Heat transfer characteristics of shuttle kilns

In a flame kiln, combustion products transfer heat to the ware through convection and radiation.
1) Convective heat transfer: It is proportional to the temperature difference between the flue gas and the ware, and proportional to the 0.8th power of the flue gas velocity in the kiln;
2) Radiative heat transfer: It is proportional to the difference between the fourth power of the absolute temperatures of the flue gas and the ware.
① If the heat transfer efficiency is improved by increasing the temperature difference between the flue gas and the ware, it is good from the point of view of heat transfer;
But it is not good from the point of view of the temperature difference between the inside and outside of the ware.
② If the flue gas velocity is increased, the entire kiln ware can be heated more uniformly and quickly.
With high-speed temperature-regulating burners, the temperature difference between the flue gas and the ware is small, but the flue gas velocity in the kiln is increased by up to ten times compared to using ordinary burners, thus ensuring the firing quality of the ware while improving the heat transfer rate and achieving the fastest possible firing allowed for the ware.
③ Modern intermittent shuttle kilns use high-speed temperature-regulating burners, and the combustion products are injected into the kiln at a very high speed (over 100 m/s). In this way, the convective heat transfer rate of the combustion products is greatly increased during the entire firing process;
Even in the high-temperature stage, the effect of convective heat transfer is significant.
④However, when using high-speed temperature-regulating burners, when the ware is stacked, a flame passage of 100-400 mm should be left between the ware piles, and its width usually increases with the increase of the kiln width.
It is best to make the airflow in the kiln create a rotating airflow to avoid the high-speed flame directly impinging on the local ware, affecting the flame flow, and causing a large temperature difference.