# Transient heat transfer

**URL:** <https://prepomax.discourse.group/t/transient-heat-transfer/1937>\
**Category:** General Questions\
**Created:** [August 9, 2024, 8:31am UTC](https://prepomax.discourse.group/t/transient-heat-transfer/1937 "2024-08-09T08:31:54Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![krzychu1904](https://avatars.discourse-cdn.com/v4/letter/k/8797f3/32.png) [@krzychu1904](https://prepomax.discourse.group/u/krzychu1904)\
**Post date:** [August 9, 2024, 8:31am UTC](https://prepomax.discourse.group/t/transient-heat-transfer/1937/1 "2024-08-09T08:31:54Z")

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Hey,  
I tried to carry out a heat transfer analysis. I created several blocks of different materials. I defined:

- material models from a library, all of them had thermal properties defined
- contacts: bonded
- Initial temperature for all surfaces: 20 degrees
- boundary condition temperature on one surface: 700 degrees
- loads: radiation 0.5  
And I added models such as the boltzman constant. The problem is that the obtained results are not correct. The lowest temperature is below zero. I tried doing a steady-state analysis and the results were already correct. Where should I look for the problem? I have attached screenshots of the results and boundary conditions  
 ![heat transfer](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/b/b0151acfe635be2e0068a959b3f4020f5c22790c.png)

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**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [August 9, 2024, 8:41am UTC](https://prepomax.discourse.group/t/transient-heat-transfer/1937/2 "2024-08-09T08:41:32Z")

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Is the initial temperature applied to all nodes in the model (the whole part or parts - also inside) ? In transient analysis, heat will need some time to propagate but cold regions should use initial temperature. Sometimes it’s also because of too coarse mesh but I would check the initial conditions first.

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**Author:** ![krzychu1904](https://avatars.discourse-cdn.com/v4/letter/k/8797f3/32.png) [@krzychu1904](https://prepomax.discourse.group/u/krzychu1904)\
**Post date:** [August 11, 2024, 5:37pm UTC](https://prepomax.discourse.group/t/transient-heat-transfer/1937/3 "2024-08-11T17:37:02Z")

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Hey,  
You’re right. The problem was caused by incorrect selection of objects. I selected all surfaces instead of objects and only external nodes were added. Thanks for help