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[titim]

Hi everyone, i have some problemes that need your help.

i have to simulate a pre-heat train from an existing unit, this train (the first part ) is composed from 6 exchanger devided in 3 exchanger in serie ( 3X2 ) as showed in the picture E101A to F  : crude pre heat train picture), and it's associated with the heater DATA SHEET, 

the datasheet show the the crude is heated from 80°F to 220°F (tube side),  and the Reflux circu de tete (top stage pump around draw) from 240°F to 150°F shell side, my questions are:

1- what is the meaning of :SURFACE PER UNIT (25000 sq.ft), and shells per unit:6  in datasheet.

2- the heat exchanger-BTU/hr (52500000) showed in the data sheet represent the total energie of the 6 exchanger or only for one.

3-the datasheet don't give us the details of the temperature of each exchanger parameter, especially the inlet and the outlet of eachone.

4- when i try to simlulate the train in hysys (also with EDR) i get some errors like, Ft correction very low(i know what that mean), or i get the 220°F in the first exchanger and not in the last one.

NB: for the excel file, actually it's an hysys file, click on open with and select hysys program.

i'm ready for any clarification and for your help. thank you.

Attached Files

•  Crude Pre heat train.png   186.62KB   1 downloads
•  E101 A to F DATASHEET.png   655.77KB   1 downloads
•  crude Pre-heat train.xlsx   2.44MB   11 downloads

Edited by titim, 31 July 2017 - 07:21 AM.

[colt16]

I believe it is possible in HYSYS to simulate the whole train as one exchanger instead of 6. Hence it is not necessary to know the intermediate temperatures but HYSYS should be able to provide it anyway.

1. It means surface area available for one unit. So total surface area is 25,000 * 6

2. It means total. You can also verify this by calculating the enthalpy at the inlet of the exchangers and the enthalpy at the outlet after the exchangers. Duty = Change in Enthalpy.

3. See above statement

4. Ft factor is a correction factor for real countercurrent flow or cocurrent flow. In a S & T exchanger it is impossible to be 100% countercurrent, especially if there us a U-tube for example. Low Ft factors means one should use more shells in combinations to have proper LMTD for each exchangers or there could be things like a temperature cross (i.e. The cold stream and hot stream meet at a common temperature (the temperature cross) and no heat exchange takes place). To prevent a temperature cross you need to have multiple shells like the one in the PFD.