Microchannels and Minichannels are being used in electronic cooling, fuel cells, automotive heat exchangers, micro refrigeration systems. They are also being considered for high heat flux applications under microgravity environment in space missions. Research laboratories and industries throughout the world are trying to explore and tap the potential uses of these small diameter channels in various products and applications. Before stepping in to any of the product design phase, fundamental issues related to their performance have to be studied and resolved. This thesis work focuses on resolving some of these fundamental issues related to flow boiling in small diameter channels and augmenting the understanding of their basic performance characteristics. The present experimental study is undertaken to determine the flow patterns, heat transfer, pressure drop and effect of gravitational orientation on the flow boiling characteristics of water in a set of six parallel minichannels, each 1054 µm wide by 197 µm deep and 63.5 mm long with a hydraulic diameter of 333 µm. The channels are machined on top of a copper block and are covered with Lexan to permit visual observation. The copper block along with the channel are heated by a cartridge heater. The observed flow patterns provide important information regarding the boiling behavior. The study is also extended to flow patterns under different gravitational orientations. Signal analysis of the associated pressure drop fluctuations is studied and a new correlation for predicting heat transfer coefficients is developed for flow in these geometries and the correlation is tested with other data sets available in the literature.

Library of Congress Subject Headings

Two-phase flow; Flow visualization; Fluid-structure interaction; Pipe--Hydrodynamics; Heat--Transmission; Reynolds analogy

Publication Date


Document Type


Student Type


Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)


Satish Kandlikar

Advisor/Committee Member

Margaret Bailey

Advisor/Committee Member

Abhijit Mukherjee


Physical copy available from RIT's Wallace Library at TA357.7.M84 B36 2004


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