Pressure drop in a plate heat exchanger

[jmex]

Hello Engineers,

I have a pressure drop for an individual plate. Now i would like to evaluate the pressure drop in a PHE where there are N number of plates. How would i do it? Is there any approach for that?

Thanks,
jmex

https://about.me/jdmech

 

[jmex]

can anyone help me with from where i can start atleast?

 

[Rputvin]

If you're confident you have an accurate pressure drop from a single plate you can model the PHE as N parallel paths. I'm assuming it was designed to not have much of a pressure gradient through the header ports.

Does your single plate information include the back of the next plate as part of the pressure drop, or are you looking at something similar to a starter plate that's not blanked off against the frame?

It's likely easier to contact the manufacturer and get their pressure drop rating. Most will have that information, along with the ability to account for changes with flow, fouling, plate mix, fluids, etc.

 

[jmex]

Hi Rputvin, thank you for your reply.

The pressure drop I have mentioned is from two plates joined and the fluid passing between them. Other plates are not considered, and also only one fluid media is considered which is passing.
Yes there will be N parallel plates and two different media (one for hot and another for cold) passing through this plates. Here I have the data for a single cold media that is passing through which i somehow arranged and found the pressure drop. Considering this pressure drop as accurate for a fluid passing between two plates, how will I calculate the pressure drop for plates arranged in parallel. I know that for a single fluid (hot or cold) i will divide the number of plates by two as it will not be passing through all the plates.
Do we have something that evaluates the pressure drop for parallel plates connected like we have in electrical current for parallel connection?

Thanks again. Much appreciated your help.

 

[TugboatEng]

Divide your flow by 1/2 N plates, calculate the pressure drop for one plate, This is your pressure drop across the exchanger.

 

[jmex]

Hi TugboatEng, thanks for your reply. How can a pressure drop for single plate be equivalent to pressure drop across exchanger? I have pd for a plate. I need to evaluate for exchanger which has N number of plates.

 

[TugboatEng]

Each pair of plates is supplied by a header and exits to a header. The supply and exit conditions for all pairs of plates are the same due to being connected to the same headers. Therefore, the pressure drop across each pair of plates must be the same.

 

[jmex]

Okay, so i just need to consider that pressure drop as for entire exchanger, right? Need to evaluate pressure drop at inlet and outlet too though which will add up for entire exchanger.

 

[Rputvin]

Pressure drop in the ports should be negligible, that's what I meant when I stated that the design should not have a pressure gradient in the headers. If there is a pressure drop inside the ports (aside from transition losses) your flow will not be equal over the plates, and your pressure drop will not be the same across all of the plates. This would cause the heat exchanger to perform unequally, foul on the rear plates more readily, and generally not perform as desired.

I'd suggest you review parallel flow path fundamentals. Here's a presentation from a university that came up in google for "pipes in parallel"

http://www.ce.memphis.edu/3180/PDFsF12/Parallel Piping System.pdf

Pressure drop in parallel paths is equal. Flow is divided.

I'd also suggest you check your results against the manufacturer who should supply this information for the complete unit.