Pool Boiling Heat Transfer in Microgravity (Experiments with CFC-113 and Water Utilizing a Drop Shaft Facility)

摘要

Microgravity pool boiling experiments were carried out utilizing the drop shaft at the Japan Microgravity Center, which enables control of microgravity to within one-ten-thousandth of terrestrial gravity for a period of 10 seconds. Vapor bubbles were generated on a Joule-heated stainless steel or ITO film backed with a thin alumina or glass substrate, which was immersed in a pool of subcooled or saturated liquid at atmospheric pressure. The CHF (critical heat flux) to CFC-113 was lowered, in microgravity, to one-fifth of that achieved under the normal terrestrial condition. In contrast, the CHF to water remained more than one-half that achieved under the terrestrial condition. This difference in the gravity dependence of CHF is presumably ascribable to the difference in the frequency of bubble detachment from the heater surface between CFC-113 and water in microgravity, which is dependent on the difference in thermophysical properties, particularly the surface tension and the heat of vaporization, between the two fluids.