Experiments on the Relationship Between the Coefficients of Friction and Heat Transfer in Nucleate Boiling

Citation

Mulligan, Hampton Emanuel (1954) Experiments on the Relationship Between the Coefficients of Friction and Heat Transfer in Nucleate Boiling. Engineer's thesis, California Institute of Technology. doi:10.7907/6KN7-5864. https://resolver.caltech.edu/CaltechETD:etd-01262004-105223

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. An experimental investigation was conducted to determine whether any relationship exists between the friction and the heat transfer coefficients in the region of nucleate boiling with forced convection. The tests were carried out with distilled water flowing through a 3/8 inch diameter tube. The water was heated by passing an electric current through the tube wall. Measurements of the velocity of the water were taken at three positions along the test section by means of pitot tubes. The pitot tubes were also used to measure static pressure drops. From the experimental data the heat transfer and friction coefficients were computed. These coefficients were determined for a heat transfer range from 1.0 to 2.0 Btu/sq in-sec and for three pressure levels, 265, 115 and 65 psia. It was found that for a constant subcooling in the nucleate boiling region the friction coefficient increases with increasing heat transfer rate, indicating that the bubbles actually do influence the momentum exchange. It was also found that the experimentally determined values of the friction and heat transfer coefficients plot about a line the equation of which is [...]. This is the relation that one would expect on the basis of Reynolds' analogy for turbulent flow either without a laminar boundary layer, or with the laminar boundary layer when the Prandtl number is unity. It appears therefore that the effect of the bubbles is a hydrodynamic one leading to an increase in heat exchange as well as in momentum exchange.

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