An Experimental Study on Heat Transfer Coefficients just before Critical Heat Flux Conditions in Uniformly Heated Vertical Annulus

균일 가열 수직 환상관에서 임계열유속조건 직전의 열전달계수에 관한 실험적 연구

Water heat transfer experiments were carried out in a uniformly heated annulus with a wide range of pressure conditions. The local heat transfer coefficients for saturated water flow boiling have been measured just before the occurrence of the critical heat flux (CHF) along the length of the heated section. The trends of the measured heat transfer coefficients were quite different from the conventional understanding for the heat transfer of saturated flow boiling. This discrepancy was explained from the nucleate boiling in the liquid film of annular flow under high heat flux conditions.