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Example calculations of determining ventilation load during both cooling and heating are given as follows:
5.2 Ventilation load during cooling (in general office building)
Classification of cooling load
(a)
Indoor infiltration heat
(b)
Indoor generated heat
(c)
Reheating load
(d)
Outdoor air load
(a) is the heat infiltrating 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 outdoor air is mixed into part of the supply air diffuser volume and introduced into the room.
The outdoor air is introduced to provide ventilation for the people in the room, and is referred to as the ventilating load.
Typical load values (during cooling)
Indoor
infiltration
Outdoor air
heat 30.3%
load 33.8%
47.6 W/m
2
53.0 W/m
Indoor
generated heat
(people, lighting
equipment) 35.9%
2
56.4 W/m
Cooling load per unit area
When the volume of outdoor air per person is 25 m
approximately 157.0 W/m
How these values are determined can be seen as follows:
Outdoor air load
Air conditions <Standard design air conditions in Tokyo>
Outdoor air
Cooling
Indoors
When the load per floor area of 1 m
the following is obtained:
Outdoor air (ventilation) load = 1.2 kg/m
3
× 25 m
/h·person (outdoor air volume) × 31.8 kJ/kg (air enthalpy difference indoors/outdoors)
2
= 190.8 kJ/h·m
(53.0 W/m
The Lossnay recuperates approximately 70% of the exhaust air load and saves on approximately 20% of the total load.
Class
Heat from walls (q
Heat from glass
Accumulated heat load in walls (q
Generated heat from people
Genarated heat from electrical equipment
Sensible heat (q
Latent heat (q
2
2
157.0 W/m
2
.
Dry bulb temp.
Relative humidity
33 °C
26 °C
2
with a ventilation volume of 25 m
3
(Specific gravity of air) × 0.2 persons/m
2
)
CHAPTER 1
)
WS
from direct sunlight (q
from conduction & convection (q
)
FS
)
FL
Type of load
Outdoor air load
People
Indoor
generated heat
Lighting equipment
Indoor infiltration heat
Total
Conditions: Middle floor of a general office building facing south.
3
/h, and the number of persons per 1 m
Wet bulb temp.
63%
27 °C
50%
18.7 °C
3
/h·person is calculated with the above air conditions,
Ventilation for Healthy Living
)
GS
GS
)
SS
Sensible heat (q
)
HS
Latent heat (q
)
HL
Sensible heat (q
Latent heat (q
(q
)
RL
2
is 0.2, the cooling load will be
Enthalpy
85 kJ/kg
53.2 kJ/kg
2
(no. of persons per 1 m
)
)
ES
)
EL
Load
2
53.0 W/m
2
26.4 W/m
2
30.0 W/m
2
47.6 W/m
2
157.0 W/m
Enthalpy difference
31.8 kJ/kg
2
)
11
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