heat transfer coefficent 1

[bigJinxy1985]

hi,

i'm currently trying to spec a heat exchanger for a cooling system as part of the calcs i have to work out the overall heat transfer coefficient using 1/U = 1/h1 + b/k = 1/h2 where h is the local heat transfer coefficient b is the breadth and k is the thermal conductivity of the material.

my question is how do i calculate the local heat transfer coefficient?

can anybody help?

 

[Latexman]

Search for a correlation that matches as close as possible what is happening in that local process. Is it boiling, condensing, natural convection, forced convection, what? Break out your old heat transfer textbook or engineering handbook or use your google-fu.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[Compositepro]

Big, this is a professional forum. We appreciate the use of proper punctuation and grammar.

 

[chicopee]

h stands for convective heat transfer coefficient. For a start, you should familiarize yourself with a heat transfer book in which you may find h values for different situations. There also numerous articles on the internet if you type convective heat transfer coefficients. Presented are two links:
en.wikipedia.org/wiki/Heat_transfer_coefficient
s3.amazonaws.com/suncam/npdocs/119.pdf · PDF file

 

[sshep]

Hey BigJinxy,

Latexman has nailed your problem. If you give some info about the nature of the system, you can get some really good advice. Often one side controls- if you are cooling vapor it could be as low as U=20 BTU/(h-sqft-F); if you are condensing steam against clean cooling water it could be as high as 350 BTU/(h-sqft-F). To you resistance equation it is typical to add fouling factors which can often dominate.

If you have an exchanger already in similar service, you should calculate the U that you are actually getting. This will help you make a reasonable call and check the design. You should recognize that h1, h2. k, and b will come directly from the exchanger design, but specifying the fouling factors is a 100% owner responsibility.

best wishes,
sshep

 

[NoHtPp]

Mr.LTX:

I appreciate reading your posts!
Q:
When you find the glass that fell out of the space shuttle payload section when the doors opened, what was it full of? -technically: if not in any atmosphere, ambiently-