The in-situ experiment of earth-air heat exchanger for a cafeteria building in subtropical monsoon climate

Abstract This in-situ experimental study reports the long-term monitoring results of an earth air heat exchanger (EAHE) used to provide ventilation in a cafeteria building, in Nantou, Taiwan. The EAHE consisted of 7 parallel buried pipes with a length of 50 m and a diameter of 0.25 m. The energy performance of the system was analyzed based on data of both sensible and latent heat exchange. The monitored results have been compared with other previous cases presented in the literature to clarify the effect of various climates and design conditions on the EAHE application. The results show that despite relatively high soil temperatures underground compared with the previous case study in temperate regions, the visible temperature difference between inlet air and outlet supply air was recorded in the summer. The annual COP can reach 27.2 while the specific surface area is 0.039 m2(m3hr−1)−1, which represents a relatively low heat transfer area compared with other cases. The conclusion is that considering uncontrollable soil temperatures, the use of a relatively low specific surface area is suitable for great cooling demand in a hot and humid climate, while the design target is on maximizing the heat transfer rate rather than a higher temperature difference.