"Tom Anderson" wrote in message
th.li
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.

I'd say that cooling the stations is a pre-requsite to air-conditioning
the trains, given how hot the Victoria Line tunnels already are. It's
less of an issue with the other Tube lines, as the trains pump a lot of
fresh air in already at the portals.