Thermal Performance Evaluation of Earth-to-Air Heat Exchanger Using a Semi-Transient Analytical Model

At the present work, a new semi-transient model for thermal performance evaluation of earth-to-air heat exchanger (EAHE) is developed. In the current model, considering transient heat transfer in the soil around the pipe, the thermal saturation of the soil is considered. The thermal saturation is referred to a decreased temperature difference between air and soil near the pipe after some hours of operations which deteriorates the thermal performance of the EAHE. The effect of the buried depth of the Earth-to-air heat exchanger is also considered on simulation. Results are validated against the already reported experimental and numerical data, and good agreement is observed. Finally, the thermal performance of the heat exchanger is investigated for Tehran city. The results showed that increasing the buried depth from one meter to two meters increases the average heat transfer rate from air to earth by 37%.  Decreasing the operation hours of the EAHE per day increases the cooling capacity of the system. For instance, working of the system for only 8 hours a day increases the cooling capacity by 66% compared to continuous operation.