Friction loss Formula

Friction loss Formula

In fluids, friction loss is the loss of pressure or height that occurs in the flow of the pipe or conduit due to the effect of the viscosity of the fluid near the pipe surface. In mechanical systems such as internal combustion engines, the term refers to the power lost by overcoming friction between two moving surfaces.

friction loss = friction loss coefficient * ( flow rate / 100) 2 * hose length /100.

The equation is written

FL = C* (Q/100)2 *L/100.

We have:

FL = friction loss.

C = friction loss coefficient.

Q = flow rate.

L = hose length.

Friction loss Questions:

1)What is the friction loss for a 100 foot of 1.75 inch fire hose flowing 250 GPM of water?

Answer: We identify each term to carry out our operation.

Coefficient (C) for 1.75" hose is 15.5
Q = 250 GPM
L = 100 ft

FL = C * (Q / 100) 2 * L / 100
FL = 15.5 * (250 GPM / 100) 2 * 100 ft / 100= 96.875 PSI
FL = 96.875 PSI

2) What is the length of a hose that flows 300 GPM of water and has a friction loss of 80 PSI, if it is 2 inches?

Answer: We identify each term to carry out our operation.

Coefficient (C) for 2" hose is 8.

Q = 300 GPM.

FL = 80 PSI.

FL = C * (Q / 100) 2 * L / 100 →

L = (100* FL) / (C* (Q/100)2)=(100*80PSI)/(8*(300GPM/100)2)=111.11 ft

L = 111.11 ft.

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