Table of Contents
- Start with the supply/exhaust airflow Q (m3/h). For balanced AHUs, Q_supply approx Q_exhaust.
- Find the outdoor design temperature T_out and the exhaust (room return) temperature T_exp. The available temperature lift is DeltaT = T_exp - T_out.
- Choose an effectiveness epsilon (typical plate 0.60-0.75, rotary 0.75-0.85). Recovered temperature into supply air: T_rec = epsilon x DeltaT.
- Q_rec [W] = rho x c_p x Q x T_rec, where rho=1.2 kg/m3 and c_p=1005 J/(kg.K). Convert Q from m3/h to m3/s (divide by 3600).
- Every Pascal of recovery-device pressure drop raises fan power: P_fan [W] = Q[Pa] x Q[m3/s] / eta_fan. Balance effectiveness against fan energy using our pressure-drop guide.
- Annual energy saved = Q_rec x operating hours x (1 - penalty) x energy price. Compare against first cost and the payback method. Pick the device type from selection by application.
- Q=10000 m3/h, T_out=-10C, T_exp=22C, epsilon=0.70 -> T_rec=22.4C, Q_rec approx 75 kW. At 4000 h/yr and 0.10 EUR/kWh that is about 30,000 EUR/yr saved.
Start with the supply/exhaust airflow Q (m3/h). For balanced AHUs, Q_supply approx Q_exhaust.
Find the outdoor design temperature T_out and the exhaust (room return) temperature T_exp. The available temperature lift is DeltaT = T_exp - T_out.
Choose an effectiveness epsilon (typical plate 0.60-0.75, rotary 0.75-0.85). Recovered temperature into supply air: T_rec = epsilon x DeltaT.
Q_rec [W] = rho x c_p x Q x T_rec, where rho=1.2 kg/m3 and c_p=1005 J/(kg.K). Convert Q from m3/h to m3/s (divide by 3600).
Every Pascal of recovery-device pressure drop raises fan power: P_fan [W] = Q[Pa] x Q[m3/s] / eta_fan. Balance effectiveness against fan energy using our pressure-drop guide.
Annual energy saved = Q_rec x operating hours x (1 - penalty) x energy price. Compare against first cost and the payback method. Pick the device type from selection by application.
Q=10000 m3/h, T_out=-10C, T_exp=22C, epsilon=0.70 -> T_rec=22.4C, Q_rec approx 75 kW. At 4000 h/yr and 0.10 EUR/kWh that is about 30,000 EUR/yr saved.