铝合金薄板强风气垫射流加热过程的对流换热系数研究

Convective heat transfer coefficient of the aluminum alloy sheet in the air cushion jet heating process

实验研究了强风气垫冲击射流加热铝合金薄板的对流换热特性。基于集总热容法计算表面对流换热系数,获得射流速度42 m/s^68 m/s(压力0.4 kPa^1.0 kPa)的表面对流换热系数与铝板温度关系。对于厚度为3 mm的薄板,若要实现工业气垫炉加热所需的4.5℃/s的加热速率,其表面平均对流换热系数应大于231 W/(m^2·K),雷诺数Re要大于17 138。利用实验数据的回归处理及最小二乘法,建立了强风气垫射流加热过程的平均对流换热准数方程,与实验数据比较,该准数方程与实验结果吻合良好,误差小于4.5%。

The experiment has been carried out on the convective heat transfer characteris- tic of the high temperature air jet impinging on the aluminium alloy sheet. The surface con- vective heat transfer coefficient at the jet velocity of 42 m/s - 68 m/s （ pressure 0.4 kPa - 1.0 kPa） has been calculated by the lumped capacity method, and the relationship between the coefficient and the sheet temperature has been obtained. To reach the heating rate of 4.5℃/s of the industrial air-cushion furnace for the 3mm thick sheet,the average surface convective heat transfer coefficient should be greater than 231 W/ （m2· K）, and the nusselt number Re should be greater than 17 138. The dimensionless equation of the average convec- tive heat transfer has been established in the air cushion jet heating process by the regression method with the experimental data and the least square method. Compared with the experi- mental data, the equation is in good agreement with the experimental results, and the error is less than 4.5%.