Free ride.

Describes a cooling design using ground water to prevent overheating in London's underground train network. More conventional air conditioning is unusable because of the problem of exhausting the excess heat. However the proposed system would require moderate extra ventilation for the carriages. Rising groundwater is a major problem in London, and remains at 12 deg. C year-round. Temperatures in summer in tube trains is as high as 28 deg. C in the tunnels rising to 34 deg. C in the crowded trains. The groundwater is passed through heat exchangers in the tunnels which cool the air. The cold air will then provide cooling of the carriages directly through the ventilation system and indirectly through conduction via the car body. Describes a mathematical model constructed to evaluate the heat transfer taking place, and investigations carried out.