Heat Exchanger Efficiency Calculator
Calculate temperature, moisture, and enthalpy transfer efficiency for heat recovery units, air-to-air heat exchangers, and HVAC energy recovery ventilators (ERVs/HRVs).
🌡️ Heat Recovery Efficiency Calculator
Use this calculator to evaluate the performance of a heat recovery unit by computing its temperature efficiency, moisture efficiency, or enthalpy efficiency. It also estimates the total heat recovered in kW (metric mode).
Moisture Efficiency: μm = (x₂ − x₁) / (x₃ − x₁)
Enthalpy Efficiency: μe = (h₂ − h₁) / (h₃ − h₁)
Where subscript 1 = outside air before the exchanger, 2 = outside air after, 3 = exhaust air before.
Enter Air Stream Conditions
📊 Efficiency Result
Temperature Transfer Efficiency:
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What is Heat Exchanger Efficiency?
Heat exchanger efficiency (also called effectiveness in some contexts) measures how closely the actual heat transfer approaches the theoretical maximum. It is expressed as the ratio of the actual change in the supply air to the maximum possible change (the difference between the entering exhaust and supply air conditions).
- Temperature efficiency — used for sensible heat recovery (HRVs)
- Moisture efficiency — used for latent/enthalpy wheels (ERVs)
- Enthalpy efficiency — total energy recovery (sensible + latent)
Typical Efficiency Ranges
| Heat Exchanger Type | Typical Efficiency | Application |
|---|---|---|
| Plate (flat) HRV | 50–75% | Residential ventilation |
| Counter-flow plate HRV | 70–90% | High-performance buildings |
| Rotary thermal wheel | 65–85% | Commercial HVAC |
| Run-around coil | 45–65% | Where cross-contamination is a concern |
| Heat pipe | 40–65% | Industrial exhaust |
| Plate-fin (gas-to-gas) | 60–80% | Process industry |
Frequently Asked Questions
An HRV (Heat Recovery Ventilator) transfers only sensible heat (temperature), while an ERV (Energy Recovery Ventilator) transfers both sensible and latent heat (temperature + moisture). ERVs use enthalpy wheels or membrane cores.
No. Efficiency above 100% indicates measurement error or incorrect data entry. In practice, efficiencies are always below 100% due to real-world heat transfer limitations.
For temperature mode: Q = ρ × V × Cp × (t₂ − t₁) / 3600, where V is air flow in m³/h, ρ is density in kg/m³, Cp ≈ 1.005 kJ/(kg·K). This gives Q in kW.
Frost formation, pressure imbalance between streams, bypass leakage, dirty filters, and part-load operation all reduce effective efficiency below the manufacturer's rated value.