Convection
Convection
(OP)
I have a hard time understanding characteristic length in convection. I am trying to figure out the natural and forced convection inside a tube that contains couple of heating elements. Air is being heated up in this tube. Using Gr/Re^2 can tell me whether forced or natural convection dominates. Both grashof number and reynolds number have characteristic length in their formulas. For reynolds number, the characteristic length should be
Diameter(tube) - Diameter (elements) * n(number of elements).
For grashof number, I am confused on whether I need to include diameter of the tube. My understaning is that since air would flow over the elements, I only need to consider the elements. Can anybody shed some light on this. Thanks
Diameter(tube) - Diameter (elements) * n(number of elements).
For grashof number, I am confused on whether I need to include diameter of the tube. My understaning is that since air would flow over the elements, I only need to consider the elements. Can anybody shed some light on this. Thanks





RE: Convection
Please submit a sketch (axial and sectional) of your tube.
RE: Convection
My gut reaction is that this may not be simple depending on how your "couple of heating elements" take up space inside your tube.
Patricia Lougheed
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RE: Convection
Anyway and as indicated above a sketch showing your real situation would put us in condition to give you a better advice.