38
CHAPTER
9
Model selection and capacity calculation
Required cooling capacity to make up for above cooling loads
= 157.0 [W/m2] × 200 [m2] =
31.4 [kW]
Class
Heat Load
(a)
Indoor penetration heat
Heat generated from walls
(qws)
Heat generated from glass
from direct sunlight
(q
GS
)
from conduction and convection
(q
G
s)
Accumulated heat load in walls
(qss)
(b)
Indoor generated heat
Generated heat from occupants
Sensible heat (q
H
s)
Latent heat (q
HL
)
Generated heat from electrical equipment
Sensible heat (q
E
s)
Latent heat (q
EL
)
(c)
Reheating load
(q
RL
)
(d)
Ventilation load
Sensible heat
(q
FS
)
Latent heat
(q
FL
)
Cooling Load Classifications
(a) The heat penetrating into the room is often 30 to 40% of the total cooling load.
(b) It applies only when heat generated in the room.
(c) It applies only when reheating is necessary.
In this example, the outdoor and return air conditions are assumed as shown in table below.
Conditions: Middle south-facing floor of a typical office building.
}
}
}
}
Ventilation
load 33.8%
53.0 W/m
2
Indoor
penetration
heat 30.3%
47.6 W/m
2
Indoor
generated heat
(persons, lighting
equipment) 35.9%
56.4 W/m
2
157.0 W/m
2
Load type
Load
Ventilation Load
53.0 W/m
2
Indoor
Generated Heat
Persons
26.4 W/m
2
Lighting Equipment
30.0 W/m
2
Indoor Penetration Heat
47.6 W/m
2
Total
157.0 W/m
2
Dry Bulb Temp. Relative Humidity
Wet Bulb Temp
.
Enthalpy
Enthalpy difference
Cooling
Outdoor Air
33
˚C
63%
27˚C
84.6 kJ/kg(DA)
31.8 kJ/kg(DA)
Return Air
26
˚C
50%
18.7˚C
52.8 kJ/kg(DA)
II: Calculation of cooling load to determine the required capacity
(1) Calculation of ventilation load
Ventilation load =
ρ
x Q
f
x Δh
=
ρ
[kg/m
3
] x Q
f
[m
3
/h ] x ( h
O
- h
R
) [kJ/kg(DA)]
=
ρ
[kg/m
3
] x S [m
2
] x n [person/m
2
] x V
f
[m
3
/h
•
person] x ( h
O
- h
R
) [kJ/kg(DA)]
(2) Other cooling load
In this example, other cooling loads are regarded as a general value in Tokyo shown in the table below.
Calculate them in an appropriate way in the actual designing.
ρ
: Density of air
Q
f
: Ventilation air volume
h
O
: Outdoor air enthalpy
h
R
: Return air enthalpy
S
: Area of floor space
n
: The number of people per unit area
V
f
: Required fresh air rates per person
1.2 kg/m
3
84.6 kJ/kg(DA)
1000 m
3
/h
52.8 kJ/kg(DA)
200 m
2
0.2 person/m
2
25 m
3
/h/person
53.0 W/m
2
Typical load values during cooling
Cooling load per unit area
When the volume of ventilation air per persons is 25 m
3
/h, and the number of persons per 1 m
2
is 0.2, the cooling load will be
approximately 157.0 W/m
2
.
Here, calculate ventilation load per unit area for convenience to summate with other loads.
Ventilation load per unit area [W/m
2
] =
ρ
[kg/m
3
] x n [person/m
2
] x V
f
[m
3
/h·person] x (h
O
- h
R
) [kJ/kg(DA)]
= 1.2 [kg/m
3
] x 0.2 [person/m
2
] x 25
[m
3
/h·person] x ( 84.6 – 52.8 ) [kJ/kg(DA)]
=190.8[kJ/h
•
m
2
] = 53.0[W/m
2
]
Содержание GUG-01SL-E
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