Experimental and numerical study on cooling performance of a novel earth-to-air heat exchanger system with an inlet plenum chamber

Previous studies have focused on the horizontal buried pipe section regarding the performance improvement of the earth-to-air heat exchanger, showing limited attention paid to the vertical air inlet section. In this study, we proposed a novel earth-to-air heat exchange system utilising an inlet plenum chamber (IPC-EAHE) to pre-treat the outdoor air in the inlet section. To evaluate its cooling performance, a numerical model was developed and validated based on a field experiment. The results showed a good agreement between simulated and experimental data, with a maximum absolute relative error of 4.43 % for the outlet air temperature. Then comparative studies between the IPC-EAHE and traditional EAHE are conducted under three airflow rates. Re-sults indicated that the IPC-EAHE has a lower and more stable outlet air temperature than traditional EAHE. Compared to the traditional EAHE, the IPC-EAHE reduces the fluctuation of outlet air temperature by 53.13 %, 29.84 %, and 26.60 % under the airflow rates of 190 m3/h, 380 m3/h, and 570 m3/h, respectively. This improves the free cooling potential of EAHE for buildings. Moreover, the IPC-EAHE can reduce the buried pipe length by around 60.30 %, 53.0 %, and 50.0 % for three airflow rates, respectively. The friction resistance loss of the IPC section is at least 20 % less than that of the traditional EAHE vertical inlet section. The above results demonstrate that the IPC-EAHE offers greater renewable energy utilization efficiency and less buried pipe length than the traditional EAHE.

Automated summary

This study proposes a novel earth-to-air heat exchange system that utilizes an inlet plenum chamber to pre-treat outdoor air for improved performance. Compared to traditional systems, this novel system reduces the fluctuation of outlet air temperature and requires shorter buried pipe length.