Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

twin heat exchangers

twin heat exchangers

twin heat exchangers

Dear all.
I have a question. Would you please help me?
In attached shell and tube twin parallel heat exchanger, Natural gas (NG) enters in tubes and propane enter in shell. Although both exchangers are completely the same, but propane level in exchangers are not equal, So the PRP-out temperature are not the same too. Why???

And surprisingly although PRP level in E-A is lower than E-B, but NG-out temperature in E-A is lower. Why???

One suggestion to overcome this issue is to connect both shell drain of heat exchangers, so they are like connected drums. What is your idea?

RE: twin heat exchangers

E-A is transferring more energy. To find out why that is, will take a deeper dive into the data and exchanger's

Good Luck,

RE: twin heat exchangers

Gas-side heat transfer (film coefficient) is highly sensitive to turbulence (Nre). Since you're obviously getting better heat transfer in E-A, one possible explanation is that the NG side of E-A has more pressure drop (resulting in higher Nre, and better HTC) due to the friction loss in the NG supply line to E-B.

Another possibility is that you have some debris obstructing NG flow into the E-B tubes.

RE: twin heat exchangers

Exit temps on HX-A are not realistic - NG exit temp should be higher than C3 vap exit temp. Check calibration of TTs'. Local TG cannot be relied on.

Level variation may be due to difference between actual density and value input at DCS for translation of HX-B dp cell readout to level. Local readout at HX-A may be the correct value(assuming this is a local LG and not a dp cell type unit), so multiply the current density at control LT in DCS by 10/7, roughly. Then level readouts at HX-B LT will be 70% also. Actual C3 density in these kettles may have further increased from simulation values due to accumulation of trace C4 (probably iC4)in feed C3. No need for level equalisation line since there is no possibility of unequal accumulation of C4 on shellside between these units.

RE: twin heat exchangers

"Local readout at HX-A may be the correct value(assuming this is a local LG and not a dp cell type unit), so multiply the current density at control LT in DCS by 10/7, roughly."

I couldn't get your point. But I must say level of both heat exchangers are based on local gauges.

RE: twin heat exchangers

Okay, so readouts are from local magnetic level guages - these are also known for producing erroneous readouts.

What does LT - LIC on HX-B show ?

RE: twin heat exchangers

LT on HX-B shows 69%

RE: twin heat exchangers

Attaboy, georgeverghese!

Good Luck,

RE: twin heat exchangers

Since mag LI and dp cell readouts on HX-B match, suggest mag LI on HX-A be removed and sent for maintenance or replaced at next turnaround if there is time (not a critical maintenance activity, since this is not in a process control or process safety function).

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close