How to Calculate Air Heater Power: Airflow and Temperature Rise

Selecting the correct air heater power https://8ruiyan.com/en/all-air-heaters/ is the most critical step in any thermal system design. Under-sizing leads to insufficient outlet temperature; over-sizing wastes energy and increases cost. The entire calculation rests on a straightforward energy balance formula.

The Basic Formula

P = Q × ρ × Cp × ΔT / η

Where:

• P = Power (kW)
• Q = Airflow (m³/s)
• ρ = Air density (≈1.2 kg/m³ at 20°C)
• Cp = Specific heat of air (≈1.005 kJ/kg·K)
• ΔT = Temperature rise (outlet – inlet, in °C or K)
• η = Heater efficiency (use 0.95–1.0 for electric, 0.7–0.9 for gas)

Simplified Practical Version

For electric heaters, you can use this quick approximation:

P (kW) ≈ 0.00034 × Q (m³/h) × ΔT (°C)

Example:
Heating 500 m³/h of air from 20°C to 80°C (ΔT = 60°C)
P ≈ 0.00034 × 500 × 60 = 10.2 kW

What About Mass Flow?

If you know mass flow (kg/s) instead of volume flow, use:

P = ṁ × Cp × ΔT / η

With ṁ = Q × ρ. This is often more accurate because density changes with temperature.

Important Notes

• Density correction: Air density drops as temperature rises. For ΔT > 50°C, recalculate ρ at the average temperature.
• Start-up vs. steady state: The formula gives steady-state power. For cold start-ups, add 10–20% margin for thermal inertia.
• Pressure drop: Higher pressure increases density, which raises power demand. Compressible effects matter above 2–3 bar.
• Altitude: At high altitudes, lower density means less power for the same ΔT.

Quick Reference Table (Electric, η≈0.98)

Airflow (m³/h)	ΔT = 20°C	ΔT = 50°C	ΔT = 100°C
100	0.7 kW	1.7 kW	3.4 kW
500	3.4 kW	8.5 kW	17.0 kW
1000	6.8 kW	17.0 kW	34.0 kW

Final Rule of Thumb

For electric air heating at sea level: 1 kW of air heater power heats roughly 300 m³/h of air by 10°C.
Always oversize your air heater power by 10% to account for voltage fluctuations, aging elements, and heat losses through ductwork. That small margin ensures your air heater delivers the required performance consistently over its entire service life.

For further problems about electric air heater, , please contact our technical team for expert advice.

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