LMTD for cross flows

[uzairsyedahmed]

Hi, I know this may be basic but it has been a while since I was out of college and wanted to confirm. It is plain easy , plug and chug , to determine the LMTD for counter flow and parallel flow since you can tell there are two distinct ends. But lets say a cross flow exchanger has water getting heated from 100 to 250 and steam getting cooled from 500 to 300. To determine the LMTD, as there is no clear end A and end B, we calculated LMTD based on COUNTER FLOW.

which is, end A being= 300 ( hot out ) - 100 ( cold in) = 200

and end B being = 500 ( hot in) - 250( cold out) = 250.

The F factor is meant to account for flow being cross and not parallel as per my understanding.

Am i right in the LMTD for cross flow above? or is it analyzing it as parallel and then applying F factor?

THanks!

 

[uzairsyedahmed]

anyone?!

 

[CRNewsom]

You are correct in your LMTD calculation. Apply the Fc factor from there. I believe that these values are available from TEMA if you do not have them.

 

[uzairsyedahmed]

Thanks! I believe the MERM has these values. thats what I remembered too, taking it as counterflow and applying Fc. just wanted to confirm