Abstract
The authors intend to report in the present paper the results of investigation as to the process of the latter stage of rapid cooling, the bubble state boiling and natural convection due to quenching of a red heated body. The series of experiments were carried out keeping the conditions of coolants constant in spite of the variations of conditions of a body.
Variety of the conditions was excecuted by changing the initial temperature, surface smoothness or diameter of the test cylinder. Arranging the data of the experiments the authors came to the next conclusion.
(1) Bubble State Boiling
The points indicating the max. value, ..max of heat transmission coefficient appear 10-20. higher than the boiling points of coolants, notwithstanding the degree of smoothness of the cooling surface. The higher the quenching temperature and the more rought the conditition of surface is, the larger the ..max value is. .. values at the period of bubble-state boiling are put into order by arranging in the equation (1), so far as the condition of surface is not too rough.
(2) Transition Point
The transition point appearing at the moment when cooling phenomena change from boiling state to that of natural convection exists close to the boiling point of a coolant, in spite of the variation of initial temperature and the diameter of test cylinder. But the temperature for the transition point is lower than the boiling point as the condition of surface is much more rough .
(3) Natural Convection
The decreasing of the quenching temperature or the smoothness of the surface lowers the value of ... Authors could not confirm how the value of .. is influenced by the size of test cylinder
In the equation (1):
Δu=uR-u0, Δu2=u2-u0, uR=surface temperature of test bady (°C), u2=boiling point of coolant (°C), u0=initial temperature of coolant (°C)
