CFD analysis of environmental impacts on a thermochromic smart window

Thermochromic (TC) glazing is an advanced smart window technology that can help to achieve nearly zero-energy buildings. The glazing temperature that affects TC thermo-optical properties directly impacts its energy-saving performance. However, the impacts of solar radiation and natural convection occurring on this temperature-sensitive material are not yet fully understood. Compared to previous focuses on material properties and energy evaluation, this study aimed to provide a different view from thermo-fluid dynamics on the heat transfer characteristics of a TC window, with impacts of environmental factors addressed. A validated Computational Fluid Dynamics (CFD) model identifies the environmental impacts on the TC glazing temperatures under the coupled radiative and convective heat transfer. Furthermore, a theoretical model was developed with an empirical factor obtained from CFD results. It enables a simple calculation to obtain the TC glazing's temperature by using solar factors, outdoor temperatures and opti-cal properties. The model suggests that the temperature difference between the TC glazing and the ambi-ent is a function of absorbed solar irradiation (/ _qtotal0:75). The predictive model is then tested using typical climate conditions in three cities in China with different solar angles, which demonstrates good agreement with an average absolute error of 5% compared to simulated glazing temperature. This estima-tion method can further assist in material design, product selection and Building Energy Simulations to achieve a TC window design that is 'smart' on seasonal change requirements for different regions.(C) 2022 Elsevier B.V. All rights reserved.

Automated summary

Thermochromic glazing is an advanced smart window technology that can achieve nearly zero-energy buildings. This study investigates the impacts of solar radiation and natural convection on the temperature of the glazing, and develops a predictive model for calculating the glazing temperature. The model shows good agreement with simulated results and can assist in material design, product selection, and Building Energy Simulations.