Heat Exchange Efficiency - Fujitsu UTZ-BD035B Technical Manual

4-4-4. HEAT EXCHANGE EFFICIENCY

 HOW TO CALCLATE HEAT EXCHANGE EFFICIENCY
The heat exchange efficiency can be subdivided into the following
three categories.
Temperature (sensible heat) efficiency
Humidity (latent heat) efficiency
Enthalpy (total heat) efficiency
The heat recovery rate can be calculated if two of the above are
available.
(Temperature efficiency and enthalpy efficiency are indicated
in catalogs, etc.)
* Each exchange ratio can be calculated in the following formula.
Item
Temperature Exchange
Effectiveness [%]
Enthalpy Exchange
Effectiveness [%]
<How to calculate air conditions after passing through the heat exchange unit>
If the temperature and humidity of the internal air and external air are determined, and if the exchange efficiency of the heat
exchange ventilating unit to be utilized is determined, air conditions of the air supplied indoors and exhausted outdoors after
passing through the heat exchange unit can be calculated in the following formula.
Temperature
Intake Side
Enthalpy
Temperature
Exhaust Side
Enthalpy
External Air Temperature (˚C) - Internal Supply Air Temperature (˚C)
Temperature Exchange
Effectiveness (%) =
External Air Enthalpy (kJ/kg) - Internal Supply Air Enthalpy (kJ/kg)
Enthalpy Exchange
Effectiveness (%) =
Internal Supply Air Temperature (˚C) = External Air Temperature (˚C) - (External Air Temperature (˚C) -
Indoor Air Temperature (˚C)) x Temperature Exchange Effectiveness (%)
Internal Supply Air Enthalpy (kJ/kg) = External Air Enthalpy (kJ/kg) - (External Air Enthalpy (kJ/kg) -
Internal Air Enthalpy (kJ/kg)) x Enthalpy Exchange Effectiveness (%)
Exhaust Air Temperature (˚C) = Indoor Air Temperature (˚C) - (External Air Temperature (˚C) - Indoor
Air Temperature (˚C)) x Temperature Exchange Effectiveness (%)
Exhaust Air Enthalpy (kJ/kg) = Indoor Air Enthalpy (kJ/kg) - (External Air Enthalpy (kJ/kg) - Internal Air
Enthalpy (kJ/kg)) x Enthalpy Exchange Effectiveness (%)
Stale Indoor
Air (RA)
Heat Exchange
Element
Heat-exchanged
Clean Air Taken
Inside
Formula
External Air Temperature (˚C) - Internal Temperature (˚C)
External Air Enthalpy (kJ/kg) - Internal Air Enthalpy (kJ/kg)
- (01-25) -
Outdoor
Indoor
Fresh External Air
(OA)
Heat-exchanged
Stale Air Ex-
hausted
X 100
X 100