Method
Sensible-load or ACH airflow with explicit user-selected mode.
It covers two cases: sensible-load method and air-change method. Equations that apply to only one of them are tagged.
Equations
V̇ = Qsρ · cp · ΔTsensible-load method
V̇ = Vr · N3600air-change method
Symbols and units
| Symbol | Quantity | Unit |
|---|---|---|
| Inputs | ||
| Qs | Room sensible load | kW |
| ρ | Air density | kg/m³ |
| cp | Air specific heat | kJ/kg·K |
| ΔT | Supply-to-room temperature difference | K |
| Vr | Room volume | m³ |
| N | Air changes per hour | 1/h |
| Results | ||
| V̇ | Airflow | m³/s |
| V̇ | Airflow | m³/h |
| V̇ | Airflow | L/s |
| V̇ | Airflow | cfm |
Assumptions and limits
- ACH is a user/reference input; no default requirement.
In practice
- The air-change rate is a project input: take it from the code, authority or client requirement for the space.
Worked example
The input values are the calculator's own verification test, run through the calculator. They show the working; they are not design values.
Method: Sensible-load method.
Inputs
| Qs | Room sensible load | 12.06 kW |
| ρ | Air density | 1.2 kg/m³ |
| cp | Air specific heat | 1.005 kJ/kg·K |
| ΔT | Supply-to-room temperature difference | 10 K |
Results
| V̇ | Airflow | 1 m³/s |
| V̇ | Airflow | 3,600 m³/h |
| V̇ | Airflow | 1,000 L/s |
| V̇ | Airflow | 2,118.88 cfm |
A preliminary check for engineer review, not an engineering approval. The project calculation to the applicable codes, authority requirements and specification governs.