Concept of Flow Potential and Flow Resistance
where hf is the loss of head in the course of flow from A to B .
Loss of heat at Friction loss in Exit loss to the
entry to the pipe pipe over its reservoir B
from reservoir A length L
where, V is the average velocity of flow in the pipe.
(contd from previous...) Concept of Flow Potential and Flow Resistance
The velocity V in the above equation is usually substituted in terms of flow rate Q , since, under steady state, the flow rate remains constant throughout the pipe even if its diameter changes. Therefore, replacing V in Eq. (35.11) as we finally get
The term R is defined as the flow resistance .
In a situation where f becomes independent of Re, the flow resistance expressed by Eg. (35.13) becomes simply a function of the pipe geometry. With the help of Eq. (35.10), Eq. (35.12) can be written as
ΔH in Eq. (35.14) is the head causing the flow and is defined as the difference in flow potentials between A and B.
This equation is comparable to the voltage-current relationship in a purely resistive electrical circuit. In a purely resistive electrical circuit, ΔV = Rl, where ΔVis the voltage or electrical potential difference across a resistor whose resistance is R and the electrical current flowing through it is I.
Fig 35.4 Equivalent electrical network system for a simple pipe flow problem shown in Fig.35.3