中文说明：
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。
English Description：
The program is written to establish the mathematical simulation model of the tube heat exchanger, and calculate the temperature, convective heat transfer coefficient, Reynolds number and heat flux on both sides of the heat exchanger