2018 Volume 58 Issue 1 Pages 140-145
This study investigates the heat transfer characteristics of a circular jet pointing upward that impinges on a moving hot steel sheet by using a laboratory-scale setup. The test liquid was water at 17°C, and the volumetric flow rate of the coolant was set to 450, 960, and 1480 mL/min. The test solid was 0.3 mm thick stainless steel (SUS430) with an initial temperature in the range 300–700°C. The moving velocity of the solid was set to 0.5, 1.0, and 1.5 m/s, and its temperature profile was measured by an infrared camera. The results showed that a region of high heat flux appeared in the area impacted by the jet. The heat transfer characteristics relied heavily on the initial temperature of the solid associated with the boiling patterns—namely, nucleate, transition, and film boiling. Along the boundary between the strong nucleate and the transition boiling regimes, the heat flux took peak values. The local minimum values of heat flux obtained between the transition and the film boiling regimes. The initial temperatures of the solid exhibiting these values were influenced by its moving velocity and the jet impact velocity. Moreover, the heat fluxes in the jet impact region for upward-impinging jets were compared with reported data for downward-impinging jets under the condition whereby the jet impact velocity and diameter in the two cases were nearly identical prior to impact. The two sets of results showed very similar trends, although the flow motions of water varied because of the effect of gravity.