Characteristics of critical heat flux at high pressure in an inclined tube

Experimental data of the critical heat flux were obtained for boiling HCFH-at high subcritical pressures flowing upward in a uniformly heated tube inclined at various angles. According to the effect of the tube inclination, the critical heat flux was classified into four characteristic regimes; the regime where the critical heat flux generally increases with the inclination angle from the horizontal position, the regime where the critical heat flux is constant independent of the inclination angle, and the other two regimes in which the critical heat flux is equal to that for the horizontal or vertical flow, respectively. The conditions of each regime were clarified and the characetristics of the critical heat flux in each regime were discussed by comparing with those for the horizontal and vertical flows. At near-vertical angles, there was found an exceptional characteristic that the critical heat flux became higher than that for the vertical flow when the mass velocity was low and the exit quality was high.