×
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

Piping Heat Loss

Piping Heat Loss

Piping Heat Loss

(OP)
Hello Everyone, I have a piping problem that is two-fold:

Situation:   A pipe, roughly 100’ long, in 30-degree F (ambient winter) weather.  The inlet water flow and temperature (approx. 100F) are known.  I am trying to figure out the water outlet temperature for two cases:

1.    The water is constantly flowing through the pipe, therefore the pipe’s temperature is near that of the water.  
2.    The pipe is initially empty, and assumed that it’s temperature has reached equilibrium with ambient.  

I am having a problem with this because I do not know what the film coefficients are, nor do I know how to calculate (or for that matter, even estimate them).  All my old textbooks refer to similar problems, except for those, there is only one unknown, either the coefficient or the outlet temperature.  I have two unknowns.  Can anyone help me figure this out?  I appreciate it.

Kayla

RE: Piping Heat Loss

First problem - steady state

Tout = Ta - (Ta-Tin).exp(-U.Pi.D.L/F.Cp)

where 1/U = 1/ha + 1/hw + e/k (...plus some diameter ratios)

Hope the notation is clear enough

In fact, hw (water side coefficient) is a function of Temperature, so the process could be:

- estimate an outlet temperature
- determine average water temperature
- evaluate fluid properties at average temperature
- determine coefficient hw
- Evaluate Tout from the equation & compare to your estimate
- iterate to achieve the desired precision.

Normally iteration converges fast as variations in temperature dont have a great impact on the hw value.

Next chapter, transient states in pipes.


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