Question 1

How is HVAC air flow calculated?

Accepted Answer

CFM = Room volume × Air changes per hour ÷ 60. Typical office needs 15-20 CFM per person.

Question 2

What is ACH in HVAC?

Accepted Answer

Air Changes per Hour—how many times room air is replaced. Hospitals need 6-12 ACH, homes typically 0.5-1.

Question 3

How does pipe diameter affect flow rate?

Accepted Answer

Flow rate is proportional to the square of diameter. Doubling pipe diameter quadruples potential flow rate at the same pressure.

Question 4

What's the difference between volume and mass flow rate?

Accepted Answer

Volume flow (gallons/min) ignores fluid density. Mass flow (kg/s) accounts for density, important when density changes with temperature or pressure.

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