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ISSN Druckformat: 2151-7975
ISSN Online: 2151-7991
EVAPORATION FROM MICROPOROUS SURFACES IN A MECHANICALLY PUMPED TWO-PHASE LOOP
ABSTRAKT
The increasing application of high-power-density electronic components, for example, in space applications or data processing centers, causes the need of heat-transfer devices that can handle the high heat fluxes dissipated by these components. A prototype of a mechanically pumped two-phase loop has been developed at the Institute for Technical Thermodynamics in cooperation with OHB System AG and ESA/ESTEC. The loop incorporates miniature evaporators that can be mounted directly on the heat-dissipating device, minimizing temperature differences between the heat-dissipating part and the cooling device. Three evaporators are arranged in parallel to investigate the performance of the loop during multievaporator operation at different heat loads at the evaporators. In this study the heat-transfer coefficients of the new sintered surface could be increased up to 20 W/(cm2 K). The fouling of the surface slows down due to a higher porosity (bigger grain size, here 60 µm). The critical heat flux of the porous surfaces measured is limited to approx. 90 W/cm2 and does not increase with the volume flux (above 30 mL/min) as it happens with the smooth reference and a new microstructured surface. The microstructured surface reaches a critical heat flux of 152.6 W/cm2 and a heat-transfer coefficient of 6.5 W/(cm2 K) which is the best overall performance of all tested structures inside this evaporator type until now. System tests with three evaporators at different heat loads show stable system behavior. The saturation pressure inside the evaporators depends on the system heat load.
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