Affect on pressure drop if no. of plates are increased on a PHE 3

[RDPall]

Hi,

Please can someone confirm that by adding additional plates to a PHE, the effective pressure drop across the PHE will decrease.
My assumption is that since that path length has increased by the increased number of plates, the pressure drop would actually Increase and not Decrease as I have been told by a supplier.

Thanks in advance for any assistance.

 

[speco]

RDPall,

The primary pressure drop in a plate and frame exchanger takes place in the path(s) between the plates. Therefore, the pressure drop decreases as the number of plates is increased. Since pressure drop is approximately proportional to the square of the (interplate) velocity, it is inversely proportional to the square of the number of plates. This assumes that the plate pattern is consistent throughout the exchanger.

Regards,

speco (

http://www.stoneprocess.com)

 

[JimCasey]

Yep, it's sorta analagous to calculating voltage across parallel resistors. Add another resistor and at the same current, the voltage DE creases.

 

[RDPall]

Thanks for the valuable feedback, Speco and JimCasey.

 

[rmw]

As you add plates (paths) not only does your pressure drop decrease, so does your velocity in all the plates, original ones as well as the addes ones. So while you have added the resistance of the new paths, you have decreased the resistance of all the original paths.

It decreases your heat transfer in each of the original paths but adds the additional heat transfer of the new paths. Rarely in my experience does it break even. Normally the heat transfer overall decreases with the addition of plates.

rmw