HTRI vs AspenEDR

[shvet]

Hello forum

I have a shell&tube condenser on Crude Distillation Unit. Nothing special, ordinary naphtha and cooling water. We made a modelling in Hysys and a brief autosizing in Aspen EDR which shows we need 2 shells and transmitted this data to Vendor. Now Vendor says they made calculations in HTRI and we need 8 shells for the same conditions.

2 shells and 8 shells. Nothing differs other than software. 2 and 8!

Vendor says this situation is quite common and AspenEDR always underestimate shell&tube cases min 20% of area comparing to HTRI and this is why they do not use AspenEDR.

At the same time we cooperate with other Vendors and some of them use AspenEDR and do not report such problems.

Comment please.

 

[georgeverghese]

8 shells in series or 8 in parallel? What about tube side - are they all in series?
8 shells in series is unusual - the max no of shells for the LMTD correction factor F is 6.

What are the design case terminal temperatures for this duty?

 

[shvet]

8 shells in series or 8 in parallel? What about tube side - are they all in series?

8 shells in series, tube side in series
actually Vendor reported: "for 2 shells in series excess surface is minus 72%"

What are the design case terminal temperatures for this duty?

Has not been calculated.

 

[georgeverghese]

So how do you run a thermal design for this duty when you dont know what the inlet and exit temps are for both tube side and shellside?

 

[shvet]

I provided modelling in Hysys and autosizing in AspenEDR. Thermal design was provided by AspenEDR based on algorithm of optimum price.