The general term “spray cooling” is for the research presented here limited to the spray cooling of hot surfaces with film boiling, starting at temperatures of about 1200 °C and finishing at the Leidenfrost point where cooling intensity changes rapidly. This is typical area of secondary cooling in continuous casting. Herein, a correlation for Heat Transfer Coefficient (HTC). The most frequently used parameter of water impingement density is in the presented correlation used together with impact pressure to get good results. This study uses both water and mist nozzles. It is shown and experimentally verified why equations based only on the water impingement density cannot provide sufficiently precise predictions of HTC.
Semisolid or mushy-state processing permits a material to partially solidify before shape making operations. The understanding of material behavior in the mushy state is critical for better control of various semisolid processes. The aim of the present study is to experimentally quantify the deformation behavior of steel in mushy states. Semisolid specimens under indentation were evaluated at various forming speeds and mushy states. The correlation between the temperature and the percentage of the solid phase is used to control the characteristics of the mushy state. It is found that the forming resistance of steel in a mushy state is dependent on the deformation rate and the solid phase percentage.
Polymers with highly conductive fillers could possibly replace standardly used materials, such as aluminum and copper alloys, for passive cooling purposes. The main problem of the composite polymer-based heat sinks is that their high thermal conductivity is uneven. The orientation of this anisotropy is set according to the position of the highly thermally conductive filler. Its orientation is influenced by the melt flow during the polymer heat sink molding process. This article shows that change of the melt flow inside the mold cavity can improve the overall cooling efficiency of a polymer heat sink, which leads to lower temperatures on the heat source used. Two polymer heat sinks of identical geometries were produced. Their high thermal conductivity was given by the use of graphite flakes as the filler. The only difference between the heat sinks was in the position of the fan gate during their production. Different temperatures of the heat source between the two heat sinks were observed for the same measurement conditions. The measurements were conducted at Heatlab, BUT/Brno.
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