A Capsule Summary of Current Research Projects of Professor Arun ...

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4. Explosive BoilingPrasanta Kumar DeyExplosive (i.e. very rapid) boiling of a liquid at high degrees of superheatscan generate large forces which can be successfully harnessed in developingnovel thermal actuators with many potential engineering applications, e.g.displacement type micro-pump. Such devices have been shown to besuitable for specialized applications ranging from biology and medicine tospace exploration and micro-electronic schooling, etc. Fluid volumes on theorder of micro litres or less are figuring prominently in an increasingnumber of engineering applications. One well known successful applicationof this concept is the thermal inkjet printer head used in HP ink jet printers.The ink droplet ejection is actuated by cyclical explosive vaporization atvery high frequency of the liquid ink and subsequent discharge throughmicro-nozzles. Nano-sized bubbles are produced by cyclic heating; thebubble produced displaces the liquid in the form of nano-litre sized dropletsthrough the nozzle. Understand the properties of explosive vapor bubble are,therefore, important technically and scientifically. A research effort has beenundertaken to extend the theoretical and experimental state-of-the art in thegeneration and control of explosive vapor bubbles in micro-systems. Theobjective is to develop criteria for surface and bulk explosive boiling. Theresearch effort will also investigate the feasibility of a micro-device basedon explosive generation of bubble in a micro-cavity.5. Phase Change Material (PCM) based Hybrid Thermal Managementof Electronic Components and Systems - Numerical and ExperimentalStudyRavi KandasamyTechnological enhancements at device, package, and system levels haveresulted in increased functionality and decreased form factors. As aconsequence, thermal management has become more critical and a thermalanalysis must be included early in the design cycle for handheld electronicsand communication products, such as cellular phones, digital cameras,personal digital assistants (PDA). The majority of integrated circuits operatebest within a limited temperature range and their packages are expected toremove excessive heat. Furthermore, a high operational junctiontemperature decreases device reliability and reduces the operating lifetimeof the device. In some specific applications, such as digital cameras, high8
junction temperatures will also directly impact the component performance,like image quality. Several researchers have made an attempt to investigatethe feasibility of using PCM for heat removal and thermal energy storageapplications but to our knowledge not many active research solution isprovided using PCMs for electronic cooling applications as of now.A research attempt is being made by designing a several suitableexperimental setup to investigate the feasibility of using phase changematerials (PCM) for application in the thermal control of portable electronicdevices. The heat transfer characteristics (freezing and melting) for variouspower levels and orientations will be determined experimentally for anelectronic package and systems using PCM. A subsidiary objective is also tocarry out several parametric numerical studies using CFD commercial toolto understand effect of orientations, various heat inputs and study the effectof odd shaped geometries which will be of industry interest in futureelectronics. Though the subject of melting of PCMs in the enclosure hasreceived improved attention in recent years because of its wide-rangingapplications and also interest in electronic industry. Studying the meltingprocess of a PCM in square and rectangular enclosure may be a stillpromising alternative solution to natural convection air cooling forelectronic components and systems in some special cases such as usingPCM heat sinks, encapsulated PCMs. To our knowledge, no experimentalwork was done on melting PCMs with discrete heat sources has beenreported for electronic cooling applications.Additionally research will also be focused on heat spreader designimprovement, enhancing thermal conductivity of PCMs, attempting multi-PCMs with single and discrete heat sources will be studied. More addedattention and focus will be on PCMs selection to meet not only lower costand lighter but also will be on chemically stable, non-toxic and nonflammablePCM would be of great interest during the selection process. Theinfluence of solid liquid interface during melting, its size and shapes, meltfraction and variation of the surface temperature and nusselt numberestimation in natural convection will be presented. Experiments will focuson measuring transient temperature profiles at multiple points, infraredimaging, flow visualization will be of interest and will be planned atdifferent stages. The effects of various factors from time to time will bevaried depending on thermal management with a PCM system in whichconvection heat transfer in an enclosure plays an important role duringmelting.9
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