| A phase-change based cooling system called E&barbelow;mbedded D&barbelow;roplet I&barbelow;mpingement f&barbelow;or I&barbelow;ntegrated C&barbelow;ooling of E&barbelow;lectronics (EDIFICE) has been developed and integrated using M&barbelow;icroe&barbelow;lectrom&barbelow;echanical S&barbelow;ystem (MEMS) technology to fabricate silicon micronozzles. Evaporative spray cooling with large latent heat not only brings heat flux removal to another high level but also avoids temperature overshoot at boiling incipience and thermal cycling. By exploiting MEMS technology, conventional components such as valves, the pump, the condenser and nozzles could be miniaturized and integrated with sensors to build an intelligent compact cooling system with adaptive cooling ability and meet the future demand in thermal management for electronics and high power laser system.; The selection of coolant is based on its thermal and fluid properties as well as environmental safety. The decision should be a compromising result to make the whole system workable instead of optimizing the performance of any particular component in the system.; Some design features in conventional macro-nozzles to introduce disturbances into liquid such as air-assisted, pressurized, simplex-swirl, jet-jet impingement atomizers have been re-evaluated and examined to see if they are still effective on microscale or suitable for MEMS fabrication processes. Using deep reactive ion etch (DRIE) and silicon-to-silicon fusion bonding, three micronozzle features such as irregular shapes, sidewall roughness and swirl are fabricated and tested for the purpose of triggering and enhancing disturbance intensity. Silicon Swiss Roll micronozzle combining sheet-like geometry and swirl has proved to be so effective to atomize fluid at injection pressure as low as 3 to 4 psig.; Silicon Swiss Roll micronozzle plate not only increases CHF values for each specified flow rate but also enlarges the CHF difference for every flow rate increment. It has shown that atomization performance is very critical to cooling performance at low flow rate. The installation of a heat exchanger for excessive liquid is needed to gain back the subcooled effect. This study provides a foundation to implement a compact adaptive high end heat flux removal system. Further study of developing a microfluidic delivery system to eliminate the reservoir and to replace the macro-hydraulic system is recommended. |
