Research on cooling performance of phase change material-filled earth-air heat exchanger

As a passive energy technology, the earth-air heat exchanger (EAHE) can greatly contribute to reducing the energy consumption of heating, ventilating, and air-conditioning (HVAC) systems. In a traditional EAHE, the cooling/heating effect is achieved through the charging/discharging process of soil sensible heat. However, this process is detrimental to fully develop its potential. Considering that the phase change-based thermal energy storage technology has outstanding advantages in this regard, a new system named phase change material (PCM)-filled EAHE is proposed to overcome this deficiency. To study the cooling performance of this new system, a three-dimensional numerical model based on the effective heat capacity method has been built in ANSYS FLUENT and validated using an indoor test rig, which was filled with some laboratory-prepared shape-stabilized PCM. Then comparative studies between the PCM-filled EAHEs and the traditional one are conducted under Chongqing (China) summer condition. The results indicate that, at the daily maximum outdoor temperature, the outlet temperature of the PCM-filled EAHE, which employs the laboratory-prepared shape-stabilized PCM, is approximately 0.83 °C lower than that of the traditional EAHE. Therefore, this PCM-filled EAHE can achieve an improvement of 20.24% in cooling capacity compared to the traditional one.