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Interfacial Phenomena and Heat Transfer
ESCI

ISSN Print: 2169-2785
ISSN Online: 2167-857X

Open Access

Interfacial Phenomena and Heat Transfer

DOI: 10.1615/InterfacPhenomHeatTransfer.2015012351
pages 385-397

DEVELOPMENT OF AN EXPERIMENTAL METHOD FOR FLOW-BOILING HEAT TRANSFER IN MICROCHANNELS

Sameer Raghavendra Rao
Rensselaer Polytechnic Institute, Troy, NY, USA; Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Yoav Peles
Rensselaer Polytechnic Institute, 110, 8th Street, Troy NY, 12180-3590; University of Central Florida Department of Mechanical and Aerospace Engineering Pegasus Blvd., P.O. Box 162450, Orlando, FL 32816-245012760, USA

ABSTRACT

In this paper, we report on an experimental method, supported by a numerical conduction model, to determine the fundamental mechanisms controlling flow-boiling heat transfer processes, such as during bubble ebullition. This is achieved by synchronizing high-speed visualization with surface temperature measurement and using the numerical model to infer the heat transfer coefficient from the surface temperature measurements. A slip coefficient, S, is defined and provides a quantitative measure of the effect of conduction heat transfer in typical flow-boiling experiments in microchannels. To demonstrate the method, three high-speed experimental measurements are detailed. Surface temperatures at high frequencies (O(10 kHz)) are obtained with micron-sized thermistors; boiling events are simultaneously visualized and used in conjunction with transient temperature measurements and the S coefficient to infer processes controlling heat transfer in a microchannel. The results demonstrate that microdomains formed by high-thermal-conductivity substrates, including silicon and copper, cannot be used to reveal transient processes at the microscale. Even results obtained using low-thermal-conductivity materials such as Pyrex and Benzocyclobutene (BCB) require conduction numerical analysis in the solid structure to decouple the convection and conduction processes.