Film Coefficients for Internal Pipe Flow

[jrjones]

I am trying to find a range of values for film coefficients on the internal of an 8" pipe. Problem is, I don't (as yet) have much info on the fluid other than it is mixed hydrocarbons, ~950°F, with a flow rate in the range of 147000 lbs/hr.
I just don't have a good feel for what the range of coefficients could be...what value is to high, etc. As it is that flow rate seems extremely high to me in terms of fluid velocity, but that is what I have for now.

While I know the relations to calculate the Nu number, I don't have a feel for the constants that go into calculating the PR and Re numbers.
Thanks in advance.

 

[Latexman]

What's the major component? C[sub]4[/sub]'s, C[sub]8[/sub]'s, C[sub]12[/sub]'s? Is it gas/vapor or liquid? Find the major component and look up the properties of that, instead of worrying about everything and doing mixture calculations, especially if you don't need a highly accurate film coefficient.

Good luck,
Latexman

 

[Latexman]

Once you find out what the components are and what phase is flowing, vapor or liquid or both, there are many references that give typical overall heat transfer coefficients. Just assume your fluid is on both sides of the exchanger and double the overall heat transfer coefficients to get a conservative estimate of the film coefficient. For example, let's say your HC is something between oil and naptha and it's a liquid at the T and P in the 8" pipe. My Perry's says U = 25-35 Btu/(ft^2.F.hr) for a liquid vs. liquid heat exchanger. So the inside local heat transfer coefficient should be greater than 50-70 Btu/(ft^2.F.hr) since we neglected the wall and fouling coefficients.

Good luck,
Latexman