When ansys or abaqus are often used for thermal analysis, the temperature to be solved is often encountered, which is unreasonable at first glance.

Such as heat transfer analysis, there will be a temperature lower than the ambient temperature.

Such as high temperature heat conduction analysis, the local temperature is higher than the highest possible temperature.

This may be due to the following reasons:

1, the boundary condition is wrong.

According to the principle of conservation of energy, if a system only has heat output, no heat input, or the input is less than the output, the temperature of the system will only keep decreasing, even if it reaches absolute 0 degrees.

These softwares of Ansys don't care about absolute zero, but follow the thermal equation formula here, regardless of the actual absolute zero, so the temperature may be -500 degrees.

If you check many times, the boundary conditions will not lead to the heat balance problem-(in fact, the students who are more professional are not the problem), then you may encounter other more difficult reasons:

2. The grid quality is poor-this is the most worthy of your attention. Dividing a suitable mesh requires strong basic knowledge of finite element and analysis experience (if meshing cannot be solved, more powerful mesh generation tools, such as ICEM, hypermesh or Ansa, may be needed).

3. Special techniques are used, such as birth and death elements, which affect the integrity of the boundary.

4. Transient transition conditions. Compared with the steady state, the intermediate result may not be the final solution, resulting in local temperature anomalies, but once t is stretched, a relatively reasonable solution can be obtained, that is, the situation close to the steady state will be close to reasonable.

5. Solver has its own defects. After all, ANSYS ansys abaqus are not professional thermal analysis software, but CFX or fluent and icepak should be better at finding a more accurate value. For example, heat generation+heat conduction analysis, even if there is no boundary heat flow, the local temperature may be lower than normal, or even negative, such as -500. C

. . . These situations generally appear in transient analysis, but not in steady-state analysis.