AHU热回收选型计算：分步方法

Step 1 – Known airflow

S从给／排风量 Q (m3/h) 开始。对于平衡型 AHU，Q_送风 ≈ Q_排风。

Step 2 – Temperature difference

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.

Step 3 – Effectiveness

选择有效度 ε（板式通常 0.60–0.75，转轮式 0.75–0.85）。送入空气的回收温度：T_rec = ε × ΔT。

Step 4 – Heat recovered

Q_rec [W] = rho × c_p × Q × T_rec，其中 rho=1.2 kg/m3，c_p=1005 J/(kg.K)。将 Q 由 m3/h 换算为 m3/s（除以 3600）。

Step 5 – Pressure drop & fan cost

回收装置每 1 Pa 压降都会提高风机功率：P_fan [W] = Q[Pa] × Q[m3/s] / eta_fan。请使用我们的 压降指南.

Step 6 – Payback

Annual energy saved = Q_rec x operating hours x (1 – penalty) x energy price. Compare against first cost and the 回收期方法。从以下选择装置类型 按应用选型.

Worked example

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.

Effectiveness versus pressure drop

The calculation above maximizes recovered heat, but a higher-effectiveness core usually costs more pressure drop, and that pressure drop is paid continuously by the fan. The true optimum is not the highest epsilon but the point where the value of extra recovered heat equals the extra fan energy it demands. Run the fan-power term in Step 5 for two or three candidate cores before choosing.

Part-load and real operation

Design-day calculations flatter a device; most hours are at part load. Check how effectiveness and pressure drop behave as airflow falls, and whether the control modulates the core or simply bypasses it. A unit that performs well only at full flow may under-deliver across the annual load profile, hurting the payback estimate.

Verifying the installed result

After commissioning, measure the actual supply-temperature rise and pressure drop and compare them to the calculation. Differences reveal fouling, bypass leakage, or a mismatch between assumed and real airflow. Re-running the steps with measured values closes the loop between design intent and delivered performance, and supports any performance guarantee.

常见问题

How do I calculate heat recovered in an AHU?
Use Q_rec equals rho times c_p times airflow times effectiveness times the temperature difference, with rho 1.2 and c_p 1005, converting cubic metres per hour to cubic metres per second.

Should I maximize effectiveness?
Not always. Higher effectiveness often means more pressure drop and fan energy, so optimize the trade-off rather than chase the highest number.

What fan-power formula applies?
Fan power equals pressure drop times airflow divided by fan efficiency. Balance this against the heat recovered when choosing a core.

How do I verify installed performance?
Measure the actual supply temperature rise and pressure drop and compare them to the calculation. Trend for fouling or bypass leakage.

常见问题

How do I calculate heat recovered in an AHU?

Use Q_rec equals rho times c_p times airflow times effectiveness times the temperature difference, with rho 1.2 and c_p 1005, converting cubic metres per hour to cubic metres per second.

Should I maximize effectiveness?

Not always. Higher effectiveness often means more pressure drop and fan energy, so optimize the trade-off rather than chase the highest number.

What fan-power formula applies?

Fan power equals pressure drop times airflow divided by fan efficiency. Balance this against the heat recovered when choosing a core.

How do I verify installed performance?

Measure the actual supply temperature rise and pressure drop and compare them to the calculation. Trend for fouling or bypass leakage.