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ABSTRACT
In this study, subcooled flow boiling was investigated in horizontal microtubes. Experiments were conducted using deionized water as the working fluid over a mass flux range of 4000–7000 kg m−2s−1 in microtubes with inner and outer diameters of ∼600 and ∼900 μm, respectively. Microtubes with lengths of 3, 6, and 12 cm were tested to clarify the effect of heated length on flow boiling heat transfer and pressure drop characteristics. A force analysis related to two-phase flow was conducted to understand the effect of forces on bubble dynamics. Pressure drop and heat transfer data in flow boiling were acquired. Experimental heat flux data were compared with partial boiling heat flux correlations, and good agreements were obtained. Pressure drop was larger in longer microtubes in comparison to shorter ones, while higher heat fluxes were obtained in shorter microtubes at the same wall superheat. Two-phase heat transfer coefficient increased with the microtube length due to lower temperature difference between wall temperature and bulk fluid temperature in longer microtubes. Higher heat fluxes achieved in shorter microtubes at the same wall superheat imply higher critical heat fluxes in shorter microtubes.
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Abdolali Khalili Sadaghiani
Abdolali Khalili Sadaghiani received his M.Sc. degree in mechatronics engineering from Sabanci University, Istanbul, Turkey, in 2015. He is working under the supervision of Prof. Ali Koşar. His research focuses on numerical and experimental studies of multiphase flows in microchannels. His research interests lie in microscale heat and mass transfer, phase change, and microfluidics.
Ali Koşar
Ali Koşar received his B.S. degree in mechanical engineering from Bogazici (Bosphorus) University, Istanbul, in 2001. He pursued his graduate study in the Department of Mechanical Engineering at Rensselaer Polytechnic Institute between 2001 and 2006. He joined the Mechatronics Engineering Program at Sabanci University in fall 2007. He is one of the pioneers in the design and development of new-generation micro heat sinks and microfluidic devices. His research interests lie in heat and fluid flow in micro-/nanoscale, forced convection, boiling heat transfer, and cavitation. He is currently a faculty member at Sabanci University.