Improving thermal performance of a passive ventilation and cooling system by integrating a phase-change material: Dynamic characteristics and parametric examinations

Abstract

The coupling of a solar chimney (SC) with an earth–air heat exchanger (EAHE) is a passive ventilation and cooling system that provides fresh air and cooling to buildings. However, inherent disadvantages of the coupled system include the mismatch of the induced airflow rate and internal cooling load and the low nighttime ventilation rate, which limit the full utilization of the coupled system. These issues can be mitigated by integrating a phase-change material (PCM) in the system of SC combined with EAHE (SCEAHE). Parametric investigations were conducted to examine the thermal performance improvement of the PCM-based SCEAHE system using a dynamic model. The numerical data revealed that solar energy was effectively extracted and reallocated by the PCM, thereby increasing the nighttime airflow rate and reducing the indoor air temperature. The phase-change temperature of the PCM not only affected the airflow rate but also the thermal environment at night and in the early morning. Therefore, a PCM with a higher phase-change temperature is recommended in this study. The latent heat of fusion had a larger impact on the induced ventilation rate than the outlet air temperature of the EAHE when the latent heat of fusion exceeded 175 kJ/kg. In addition, a PCM with a thermal conductivity <1 W/(m·K) is suggested. In practical application, a thickness range of 0.04–0.05 m is the most suitable. The specific heat of the PCM had slight influence on the thermal performance of the proposed system.