Electronic systems used in communication devices and mission critical systems such as directed-energy weapons and spacecraft call for requirements to dissipate high heat flux in limited spaces. This study attempts to model the heat transfer in an electronic module, dissipating heat to a coolant in a microchannel as well as to ambient by natural convection and radiation. These results have been used to compare the effectiveness of a new cooling system, embedded with phase changing materials within the heat spreaders. The heat transfer model takes care of the heat stored in the phase changing material, heat transferred by natural convection and radiation effects, in addition to the convection heat transfer in the microchannel cooling passage. Hence, the developed model can successfully take into account the effect of the variation in operating atmospheric conditions which are significant in systems employed in harsh thermal environments. Simulations have been performed for a wide range of heats and appropriate coolant flow rates are being set for a prescribed safe operating temperature of the processor. Simulations for cooling systems with phase changing materials embedded

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Modeling, simulation, and thermal performance analysis of a thermocycler for the Continuous Flow Polymerase Chain Reaction (CF-PCR), with a phase-changing material (PCM) laden annealing flow path, is presented. The incessant threat of microorganisms such as virus, bacteria, and fungi has fostered effective, quick, and miniature detection devices in order to curtail the wide-spreading of infections. Microfluidics-based CF-PCR systems are compact and are ideal for faster response. The thermal cycling process involves the exposure of a given liquid sample to different temperature conditions when it is taken through the continuous flow path, by which a prescribed periodic change of temperature suitable for deoxyribonucleic acid (DNA) amplification is achieved. A rapid temperature reduction and maintenance of isothermal conditions to facilitate the annealing phase of CF-PCR process by a PCM assisted cooling is envisaged in the present study. Unsteady, two-dimensional, incompressible fluid flow and internal convection heat transfer in a microchannel annealing path with melting of tetracosane boundary has been simulated using SIMPLEC algorithm based finite volume solver. Solver validation is carried out against the experimental data on internal convection heat transfer in a rectangular microchannel. A detailed numerical study has been performed to assess spatiotemporal heat transfer characteristics of internal convection in the microfluidic path when the flow triggers the melting of encapsulated PCM. The present study evidences the swift temperature reduction and management of isothermal conditions congenial for the annealing process in the CF-PCR system for various sample flow rates and PCM mass.

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