Size an air handling unit from its airflows and the outdoor, room and supply air: cooling and heating coils, humidifier, fan heat and room loads, with the air at every point and the process on a psychrometric chart.
HVAC Unit Sizing Calculator
jerinsantosh.com
Units
Weather
Size from
Supply fan
Dry bulb (°C)
Humidity
Outdoor
°C
Room
%
Supply
°C
Assumed lowest coil ADP: chilled water 7.5 °C (5.5 °C lowest chilled water supply), DX 4 °C; air leaves the coil or humidifier at 99.5% RH at most. Winter preheat leaves at 5 °C at most; the reheat coil does the rest. Fan power = airflow × (ISP + ESP) ÷ fan efficiency, all of it heating the air (motor in the airstream).
Cooling coil
– kW – TR
- Room achievable
- –
- Supply air used
- –
- Supply fan airflow
- –
- Cooling coil
- –
- Preheat coil
- –
- Reheat coil
- –
- Coil sensible / latent
- –
- Coil ADP / bypass factor
- –
- Condensate
- –
- Humidifier
- –
- Fan power / temperature rise
- –
- Room sensible
- –
- Room latent
- –
- Room sensible heat ratio
- –
- Return / relief air
- –
| 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 |
|---|