You can set the junction temperature and cooling solution for PowerPlay power analysis in the Quartus® II software Assignments>Settings>Operating Settings and Conditions>Temperature menu.
When you select “No heat sink with xxxx” for “Use cooling solution” in the “Thermal resistances” menu, the “Board thermal modeling” menu is grayed out.
In order to set a board thermal model without a heat sink, follow these steps:
1) Select "No heat sink with xxxx" in "Use cooling solution" that you want to use.
2) Confirm values of “Junction-to-case” and “Case-to-ambient”.
3) Select "Custom" in "Use cooling solution".
4) Enter the values for “Junction-to-case” and “Case-to-ambient”.
5) Enter 0 for “Case-to-sink”.
6) Select option and enter values for "Board thermal modeling".