Heat Transfer Characteristic during Inclination Circular Jet Impingement on the Hot Plate Surface

Abstract

The heat transfer process of the inclination round jet impingement is studied experimentally for improving the cooling capacity and uniformity of the ultrafast cooling used in Thermo-mechanical Control Process. The heat transfer characteristic is presented for jet inclination angle from 0 to 60 . The video images of heat transfer process and heat flux curves demonstrate that the wetted region extends asynchronously due to the uneven water flow distribution. In the forward flow direction, the larger parallel flow velocity results to the fast wetting front propagation speed, and this is because the higher shear force under inclined condition is helpful to speed up the detachment of the bubbles on the surface. But in lateral and reverse directions, the situation is the opposite. The degree of asymmetry of the wetted region becomes remarkable, and at the same jet impingement cooling time, the wetted area increases at first and then shrinks with the increasing inclination angle. The larger jet velocity increases the maximum heat flux, and accelerates the wetting front propagation, especially in the parallel flow region. Thus, inclination jet impingement with the reasonable angle and jet velocity improves the heat transfer capability and plate surface cooling uniformity within the measurement region.

Effect of Jet Inclination and Coolant Flow Rate on Thermal and Rewetting Behavior during Bottom Jet Impingement on Hot Horizontal Surfaces

“…This indicates that downhill flow direction exhibits higher cooling ability and cooling uniformity compared with the uphill flow direction. Similar observations have been made by Wang et al during their investigation.…”

“…The comparison of maximum surface heat flux obtained from the present study with the results of Xie et al and Wang et al is shown in Figure . Studies have been made to estimate the maximum heat flux during the cooling of hot horizontal plates for various jet inclination angles ( θ =90°–15°) . Xie et al performed tests with top jet water impingement on 20 mm thick steel plate (AISI 314) for a varied range of jet inclination angles ( θ = 90°–30°).…”

“…The maximum value of surface heat flux was found to vary within 1.075–1.345 MW m −2 . The thermal behavior of 20 mm thick stainless steel (AISI 304) during top jet water impingement using a nozzle of 4 mm diameter was reported by Wang et al . The initial surface temperature was maintained at 660 °C.…”

“…Because of this uneven flow distribution of cooling fluid, cooling uniformity of the test surface in the downhill direction is improved in case of oblique jets compared with orthogonal jet impingement cooling. This has motivated various researchers to study the heat transfer behavior of oblique jet …”

“…In general, two different methods are used to define the inclination of the jet to the test surface. The angle of inclination of the jet is denoted either 0° or 90° to define the orthogonal jet impingement on the test surface. Here, we have considered the angle of inclination as 90° to denote orthogonal impingement.…”