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Head

pressure pressure measurement

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#1 nameless

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Posted 08 November 2014 - 03:22 AM

Dear All,

What exactly is head and what is it's significance in pressure measurement?

According to wiki, head is a concept that relates the energy in an in compressible fluid to the height of an equivalent static column of that fluid.Does that mean we are relating the total energy of a moving fluid to the energy(potential)of a fluid at rest?The moving fluid possess potential energy as well so why are we relating it to energy of a fluid at rest.I suppose potential energy is the only type of energy possessed by a fluid at rest.Sorry If the question sounds nebulous.I just don't get the intuition behind it



#2 breizh

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Posted 08 November 2014 - 04:38 AM

http://www.cheresour...echanics-books/

Nameless,

Consider reading this post and check for the reference I posted .

Good luck,

Breizh


Edited by breizh, 08 November 2014 - 04:50 AM.


#3 nameless

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Posted 08 November 2014 - 09:27 AM

Thanks Breizh!

Can you elucidate to me what is the difference between potential energy and pressure energy of a fluid?

 

From what I understand,potential energy is the energy which a body possess due to its position against gravity,therefore the energy should be equal to gravitational force.

Pressure energy is the energy exerted by a body due to its weight,which is again due to gravitational force.

Therefore,aren't pressure energy and potential energy one and the same?


Edited by nameless, 08 November 2014 - 09:45 AM.


#4 katmar

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Posted 08 November 2014 - 12:14 PM

The pressure at the base of a column of liquid is given by the well-known equation

 

Pressure = ρ.g.h

 

ρ = fluid density

g = acceleration of gravity

h = height of liquid column (= head)

 

This makes it possible to use pressure and head interchangeably if we know the liquid density and the acceleration of gravity.  It is much easier to visualize a head of 10 metre of water column than it is to visualize a pressure of 100 kPa and this makes head a comfortable concept to use.  Also, chemical processes use mainly centrifugal pumps which deliver the same head for any liquid (within reason) when measured in terms of the pumped liquid. I think these are the 2 main factors that make head a popular choice in place of pressure.






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