变压器温度场计算边界辐射-对流复合换热等效方法研究

Study on equivalent method of boundary radiation-convection heat transfer for transformer temperature field calculation

针对变压器温度场计算中边界条件难以准确设定的问题,提出了基于传热学数学描述的变压器边界辐射-对流复合换热的等效方法,通过合并辐射、对流的传热通式得到描述边界条件的复合传热表面系数,根据不同变压器温升试验的环境条件得到对应的复合传热表面系数,并将其作为边界条件进行温度场计算,对比试验结果与仿真结果,不同条件下的4组算例各测温点温度计算平均误差在2~3℃范围内,符合工程要求,验证了边界辐射-对流复合换热等效方法的可行性和准确性,通过计算可以发现在自体散热过程中辐射散热导致的复合传热表面系数平均增量最大占比仅为复合传热表面系数的0. 2%,符合工程常识且为其提供了理论依据,通过正交实验表和极差分析法对比各因素对热点温度的影响程度,比较极差值大小可知,影响热点温度的主要因素为负载率、环境温度、风速,当精度要求不高时可简化或忽略辐射和湿度影响。

Aiming at the problem that it is difficult to accurately set the boundary conditions in the calculation of transformer temperature field,an equivalent method of transformer boundary radiation-convection heat transfer based on mathematical description of heat transfer is proposed.The total heat transfer coefficient of boundary condition was derived by combining the heat transfer formulas of radiation and convection which considering wind speed and humidity.The experimental results and simulation results were compared to verify the correctness of total heat transfer coefficient of boundary condition,and the calculation average errors of which is at the range of 2~3℃.Through calculation,it is found that the average increase of the total heat transfer coefficient caused by radiation heat dissipation during the self-heat dissipation process is only 0.7%,which is in line with engineering knowledge and provides a theoretical basis for it.The orthogonal test table and the range analysis method were used to compare the influence degree of each factor on the hot spot temperature.Load rate,ambient temperature and wind speed are main factors.