Comparative analysis of earth to air heat exchanger configurations based on uniformity and thermal performance

The multi-pipe earth to air heat exchanger (MEAHE) system is widely applied in the agricultural greenhouse for energy savings. The non-uniform airflow acts significantly on the overall performance, and the objective of the paper aims to investigate the influence of airflow uniformity on thermal performance. A mathematical model of the multi-pipe earth air heat exchanger was established with the CFD method, and the simulation results were validated by the experimental data in the literature. The uniformity and thermal performance of the multi-pipe earth to air heat exchanger were first investigated, and then the non-uniform airflow division under the different supply types was compared. Finally, the effect of main pipes diameter to parallel pipes diameter ratio on the thermal performance of earth to air heat exchanger was investigated. The study acknowledges that the heat transfer rate between soil and air of Z-type earth to air heat exchanger decreased by 10.7% than the uniform type earth to air heat exchanger. The study also revealed that the airflow and thermal uniformity of U-type and L-type was much better than Z-type earth to air heat exchanger. There are optimum main pipes diameter to parallel pipes diameter ratio with consideration of thermal performance and pressure drop. The results could be considered as the reference for the development and optimization of the earth to air heat exchanger in the greenhouse during the practical engineering.

Automated summary

This study investigated the influence of airflow uniformity on thermal performance of a multi-pipe earth to air heat exchanger system using a mathematical model and experimental data. The results showed a decrease in heat transfer rate of Z-type earth to air heat exchanger compared to uniform type, and better airflow and thermal uniformity in U-type and L-type designs. Optimum main pipes diameter to parallel pipes diameter ratio was also identified for thermal performance and pressure drop consideration.