Numerical simulation of dynamical thermal environment in underground structures

Ground heat resource, a kind of renewable energy source, its utilization has attracted great attention in many countries. In this paper, the characteristic of unsteady fluid-solid coupling heat exchange of underground structures is analyzed and the mathematical model of the unsteady heat exchange between air and the envelope of deep underground structures is established. In order to facilitate computation, a coefficient of response is adopted for boundary conditions. Also the corresponding computer program is developed. Based on this, the thermal environment is researched in the underground plant of a typical hydropower station. Result shows that the unsteady heat transfer through envelope of underground structures all the year round is the very reason why the underground structure is warm in winter and cool in summer. In addition, this paper discusses the relations between heat exchange value through envelope and other conditions such as inflow air temperature, air change times, heat source intensity and shape of a structure. This paper will be an essential basis for the design of ventilation and air-conditioning system in underground structures.