Hoval RoofVent CON-9, Design Handbook

Page: 138 / 280

136
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 B 'RoofVent
®
LHW.'
Design data
■ Necessary fresh air flow rate or air change rate
1)
■ Hall geometry (length, width, height)
■ Design conditions
■ Desired room temperature (in the occupied area)
■ Extract air conditions
2)
■ Cooling load
1)
Check if local regulations and project-specific requirements allow the
reduction of the fresh air flow rate when outside temperatures are low. If
so, use mixed air operation (50% fresh air, 50 % recirculation) for your
design calculation.
Example
Fresh air flow rate ......................................20'000 m³/h
Hall geometry (L x W x H) .................... 50 x 18 x 10 m
Design conditions ...................................... 28 °C/40 %
Desired room temperature...................................22 °C
Extract air conditions ................................. 24 °C/50 %
Cooling load....................................................... 42 kW
2)
The extract air temperature is generally higher than the temperature in the
occupied area. This is the result of unavoidable temperature stratifica-
tion in high spaces, but is reduced to a minimum with the Air-Injector. A
temperature gradient of only 0.2 K per metre hall height can therefore be
assumed. Room temperature:..............................................22 °C
Temperature gradient: .................................. 10 · 0.2 K
Extract air temperature: ....................................= 24 °C
Required number of units n
req
Based on the air flow rate per unit (see Table F4), calculate
the required number of units.
n
req
= V
req
/ V
U
V
req
= required fresh air flow rate in m³/h
V
U
= air flow rate per unit in m³/h
n
req
= 20'000 / 7'000
n
req
= 2.86
Select 3 TWP-9s.
Actual fresh air flow rate V (in m³/h)
V = n · V
U
n = Selected number of units
V = 3 · 7'000
V = 21'000 m³/h
Necessary output to cover fabric cooling losses
(sensible cooling capacity) per unit Q
TG
(in kW)
Q
TG
= Q
Teff
/ n
Q
TG
= 42 / 3
Q
TG
= 14 kW
Checking the cooling capacity
Compare the required output for coverage of the fabric
cooling losses per unit with the data in Table F8. Increase
the number of units if the cooling capacity is insufficient.
Actual output Q
TG
= 15 kW
Required output = 14 kW
→ OK
RoofVent
®
twin pump
Design example