Performance Analysis of Earth-air Heat Exchangers in Hot Summer and Cold Winter Areas

Abstract

As one of the energy-efficient heating technologies, earth air heat exchangers (EAHE) use renewable energy (i.e. geo-thermal energy) to first heat outdoor air, and then supply it to indoors for space heating in winter. The aim of this paper is to study the thermal performance of EAHE in winter in hot summer and cold winter areas. An experimental setup of EAHE was established in Changsha, China. Different variables, including soil temperature, supply air temperature and outdoor air temperature were measured for one week. The thermal performance was evaluated based on the data analysis. Results show that the supply air temperature reached the soil temperature around the pipe at the same length of 20m for different inlet air temperature. The COP and Q decreased along with the increase of inlet air temperature but increased along with the pipe length. Moreover, the thermal saturation of soil occurred in the fifth day of the week, and thermal interference between pipes can be ignored under the 1m distance between pipes. Our future work includes developing a numerical model to analyze and optimize the thermal performance of EAHE, thereby providing a reference for its design and application in hot summer and cold winter areas in China.