The main trick is to use the cut and cover lines, not the deep ones. They're almost always much cooler.
Allegedly (i.e. I heard it while working for the Central line back in 1989) the deep bore tunnels are gradually warming up by something like half a degree a decade (over and above any more obvious short-term fluctuations). It seems the heat generated by people and train-tunnel turbulence is only very slightly greater than the system's ability to dissipate it. To be honest, I'm not sure I believe this, but if it turns out to be true then even a very subtle tweaking of the thermodynamics ought to be sufficient to let the tube gradually cool down.
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Date: 2003-07-23 06:54 am (UTC)The main trick is to use the cut and cover lines, not the deep ones. They're almost always much cooler.
Allegedly (i.e. I heard it while working for the Central line back in 1989) the deep bore tunnels are gradually warming up by something like half a degree a decade (over and above any more obvious short-term fluctuations). It seems the heat generated by people and train-tunnel turbulence is only very slightly greater than the system's ability to dissipate it. To be honest, I'm not sure I believe this, but if it turns out to be true then even a very subtle tweaking of the thermodynamics ought to be sufficient to let the tube gradually cool down.