In message , Basil Jet
writes
On 2016\07\31 18:25, wrote:
On Sun, 31 Jul 2016 13:19:28 +0100, Colin Reeves
wrote:

On 30/07/2016 20:50, D A Stocks wrote:

Eurotunnel manage something like that in the Channel Tunnel, and they
don't have stations every few hundred yards where they can remove the
excess heat generated.

But, the holes that the trains run through are vastly larger than tube
tunnels - and they have the service tunnel as well. Much more scope for
cooling if needed!

There are doors to the service tunnel and it is at higher pressure in
case of fire so it doesn't really play a part in heat removal. There
are air shafts linking the two running tunnels and there are cold
water pipes in each tunnel to provide cooling.

Are the pipes supposed to transfer heat to the rock around the tunnel
or out the ends of the tunnel? I can't imagine the latter working very
well in a 50km tunnel.

Wasn't the need for an upgraded cooling system one of the major reasons
for the cost over-run and delayed opening of the tunnel?

http://batisseurs-tunnel.com/wp-content/uploads/2015/03/1-Le-Projet-Tunnel-sous-La-Manche_C1.pdf
says

Cooling system: compensates heat from air friction generated by trains,
and heat produced by engines or electrical equipments. It is based on a
closed circuit chilled water, and includes 2 cooling plants, total
40 MW, located at Sangatte and Shakespeare Cliff, supplying cold water
(4 degree C, 220 l/s) through 200 km of pipes of diameters 400 and
320 mm.

There's more in
https://books.google.co.uk/books?id=...epage&q=channe
l%20tunnel%20cooling%20system:MW&f=false
but it's a pdf image of an article so difficult to copy and paste.
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Goalie of the Century