비등 열전달에서 임계열유속점의 예측에 대한 연구

Abstract

본 연구는, 설정된 모델로부터 푸울 비등시 임계 열유?潭÷? 영향인자들을 계산했고, 임계열유속 및 임계온도를 예측하였다. 설정 모델에서, 증기 기주는 가열면에 고정되어 삼각형 분포로 배열되어 있으며, 열경계층으로의 열전달은 2 차원 정상열전도에 의하여 결정했고, 기액계면에서의 증발율은 분자 운동학이론 결과식을 사용했다. 각각의 액체 접촉각에 대한 임계점에서의 건면적비는 기하학적 및 열적 조건으로부터 추정했고, 임계온도 및 임계열유속은 핵비등영역내의 두점의 실험치를 사용하여 계산했다. 임계점에서의 건면적비는 접촉각이 작을수록 감소하며, 임계열유속 및 임계온도는 접촉각이 작을수록 증가하는 경향을 보였다.

In this paper, governing parameters at critical heat flux(CHF) point of pool boiling are calculated, and critical heat flux and temperature are predicted from the model which is valid near the CHF point. In the model, vapor stems are assumed to be distributed with a triangular grid, and the heat transfer rate into the thermal layer is determined by solving a two dimensional steady state heat conduction equation. The evaporation rate is given by the kinetic theory. The void fractions for the various contact angles are estimated through the geometric and thermal conditions. And the critical temperature and flux are calculated from the two experimental data set of the nucleate boiling region. The void fraction at the CHF point is strongly affected by the value of contact angle. Lower contact angle gives lower void fraction. But lower contact angle gives higher critical temperature and higher critical heat flux.

In this paper, governing parameters at critical heat flux(CHF) point of pool boiling are calculated, and critical heat flux and temperature are predicted from the model which is valid near the CHF point. In the model, vapor stems are assumed to be distributed with a triangular grid, and the heat transfer rate into the thermal layer is determined by solving a two dimensional steady state heat conduction equation. The evaporation rate is given by the kinetic theory. The void fractions for the various contact angles are estimated through the geometric and thermal conditions. And the critical temperature and flux are calculated from the two experimental data set of the nucleate boiling region. The void fraction at the CHF point is strongly affected by the value of contact angle. Lower contact angle gives lower void fraction. But lower contact angle gives higher critical temperature and higher critical heat flux.