气体射流冲击对流换热系数试验研究

Research on convective heat transfer coefficient with air jet impinging

在气体射流冲击试验装置上,冲击温度105～135℃,气流速度6．7～14．4m／s,相对湿度0～30％的范围内,进行了对流换热系数的研究,得到如下结论:物料表面温度T接近饱和温度T_s时,对流换热系数值出现转折,拐点前对流换热系数h为拐点后的3～12倍。在表面温度T＜T_s时,可获得较大的对流换热系数,对流换热系数h随温度、气流速度和湿度的增大而增大,最大可达1403W／(m^2·K)。在表面温度T＞T_s时,对流换热系数值明显变小,且与0％相对湿度的对流换热系数值接近一致;在气流速度为恒定时,温度和湿度对对流换热系数影响不明显;在温度为恒定时,对流换热系数随气流速度的增加而增大,湿度变化对其影响不明显,对流换热系数h在120～136W／(m^2·K)范围内。

With the airflow temperature 105～135℃,airflow rate 6.7～14.4m/s and relative humidity 0～30%.Re- search on convective heat transfer coefficient h in the air imping ment oven,the result indicates that when the temperature T is close to the saturation temperatures of gas(T_s),convective heat transfer coefficient h have changed,h_T＜T_S is 3～12 times greater than h_T＞T_s;When the temperature T＜T_s,convective heat transfer co- efficient h becomes greater while the humidity or the airflow rate is greater.The greatest h can get to 1403W/ (m^2·K);When the temperature T＞T_s,the value of h becomes smaller than ever,agreed on the value at humid- ity 0.With the variety of temperature & humidity,the changes of h is not significant at the constant airflow rate. At the constant temperature,the value of h increased with increased airflow rate,and the changes of h is no obvi- ous with increased humidity.The value of h ranged from 120 to 136 W/(m^2·K).