Hydraulic diameter of finned tube 1

[Engprofile]

Hi,

I am trying to determine the hydraulic diameter of a finned tube but I am unsure how work this out. I have attached a diagram showing the tubes and dimensions. The distance between the ends of the fins is 0.5mm. If someone could help with this simple problem that would be great.

 

[chicopee]

About improving your sketch to show fluid passages and to identify what's what with the horizontal and vertical elements. Right now there is no way of knowing what the fins do.

 

[BrianCNTFM]

From memory determine diameter of tube that would give you same surface area as length of finned tube and use this as De.

Regards Brian

 

[25362]

There are various "equivalent" diameters used for estimating the Nusselt and the Reynolds number, beside d[sub]o[/sub]. Here is one taken from the literature:

Hydraulic equivalent diameter of finned tubes (d[sub]He[/sub])


d[sub]f[/sub] = external diameter of fin
d[sub]o[/sub] = external diameter of bare pipe
p = face-to-face distance between adjacent fins
t = fin thickness

d[sub]He[/sub] = [(d[sub]f[/sub][sup]2[/sup]- d[sub]o[/sub][sup]2[/sup])/2p + d[sub]f[/sub]t/p + d[sub]o[/sub](1 - t/p)] ÷ [1 + (d[sub]f[/sub] - d[sub]o[/sub])/p]​

 

[Engprofile]

Great thanks, I will try these and see what sort of results I get.

I have found another correlation in the wolverine handbook which can be used to calculate the heat transfer coeffiecient on the air side without the need for working out a hydraulic diameter.

Makes things a bit easier but I will try and work out the h value using the hydraulic diameter to get reynolds number.

 

[25362]

Please note that p means the distance betweeen "equal" faces meaning it includes one t.