Mitsubishi Electric Lossnay series Technical Manual page 22

5.3 Ventilation Load During Heating
•
Classification of Heating Load
Class
Indoor heat
(a)
loss
Ventilation
(b)
load
During heating, the heat generated by occupants and electrical equipment in the room can be subtracted from the heating load.
If the warming-up time at the start of heating is short, however, the generated heat may be ignored in some cases.
Percentage of Load
Ventilation
Indoor heat
air load 41.9%
loss 58.1%
2
5.2 W/ft
7.2 W/ft 2
(56.0 W/m 2 )
2
(77.7 W/m
•
Heating Load Per Unit Area
When the ventilation air volume per occupant is 15 CFM (25 m
is 0.2), the heating load will be approximately 12.4 W/ft
•
Internal Heat Loss
In terms of load classification, the internal heat loss is the value of the ventilation air load subtracted from the approximate
heating load.
Internal heat loss = 12.4 W/ft
•
Ventilation Load
Standard design air conditions in Tokyo
Outdoor Air
Heating
Indoor Air
<US unit>
When the load per 1 ft
detailed above, the following is obtained:
Ventilation air load = 0.749 Ib/ft
<SI unit>
When the load per 1 m
detailed above, the following is obtained:
Ventilation air load = 1.2 kg/m
The Lossnay recuperates approximately 70% of the ventilation load and saves on approximately 30% of the total load.
Heat Load
Heat escaping from walls (q
Heat escaping from glass (q
Heat loss from conduction and convection (q
Accumulated heat load in walls (q
Sensible heat (q )
FS
Latent heat (q )
FL
Ventilation Air Load
Internal Heat
) Conditions: Middle south-facing floor of a typical office building.
12.4 W/ft 2
(133.7 W/m 2 )
2 2
– 5.2 W/ft = 7.2 W/ft
Dry Bulb Temp. Relative Humidity
32 °F (0 °C) 50%
68 °F (20 °C) 50%
2
of floor area with a ventilation volume of 15 CFM·occupant is calculated with the air conditions
3
× 0.0186 occupants/ft
2
of floor area with a ventilation volume of 25 m
3
× 0.2 occupants/m
•
CHAPTER 1
)
WS
)
GS
)
GS
)
SS
Type of Load
Total
3
/h), and the number of occupants per 1 ft
2 2
(133.7 W/m ).
2 2 2
(133.7 W/m – 56.0 W/m
Wet Bulb Temp.
26.6 °F (–3 °C)
56.7 °F (13.7 °C)
2
× 15 CFM·occupant × 14.4 Btu/Ib = 0.30 Btu/min·ft
3
/h·occupant is calculated with the air conditions
2 3
× 25 m /h·occupant × 33.5 kJ/kg = 201.0 kJ/h·m
Ventilation for Healthy Living
Load
5.2 W/ft 2 (56.0 W/m
2
7.2 W/ft (77.7 W/m
2
12.4 W/ft (133.7 W/m
2
= 77.7 W/m )
Enthalpy Enthalpy Difference
2.1 Btu/Ib (5.0 kJ/kg)
14.4 Btu/Ib (33.5 kJ/kg)
16.6 Btu/Ib (38.5 kJ/kg)
2
(56 W/m
2 )
2
)
2
)
2 2
is 0.0186 (1 m
2 2
(5.2 W/ft )
2
)
U-13