MEMS-Based Boiler Operation from Low Temperature Heat Transfer and Thermal Scavenging

Abstract

Abstract:Increasing world-wide energy use and growing population growth presents a critical need for enhanced energy efficiency and sustainability. One method to address this issue is via waste heat scavenging. In this approach, thermal energy that is normally expelled to the environment is transferred to a secondary device to produce useful power output. This paper investigates a novel MEMS-based boiler designed to operate as part of a small-scale energy scavenging system. For the first time, fabrication and operation of the boiler is presented. Boiler operation is based on capillary action that drives working fluid from surrounding reservoirs across a heated surface. Pressure is generated as working fluid transitions from liquid to vapor in an integrated steamdome. In a full system application, the steam can be made available to other MEMS-based devices to drive final power output. Capillary channels are formed from silicon substrates with 100 µm widths. Varying depths are studied that range from 57 to 170 µm. Operation of the boiler shows increasing flow-rates with increasing capillary channel depths. Maximum fluid mass transfer rates are 12.26 mg/s from 170 µm channels, an increase of 28% over 57 µm channel devices. Maximum pressures achieved during operation are 229 Pa.

Experimental and computational investigation of a MEMS-based boiler for waste heat recovery

“…Such modification minimized the pre-condensation of vapor inside the steamdome. A maximum efficiency of approximately 88% was demonstrated by the boiler, an improvement of about 50% compared to previously published work [28]. Furthermore, the operating pressure of the boiler elevated as well.…”

“…These values showed improvement versus boilers presented in prior efforts where a larger dimension acrylic steamdome was utilized [28,30]. The use of a thin glass wafer as a steamdome eliminated a significant heat sink effect previously encountered.…”

“…The glass was preferred as a material of fabrication because of its insulating properties. The glass also represented significant mass reduction as compared to prior work [28,30]. This reduced the steamdome thermal impact as part of boiler operation.…”

“…Capillary channels themselves were designed based on prior experimental work [28][29][30] as well as expectations from open channel models [29,31]. Two components were brought together to form the boiler.…”

Experimental and lattice Boltzmann simulated operation of a copper micro-channel heat exchanger

“…Many standard thermodynamic cycles have low efficiencies where much of the thermal energy generated is rejected to the surrounding environment [1].…”