While the surrounding seabed can be a nice thermal sink to stabilize temperatures, the aggregate around it could be fairly good insulator, there are tubes in London that have warmed the underground to such an extent that it would take months to cool down. Understandably, lots of the heat in the London tunnels is from braking which shouldn't be occurring in this tunnel.
Point is, I don't think one could model the Fehmarnbelt tunnel as open air or assume that the surrounding material is an infinite heat sink.
Point is, I don't think one could model the Fehmarnbelt tunnel as open air or assume that the surrounding material is an infinite heat sink.
https://citymonitor.ai/transport/londons-tube-has-been-runni...