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Re: Heating Coils revisited

George Booth <booth at lvld_agilent.com> wrote:

> Lift tubes are, what, 1" in diameter?  Assuming that is correct, each lift tube
> has an area of about 5 sq. cm. Assume 4 tubes in an 85 gallon aquarium or about
> 20 sq. cm. total area. To get 110 cu cm per minute (leaping again), you need a
> flow speed in the tubes of about 5 cm per minute. That would seem pretty fast to
> be generated by a 1cm head, as mentioned above.

I agree with everything you said except the 1 cm head. For a flow rate of 5 cm
per minute, no visible head will be present in the lift tube. My system operates 
at about two-four times that flow rate with a single tube and I *think* I can see 
a tiny difference, < 1mm, in level between the interior and exterior of the tube.

Btw, the point you made about uneven flow thru the substrate is a very good
one. I attempted to minimize those "leaks" by siliconing the lift tube and
other parts of the UGF plate. I also rested the plate edges not directly on
the glass bottom, but on top of a thin piece of foam to act as a seal. Even
with those precautions, nothing prevents water to flow preferentialy thru
regions where the substrate is, say, thinner or with a more porous structure.

This is another reason to prefer a system of perforated pipes injecting water 
at fewer selected points instead of a plate that pretends to seep water uniformly
thru the entire substrate. That condition will never be reached in practice.

- Ivo Busko
  Baltimore, MD