On Thu, 23 Jul 2009, Recliner wrote:

"Tom Anderson" wrote in message
rth.li
On Thu, 23 Jul 2009, Peter Masson wrote:

"Tom Barry" wrote

If they'd only had aircon...

Among the problems with aircon on the tube lines is - where do you
dump the heat? Presumably on, say, the Central or Piccadilly lines
it would be possible to devise a system whereby the heat was
retained on the train until it got to the open air, and then dumped,
but Victoria Line trains stay underground all the time they are in
service. No use cooling the trains if you just heat the tunnels even
more.

You'd have to install a fake open air. By which i mean some point on
the line where trains could stop and offload their heat - some
apparatus they sit inside which blows a gale of super-cooled damp air
(or even water) into their heat exchangers, and sucks the warmed
exhaust out again. You wouldn't want to do it in passenger service,
but if you could build ten minutes into the schedule at one end, it
could be done during turn-around. Admittedly, this would involve
changing the Victoria operating principle quite a bit, but at least
it's technically feasible. Ish.

I think it makes a lot more sense to just take more heat out of the
stations and maybe the tunnels as well. That means more surface
ventilation fans running (which is think is already happening) and some
sort of additional cooling, such as the plan to use heat exchangers with
the cold ground water being pumped out. That way, the passengers in the
stations benefit as well, and you don't need to complicate the already
cramped trains any more than they are already.

But you don't cool the interiors of the trains as much as you would with
on-board AC.

I don't doubt that a station cooling approach gets a better
degrees-per-pound ratio, averaged over the whole underground space at
least, and so is a more sensible option. But i do wonder if there aren't
workable ways to get the insides of the trains cooler than is achievable
that way.

tom

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When I see a man on a bicycle I have hope for the human race. --
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