Analysis and experiments on the periodically fluctuating air temperature in a building with earth-air tube ventilation

A more thermally comfortable indoor environment with cooler indoor air in summers but warmer air in winters could be achieved by the use of earth-air tube ventilation. The periodically fluctuating behavior of indoor air temperature, which characterizes the indoor thermal environment, is not determined from the earth-air tube system alone but by the coupling of earth-air tube ventilation and the thermal mass contained in a building. A model for the coupling effects of earth-air tube ventilation and building thermal mass on periodically fluctuating air temperature has been previously developed (Yang et al., Energy and Buildings 81: 182-199, 2014). This paper integrates both the yearly and daily fluctuations of air temperature into unified equations. A method for determining the penetration depth of the oscillating tube-air temperature wave in the surrounding soil is proposed to enhance the model accuracy. An experiment was conducted to test the model, and the model predictions show good agreement with the measured data. The roles played by the key engineering parameters with respect to the overall efficiency of the combined system were analyzed. The findings suggest that the effectiveness of an earth-air tube ventilation system cannot be quantified in isolation from the building characteristics. This model is helpful to the optimization of the coupled system.