×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Flow boiling regimes question

Flow boiling regimes question

Flow boiling regimes question

(OP)
I am reviewing some of my heat transfer texts and finding them woefully inadequate in explaining flow boiling.  I have reviewed pool boiling and the correlations associated with it.  I am comfortable with understanding where I am on a pool boiling curve and the variables which affect the shape / placement of the curve on the pool boiling graph. I even am comfortable with doing a pool boiling calculation.  Where I fall down is in understanding how to know, for flow boiling, where I am on this same curve (I  understand that the shape changes particularly for nucleate boiling and the location of DNB/CHF).  I have looked at a number of correlations for nucleate boiling, but don't understand how I know when I am in a nucleate boiling regime (versus say transition or film boiling).  If it is a matter of excess temperature (Twall - Tsat), I don't see how the flow boiling correlations I have reviewed accommodate this factor, except for to maybe calculate it implicitly using said correlation and iterate until things balance. Any insight into this issue would be greatly appreciated.

Thanks,
rjw57

RE: Flow boiling regimes question

Have you reviewed the text by Kakac and Liu ? It was published in 1998 and is named "Heat Exchangers Selection, Rating, and Thermal Design". They have an extensive section on flow boiling on pages 220-247.

There is little discussion in the literature of problem areas in evaluating flow boiling. Some situations such as stratified flow or mist flow will cause a big drop in heat transfer. Another problem is the one you mention which is high temperature difference (Twall -Tsat). As a long time thermal design engineer,I have used a maximum temperature difference of 80 F. for hydrocarbons. This has been used for years without a problem.

  

RE: Flow boiling regimes question

As a folowup to srfish, S. Kakac has a newer text " Boilers evaporators and condenser" 1991 , J Wiley + Sons, isbn 0-471-62170-6 , chapter 6  and 7. . In particular, the CHF correlations by Dorschuck and dryout by Kieffer, Kohler, Hein and Wittchow are considered to be the mopst reliable correlations for flow boiling of water.

For insight into their methods , see papers by Keifer, Kohler and Hein ( Siemen KWU Erlangen) as published in 1985-1995 in the In'tl journal of multiphase flow.

RE: Flow boiling regimes question

(OP)
Thanks srfish & davefitz

I will look into these publications shortly.  I have just found some vertical and horizontal flow boiling correlations (described as flow pattern mapping)in a text I own which are attributed to Kattan-Thome-Favrat and are applicable to a large range of regimes in both vertical and horizontal flows.  The correlations are different for horizontal vs. vertical flows of course.  Are either of you familiar with this work?

Thanks,
rjw57

RE: Flow boiling regimes question

I am not familar with Kattan-Thome-Favrat. The correlation I have used is Chen.

Good Luck

RE: Flow boiling regimes question

The KWU correlations ahve been extended to horizontal and inlcined tubes, as explained in the published papers by Kiefer- Kohler-Hein  in In't J Multiphase flow.

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!


Resources