Parametric study on the thermal performance of phase change material-assisted earth-to-air heat exchanger

Abstract

As a passive technology, the earth-to-air heat exchanger (EAHE) can be used to reduce energy consumption within a building. This paper presents a novel design for an EAHE system assisted by a phase-change material (PCM). To study the thermal performance of the newly proposed PCM-assisted EAHE (PCM-EAHE) system, a transient three-dimensional model has been built in FLUENT. A range of validated numerical models is established and utilized to investigate the effects of design and operation parameters (i.e., phase-change temperature, PCM container diameter, pipe length, pipe diameter and air velocity) on the thermal performance of the system. The results indicated that the phase-change temperature should be consistent with the time-average ambient air temperature. Furthermore, the polynomial regression models for predicting the outlet air temperature with high accuracy are obtained using statistical product and service solutions (SPSS). The optimal air velocity levels for enhancing the heat transfer performance are 4.5 m/s and 6.8 m/s during the charging and discharging processes, respectively. Therefore, it is recommended to apply the PCM-EAHE system to new and existing buildings.