# Why does higher concentration of electonic components decrease the airflow requirement for cooling a PC system?

This source describes in detail a formula used to calculate the airflow requirement in order to cool a computer system.

$$Q = \dfrac{P_{loss}}{c_p \cdot \rho \cdot \Delta T}\cdot k$$

Clearly, the higher the packing density (k) the higher the airflow requirement.

From the same source:

The k constant describing the packing density (concentration) of the components that prevent the free flow of air (k=80-95 rare placement, k=60 dense components)

k = 60 for high component density (ultra small pc)

k = 85 for low component density (spacious full tower)


Meaning a small crammed PC case full of high-end components needs less airflow to be cooled than a spacious tower with the same high-end components. At this point, things make no sense. It should be like this:

k = 60 for low component density (spacious full tower)

k = 85 for high component density (ultra small pc)

60 = low, 85 = high


Do you think it's a typo?

EDIT

In this chart from the same source the airflow is lower with higher density components: • I think considering the mass flow instead of volumetric flow might be helpful. If the high density component build requires a higher inlet air pressure, the corresponding density of the inlet stream is higher - thus more mass enters the chassis. If we remember Q_dot = m_dotCpdt, then the higher m_dot value in this case means more heat can be absorbed from the electric components. May 10, 2020 at 12:49
• Can you make this more clear? May 10, 2020 at 13:23
• If you could clarify what is confusing, I will try to re-write my comment accordingly. May 11, 2020 at 10:06