Discussion Central

1.  Two Phase Flow Heat Transfer

Posted 11 days ago

Hello,
I am looking into improving heat transfer in a vertical pipe, where hot product is being cooled by a cryogenic liquid injected(liquid-liquid contact).  The cryogen boils and bubble flow is obtained but not long enough to allow appropriate temperature drop.

Measuring temperature in two phase flow can be quite tricky in a vertical pipe and was looking for suggestions on best way to see an improvement(pressure drop measurement vs. temperature measurement).

The purpose is to reduce the hot media in the pipe roughly 130 degrees F delta.  Thus far, we have looked at pipe diameter change(currently 4") versus increase pipe length to improve residence time of the bubbles(nucleation boiling).  I do not wish to decrease the flow rate of the hot product as this would impact throughput in the plant.

If anyone has any history or good references to look at it would be much appreciated.

Thanks,




2.  RE: Two Phase Flow Heat Transfer

Posted 11 days ago
I'm not sure I am visualizing the process correctly, but I would expect that once you cryogen vaporizes that you're not getting any further significant heat transfer. I would think the majority of your enthalpy change would be due to the phase change (not sure if the cryogen is supercritical at your conditions, so I'm reluctant to just say heat of vaporization, but that's basically how I'm thinking about it). Also once your cryogen is vaporized, even if the bulk vapor is still cold enough to have some effect, you're heat transfer seems like it would be limited because heat transfer from, say, the middle of a bubble to the bubble-liquid interface would be relatively slow.

How does an overall enthalpy balance look? Is it simply a case of needing more cold stuff?

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Steve Cutchen
Investigator
US Chemical Safety Board
Houston TX
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3.  RE: Two Phase Flow Heat Transfer

Posted 10 days ago

How is the cryogen being injected?  Smaller bubbles would take longer to rise and provide more heat transfer area.  If you used a spray nozzle to inject the cold liquid you should get smaller bubbles and better cooling.

 

Harold Reed, M.S.

Sirius Technical Services Contract Engineer

For Evonik Corporation

Process Technology and Engineering, Americas

Phone  +1 251 443 2428

Mobile +1 251 802 7518

Fax        +1 251 443 4078

harold.reed@dgextern.com

 






4.  RE: Two Phase Flow Heat Transfer

Posted 7 days ago

Here are a couple of very good reference books, old, but theory has not changed:

 

  1. Gas Hetstroni, Handbook of Multiphase Systems, Hemisphere Publishing (McGraw Hill), 1982

 

  1. G W Govier and K Aziz, The Flow of Comlex Mixtures in Pipes, Van Nostrand Reinhold Co, 1972

 

Jimmy D Kumana

Kumana & Associates

Houston, Texas, USA

Tel. +1 (281) 437-5906, Cel. +1 (646) 546-2484

If you think that it is expensive to hire an expert to do the job, wait until you find out how much more it will cost you to hire an amateur. ― Paul N. "Red" Adair, 1915-2004