Researchers at EPFL have precisely quantified convection heat transfer in rail tunnels. Using the new model, they estimated how much energy Lausanne could save by fitting the future M3 metro line with a geothermal heat-recovery system.
Heat transfer happens in various ways in rail tunnels. For instance, when trains brake or accelerate, they produce heat that warms the surrounding air. That hot air mixes with other air in the tunnel and with heat radiating from the ground.
Until now, engineers have been unable to accurately calculate the amount of heat that tunnel air contains. Researchers at EPFLs Soil Mechanics Laboratory (LMS) have overcome that problem by precisely estimating the convection heat transfer coefficient. Their findings have been published in Applied Thermal Engineering.
This breakthrough paves the way for innovative applications involving so-called energy tunnels that can supply energy to built environments. The team also tested its model on Lausannes future M3 metro line which, once complete, will carry passengers between the citys train station and the Blécherette district to the north.