Void fraction and incipient point of boiling during the subcooled nucleate flow boiling of water

Abstract Void fraction has been determined with high-speed photography for subcooled nucleate flow boiling of water. The data obtained and the data of various investigators for adiabatic flow of stream-water mixtures and saturated bulk boiling of water have yielded a correlation which covers the following conditions: geometry: vertically orientated circular tubes, rectangular channels and annuli; pressure: 2–15.9 MN/m2; mass velocity: 388–3500 kg/m2 s; void fraction: 0–99%; hydraulic diameter: 0.0047–0.0343 m; heat flux: adiabatic and 0.01–2.0 MW/m2. The accuracy of the correlation is estimated to be 12.5%. The value of the so-called distribution (or flow) parameter has been experimentally determined and found to be equal to 1 for a vertical small-diameter circular tube. The incipient point of boiling for subcooled nucleate flow boiling of water has been determined with highspeed photography. The data obtained and the data available in the literature have yielded a correlation which covers the following conditions: geometry: plate, circular tube and inner tube-heated, outer tubeheated and inner- and outer tube heated annulus; pressure: 0.15–15.9MN/m2; mass velocity: 470–17355 kg/m2s; hydraulic diameter: 0.00239–0.032 m; heat flux: 0.13–9.8 MW/m2; subcooling: 2.6–108 K; material of heating surface: stainless steel and nickel. The accuracy of the correlation is estimated to be 27.5%. Maximum bubble diameters have been measured at the incipient point of boiling. These data and the data from literature have been correlated for the pressure range of 0.1–15.9 MN/m2.

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