Torrentz will always love introduction to heat transfer 6th edition pdf bergman. The characteristic of the heat transfer coefficient of the boron steel for hot stamping process was studied in this paper.
For obtaining the 1400 MPa high strength product by the hot stamping process, the microstructure of blank has to be transformed from austenite to fully martensite by the quenching process in closed tools. The heat transfer coefficient between the blank and tools then becomes an important role which may affect the cooling rate and the final microstructure distribution of the blank. In this study, the experimental platform was built, and the inverse calculating method was used for obtaining the heat transfer coefficient. The influence of the contact pressure on the heat transfer coefficient was also investigated, and it reveals that the contact pressure affect the interface heat transfer most. From the FEM simulations, it also shows that the temperature histories of the blank and tools are good agreement to the experiment results, which imply the feasibility of the experiment platform and the method for obtaining the heat transfer coefficient. Selection and peer-review under responsibility of the Department of Materials Science and Engineering, Nagoya University.
2014 Published by Elsevier Ltd. Spreading and receding behaviors were observed for impinging droplets on heated textured surface. The effect of texture area fraction, surface temperature, and Weber number were examined. In the receding regime, droplets receded faster with the increase in surface temperature.
A cooling effectiveness model for a textured surface was suggested by considering wetting states. The cooling effectiveness decreased with the increase in hydrophobicity. This article reports the dynamic wetting behavior during spreading and receding phases and the heat transfer characteristics for impinging droplets on heated textured surfaces. In particular, the present study suggests newly the modified equations of the total thermal energy absorbed by droplet and the cooling effectiveness for textured surfaces with consideration of three different wetting states: non-wetting, partial-wetting and total-wetting states. Captured images by using the high-speed cameras were analyzed to examine the influence of impact Weber number, surface temperature, and texture area fraction.
It was found that for the textured surfaces, the maximum contact diameter of impinged droplet decreased owing to decrease in the surface energy. At increased surface temperatures, the maximum contact diameters slightly increased and the maximum recoil diameters decreased because of change in liquid viscosity. For the textured surfaces, the cooling effectiveness increased with the Weber number and its change substantially depended on the wetting state. It shows that the control of wetting state would be important in heat transfer of an impinging droplet on solid surface. Check if you have access through your login credentials or your institution.
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12 times the mass of all the heavier elements combined. Janssen recorded the helium spectral line during the solar eclipse of 1868 while Lockyer observed it from Britain. Lockyer was the first to propose that the line was due to a new element, which he named. United States, which is by far the largest supplier of the gas today.
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