Head loss due to friction

E = Head loss due to friction in feet of flowing fluid... 

Equation 3.11 is due to Blasius(6) and the others are derived from considerations of velocity profile. In addition to the Moody friction factor / = 8R/pu2, the Fanning or Darcy friction factor / = 2R/pu2 is often used. It is extremely important therefore to be clear about the exact definition of the friction factor when using this term in calculating head losses due to friction. 

To calculate —APf it is therefore necessary to evaluate e/d and obtain the corresponding value of

head loss due to friction hf as ... 

With the friction factors used by Moody and Fanning, / and / respectively, the head loss due to friction is obtained from the following equations ... 

A large tank containing water has a 51 mm diameter hole in the bottom. When the depth of the water is 15 m above the hole, the flow rate through the hole is found to be 0.0324 m3/s. What is the head loss due to friction in the hole ... 

Pumps are devices for supplying energy or head to a flowing liquid in order to overcome head losses due to friction and also, if necessary, to raise the liquid to a higher level. The head imparted to a flowing liquid by a pump is known as the total head Ah. If a pump is placed between points 1 and 2 in a pipeline, the heads for steady flow are related by equation 1.14... 

In equation 1.14, z, P/(pg), and u2/(2ga) are the static, pressure and velocity heads respectively and hf is the head loss due to friction. The dimensionless velocity distribution factor a is for laminar flow and approximately 1 for turbulent flow. 

In equation 4.2, hfs is the head loss due to friction, zs is the static head and Ps is the gas pressure above the liquid in the tank on the suction side of the pump. If the liquid level on the suction side is below the centre-line of the pump, zs is negative. 

An incompressible fluid flows upwards in steady state in a cylindrical pipe at an angle 8 with the horizontal. Assume that the head loss due to friction is negligible. 

Here A/jf is the head loss due to friction and is directly related to the pressure loss due to friction A/ f by A/ f = pgAhf. 

Therefore, the total pressure or head loss due to friction in pipework due to the pipe and fittings is given by... 

In equation 6.33, if there were no losses, the coefficient of discharge of the meter would be unity, and for a flowrate G the loss in head would be (hv — hf) where hf is the head loss due to friction. 

The roughness of the pipe affects the ratio e/d. The rougher the pipe surface, the higher will be e/d and there will be an increase in R/pu2. This will increase the head loss due to friction and will ultimately increase the power required. 

The maximum head loss due to friction is still equal to 21.55 m as the pump head is unchanged. 

The first, second, and third terms in Equation 3-2 represent pressure head, velocity head, and static differences respectively. Equation 3-2 is used for investigating energy distributions or determining pressure differentials between any two points in a pipeline. Incorporating the head loss due to friction, hL, with constant pipe diameter, i.e., V, = V2, Equation 3-2 becomes... 

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