models, based on laws of conservation of mass, momentum and energy, are used to predict flow velocity and pressure drop. Both in-line and stag-gered arrangements are studied and their relative performance is compared for the same thermal and hydraulic conditions. A parametric study is also performed to show the effects of bypass on the overall performance of heat sinks.
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