瞬态温度场计算后低于初始温度，热力学参数的取值是否合
请教各位：受热作用的的空心瞬态温度场分析模型，荷载简化后有Distributed Heat Flux和Convection，单元为2D热传导单元，边界上单元为热对流单元，初始温度为19.5度，荷载加到外边界上，计算的结果比初始温度还低，不明白怎么回事？长度单位为m，混凝土热传导参数：thermal conductivity为2.54，heat capacity/mass，c为988，，热对流参数：convection为11。J:\122.jpg
问题：1、温度荷载的施加是否合适，应该怎么加？
2、混凝土的各项热力学参数取值是否合理？
3、模型中温度单位采用开尔文，还是摄氏度，是否可以直接输入摄氏温度？
4、时间函数的单位必须是秒吗，如果采用小时，其他参数要不要换算？
4、对建模还有什么建议。 1. To make the unit consistent should not be hard. You can certainly sort it out.
2. It doesn't matter whether you use K or C as long as the units are consistent.
3. For time, you can also use seconds or hours depending on what unit you are using for other parameters.
If you are sure, the units are correct. Then it is possible that the temperature is lower than the one on the boundary.
There is a principle called Maximum Discrete Principle which means that in order to make the temperature higher than the temperature on the boundary, there is a critical time step size one has to choose. Please refer to the following link for details.
http://www.cs.elte.hu/applanal/preprints/farago_horvath_2.pdf
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