EXPERIMENTAL STUDY OF SUBCOOLED NUCLEATE BOILING OF WATER FLOWING IN 1/4-INCH-DIAMETER TUBES AT LOW PRESSURES

摘要

Nucleate boiling of sub cooled water flowing vertically upward through 1/4inch electrically heated tubes was experimentally investigated over the following range of conditions:exit pressure, 17 to 100 pounds per square inch absolute;flow rate, 0.52X10° to 3.45X10° pounds per hour per square foot;heat flux, up to 3.0Xl06 Btu per hour per square foot;wall temperature, up to 520° F;liquid subcooling, up to 180° F;and tube length, 25, 50, and 100 diameters . Measurements of local heat flux, axial distribution of tube wall temperature, tube inlet and exit fluid temperatures and pressures, and inlet pressure fluctuations were obtained. Plots of heat flux, pressure drop, and pressure fluctuations are presented as functions of exit fluid temperature, wall temperature, and saturation temperature. Wall temperatures were nearly independent of fluid bulk, temperature and mass flow for the fully developed nucleate boiling range investigated. Pressure drops in excess of 18 times the isothermal liquid-phase pressure drop were measured. High-frequency largeamplitude pressure fluctuations, believed to be caused by bubble collapse, were recorded.