ANALYTICAL MODEL FOR HEAT TRANSFER IN AN UNDERGROUND AIR TUNNEL

A simplified analytical model is developed to determine the energy performance of an underground air tunnel. The model assumes that the air tunnel-ground system reaches periodic and quasi-steady state behavior after some days of operation. The model can predict the air temperature variation along the air tunnel for any hour of the day. It can also determine the daily mean and amplitude of the total cooling/heating effect of the tunnel. Parametric analysis is conducted to determine the effect of tunnel hydraulic diameter and air flow rate on the heat transfer between ground and air inside the tunnel. The model is validated against measured data.