Hoval RoofVent CON-9, Design Handbook

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254
4 Design example
Note
The following design example relates to cooling mode. The design rating for heating mode can
be performed analogously to the design example above in Section I 'RoofVent
®
LH.'
Design data
■ Minimum fresh air flow rate or minimum air change rate
■ Minimum fresh air rate
■ Hall geometry (length, width, height)
■ Design conditions
■ Desired room temperature
■ Extract air temperature
■ Cooling load
■ Cooling medium
Note
If more than 40 % of fresh air is constantly required,
a unit with energy recovery is more economical.
1)
As a rule, the extract air temperature is higher than the temperature in the
occupied area. This is the result of unavoidable temperature stratification in
high spaces, but is reduced to a minimum with the Air-Injector. A tempera-
ture gradient of only 0.2 K per metre hall height can therefore be assumed.
Example
Minimum fresh air flow rate .......................17'500 m³/h
Minimum fresh air rate ......................................... 20 %
Hall geometry Space (L x W x H) ......... 108 x 40 x 9 m
Design conditions ...................................... 30 °C/40 %
Desired room temperature...................................24 °C
Extract air temperature ........................................26 °C
Cooling load..................................................... 260 kW
Cooling medium.................................... LPCW 6/12 °C
Room temperature:..............................................24 °C
Temperature gradient: .................................... 9 · 0.2 K
Extract air temperature: ....................................≈ 26 °C
Required number of units n
req
Based on the air flow rate per unit (see Table J4), select a
trial unit size. (Depending on the results of further calcula-
tions, repeat the layout design for another unit size if neces-
sary.)
n
req
= V
req
/ (V
U
· R)
V
req
= Required fresh air quantity in m³/h
V
U
= Air flow rate for the selected unit size in m³/h
R = Minimum fresh air rate in %
Approximate selection: Unit size LK-9
n
req
= 17'500 / (7'650 · 0.2)
n
req
= 11.44
Select 12 LK-9s.
Actual fresh air flow rate V (in m³/h)
V = n · V
U
· R
n = Selected number of units
V = 12 · 7'650 · 0.2
V = 18'360 m³/h
Recirculation air flow rate V
R
(in m³/h)
V
R
= n · V
U
· (1 – R)
V = 12 · 7'650 · (1 – 0.2)
V = 73'440 m³/h
RoofVent
®
LK
Design example