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See below for Calculation examples of determining ventilation load during both cooling and heating.
5.2 Ventilation Load During Cooling (In an Office Building)
•
Cooling Load Classifications
Office Building
(a)
Indoor penetration heat
(b)
Indoor generated heat
(c)
Reheating load
(d)
Outdoor air load
(a) Is the heat penetrating the room, and often is 30 to 40% of the entire cooling load?
(b) Is the heat generated in the room?
(c) Is applies only when reheating is necessary?
(d) Is the heat generated when ventilation air is mixed into part of the supply air diffuser volume and introduced into the room?
The ventilation air is introduced to provide ventilation for the room occupants, and is referred to as the ventilating load.
Typical Load Values During Cooling
Indoor
penetration
Ventilation air
heat 30.3%
load 33.8%
2
4.4 W/ft
4.9 W/ft
2
(47.6 W/m
2
)
2
(53.0 W/m
)
Indoor
generated heat
(occupants, lighting
equipment) 35.9%
5.2 W/ft
2
(56.4 W/m
2
)
Cooling Load Per Unit Area
When the volume of ventilation air per occupants is 15 CFM (25 m
0.2), the cooling load will be approximately 14.6 W/ft
•
Ventilation Load
Standard design air conditions in Tokyo
Outdoor Air
Cooling
Indoor Air
<US unit>
When the load per floor area of 1 ft
above, the following is obtained:
Ventilation air load = 0.0749 Ib/ft
× 15 CFM·occupants (ventilation air volume) × 13.7 Btu/Ib (air enthalpy difference indoor/outdoor) = 0.286 Btu/min·ft
<SI unit>
When the load per floor area of 1 m
above, the following is obtained:
Ventilation air load = 1.2 kg/m
3
× 25 m
/h·occupants (ventilation air volume) × 31.8 kJ/kg (air enthalpy difference indoor/outdoor) = 190.8 kJ/h·m
The Lossnay recuperates approximately 70% of the exhaust air load and saves on approximately 20% of the total load.
Heat generated from walls (q
Heat generated from glass
Accumulated heat load in walls (q
Generated heat from occupants
Generated heat from electrical equipment
Sensible heat (q
Latent heat (q
Ventilation Air Load
Indoor
Generated Heat
Indoor Penetration Heat
Conditions: Middle south-facing floor of a typical office building.
2
14.6 W/ft
2
(157.0 W/m
)
2
(157.0 W/m
Dry Bulb Temp.
Relative Humidity
91.4°F (33 °C)
63%
78.8°F (26 °C)
50%
2
with a ventilation volume of 15 CFM·occupant is calculated with the air conditions detailed
3
(Specific gravity of air) × 0.0186 occupant/ft
2
with a ventilation volume of 25 m
3
(Specific gravity of air) × 0.2 occupant/m
•
CHAPTER 1
Ventilation for Healthy Living
Department Store, Shop
)
WS
from direct sunlight (q
from conduction and convection (q
)
SS
Sensible heat (q
Latent heat (q
(q
RL
)
FS
)
FL
Load Type
Occupants
Lighting Equipment
Total
3
/h), and the number of occupants per 1 ft
2
).
Wet Bulb Temp.
80.6°F (27 °C)
36.5 Btu/Ib (85 kJ/kg)
65.7°F (18.7 °C)
22.9 Btu/Ib (53.2 kJ/kg)
2
(number of occupants per 1 ft
3
/h·occupant is calculated with the air conditions detailed
2
(number of occupants per 1 m
)
GS
)
GS
)
HS
)
HL
Sensible heat (q
)
ES
Latent heat (q
)
EL
)
Load
2
4.9 W/ft
(53.0 W/m
2.5 W/ft
2
(26.4 W/m
2
2.8 W/ft
(30.0 W/m
4.4 W/ft
2
(47.6 W/m
2
14.6 W/ft
(157.0 W/m
2
is 0.0186 (1 m
Enthalpy
Enthalpy Difference
13.6 Btu/Ib (31.8 kJ/kg)
2
)
2
)
2
2
)
2
)
2
)
2
)
2
)
2
is
2
2
(4.9 W/ft
)
2
(53.0 W/m
)
U-11
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