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Abstract
Two-phase heat transfer and pressure drop results for a chip-scale, uniformly heated, microgap channel, with nominal gap heights of 100, 200, and 500 μm and using HFE-7100 and FC-87 as the working fluids, are reported. Average heat transfer coefficients in the range of 5 to 30 kW/m2-K were observed, for exit qualities up to 60%. Local heat transfer coefficients, obtained through an inverse computational technique, are found to vary strongly with thermodynamic quality and to fall within ±30% of the predictions of the venerable Chen correlation.
NOMENCLATURE
| A | = | surface area, m2 |
| Cp | = | specific heat capacity, J/kg-K |
| D | = | diameter, m |
| EoD | = | Eötvös number, dimensionless |
| F | = | Froude number, dimensionless |
| g | = | gravitational constant, m/s2 |
| G | = | mass flux, kg/m2-s |
| h | = | heat transfer coefficient, W/m2-K |
| hfg | = | latent heat of vaporization, J/kg |
| I | = | current, ampere |
| = | mass flow rate, kg/s | |
| P | = | pressure, N/m2 |
| q | = | power dissipation, W |
| q” | = | heat flux, W/m2 |
| T | = | temperature, K |
| T | = | T parameter in Taitel–Dukler unified model, dimensionless |
| U | = | velocity, m/s |
| V | = | voltage, volts |
| x | = | vapor quality, dimensionless |
| X | = | Martinelli parameter, dimensionless |
Greek Symbols
| β | = | angle of inclination |
| ϵ | = | discrepancy between predicted and measured heat transfer coefficient |
| ρ | = | density, kg/m3 |
| σ | = | surface tension, N/m |
Subscripts
| Cross-Section | = | channel cross section |
| G | = | gas |
| L | = | liquid |
| Loss | = | loss in heat flux |
| S | = | superficial |
| Sat | = | saturation condition |
Additional information
Notes on contributors
Emil Rahim
Emil Rahim received his Ph.D. in mechanical engineering from the University of Maryland, College Park, in 2011. He worked at TherPES laboratory under the direction of Professor Avram Bar-Cohen at the University of Maryland. He was invited by the National Science Foundation (NSF) to the Fourth International Conference on Nanochannels, Microchannels, and Minichannels to present his research and discuss “The Future of Nanoscale and Microscale Research from My Perspective” in June 2006, in Limerick, Ireland. He also worked at the Heat and Mass Transfer Laboratory (LTCM) at the Swiss Federal Institute of Technology (EPFL) in the summer of 2007.
Avram Bar-Cohen
Avram Bar-Cohen is a Distinguished University Professor at the University of Maryland, College Park, and a program manager in the Microsystems Technology Office of the Defense Advanced Research Projects Agency (DARPA), Arlington, VA; he is serving in this capacity while on leave from his position as a Distinguished University Professor at the University of Maryland, where he most recently also served as the chair of the Mechanical Engineering Department (2001–2010). Bar-Cohen earned a Ph.D. in mechanical engineering from the Massachusetts Institute of Technology, and prior to joining the University of Maryland, Bar-Cohen directed the University of Minnesota Center for the Development of Technological Leadership and held the Sweatt Chair in Technological Leadership. His publications, lectures, short courses, and research, as well as professional service in ASME and IEEE, have helped to create the scientific foundation for the thermal management of electronic components and systems and pioneered techniques for energy-efficient sustainable design of manufactured products. He has received numerous awards, including the prestigious International Centre for Heat and Mass Transfer 2008 Luikov Medal, ASME Heat Transfer Memorial Award (1999), and the IEEE CPMT Society Outstanding Sustained Technical Contributions Award (2002). He is among a very select number of ASME honorary members and is a fellow of the IEEE.