TR to CFM Calculator: engineer's guide
A ton of refrigeration produces a certain sensible cooling. The airflow needed to deliver that sensible capacity depends on the supply-to-room temperature difference.
Open the TR to CFM calculator →
What this calculator does
The calculator converts TR to sensible kW, applies the entered SHR, and computes the CFM required at the chosen supply-to-room delta-T.
Formulas used
- Sensible cooling:
Qs (kW) = TR × 3.517 × SHR - Airflow:
CFM = Qs × 3.16 / ΔT (°F) - Rule of thumb:
≈ 400 CFM per TR at SHR 0.80 and ΔT 20°F
Variables
- SHR = sensible heat ratio, 0.6 to 1.0
- ΔT = supply-to-room temperature difference, °F or °C
Worked example
Scenario: 10 TR cooling, SHR 0.80, supply delta-T 20°F.
- Qs = 10 × 3.517 × 0.80 = 28.14 kW
- CFM = 28.14 × 3.16 / 20 ≈ 4445 CFM
- Round to 4500 CFM; verify duct velocity below 6 m/s.
Common mistakes to avoid
- Using 400 CFM/TR for a kitchen (SHR much lower)
- Using total TR instead of sensible portion
- Ignoring altitude density correction
Frequently asked questions
When does 400 CFM/TR break?
For SHR below 0.75 (kitchens, restaurants, humid climates) — airflow drops. For SHR above 0.95 (server rooms) — airflow rises well above 400 CFM/TR.
What supply delta-T?
18 to 22°F for comfort cooling, 25 to 30°F for cold-air distribution, 6 to 10°F for displacement ventilation.
Standards and references
ASHRAE 62.1, ASHRAE 55, SMACNA
Related tools on this site
Open the calculator that pairs with this guide: TR to CFM Calculator.
Verification note
This guide is planning support only. Final design must be verified against the applicable project specification, authority requirements, manufacturer data, and the standards cited above. Consult a licensed engineer for construction-issue calculations.