Fujitsu UTZ-BD035B Technical Manual page 29

 TOTAL HEAT EXCHANGE
In the case of ventilation with the total heat exchange mode, the air condition supplied indoors is at point S; in summer,
precooling is performed from the external air temperature to the indoor intake temperature, and dehumidifying is performed
from the external absolute humidity to indoor intake absolute humidity; and in winter, preheating is performed from the
external air temperature to the indoor intake temperature, and the external absolute humidity is further humidified to indoor
intake absolute humidity prior to being supplied indoors.
When the total heat exchange is utilized, the calorie to be recovered can be calculated in the following formula.
Recovered Total Calorie: q
X (External Air Enthalpy (kJ/kg) - Internal Air Enthalpy (kJ/kg)) x Total Heat Exchange Efficiency x 0.28 [w·h/kJ]
 SENSIBLE HEAT EXCHANGE
The following figure indicates various air conditions when external air is taken in through sensible heat exchange.
In the case of sensible heat exchange ventilation, the recovered calorie can be calculated in the following formula.
Recovered Sensible Heat Calorie: q
 Enthalpy
Referring to how many calories are contained in moist air under a certain condition per 1kg of dry air in it, based on the
supposition that the calorie contained in 1kg of dry air at 0˚C is 0 kcal. The unit is kJ/kg.
SI Unit Conversion Table
1kcal/kg = 4.2kJ/kg
1kcal/h = 1.16W
[w] = (Air Specific Gravity 1.2 [kg/m
T
[w] = Air Specific Gravity [1.2 kg/m
T
x Isobaric Specific Heat of Dry Air (1.006 [kJ/kg·°C]) x (External Air Temperature
[°C] - - Internal Air Temperature [°C]) x Sensible Heat Exchange Efficiency x 0.28
[w·h/kJ]
Efficiency (%)1 - Efficiency (%)
Condition of Internally Supplied
Air with Heat Exchange Venti-
lation Unit
External Air Indoor Supply
Temperature Air Tempera-
( ) ture ( )
3
]) x (Process Airflow [m
3
in the normal condition] x Process Airflow [m
1 - Efficiency (%)
Efficiency (%)
Condition of Internally
Supplied Air with Heat
Exchange Ventilation Unit
Supply Air
Indoor Tem- Indoor Tem-
Tempera-
perature ( ) perature ( )
ture ( )
Dry Bulb Temperature ( )
- (01-26) -
3
/h])
Absolute Humidity of
External Air
Absolute Humidity of
Internal Air
Absolute Humidity of
Internal Air
Absolute Humidity
of External Air
External Air
Temperature
( )
3
/h]