Cyclic operation of a MEMS-based resonant micro heat engine: Experiment and model

2010 ◽  
Vol 107 (10) ◽  
pp. 104901 ◽  
Author(s):  
H. Bardaweel ◽  
R. Richards ◽  
C. Richards ◽  
M. Anderson
Keyword(s):  
Heat Engine ◽  
Cyclic Operation ◽  
Micro Heat Engine

Micro Thermal Engines: Is There Any Room at the Bottom?

1999 ◽  
Author(s):  
Richard B. Peterson
Keyword(s):  
Heat Transfer ◽  
Scaling Laws ◽  
Critical Role ◽  
Heat Engine ◽  
Engine Performance ◽  
Characteristic Size ◽  
Operating Efficiency ◽  
Simple Scaling ◽  
Small Structure ◽  
Micro Heat Engine

Abstract Richard P. Feynman introduced the field of microscale and nanoscale engineering in 1959 by giving a talk on how to make things very small. Feynman’s premise was that no fundamental physical laws limit the size of a machine down to the microscopic level. Is this true for all types of machines? Are micro thermal devices fundamentally different than mechanically-based machines with respect to their scaling laws? This paper demonstrates that micro thermal engines do indeed suffer serious performance degradation as their characteristic size is reduced. A micro thermal engine, and more generally, any thermally-based micro device, depends on establishing a temperature difference between two regions within a small structure. In this paper, the performance of a micro thermal engine is explored as a function of the characteristic length parameter, L. In the development, the important features of thermal engines are discussed in the context of developing simple scaling laws predicting the dependency of the operating efficiency on L. After this is accomplished, a general model is derived for a heat engine operating between two temperature reservoirs and having both intrinsic and extrinsic sources of irreversibility, i.e. thermal conductances and heat leakage paths for the heat flow. With this model and typical numerical values for the conductances, micro heat engine performance is predicted as the characteristic size is reduced. This paper demonstrates that under at least one particular formulation of the problem, there may indeed be some room at the bottom. However, heat transfer does play a critical role in determining micro engine performance and depending on how the heat transfer through the engine is modeled, vanishingly small efficiencies can result as the characteristic engine size goes to zero.

Characterization of a dynamic micro heat engine with integrated thermal switch

2006 ◽  
Vol 16 (9) ◽  
pp. S262-S269 ◽  
Author(s):  
L W Weiss ◽  
J H Cho ◽  
K E McNeil ◽  
C D Richards ◽  
D F Bahr ◽  
...  
Keyword(s):  
Heat Engine ◽  
Thermal Switch ◽  
Micro Heat Engine

Low Frequency Operation of the P3 Micro Heat Engine

2002 ◽  
Author(s):  
Scott A. Whalen ◽  
Michael R. Thompson ◽  
Cecilia D. Richards ◽  
David F. Bahr ◽  
Robert F. Richards
Keyword(s):  
Combustion Engine ◽  
Thermal Power ◽  
Electrical Power ◽  
Heat Engine ◽  
Low Frequency ◽  
Thermodynamic Cycle ◽  
Mechanical Power ◽  
Peak Voltage ◽  
Macro Scale ◽  
Micro Heat Engine

The development and low frequency testing of a micro heat engine is presented. Production of electrical power by a dynamic micro heat engine is demonstrated. The prototype micro heat engine is an external combustion engine in which thermal power is converted to mechanical power through a novel thermodynamic cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. This design is well suited to photolithography-based batch fabrication methods and is unlike any conventionally manufactured macro-scale engine. A peak-to-peak voltage of .84 volts, and power output of 1.5 microwatts have been realized at operating speeds of 10 Hz. Measurements are also presented for the engine operating at resonant conditions. Cycle speeds up to 240 Hz have been obtained, with peak-to-peak voltages of 70 millivolts.

Mathematical Modeling of Capillary Pumping Within Micron Sized Channels

2013 ◽  
Author(s):  
Yuelei Yang ◽  
Dan Zhang
Keyword(s):  
Mathematical Modeling ◽  
Experimental Data ◽  
Mathematical Model ◽  
Capillary Pressure ◽  
Heat Engine ◽  
Velocity Profiles ◽  
Vof Method ◽  
Numerical Results ◽  
Micro Heat Engine ◽  
Volume Of Fluids

This paper introduces a mathematical model which can be used to simulate the capillary pumping process of a micro heat engine. The micro heat engine has micron sized channels where the capillary pumping occurs. The classic Volume of Fluids (VOF) method is applied to obtain the velocity profiles of the fluids and to track the motions of the liquid-gas interfaces. The numerical results based this model have been compared with the experimental data and the initial retard of the pumping has been found and this phenomenon can be explained by the initial capillary pressure build-ups across the liquid-gas interfaces.

PZT and Electrode Enhancements of Mems Based Micro Heat Engine for Power Generation

2002 ◽  
Vol 730 ◽  
Author(s):  
A.L. Olson ◽  
L.M. Eakins ◽  
B.W. Olson ◽  
D.F. Bahr ◽  
C.D. Richards ◽  
...  
Keyword(s):  
Bottom Electrode ◽  
Mechanical Energy ◽  
Electrical Power ◽  
Heat Engine ◽  
Mems Devices ◽  
Stress Concentrations ◽  
Process Yield ◽  
Micro Heat Engine ◽  
Reducing Stress ◽  
And Diffusion

AbstractThe P3 Micro Heat Engine relies on a thin film PZT based transducer to convert mechanical energy into usable electrical power. In an effort to increase process yield for these were used on sputtered Ti/Pt bottom electrodes to compare roughness, grain size, and diffusion for annealing temperatures between 550 and 700 °C. For an optimized bottom electrode, process yield for various sized top electrodes were then studied for PZT thickness between 0.54 and 1.62 for reducing stress concentrations. Two PZT etching geometries on 2.3 μm thick Si/SiO2 membranes, with 1.5-3.5 mm side-lengths, were examined and one was used to increase the strain at failure by at least 40%. Integrating improvements in process yield and strain at failure, single PZT based MEMS devices capable of generating power of up to 1 mW and in excess of 2 volts have been demonstrated operating at frequencies between 300 and 1,100 Hz.

Power production by a dynamic micro heat engine with an integrated thermal switch

2007 ◽  
Vol 17 (9) ◽  
pp. S217-S223 ◽  
Author(s):  
J H Cho ◽  
L W Weiss ◽  
C D Richards ◽  
D F Bahr ◽  
R F Richards
Keyword(s):  
Heat Engine ◽  
Power Production ◽  
Thermal Switch ◽  
Micro Heat Engine

Design, fabrication and testing of the P3 micro heat engine

2003 ◽  
Vol 104 (3) ◽  
pp. 290-298 ◽  
Author(s):  
S Whalen ◽  
M Thompson ◽  
D Bahr ◽  
C Richards ◽  
R Richards
Keyword(s):  
Heat Engine ◽  
Micro Heat Engine

Characterization of the Thermodynamic Working Cycle in a MEMS-Based Micro Heat Engine

2003 ◽  
Author(s):  
S. A. Whalen ◽  
L. W. Weiss ◽  
C. D. Richards ◽  
D. F. Bahr ◽  
R. F. Richards
Keyword(s):  
Mechanical Energy ◽  
Michelson Interferometer ◽  
Heat Engine ◽  
Working Fluid ◽  
Resistance Thermometer ◽  
Working Cycle ◽  
Displacement Profile ◽  
Micro Heat Engine ◽  
Center Deflection

This work examines the conversion of thermal to mechanical energy in a micro heat engine by characterizing the heat engine’s working cycle. Results are given for dynamic measurements of pressure, volume, and temperature throughout the working cycle of the engine. Engine pressure is determined from the deformation of the two membranes in contact with the working fluid. A Michelson interferometer is used to measure the center deflection and displacement profile of both of these membranes. Pressure is determined from the membrane deflection using experimental static pressure-deflection curves. Engine temperature is measured using electrical resistance thermometry, via a micro resistance thermometer fabricated on the surface of a silicon membrane exposed to the working fluid in the engine cavity.

The Mechanical Behavior of a Micromachined PZT Membrane

2003 ◽  
Author(s):  
I. Demir ◽  
R. F. Richards ◽  
D. F. Bahr ◽  
C. D. Richards
Keyword(s):  
Thin Film ◽  
Mechanical Behavior ◽  
Material Properties ◽  
Energy Minimization ◽  
Variational Approach ◽  
Piezoelectric Ceramic ◽  
Electrical Power ◽  
Heat Engine ◽  
Silicon Membrane ◽  
Micro Heat Engine

The mechanical behavior of a micromachined PZT membrane for power applications is investigated. The membrane is a bulk-micromachined silicon membrane that supports a thin film of piezoelectric ceramic (PZT) sandwiched between platinum and gold electrodes. The membrane undergoes large periodic deflections to convert mechanical power to electrical power in a micro heat engine. An analysis using a variational approach is developed to find an approximate closed from solution based on energy minimization. Experiments were conducted to obtain material properties, residual stresses, and pressure deflection relationships. The modeled results compare well to the experimental results.

Development of Scaling Model for a MEMS-Based Micro Heat Engine

2010 ◽  
Author(s):  
H. Bardaweel ◽  
B. S. Preetham ◽  
R. Richards ◽  
C. Richards ◽  
M. Anderson
Keyword(s):  
Combustion Engine ◽  
Heat Engine ◽  
Working Fluid ◽  
Thin Membranes ◽  
Micro Heat Engine ◽  
Heat Of Evaporation ◽  
Major Factors ◽  
Engine Components ◽  
External Combustion ◽  
Thermal Physical Properties

In this work we investigate issues related to scaling of a MEMS-based resonant heat engine. The engine is an external combustion engine made of a cavity encapsulated between two thin membranes. The cavity is filled with saturated liquid-vapor mixture working fluid. We use both model and experiment to investigate scaling of the MEMS-based resonant heat engine. The results suggest that the performance of the engine is determined by three major factors: geometry of the engine, speed of operation, and thermal physical properties of engine components. Larger engine volumes, working fluids with higher latent heat of evaporation, slower engine speeds, and compliant expander structures are shown to be desirable.

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