OPTICAL MEASUREMENT OF TRANSIENT PHENOMENON OF LIQUID-HELIUM BOILING UNDER VERY HIGH CENTRIFUGAL OPERATION

Optical observation is one of the best ways of measuring the transient phenomenon of liquid helium boiling. Especially for very high centrif ugal operation, as in superconducting generators, a high speed observa tion technique is required, since the transient time is very short com pared to that for normal gravity operation. Photographic measurement i s a suitable observation technique because of its high speed response. This paper shows that the transient time of convection is a function of centrifugal acceleration and is proportional to the -1/3 power of i t. Also, a remarkable phenomenon, which is referred to as a 'bubble cl uster bridge' and which has not been observed in the stationary experi ment, occurs at the beginning of heating. A new type of optical sensor is applied to measure the transient phenomenon of convection as an au xiliary observation. The result shows that the bubble departure time f rom the heater surface is also proportional to the -1/3 power of centr ifugal acceleration.