Hygro-thermal performance of ventilated underground cavities

The risk assessment regarding overheating in underground structures is becoming quite common among the designers, when internal heat gains are severe or they occur for a long time. Typical is the case of subway tunnel networks, but many other recent examples may be easily found. Quite often however, not only the air temperature pattern is relevant, but also humidity may play an important role, especially if underground water infiltrations are not negligible. In fact, water evaporation or condensation may significantly affect the temperature profiles; on the other hand, high humidity ratios may hamper some activities performed in the cavities. The present paper aims to present a design tool to simulate the hygro-thermal behaviour of ventilated underground cavities. The model can be used to simulate steady-state or transient conditions: it solves the heat and mass transfer equations in the cavity, providing also a criterion for the evaluation of the fog in the air.