London Banter - View Single Post

Colin Rosenstiel · July 1st 08, 09:01 PM posted to uk.transport.london

In article ,
(Tom Barry) wrote:

Batman55 wrote:
It seems odd that as LUL attempts to cool down the tube, it is
introducing giant electric projectors at many stations, along
with the illuminated moving panels on the escalators. The stories
in Railway Herald this week, page 5 about cooling down, and page
6 about the heat producing equipment, seem to show a lack of
joined up thinking!

What might be more sensible is for equipment at every sub surface
station to be reviewed and every heat producing item examined to
see how its heat output could be reduced or eliminated. Every
little bit might help!

According to TfL, the heating effect arises because of the
incremental heating and cooling caused by each passing train's
energy consumption. The frequency of trains means the cooling of
the tunnel walls is that little bit less than the heating, so over
the years the ground heats up because it never gets a long enough
break between trains. This is rather borne out by the original
Bakerloo Line claim that it was an nice, cool way to travel in the
heat of the summer - it was decades before the effect was realised.
Presumably if you could shut the tube for a few years you could
reverse it, but I can spot a couple of problems with that idea.

I suspect, therefore, that things like lighting and electronics in
stations (which are better ventilated than the tunnels anyway) are
of minute benefit compared with reducing the heat produced in the
tunnels by each train by a little bit. Indeed, one of the ideas
being looked at is blowing cold air over the brakes of trains
standing at stations, so they don't take the heat into the tunnel
when moving off. Obviously this merely transfers it to the
station, whence it can be removed somewhere. Regen braking has a
place here, too, if you can shove the heat from the necessary
resistors outside.

If it's regen braking, rather than rheostatic, the heat goes as energy to
other trains and not into resistors.

--
Colin Rosenstiel