Experimental investigation on the influence of surface conditions on boiling heat transfer during quenching of a cylinder in subcooled water

Abstract

In this study, comparative experiments were conducted on the quenching boiling in distilled water of SS, FeCrAl and Zr-4 cylinders to investigate their flow and heat transfer performance. The high-speed camera was used to visualize the transient quenching boiling behavior. By employing the validated inverse heat conduction problem (IHCP) method, the surface temperature and heat flux were obtained based on measured temperature inside the cylinder. The experiment results indicate that within the increase of coolant subcooling degree, surface roughness, and decrease of the product of the thermophysical properties of solid materials (ρkc_p), the duration of quenching boiling decreases, the minimum film boiling temperature (T_min) increases, and the heat transfer performance is enhanced. Moreover, the influence of coolant subcooling degree on quenching boiling process is more pronounced than that of surface roughness. The micron-scale microstructure of the rough surface has a minimal effect on the heat transfer of the vapor film, but it triggers the early collapse of the vapor film and raises T_min. It is noteworthy that under the lower subcooling condition of 5℃ in the experiment, there are notable differences in the types of vapor film collapse between the rough surface and smooth surface, namely Coherent Collapse and Propagative Collapse. Compared with SS and FeCrAl, the quenching heat transfer of Zr-4 is more susceptible to surface oxidation. Furthermore, a new correlation for T_min is developed, that couples the influence of the surface roughness, coolant subcooling degree, and solid thermophysical properties, with most predicted values falling within a 10% margin of error.