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I am designing an enclosure with 2 identical heatsinks. The thermal resistance is rated at 1.50°C/W @500LFM. If I use 1 fan in the enclosure that produces an airflow of 500 LFM, will each heatsink (theoretically) have a thermal resistance of 1.50°C/W? If so, can I go even further with the thermal calculations and estimate the case temperature rise of the packages fastened to each heatsink, using that 1.50°C/W value?

Thank you all, first time posting here.

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    \$\begingroup\$ Agree with Roy. What you probably need to do is work out the overall temperature rise in the enclosure. You can figure this out if you know two things: 1) total dissipation inside the enclosure and 2) ACTUAL airflow in/out of the enclosure. Note that fans may be rated with zero back pressure. Actual airflow is likely to be less. \$\endgroup\$
    – mkeith
    Dec 9 '20 at 22:25
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Each heatsink will have the same thermal resistance to the air in the enclosure.

What will change is the temperature of the air. Say for instance the airflow crosses one heatsink and then the second. The air will be heated by the first heatsink and then run over the second. So for your thermal calculation you will need to take into account the fact that the air is warmer as it hits the second heatsink.

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