Periodic boiling in parallel micro-channels at low vapor quality |
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| Institution: | 1. Science and Technology on Scramjet Laboratory, National University of Defense Technology, Changsha, Hunan 410073, People’s Republic of China;2. School of Engineering, University of Edinburgh, The King’s Buildings, Mayfield Road, Edinburgh EH9 3JL, UK;3. UVHC, TEMPO, Universite Valenciennes, F-59313, France;1. Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing, 100124, PR China;2. School of Power, Energy and Mechanical Engineering, North China Electric Power University, Baoding 071003, PR China;1. Air Conditioning and Refrigeration Center, Department of Mechanical Engineering, University of Illinois at Urbana Champaign, 1206 West Green Street, Urbana, IL 61801, USA;2. CTS, 2209 Willow Rd., Urbana, IL, USA;1. Institute of Refrigeration and Cryogenics, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;2. Beijing Key Laboratory of Space Thermal Control Technology, Beijing Institute of Spacecraft System Engineering, Beijing 100094, China |
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| Abstract: | Based on experimental investigations the present study evaluates instability and heat transfer phenomenon under condition of periodic flow boiling of water and ethanol in parallel triangular micro-channels. Tests were performed in the range of hydraulic diameter 100–220 μm, mass flux 32–200 kg/m2 s, heat flux 120–270 kW/m2, vapor quality x = 0.01–0.08. The period between successive events depends on the boiling number and decreases with an increase in the boiling number. The initial film thickness decreases with increasing heat flux. When the liquid film reached the minimum initial film thickness CHF regime occurred. Temporal variations of pressure drop, fluid and heater temperatures were periodic. Oscillation frequency is the same for the pressure drop, for the fluid temperature at the outlet manifold, and for the mean and maximum heater temperature fluctuations. All these fluctuations are in phase. The CHF phenomenon is different from that observed in a single channel of conventional size. A key difference between micro-channel heat sink and single conventional channel is amplification of parallel-channel instability prior to CHF. The dimensionless experimental values of the heat transfer coefficient are presented as the Nusselt number dependence on the Eotvos number and the boiling number. |
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