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 centrifugal operation, as in superconducting generators, a high speed observation technique is required, since the transient time is very short compared to that for normal gravity operation. Photographic measurement is 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 it. Also, a remarkable phenomenon, which is referred to as a 'bubble cluster bridge' and which has not been observed in the stationary experiment, occurs at the beginning of heating. A new type of optical sensor is applied to measure the transient phenomenon of convection as an auxiliary observation. The result shows that the bubble departure time from the heater surface is also proportional to the -1/3 power of centrifugal acceleration.