Establishment of inverse calculation program for interface heat transfer coefficient in sand mold casting

It mainly arranges and analyzes the measured and back calculated data, calculates the interface heat flow and interface heat transfer coefficient through the measured temperature data, and analyzes the variation law.

(1) The measured data were collected and processed into a form that can be calculated by MATLAB back calculation program. The temperature field of sand mold of flat casting and the temperature field changes of sand mold and sand core of Ring Castings with different sizes were compared.

(2) The variation of interfacial heat flux and interfacial heat transfer coefficient with time is inversely calculated. For Ring Castings with equal thickness, the peak value of interfacial heat flux and interfacial heat transfer coefficient decreases with the increase of internal and external dimensions; When the core temperature reaches saturation, the interface heat flow of the inner core will produce reverse heat flow. With the increase of the ring size, the occurrence time of the reverse heat flow will be delayed; The interfacial heat transfer coefficient is the largest at the initial stage of solidification, and the interfacial heat transfer coefficient of the inner sand core of the same ring casting is greater than that of the outer sand mold. With the increase of ring size, the interfacial heat transfer coefficient of sand mold and sand core will decrease;

(3) The change of interfacial heat transfer coefficient with temperature can be regarded as an “s” curve similar to temperature. The change of interfacial heat transfer coefficient is mainly concentrated between the solid and liquid phase lines, and the high-temperature area above the liquid phase line and the low-temperature area below the solid phase line remain basically unchanged. For the smaller sand core, the blocked shrinkage of the casting and the increase of the heating time of the sand core will increase the maximum and minimum values of the “s” curve, and the “s” curve will extend towards the solidus temperature.

(4) Through the comparison of the temperature difference between the measured temperature and the back calculation temperature of 50 / 100mm Ring Castings TC2 and TC6 and flat castings TC2 thermocouple position, it is found that the back calculation error is large in the first 100s. With the increase of the back calculation iteration time, the back calculation error will gradually reduce to less than 2 โ„ƒ after 200s, which verifies the convergence and stability of the back calculation program.

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