This paper presents detailed fabrication and operational characterization of a MEMS based microboiler designed to scavenge waste thermal energy from sources like transportation or industry. Microboiler operation is based on capillary action that drives the working fluid from surrounding reservoirs to the surface that is heated by the waste thermal energy. As a result of phase change from liquid to vapor, pressure is created inside the enclosed central steamdome. This pressurized vapor can be made available to another MEMS device (PZT membranes, thermoelectric, etc.) to produce useful power output. In contrast to previous work, the new miniature microboiler design has undergone several modifications that improve operating efficiency. Capillary channels that were designed in linear fashion have been upgraded to a radial layout. This modification facilitated boiler enhancements in capillary flow, operating pressure, and rate of mass transfer. Capillary channels are formed from the silicon substrate with 50 μm widths and 100 μm depths. Power inputs of 2W, 3W and 4W are utilized to characterize performance. Maximum energy absorption via phase change of working fluid was 1.6 mW given a source temperature of 128 °C. The maximum steady state operating pressure achieved during testing was 3.65 kPa.
- Heat Transfer Division
Investigation of Microboiler for Discarded Thermal Scavenging
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Thapa, S, Fang, J, Wood, D, & Weiss, L. "Investigation of Microboiler for Discarded Thermal Scavenging." Proceedings of the ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology. Minneapolis, Minnesota, USA. July 14–19, 2013. V002T07A013. ASME. https://doi.org/10.1115/HT2013-17069
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