Total condenser area must greater than partial condenser?

[knapee]

Dear Sir/Madam


I wonder that the area of total condenser(TC) should be greater than partial condenser(PC) or not.
I got a weird htri result: the area of TC I got is less than the area of PC.
(Pls see the process drawing is attached in the post)

The air/solvent is purged and dosed in the polyester acrylate reactor, and vapor to the top partial condenser (PC) to condensing,
and then to be condensed further in the total condenser(TC).

Furthermore, the PC is cooled by cooling water, and heated from 30C to 40C at inlet P=4.033kg/cm2A.
Lean air (including T2(toluene),C2(cyclohexane),and H20) is cooled from 110C to 50C, and vapor fraction is decrease from 1 to 0.046.
Then, the lean air in the TC is further cooled by chilling water, and chilling water is heated from 10C to 15C at inlet P=4.033kg/cm2A.
Accordingly, the lean air is cooled from 50C to 30C and vapor fraction is decreased from 0.046to 0.03.


There is another issue bother me : the flow rate of the air/solvent required to be into the PC
should be equal to the same flow rate that is further condensed in the TC or not.

Cause I used the same flow rate to input in the HTRI's hot fluid properties and process condition for the PC and TC,
I wonder it may result in this illogical answer (TC area < PC area)
(HTRI is attached in the post)


The TEMA type AES is used here in case any leakage happening, but there is a wired htri warning message:
TEMA Front head location: the value enters was not recognized. “Bottom" will be assumed.

I really appreciate your kindly advice in the query.
Thank you very much.

 

[Latexman]

The PC starts with very little inerts. The TC has a lot of inerts. Presence of inerts just kills the htc.

Good luck,
Latexman

 

[knapee]

Dear Latexman

Thank your professional help to remind me that non-condensable gas will be cost a lot of heat transfer area.
But, only the molar fraction of the non-condensable, such as 0.98~1 could increase
the heat transfer area a lot. Is that possible that the molar fraction of the non-condensable gas is 0.1 in the first partial condenser, and then increase to 0.99 in the second total condenser.

The other issue is the fouling resistance, what is best fouling resistance for this mix
cyclohexane, toluene, nitrogen, and oxygen gas-liquid mixture stream ?
It seems the fouling resistance in the first condenser (partial one) got higher resistance than that of the second condenser (because the temperature in first condenser is higher than the second one). It seems unpredictable in this fouling resistance issue. I also refer to TEMA section 10, Ex. the MEA and DEA solution is almost 0.002 and gas is 0.001~0002, but these seem not fit for my case.

Please help me out in this issue.

I really appreciated your advice and comment.

 

[Latexman]

A smaller U in the TC due to non-condensables may be only part of the answer. What is the required heat duty of the PC and the TC? Also, what is the [&Delta;]TLM of the PC and the TC?

Good luck,
Latexman

 

[IngGasP]

Hi Latexman!

Coud you explain more what do you mean by this statement:
The PC starts with very little inerts. The TC has a lot of inerts. Presence of inerts just kills the htc.

What stands for HTC and HTRI, and what do you mean by Presence of inerts just kills the htc.

Good luck

 

[Latexman]

Non-condensables (i.e. inerts) in a condenser reduce the heat transfer coefficient (htc) greatly. The partial condenser has little non-condensables compared to the condensables. The total condenser has a lot of non-condensables compared to the condensables. The same mass flow rate of non-condensables goes through the PC first, then the TC. The condensables in the PC drain back to the reactor.

Good luck,
Latexman

 

[sshep]

The TC is obviously smaller than the PC because the duty on the TC is less than 10% of that on the PC:

A=Q/U/MTD
PC: 0.2767E6/111/41.5= 60sqm
TC: 0.0213E6/130/27.1= 6sqm

Just a guess: The warning probably has to do with your shell orientation being not vertical. The inlet head location (bottom inlet) option was previously only allowed for vertical exchangers (upflow vs downflow). If what you really want is the nozzle location to be at the bottom of the inlet channel, this is a different input.

best wishes,
Sean

 

[silebilee]

Total condenser may initially be in the shear controlled regime,but with the condensation increase, it will change to the gravity
Controlled regime. Most horizontal baffled total condenser have "Vertically cut baffles(parallel cut)" instead of "Horizontal cut(your htri case) baffles" to allow the flow of condensate along the bottom of the shell.

The same approach also applied to a partial condenser, and it can be refer to the article “ Don’t let Baffling Baffle you” by R.Mukherjee in April 1996, CEP magazine.