Image based heating rate calculation from thermographic data considering lateral heat conduction

During the aircraft icing process caused by super-cooled droplet impingement, the surface temperature and heat flux distributions of the skin would vary due to the solid substrate heat conduction. An unsteady thermodynamic model of the phase transition was established with a time-implicit solution algorithm, in which the solid heat conduction and the water freezing were analyzed simultaneously. The icing process on a rectangular skin segment was numerically simulated, and the variations of skin temperature distribution, thicknesses of ice layer and water film were obtained. Results show that the presented model could predict the icing process more accurately, and is not sensitive to the selection of time step. The latent heat released by water freezing affects the skin temperature, which in turn changes the icing characteristics. The skin temperature distribution would be affected notably by the boundary condition of the inner skin surface, the lateral heat conduction and thermal property of the skin. It was found that the ice accretion rate of the case that the inner surface boundary is in natural convection at ambient temperature is much smaller than that with constant ambient temperature there; due to the skin lateral heat conduction, the outer skin surface temperature increases first and then decreases with uneven distribution, leading to an unsteady ice accretion rate and uneven ice thickness distribution; a smaller heat conductivity would lead to a more uneven temperature distribution and a lower ice accretion rate in most regions, but the maximum ice thickness could be larger than that of higher heat conductivity skin. Therefore, in order to predict the aircraft icing phenomenon more accurately, it is necessary to consider the solid heat conduction and the boundary conditions of the skin substrate, instead of applying a simple boundary condition of adiabatic or a fixed temperature for the outer skin surface.

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Study on Mechanism of Glass Molding Process for Fingerprint Lock Glass Plates

Crystals ◽

10.3390/cryst11040394 ◽

2021 ◽

Vol 11 (4) ◽

pp. 394

Author(s):

Wuyi Ming ◽

Haojie Jia ◽

Heyuan Huang ◽

Guojun Zhang ◽

Kun Liu ◽

...

Keyword(s):

Residual Stress ◽

Heat Conduction ◽

Cooling Rate ◽

Heating Rate ◽

Relaxation Model ◽

Glass Panel ◽

Forming Process ◽

Molding Process ◽

Shape Deviation ◽

Glass Forming

Curved glass is widely used in 3C industry, and the market demand is increasing gradually. Glass molding process (GMP) is a high-precision, high-efficiency 3D glass touch panel processing technology. In this study, the processing parameters of fingerprint lock glass panels were deeply analyzed. This paper first introduces the molding process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Firstly, it introduces the forming process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Secondly, the simulation model of a fingerprint lock glass plate was simulated by MSC. Marc software. The stress relaxation model and structure relaxation model are used in the model, and the heat transfer characteristics of glass mold are combined to accurately predict the forming process of glass components. The effects of molding temperature, heating rate, holding time, molding pressure, cooling rate and other process parameters on product quality characteristics (residual stress and shape deviation) were analyzed through simulation experiments. The results show that, in a certain range, the residual stress is inversely proportional to the bending temperature and heating rate, and is directly proportional to the cooling rate, while the shape deviation decreases with the increase of temperature and heating rate. When the cooling rate decreases, the shape deviation first decreases and then increases. Furthermore, a verification experiment is designed to verify the reliability of the simulation results by measuring and calculating the surface roughness of the formed products.

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