Sizing(Design) of a Heat Exchanger that can Process 20,000 Barrels/Day 1

[FcJazz]

Good day everybody,
This is my first posting to the Eng-Tips Forum.
I need your help, in the form of practical knowledge or links on how to solve this problem.
I am currently working on a U-tube Heat Exchanger design that can process 20,000 barrel of crude oil per day.
The parameters are as follows:
1. The heat exchanger has to cool the crude oil from 100o c to 40o c using seawater.
2. The seawater originally at a temperature of 25o c, will have to be re-emptied into the sea at a temperature of 35o c.
Requirements.
1. I want to know how to calculate the amount of seawater needed for this cooling operation.
2. I want to know how to determine the size(capacity) of the heat exchanger. Also determining the number and size(length) of each tube in the heat exchanger.
3. If the material to be used for constructing this heat exchanger is either carbon steel, stainless steel or titanium, what corrosion forms should I expect and how can I control these forms of corrosion.
Thanks in anticipation of your response.

 

[MortenA]

Go to a vendor or pay for a consultant.

Best regards

Morten

 

[racookpe1978]

Go back to your original textbooks. (Hint.)

You have two fluids in contact through a U-tube (2-pass ?) heat exchanger. You have a (known) inlet and (desired) outlet temp for each fluid. You have a known fluid flow - - though 20,000 BpD is pretty small.

Figure out the area of tube (inside and outside) you need. Now, make yopur assumptions. What diameter HX? What diameter tubes? What wall thickness/pressure/corrosion allowance.

Do the basic homework - on your end! - first, then ask for advice on the more arcane parts of the problem.

Hint 2. Your choices will be carbon steel = more expensive than you'd want to pay, stainless steel = much too expensive than what you hope to pay, Titanium = excruciatingly too expensive.

How long do you want it to stay leak free? What "kind" of crude oil? How corrosive is the crude? What is in the crude? How often will you inspect? How do you prevent oil-to-water contamination? How do you detect oil-to-seawater contamination BEFORE you let oil get in the water?

 

[IRstuff]

Well, just in rough calcs, you need roughly 20 kbbl/day*(100-40)/(35-25) = 120 kbbl/day. This ignores lots of reality.

Is this for school?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[srfish]

This sure looks like it is for school.

 

[btrueblood]

One could make a career out of coming up with the answers to those three questions. Many do. They train for years to learn how to answer the questions. Like Morton said, find one of those people to help you, and pay them what they want.

 

[MortenA]

with regards to materials - with sea wtare and CS you should expect very high corrosion rates.

Best regards

Morten

 

[gruntguru]

Well, just in rough calcs, you need roughly 20 kbbl/day*(100-40)/(35-25) = 120 kbbl/day. This ignores lots of reality.

Ignored reality includes Cp (Water roughly 2.3 times oil) and rho (water roughly 10% greater than oil). So 120,000 becomes 45,000 bbl/day.

Engineering is the art of creating things you need, from things you can get.

 

[SNORGY]

FcJazz:

It really does come down to playing with UA(LMTD) = mCpdT, where the nebulous part of the problem is to arrive at a reasonable U-value or UA-value. You can probably rough in an approximate size through some iterations before you turn it over to a vendor or consultant to model using more accurate tools and make decisions on things like baffle cuts and spacing, passes, etc.. (That would be the "...hire a consultant..." part of the problem, but there is some up front work that you can do.)

With respect to metallurgy, carbon steel is in my mind probably the least desirable of the options you mentioned. If you put the sea water on the shell side you might consider an internally clad shell, thermal spray or a high temperature coating, thereby keeping your non-CS metallurgy confined to the tubes and tubesheets. I would avoid austenitic stainless steel in sea water service due to the obvious presence of chlorides, so maybe naval brass or NAB? Again, a vendor, consultant or metallurgist can be of great benefit. Then once you come to a landing on metallurgy, you would need to incorporate the actual material properties to refine the thermal performance.

Titanium is probably the best of the three options you mentioned, but probably rather costly.

Regards,

SNORGY.

 

[IRstuff]

"Ignored reality includes ..."

As does the simple fact that calc had zero margin. When you add back in operating margin, you're back into the 120 kbbl/day regime.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[willard3]

Another person unfamiliar with thermodynamics and heat transfer trying to use this board as a design resource......not what it's for.

Hire a professional.

 

[gr2vessels]

FcJazz,
The answer to your question is only available for highly trained engineers (several needed to complete the design of your exchanger).
These engineers are professional people keen to help another professional in heat transfer processes, who have available sofisticated software for aid in design and more importany, many many years of experience in this specialised field.
In comparison, your question sounds like how to build a rocket to take you on holiday to Mars. Put it mildly, is naive.
Obviously, you don't have tertiary /engineering education hence your question is difficult to answer to the level of your understanding.
Don't give up. Everything has a start and the best way to start is reading thermodinamics books and heat transfer processes literature available on the internet for free.
Come back with specific questions and I'm sure everybody will be happy to answer those questions, to see you progressing on this field of engineering.
Cheers,
gr2vessels