Experimental study on critical heat flux of steady boiling for high-velocity slot jet impinging on the stagnation zone

In this paper, the critical heat flux (CHF) of high-velocity slot jet impinging on the stagnation zone under saturated boiling and subcooled boiling were investigated experimentally. Two non-dimensional semi-theoretical and semi-empirical correlations to predict the CHF under saturated and subcooled boiling conditions were proposed from experimental data respectively. The mechanism of the subcooling and impact velocity effect on the CHF of jet impinging under steady boiling conditions were quantitatively explained. The high impact velocity has been observed to affect the CHF by two means. On one hand, the jet flow breaks through the vapor layer and brings fresh fluid, which always plays a role in strengthening the CHF. On the other hand, the high-velocity causes an increase of wall stagnation pressure, which will increase the CHF initially. When the wall stagnation pressure approaches 1/3 of the critical value, the CHF turns to decrease gradually. According to this trend, there should exist an ultimate CHF of steady boiling for jet impinging on the stagnation zone. The concepts of ultimate impact velocity and corresponding ultimate CHF are also obtained from the theoretical analysis.