Resonant operation and cycle work from a MEMS-based micro-heat engine

Weiss, Leland

doi:10.1007/s00542-008-0716-y

Cited by 13 publications

(4 citation statements)

References 9 publications

(10 reference statements)

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“…These included an internal "wick" structure on the lower, heat addition membrane. This allowed the lower the membrane to continually re-wet with working fluid [82][83][84]. An external thermal switch was also developed to allow discrete thermal inputs into the engine from a continuous, external thermal source.…”

Section: Heat Engines With Compliant Cylinder or Cavitymentioning

confidence: 99%

Power Generation via Small Length Scale Thermo-Mechanical Systems: Current Status and Challenges, a Review

Burugupally

Weiss

2018

Energies

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There has been significant interest and work toward the development of small length scale (micrometer to centimeter) energy conversion systems—heat engines and thermal energy harvesters—that operate on different thermal sources. Small combustion driven heat engines offer high power densities and longer operating durations, and present an opportunity to replace large and heavy chemical batteries. Thermal energy harvesters provide a great opportunity to harness the freely available thermal energy: solar, geothermal, and human body heat. These systems can contribute to significant energy savings when coupled to an existing, larger power generation system (e.g., vehicles and diesel generators) for the purpose of energy recovery. In this review, we discuss technological challenges, opportunities, and recent progress in small length scale energy conversion systems with special focus on free piston devices (engines and expanders) and phase-change driven devices. We discuss in detail four important design considerations that can have significant effect on small length scale device performance.

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Section: Heat Engines With Compliant Cylinder or Cavitymentioning

confidence: 99%

Power Generation via Small Length Scale Thermo-Mechanical Systems: Current Status and Challenges, a Review

Burugupally

Weiss

2018

Energies

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“…In experimental efforts, the ability of the membrane-based actuator to operate at resonant frequency generated a unique working cycle as a result [28].…”

Section: Rankine Cycle Efforts Have Leveraged the Advantage Of Externmentioning

confidence: 99%

Investigations of a new free piston expander engine cycle

Preetham

Weiss

2016

Energy

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This work examines the design and operation of a new, small-scale Free Piston Expander (FPE) engine that operates using low temperature waste heat sources to produce useful power output. The FPE is based on a sliding-piston architecture that eliminates challenges associated with MEMS-based rotating systems. A nonlinear lumped-parameter model is derived to study the factors that control the performance of the FPE engine and its unique operating cycle. This basic analysis considers a closed cycle operation of the FPE with low thermal or heat inputs and dimensions on the order of several millimeters. Key system design and operating parameters such as piston mass, external load, and heat input are varied to identify conditions and trends for optimal performance. The model indicated the pressure-volume diagram resembles a constant pressure cycle for a certain set of operating conditions but is also condition dependent. Increased heat inputs to the FPE reduced the engine natural or operating frequency while increasing the power output. Thermal efficiencies of the FPE are shown to be predictably low, on the order of 0.2 % due to the small heat input and operating temperature gradients associated with waste heat. Key design features are identified that reveal FPE efficiency, operating frequency, and output power are dependent on piston mass, external load, input heat-rate, and duration of heat input.

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“…Other micro-engine concepts have relied on power output that does not yield rotary motion. Work by Weiss et al included a flexing-expander membrane-based device that outputs power via membrane expansion [12][13][14]. The device consisted of two membranes, separated by a gasket and filled with working fluid that boils at low temperature.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2012

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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.

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Resonant operation and cycle work from a MEMS-based micro-heat engine

Cited by 13 publications

References 9 publications

Power Generation via Small Length Scale Thermo-Mechanical Systems: Current Status and Challenges, a Review

Power Generation via Small Length Scale Thermo-Mechanical Systems: Current Status and Challenges, a Review

Investigations of a new free piston expander engine cycle

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

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