7.5 Series and Parallel Connection
275
rises for given flow rate. The EG part in the characteristic of the small fan represents
the negative pressure difference over the fan required to suck a flow rate through
this working fan larger than what it can deliver without load. The BG part of the
resulting characteristic is not useful. The series operation has only very marginal
meaning for the load characteristic L1 (the small fan only contributes a little). It has
no advantage for the load characteristic L2 (flow is sucked through the small fan).
Q
B 1
P 1
L 1
m
H
1
H
1
H
1
H
3
H
2
H
1
H 1
3
H 3
2
P
2
H 2
1
P
N
Fig. 7.19 Parallel connection of pumps; right net characteristic of a pump and the load by a branch
in the pipe network
Fig. 7.20 Series connection of fans