6.2 Fans
209
SP
TP
FTP
In order to be able to perform these calculations, information should be available
on the dynamic pressure at the fan discharge. In the absence of data, this can be
assumed the same as that existing in the fan inlet. Therefore:
Pw u = FTP Q = (127.5 + 313.8) Pa · 20
m
3
s
= 8826 W
Exercise 6.3 Determine the useful power of a forcing system if it is capable of
generating an airflow of 20 m
3 s
−1 in a duct of 2.3 m
2 of cross section and the static
losses between the fan outlet and the duct end are 1000 Pa. Assume no shock losses
occur at the entrance.
Solution
A forcing system follows the layout of the figure.
TP
SP
FTP
P
The average velocity inside the duct can be calculated from:
209
SP
TP
FTP
In order to be able to perform these calculations, information should be available
on the dynamic pressure at the fan discharge. In the absence of data, this can be
assumed the same as that existing in the fan inlet. Therefore:
Pw u = FTP Q = (127.5 + 313.8) Pa · 20
m
3
s
= 8826 W
Exercise 6.3 Determine the useful power of a forcing system if it is capable of
generating an airflow of 20 m
3 s
−1 in a duct of 2.3 m
2 of cross section and the static
losses between the fan outlet and the duct end are 1000 Pa. Assume no shock losses
occur at the entrance.
Solution
A forcing system follows the layout of the figure.
TP
SP
FTP
P
The average velocity inside the duct can be calculated from: