Dynamic interactions between the ground heat exchanger and environments in earth-air tunnel ventilation of buildings

Earth-air tunnel ventilation is an energy efficient method of preheating or cooling of supply air to a building. The purposes of this study are to investigate the performance of earth-air heat exchangers under varying soil and atmosphere conditions and the interactions between the heat exchanger and environments. A computer program has been developed for simulation of the thermal performance of an earth-air heat exchanger for preheating and cooling of supply air, taking account of dynamic variations of climatic, load and soil conditions. The program solves equations for coupled heat and moisture transfer in soil with boundary conditions for convection, radiation and evaporation/condensation that vary with the climate both at the soil top surface and inside the heat exchanger. The importance of dynamic interactions between the heat exchanger, soil and atmosphere is illustrated from the comparison of the heat transfer rates through the heat exchanger. The predicted heat transfer rate varies with operating time and decreases along the passage of air in the heat exchanger. Neglecting the interactions would significantly over-predict the heat transfer rate and the amount of over-prediction increases with operating time. (C) 2014 Elsevier B.V. All rights reserved.