编写程序建立套管换热器数学仿真 模型，并计算换热器两侧流体沿程温度、对流换热系数、雷 诺数与热流密度的变化规律。(The mathematical simulation model of casing heat exchanger was established by programming, and the variation of temperature, convective heat transfer coefficient, Reynolds number and heat flux along the two sides of the heat exchanger were calculated.)