Impact of PCM Enclosure Shape on the Performance of TES for Passive Building Envelope Design

Abstract

This work aims to explore the design of a passive building envelope aimed at improving energy efficiency by effectively incorporating phase change materials (PCM). The research employs a numerical method to analyze different wavy-wall enclosures within a uniform aspect ratio computational domain under varying boundary conditions. The numerical model is validated against experimental results under variable temperature and constant heat flux boundary conditions, demonstrating high accuracy. The comparative analysis of four cases focuses on local temperature distribution and liquid fraction. Case 1 exhibits a rapid temperature increase with a pronounced gradient, suggesting a quicker yet less consistent heat transfer. It is observed that melting fraction times are reduced by 36.63%, 0.59%, and 21.40% for Case 1, 2, and 3, respectively, compared to Case 0. From the comparative analysis, Case 1 exhibits the highest enhancement in melting fraction, achieving a 43.4% improvement under isothermal conditions and a 22.8% enhancement under constant heat flux. In contrast, Case 3 and Case 2 show lower improvements of 21.8% and 13.5% in isothermal conditions and 15.3% and 10.5% under constant heat flux, respectively. The superior performance of Case 1 is attributed to its optimized encapsulation shape, which offers a higher surface-area-to-volume ratio, leading to faster and more uniform heat transfer. Overall, the findings underscore the critical role of encapsulation design and material properties in maximizing thermal performance, providing valuable insights for developing passive building envelopes suited to diverse climates.