7 replies to this topic

[Kentucky08]

Good day, everyone,

 

I am currently studying how to determine the required length of a jacketed pipe to cool glycerine from 85 °C down to at least 60 °C. I’m preparing in advance so that, should I be assigned a related task at work, I can provide a well-supported solution.

 

Please refer to the attached file, where I’ve outlined my current approach. The cooling medium is water, assumed to enter at 30 °C and exit at 35 °C.

 

I have a few questions regarding my methodology:

1. Is it appropriate to size a jacketed pipe in the same manner as a double-pipe heat exchanger?
   I used Kern’s method along with formulas from Perry's Chemical Engineers' Handbook, 9th Edition to estimate the heat transfer area and required length.

2. Is it logically correct that the calculated length increases when I increase the inner or annular pipe diameter?
   Based on my trials, increasing the pipe sizes leads to a longer required length, which I found counterintuitive and would like to understand better.

I would greatly appreciate any guidance or insight from your experience. I’m aware that many members here are highly skilled engineers, and I’m hoping to learn from your expertise.

 

Thank you in advance.

 

Best regards,

Kentucky08

[breizh]

Hi,

Let you consider these papers,

Don't forget to post your work.

 

CheCalc ‐ Double Pipe Heat Exchanger

 

Breizh

Attached Files

•  Double Pipe Heat Exchanger Design Rev1 - Copy.pptx   3.6MB   38 downloads
•  Double Pipe Heat Exchanger Design.pdf   1.25MB   27 downloads

[latexman]

#1 Yes

#2 Diameter increases.  With constant flow, velocity decreases and heat transfer coefficients decrease.  Longer lengths needed.

[deft clay]

#1 Yes

#2 Diameter increases.  With constant flow, velocity decreases and heat transfer coefficients decrease.  Longer lengths needed.

 

This is correct. You might next ask, "why would anyone go with a larger pipe at all?"

 

To add on to the post and help your intuition, the tradeoff in this case is pressure drop. You are trading pressure drop for pipe material and plot space.

[Kentucky08]

Hi,

Let you consider these papers,

Don't forget to post your work.

 

CheCalc ‐ Double Pipe Heat Exchanger

 

Breizh

Thank you so much for these materials, Sir!

 

Hi,

Let you consider these papers,

Don't forget to post your work.

 

CheCalc ‐ Double Pipe Heat Exchanger

 

Breizh

Thank you for these materials, Sir!

[Kentucky08]

#1 Yes

#2 Diameter increases.  With constant flow, velocity decreases and heat transfer coefficients decrease.  Longer lengths needed.

Thank you for answering my two questions, Sir Latexman. They will definitely helped me understand more the topic.

[Kentucky08]

 

#1 Yes

#2 Diameter increases.  With constant flow, velocity decreases and heat transfer coefficients decrease.  Longer lengths needed.

 

This is correct. You might next ask, "why would anyone go with a larger pipe at all?"

 

To add on to the post and help your intuition, the tradeoff in this case is pressure drop. You are trading pressure drop for pipe material and plot space.

 

Am I correct when I say, larger pipe may give longer lengths but we wanna tradeoff for the lower pressure drop it gives?

[latexman]

Am I correct when I say, larger pipe may give longer lengths but we wanna tradeoff for the lower pressure drop it gives?

 

Yes.