접촉각 변화에 따른 핵비등과 천이비등 곡선의 예측

Abstract

본 연구의 목적은 임계열유속점의 영향인자들을 근거로 하여, 핵비등과 천이비등 곡선을 예측하려 한다. 임계점에서의 인자들과 열전달 문제들의 해는 이미 발표된 논문의 결과들을 인용했다. 열유속과 비등곡선들은 과열온도에 대한 건면적비 관계식과 기주간의 거리에 대한 건면적비 관계식을 사용하여 계산했다. 예측된 열유속과의 비교를 위하여 증류수를 사용한 푸울 비등실험도 수행했으며, 실험조건으로는 면의 접촉각으로 정량화한 가습성을 변화시켰다.

각각의 접촉각에서 예측된 비등곡선들은 그 모양이 일반적인 비등곡선과 일치하며, 다음의 경향을 보이고 있다. 즉 동일한 과열온도의 경우, 핵비등 영역에서는 접촉각이 커질수록 열유속도 증가하나 천이영역에서는 이와 반대되는 경향을 보이고 있다. 예측된 열유속도 핵비등 영역에서는 실험치들과 거의 일치한, 천이영역에서는 실험치보다 낮은 값을 나타내고 있다.

This study aims to predict a boiling curve of the nucleate and transition boiling region on the basis of the parameters affecting the CHF point. The parameters on the CHF point and the solutions of heat transfer problems are taken from the published paper, ref.(6). The heat flux is calculated and its curve is drawn by the use of the void fraction relation to the superheat and to the distance between vapor stems.

The experiment of water pool boiling was conducted according to the wettability which is qualified by the contact angle, and these data are compared with the predicted heat flux.

The predicted boiling curves for various contact angles are in good agreement with the general curves in shape. And show the trend that higher contact angle gives higher heat flux at same superheat in the nuclete boiling region, but higher angle give lower heat flux in the transition boiling region. The predicted heat flux is almost the same in comparison to the experimental data in the nucleate region, however, it is low in the transition region.

This study aims to predict a boiling curve of the nucleate and transition boiling region on the basis of the parameters affecting the CHF point. The parameters on the CHF point and the solutions of heat transfer problems are taken from the published paper, ref.(6). The heat flux is calculated and its curve is drawn by the use of the void fraction relation to the superheat and to the distance between vapor stems.

The experiment of water pool boiling was conducted according to the wettability which is qualified by the contact angle, and these data are compared with the predicted heat flux.

The predicted boiling curves for various contact angles are in good agreement with the general curves in shape. And show the trend that higher contact angle gives higher heat flux at same superheat in the nuclete boiling region, but higher angle give lower heat flux in the transition boiling region. The predicted heat flux is almost the same in comparison to the experimental data in the nucleate region, however, it is low in the transition region.