4.8 Resistances in Series
113
Therefore:
R eq = R 1 + R 2 + R 3
Thus, generalizing for n resistances (Eq. 4.19):
R eq =
n
i=1
R i
(4.19)
Therefore, in a series circuit of n resistances, the equivalent resistance (R eq ) is the
sum of the individual resistances (R i ).
4.9 Resistances in Parallel
In a parallel circuit, the total circulating airflow rate (Q) is the sum of the flows of each
of the branches, and the pressure loss ( in each branch is the same (Fig. 4.10).
So, mathematically:
Q = Q 1 + Q 2 + Q 3
Therefore, applying Eq. 4.13 to each branch, we have:
P
R eq
=
P 1
R 1
+
P 2
R 2
+
P 3
R 3
Given that:
= 1 = 2 = 3
Fig. 4.10 Association of
aerodynamic resistances in
parallel
R 1
R 2
R 3
Q 1
Q 2
Q 3
ΔP
Q