On Thu, 16 Jul 2009 21:34:31 +0100, Tim Lamb wrote:

I suspect it probably is the north sea surface temperature in mid
winter doesn't get down to 5C, 8C is sort of average. It's about
15C
ATM... With the river being fed "warm" effluent as well...

Maybe.

The SST of the North Sea currently ranges from 13C around Shetland to
17C of the SE corner.

http://www.wetterzentrale.de/topkarten/fsfaxbra.html

Follow the "Wassert" link in the large center box.

That's where the design is critical have a big enough area over
which
to extract the heat such that it doesn't freeze or the delta T get
too
small.

Quite. I expect the EA will come up with some unaffordable
abstract/discharge fees and the project reverts to the multiple slinky
model.

But with a flow of relatively warm water just above your buried
slinky I suspect the slinky can be somewhat smaller than one buried
in normal ground. Heat can be transported in quicker by the flowing
water compared to (more or less) just conduction in a ground buried
slinky.

Bet the EA would ob ject to the laying of slinky in river bed though.
Or English Nature if they got to hear of it, probably a rare Crayfish
or their might be a rare Crayfish and they'll want a full wildlife
and impact survey carried out... FFS, there will be a bit of
disturbance during the installation but after that bugger all, water
temps down stream might a tad lower but I bet they'd soon recover.

--
Cheers
Dave.