Parametric investigation of flow and heat transfer on the reflooding quenching of a cylinder rod in forced convection

Abstract

A reflooding quenching boiling experiment in forced convection was conducted to investigate the flow and heat transfer performance of a FeCrAl cylindrical rod under various subcooling degrees and flow rates. Employing image processing and inverse heat conduction problem (IHCP) methods, the research provides insights into vapor film thickness, quenching front propagation, wall temperature cooling rate and minimum film boiling temperature. Key observations include the presence of numerous extremely small bubbles dispersing around the rod and a third quenching front appears in the middle of the rod under higher subcooling condition at 25 °C, attributed to a thinner vapor film, smaller bubbles resulting from film rupture and the inertia of fluid flow. Within the experimental range, the impact of the subcooling degree on the fluid flow and heat transfer performance during the quenching boiling process is more pronounced than that of the coolant flow rate. The evolution of the vapor film indicates a substantial reduction of 78.76 % in film thickness and a significant increase of 185.71 % in propagation velocity with an increase in subcooling degree, while an elevation in flow rate lead to a 29.84 % decrease in film thickness and a 45 % increase in propagation velocity. Heat transfer performance benefits from increased subcooling degrees throughout the entire quenching boiling process, whereas flow rate impacts the heat transfer performance of film boiling alone. Furthermore, by incorporating the impact of flow velocity, a predictive formula for Tmin is established with an error margin within ±5 %.