霜層被覆面を用いた大気圧飽和液体窒素の非定常プール沸騰熱伝達の促進

抄録

Utilization of liquefied gas is widely used in the field of low temperature science and engineering. This study is a fundamental research on enhancement of heat transfer of saturated pool boiling during cooling process using liquefied gas. In this study, we investigated the influence of roughness and thermal conductance of a boiling surface on the pool boiling heat transfer to saturated liquid nitrogen at atmospheric pressure. A cooled sample was a copper sphere, 25 mm in diameter. The copper surface was polished by buffing or sandpaper for each experimental condition. The thermal conductance of the copper surface was changed by the frost layer coated on it. As a result, it is confirmed that the critical heat flux and the heat transfer coefficient of transition-nucleate boiling ware increase when the frost layer is used as the thermal resistance layer. In the nucleate boiling region, the heat transfer coefficient and the critical heat flux improve as the heat transfer surface becomes rough.