Size a 100% outdoor air unit (DOAS or fresh air unit) and compare heat recovery options: plate heat exchanger, sensible or enthalpy heat wheel, run-around coil, heat pipe or a wrap-around heat pipe. It works out the recovered heat, the cooling, preheat and reheat coils, humidifier and fan heat, with the air at every point on a psychrometric chart.
Effectiveness as AHRI 1060: supply-side change = ε × (smaller airflow ÷ outdoor airflow) × (outdoor − room). The device’s pressure drop is added to the supply fan’s ISP and ESP. Assumed lowest coil ADP: chilled water 7.5 °C, DX 4 °C; the coil leaves at 99.5% RH at most. Winter preheat leaves at 5 °C at most.
Cooling coil
– kW – TR
- Supply air used
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- Heat recovered
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- Recovered sensible / latent
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- Effectiveness used
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- Saving against no recovery
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- Cooling coil
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- Preheat coil
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- Reheat coil
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- Coil sensible / latent
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- Coil ADP / bypass factor
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- Condensate
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- Humidifier
- –
- Fan power / temperature rise
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- Room sensible taken by supply
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- Room latent taken by supply
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- Exhaust leaving
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Compare recovery options
| Recovery | Effectiveness sensible / latent % |
Recovered kW |
Cooling coil kW |
Cooling W/(L/s) |
Heating coils kW |
Humidifier kg/h |
Fan kW |
Plant load kW |
Saving % |
|---|
Cooling per airflow: the cooling coil load over the supply airflow. Plant load: cooling and heating coils plus a steam humidifier’s heat, each option at its own effectiveness and pressure drop. Pick an option’s name to use it.
| Air | Dry bulb °C |
Wet bulb °C |
Dew point °C |
RH % |
Humidity ratio g/kg |
Enthalpy kJ/kg |
Specific volume m³/kg |
Airflow L/s |
|---|