Abstract
Fig. 1 of this report shows the typical values of heat transfered Q0 and the coefficient of heat transfer α obtained from our previous experiment, in which high temperatune bodies were quenched into water. As may be noted from this illustration, both the heat transfered and its coefficient are not constant throughout the cooling time, but have a maximum and a minimum value. The explanation of such a change of state can be mentioned as follows.
(i) The state A to C in Fig. 1.
Q0 is divided into two parts; the convection heat quantity Qa and the conduction heat quantity Qc in liquid. The former increases with the progress of state but the latter decreases contrariwise, so that Q0, the sum of Qa and Qc, changes from A to C through B as shown in the above figure. The evaporation in the state between A and C was considered to be the film state boiling, and the effect of radiation heat was found to be negligible small by our computation.
(ii) The state C to E in Fig. 1.
Qa and Qc both decrease with the lapse of time, and the bubble state boiling disappears at point D and its vicinity. Since then a body is cooled only by the convection of turbulent flow of liquid.
It may be said that the cooling ability of a cooling medium depends chiefly upon the intensity of cooling in the state between A and C. We studied the various behaviors of physical properties acted at the rapid cooling.
