The heat flux was measured at the second burnout point of pool boiling over the range of high subcooling of 30 K to 88 K, under atmospheric pressure. The relation between the heat flux and subcooling ...was obtained by a mathematical model based on the mass-transfer mechanism of evaporation and condensation through a coalescent vapor bubble, and by a kinetic theory of molecules. The relationship equation gave fairly good agreement with the experimental results and showed that the second burnout heat flux did not increase unlimitedly with subcooling, but that it had a maximum value at a certain subcooling.
This report describes liquid-solid contact behavior in the subcooled pool transition-type boiling regime and the minute bubble emission boiling regime, detected by a void probe that uses a ...series-resonance circuit. This probe can approach the heated surface within two to three micrometers. The liquid-solid contact state discussed in this report means the nucleate boiling state caused by liquid invasion or Leidenfrost state caused by liquid rush onto the dry part on the heated surface. The dried area on the heated surface was estimated on the basis of the void signal, and the relation between the dried area on the heated surface and the measured heat flux was clarified by introducing a nucleate boiling model.
The authors obtained more accurate solutions of the boundary layer momentum and energy equations for a wedge-type flow by the electronic computer using the Runge-Kutta method and deduced an ...approximate equation of the temperature gradient at the wall with a high accuracy. When a two-dimensional water jet with finite nozzle width strikes normally on a flat surface, it forms a flow field which can be divided into two flow regions ; the first one is an impingement zone and the other is a uniform parallel flow zone. It is the purpose of this paper to estimate local heat transfer coefficients in such a flow field, where the velocity gradient just outside the boundary layer changes along a flat surface and to study theoretically the effect of the nozzle height above the flat plate on the local heat transfer coefficient Furthermore the calculated results were compared with experimental ones of local heat transfer coefficients along a flat surface with constant heat flux.
Pool boiling experiments were conducted on a 10 mm dia. heated surface facing upwards in the range of subcooling from 15 to 50K at atmospheric pressure. The heat transfer mechanism in the ...transitional boiling region can be estimated by a mathematical model based on the mass transfer mechanism of evaporation and condensation through a coalescent vapor bubble. The changes with time of the mass flux of condensation and the dried area on the heated surface, which are important factors governing the characteristics of transition boiling heat transfer, are estimated by a model based on this mass transfer mechanism. An explanation was obtained on the mechanism of liquid invasion onto the heated surface from the correspondence between the change with time of the dried area and local temperature fluctuations of the heated surface.
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