Flow work is the energy possessed by a fluid by virtue of its pressure.
Let us consider any two normal sec-tions XX and YY of a pipe line through which a fluid is flowing in the direction as shown in Fig. 1.10.
Let L = distance between sections XX and YY
A = cross–sectional area of the pipe line
p = intensity of pressure at section l.
Then, force acting on the volume of fluid of length ‘L’ and
cross–sectional area ‘A’ = p x A.
Work done by this force = p x A x L = p x V,
Where;
V = A x L = volume of the cylinder of fluid between sections XX and YY
Now, energy is the capacity for doing work. It is due to pressure that p x V amount of work has been done in order to cause flow o£ fluid through a length ‘L‘,
So flow work = p x V mechanical unit
Displacement Work
When a piston moves in a cylinder from position 1 to position 2 with volume changing from V1to V2, the amount of work W done by the system is given by
The value of work done is given by the area under the process 1 – 2 on diagram (Fig. 1.11)
