Copper -Fin Tube Heaters & Minimum Flow
Copper -Fin Tube Heaters & Minimum Flow
(OP)
Why do copper fin-tube water heaters require minimum flows? What would happen if it was provided 40F inlet water, and set to 200F outlet water?
a) Is it an issue of scale build-up?
b) Is it an issue of melting fins?
What is the reason for (a) or (b)--Does it occur only because there is unequal flow distribution among the various tubes, or is the distribution relatively equal and it occurs anyway?
Are there fin-tube products that don't have these limitations?
I ask because I'd like to design a new fin-tube heat exchanger that doesn't require minimum flows and I'd like to know what to look out for...
Thanks.
a) Is it an issue of scale build-up?
b) Is it an issue of melting fins?
What is the reason for (a) or (b)--Does it occur only because there is unequal flow distribution among the various tubes, or is the distribution relatively equal and it occurs anyway?
Are there fin-tube products that don't have these limitations?
I ask because I'd like to design a new fin-tube heat exchanger that doesn't require minimum flows and I'd like to know what to look out for...
Thanks.





RE: Copper -Fin Tube Heaters & Minimum Flow
RE: Copper -Fin Tube Heaters & Minimum Flow
Is poor heat transfer the only problem, or can damage occur to the unit? Typically the warranty of such a product is voided with insufficient flow, so it must be something worse than merely reduced heat transfer.
RE: Copper -Fin Tube Heaters & Minimum Flow
TTFN
Eng-Tips Policies FAQ731-376
RE: Copper -Fin Tube Heaters & Minimum Flow
Scaling and/or fin-melting would not be prevented if those are the failure modes (or maybe there's another I haven't thought of). But boiling could be prevented with sufficiently advanced controls.
Is the problem solely boiling, or are there other factors?
RE: Copper -Fin Tube Heaters & Minimum Flow
Minimum flow would also be to prevent hot spots and potential boiler failure.
RE: Copper -Fin Tube Heaters & Minimum Flow
RE: Copper -Fin Tube Heaters & Minimum Flow
You mention hot spots--do these products typically have a significantly imbalanced flow distribution?
RE: Copper -Fin Tube Heaters & Minimum Flow
You mention hot spots--do these products typically have a significantly imbalanced flow distribution?
snip
If you have low reynolds numbers, you have hot spots.......
If you have hot spots, you will have thermal failure from expansion even in homogeneous and isotropic materials.