포화상태 풀비등시 단일기포의 성장에 관한 연구

Abstract

Nucleate boiling experiments on heating surface of constant wall temperature were performed using R113 for almost saturated pool boiling conditions. A microscale heater army and Wheatstone bridge circuits were used to maintain a constant wall temperature condition of heating surface and to measure the heat flow rate With high temporal and spatial resolutions Bubble images during the bubble growth were taken as 5000 frames per second using a high-speed CCD camera synchronized With the heat flow rate measurements The bubble growth behavior was analyzed using the new dimensionless parameters for each growth regions to permit comparisons With previous experimental results at the same scale. We found that the new dimensionless parameters can describe the whole growth region as initial and later (thermal) respectively The comparisons showed good agreement in the initial and thermal growth regions. In the initial growth region<br/> including surface tension controlled, transition and inertia controlled regions as divided by Robinson and Judd,<br/> the bubble growth rate showed that the bubble radius was proportional to t2/3 regardless of working fluids and heating conditions. And ill the thermal growth region as also called asymptotic region, the bubble showed a growth rate that was proportional to t1/5, also. Those growth rates were slower than the growth rates proposed ill previous analytical analyses The requited heat flow rate for the volume change of the observed bubble was estimated to be larger than the heat flow rate measured at the wall. Heat, which is different from the Instantaneous heat supplied through the heating wall, can be estimated as being transferred through the interface between bubble and liquid even With saturated pool condition. Tins phenomenon under a saturated pool condition needs to be analyzed and the data from this study can supply the good experimental data With the precise boundary condition (constant wall temperature).<br/>