Natural convection outside helical coil
Natural convection outside helical coil
(OP)
Hi everyone,
I'm ending some calculations of a helical coil immersed in a liquid solution.
Inside the tube runs superheated steam that condensates along it. Here i don't have problems, even though we're talking about condensation.
My problem is to calculate the heat transfer coef. outside the Helical coil inserted in a vertical tank with 80m3 and aprox 8m height. To determine the heat transfer coef. outside the helical coil (inside the tank) i've used natural convection outside an horizontal tube. This isn't in fact what i have, but is an approximation, and as we all know, the experience in this kind of calculations matters, so the overall coef. seems ok and between normal values for this kind of applications.
BUT, i would be much pleased if my calculations were 100% correct, so i've searched a lot in every reference book like Incropera, Holman, VDI Atlas, Steam, Kern, etc and also here in ENG TIPS in other forums, but when appears a reference to a helical coil, it's often related with heat exchangers in counter-flow (witch isn't whats going on here because i have natural convection) or the approach is often related with inside coil heat transfer calculations.
Is it possible for someone to give me some references to look in to determine the natural convection coef. outside a helical coil?
Thanks!
I'm ending some calculations of a helical coil immersed in a liquid solution.
Inside the tube runs superheated steam that condensates along it. Here i don't have problems, even though we're talking about condensation.
My problem is to calculate the heat transfer coef. outside the Helical coil inserted in a vertical tank with 80m3 and aprox 8m height. To determine the heat transfer coef. outside the helical coil (inside the tank) i've used natural convection outside an horizontal tube. This isn't in fact what i have, but is an approximation, and as we all know, the experience in this kind of calculations matters, so the overall coef. seems ok and between normal values for this kind of applications.
BUT, i would be much pleased if my calculations were 100% correct, so i've searched a lot in every reference book like Incropera, Holman, VDI Atlas, Steam, Kern, etc and also here in ENG TIPS in other forums, but when appears a reference to a helical coil, it's often related with heat exchangers in counter-flow (witch isn't whats going on here because i have natural convection) or the approach is often related with inside coil heat transfer calculations.
Is it possible for someone to give me some references to look in to determine the natural convection coef. outside a helical coil?
Thanks!





RE: Natural convection outside helical coil
Also, it doesn't sound like a hand calculation will work all that well there, you have a lot of different parts to the convection process in the coil, in a section of the coil, water will heat up and rise to another section of the same coil which will be heated up even more affecting the solution to that new section of the coil. If the coil is copper, then you can make some assumptions like, the coil can be treated as constant temperature.
RE: Natural convection outside helical coil
What tou say about the convection phenomena is correct and thats why i asked for some help with specific formulas for this application.
The tube material is SS 316.
Thanks
RE: Natural convection outside helical coil
Though, if you want a basic overestimate of the heat transfer, you could do a metal hollow tube in a tank of water with natural convection.
RE: Natural convection outside helical coil
Thanks again for the reply!
I agree 100% with you. This is a specific phenomena that varies with a ton of things like dimension of the coil, outside fluid properties, etc... So i've searched a lot and in several books, articles and foruns the conclusion was the same that we are facing now.
I also agree with you that in this specific situations, if we really want to obtain exact results we need to simulate this in a software.
For pratical situations in industry, of course i will continue to use my calculations that have been working until now, but in the future i will give a try a simulation in a software like ansys or autodesk cfd to compare the results.
Some day, when i try to put this in a software, i will share some results here. For now i think this post is finished.
Thank you once more for the replies!