pressure does not alter the physical description of the bubble growth. It may be observed 

 (Table II) that 



P'(15°C) 



0.2, (32) 



p'aoo c) 



and further that 



.4(15° C) 



.4(100° C) 



0.03. (33) 



The consequence of these values is clear: the thermal effects in the growth of cavitation 

 bubbles are unimportant; only inertia effects are of significance. The Rayleigh velocity 

 will be the growth velocity for such bubbles [5]. 



Effect of rapid increase of liquid temperature 



It has already been remarked that for the heating rates ordinarily encountered 

 the temperature rise in the bulk liquid is unimportant when the bubble growth is followed 

 for times of the order of 10 or 100 millisec. The only parameter which is affected by 

 the rate of temperature rise is the delay time and the values which have been given above 

 correspond to a rise in liquid temperature a = 0.01 °C/sec. Very large rates of liquid 

 temperature rise may be encountered in a power surge in a liquid-cooled or liquid- 

 moderated nuclear reactor. For this reason solutions of the bubble growth equations 

 have been carried through for the temperature increase rates given by a = 200 °C/sec 

 and a — 2,000°C/sec; the former value corresponds roughly to temperature rise rates 

 observed in some reactor safety tests [6]. 



The results of the calculations at 1 atmosphere pressure are shown in Figs. 11 

 and 12 for 3°C superheat, and in Figs. 13 and 14 for 6°C superheat. The results at 

 approximately 19 atmospheres pressure are shown in Figs. 15 and 16 for 3°C super- 

 heat, and in Figs. 17 and 18 for 6°C superheat, the effect of increasing the rate of 

 temperature rise, a, is easily understood. The delay time is decreased noticeably, but 



the value of R mKX is essentially unchanged. The maximum growth velocity occurs so 

 early in the bubble history that the bulk liquid temperature is almost unchanged from 

 its initial value. As the bubble growth goes into the asymptotic phase, the radius-time 

 curves are very nearly parallel and the asymptotic behavior is given as before by R r~> t%. 

 This variation of bubble radius with time cannot persist for too long a time for large 

 values of a. It may be shown that the bubble radius changes from a fi& variation to a 

 t% variation at later times. The details of this analysis will be presented elsewhere. 



312 



