Research on coupling application of earth air tunnel heat exchanger system and ventilation unit with heat exchange

A composite outdoor air system consisting of earth air tunnel heat exchanger system and ventilation unit with heat exchange is proposed, and the influence of duct diameter, duct burial depth, supply air speed and soil type on the thermal performance of the system is studied by numerical simulation. The results show that when the composite outdoor air system is used as an independent heat source in winter, it has sufficient heating capacity for outdoor low-temperature air, and the maximum temperature rise is about 30 ℃. The system has a calming effect on outdoor air temperature fluctuations, and the extension over time is more obvious, improving indoor thermal adaptability. It is recommended that the diameter of the duct be 150 to 250 mm, the depth of the duct buried be 20 m, and the supply speed be 3 to 5 m/s when applying the composite outdoor air system in Beijing.