In several practical situations, flow takes place under a given head through different pipes jointed together either in series or in parallel or in a combination of both of them.
n this case, rate of flow Q remains same in each pipe. Hence,
If the total head available at Sec. 1 (at the inlet to pipe A) is H1 which is greater than H2 , the total head at Sec. 2 (at the exit of pipe C), then the flow takes place from 1 to 2 through the system of pipelines in series.
Application of Bernoulli's equation between Secs.1 and 2 gives
H1 - H2 = hf
where, hf is the loss of head due to the flow from 1 to 2. Recognizing the minor and major losses associated with the flow, hf can be written as
Friction loss Loss due to
entry to pipe B
in pipe AFriction loss
in pipe B
The subscripts A, B and C refer to the quantities in pipe A, B and C respectively. Cc is the coefficient of contraction.
Velocities VA, VB and VC in Eq. (36.1) are substituted from Eq. (36.2), and we get
Equation (36.4) states that the total flow resistance is equal to the sum of the different resistance components. Therefore, the above problem can be described by an equivalent electrical network system as shown in Fig. 36.2.