The airflow needed for a system to sustain itself at 80°C with 25°C ambient temperature can be calculated with this formula:
Airflow = (P * t) / (ΔT * D * SHC) [m3/s]
P = Power [watts] t = Time [seconds] ΔT = Difference in Temperature [°C or K] D = Density of Air [kg/m3] SHC = Specific Heat of Air [J/(kg*K)]
For a 105W CPU to remain at 80°C the airflow needs to be:
Airflow = (105 * 1) / (55 * 1.2 * 1000) Airflow = 0.00159m3/s or 5.27m3/h
This means any small 80mm fan typically used for case mods to improve airflow by a little:
Can cool a 3900X beast CPU that requires an air cooler with a beefy heatsink and a large fan:
How can I further improve this formula to take into account the thermal resistance of the heat source and some fluid dynamics inside the case when it's simplified to just a box?
I know this is more of a thesis amount of work that's needed to be done but I'm only looking at a very rough estimate.