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Shear Stress in Plate and Frame Heat Exchanger

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Hari1207

Hari1207

Mechanical
Joined
Mar 9, 2020
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14
Location
SA
Hello to all!

This is the first time I'm going to handle Plate & Frame Heat Exchanger.

I would like to know what is the importance of shear stress in Plate & Frame Heat exchanger. How it is developing the heat transfer rate?

Also in my project specification, it was stated minimum Shear stress of 30 Pa to be achieved. But my results are very less and it is around 10 to 15 Pa for different cases.

If anyone explains me this, will be easy for me to understand.

Thanks in advance to all.
 
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Just a guess. Maybe the client needs a minimum level of shear stress so the fluid scours (cleans) the heat transfer surfaces, or they have a fouling issue. What is your equation for shear stress between the two plates?

Good Luck,
Latexman
Pats' Pub's Proprietor
 
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Latexman is correct, the reason for specifying a minimum required shear stress is to help prevent fouling of the exchanger, not for heat transfer. High shear stresses prevent deposits from accumulating on the surfaces of the plates due to the scrubbing effect.


-Christine
 
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Thanks respected Latexman & Christine74.

Got your point that shear stress helps to reduce fouling effect.

There are no equations prescribed in my specifications. It is being calculated by Software.

Also I presume that in order to achieve more shear stress, we need more allowable pressure drop on both Hot & cold side right?

Could you please explain on the above concept?

Thanks again.
 
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Essemtially. More dP and more flow uo get higher velocities.

If you could, narrowing the gap between plates would do it too, but that may not be practical and stay in a commercial plate and frame heat exchanger.

Good Luck,
Latexman
Pats' Pub's Proprietor
 
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