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Photographic Study of Nucleate Pool Boiling on a Horizontal Surface
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1965
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Radiative Heat TransferPhotographic StudyEngineeringFluid MechanicsNucleate BoilingConvective Heat TransferChemical EngineeringHeat Transfer ProcessBubble DynamicHeat FluxNucleationThermophysicsThermodynamicsMaterials ScienceHorizontal SurfaceHeat TransferMultiphase FlowSurface ScienceThermal EngineeringChemical KineticsThermophysical PropertyBoiling
A photographic study of saturated nucleate pool boiling at one atmosphere was conducted on flat horizontal platinum and copper surfaces, capturing over 1,000 still images and 12 high‑speed videos to measure bubble break‑off diameters and active site populations up to 58,600 Btu/hr·ft². The study identified at least three, possibly four, heat‑transfer regions in nucleate boiling, with vapor structures progressing from discrete bubbles to columns, mushrooms, and patches as surface temperature rises, leading to the conclusion that models based on a single bubble mechanism are in serious error.
A photographic study was made of saturated nucleate pool boiling at a pressure of one atmosphere. Over 1000 still photographs and 12 high-speed motion pictures were taken of water boiling from a 2-in-dia flat horizontal surface facing upward. Two surfaces were studied, a 2/0 polished platinum surface and a 4/0 polished copper surface. The platinum surface was studied in the heat flux range of 14,700 to 176,000 Btu/hr, sq ft, and the copper surface from the incipient boiling heat flux of 10,500 Btu/hr, sq ft to the maximum flux of 493,000 Btu/hr, sq ft. Data were obtained for the breakoff diameters of discrete bubbles, and for the populations of active sites at heat fluxes up to 58,600 Btu/hr, sq ft. At least three, and possibly four, heat-transfer regions were found to exist in nucleate boiling, depending upon the mode of vapor generation. The vapor structures on the surface progressed through a sequence of first discrete bubbles, then vapor columns and vapor mushrooms, and finally vapor patches, as the surface temperature was increased. These individual vapor structures, or combinations of them, determine the mechanism of heat transfer in the four nucleate boiling regions. It was concluded that any heat-transfer model or design equation which is based on the dynamics of individual bubbles, or on any other single mechanism, must be in serious error.