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Sunday, 14 October 2018

FLOW THROUGH NOZZLE

We were discussing the basics of shear stress in turbulent flowminor head losses in pipe flowhydraulic gradient and total energy line, basic concept and working of syphonflow through pipes in seriesflow through pipes in parallel, flow through branched pipes and power transmission through pipes, in the subject of fluid mechanics, in our recent posts. 

Now we will go ahead to see the concept of flow through nozzle, power transmission through nozzle, efficiency of power transmission through nozzle and we will also find here the condition for maximum transmission of power through nozzle, in the subject of fluid mechanics, with the help of this post. 

What is a nozzle? 

Nozzle is an engineering device which will accelerate the fluid and hence fluid velocity or kinetic energy of fluid will be increased while pressure of fluid will be reduced. 

Let us see the nozzle which is fitted at the end of a long pipe as displayed in following figure. Total energy at the end of pipe will be summation of pressure energy and kinetic energy. Total energy will be converted in to kinetic energy by fixing a nozzle at the end of pipe and therefore velocity of fluid flowing through nozzle will be increased. 

Nozzles are used to increase the velocity of flowing fluid and let us find here the few examples of application of nozzle as mentioned below. 
  1. In case of Pelton turbine, the nozzle is used at the end of pipe for increasing the velocity. 
  2. In case of fire extinguisher, a nozzle is used at the end of hose pipe for increasing the velocity of flow. 

Let us consider the following data from above figure. 
D = Diameter of the pipe 
L = Length of the pipe 
A = Area of the pipe 
V = Velocity of flow in pipe 
H = total head at the inlet of the pipe 
d = Diameter of nozzle at outlet 
v = Velocity of flow at outlet of nozzle 
a = Area of the nozzle at the outlet 
f = Co-efficient of friction for pipe 

Velocity of flow at the outlet of nozzle

Velocity of flow at the outlet of nozzle will be given by following formula as mentioned here

Discharge through the nozzle

Discharge through nozzle will be given by following formula as mentioned here 

Power transmission through nozzle

Power transmitted through nozzle will be given by following formula as mentioned here 

Efficiency of power transmission through nozzle

Efficiency of power transmission through nozzle will be determined with the help of following formula as mentioned here. 

Condition for maximum transmission of power through nozzle   

Above expression is the condition of maximum transmission of power through nozzle. We can conclude from above equation that power transmitted through a nozzle will be maximum when the head loss due to friction will be one-third of the total head at inlet of the pipe. 

Diameter of nozzle for maximum transmission of power through nozzle  
Diameter of nozzle for maximum transmission of power through nozzle will be given by following formula as mentioned here. 

Further we will go ahead to find out the concept of water hammer in the pipesin the subject of fluid mechanics, with the help of our next post.  

Do you have any suggestions? Please write in comment box. 

Reference: 

Fluid mechanics, By R. K. Bansal 
Image courtesy: Google 

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