Thermal environment analysis of a radiant floor cooling and underfloor air-conditioning system based on detailed building physics using coupled BES–CFD

Stratified air conditioning is a widely utilized technique in large space buildings due to its significant advantages in reducing energy consumption and enhancing indoor air quality. This method creates distinct thermal layers within a space, allowing for more targeted and efficient climate control.

Radiant floor cooling and floor supply air conditioning system are commonly employed technologies for achieving stratified air conditioning in large spaces. The vertical temperature distribution is a critical feature in the thermal environment of stratified air conditioning systems and is crucial for achieving energy efficiency and optimal thermal comfort. To comprehensively and accurately predict the thermal environment in these spaces, it is essential to perform numerical simulations that consider coupled heat transfer and airflow processes.

This study leverages the complementary strengths of building energy simulation (BES) and computational fluid dynamics (CFD) to develop a coupled analysis method for more precise prediction of heat transfer and airflow. BES provides a long-term, macro-level analysis of thermal performance and energy consumption, while CFD allows for detailed micro-level analysis of airflow and temperature distribution within the space. By integrating these two programs, this study developed a coupled analysis method that enhances the precision and reliability of predictions regarding heat transfer and airflow dynamics.

Through a combination of theoretical analysis and numerical experiments, the proposed coupled method has been refined to ensure stability and efficiency. Moreover, using this coupled method, the convective field and temperature stratification in spaces cooled by radiant floor cooling and floor supply air conditioning system were precisely predicted, providing a comprehensive evaluation of the thermal environment.

In this study, the indoor thermal environment of an actual office space employing these systems was analyzed using both measured data and the proposed method. The results were compared to validate the predictive accuracy of the coupled analysis method in practical applications. Furthermore, the research extended to simulate the thermal environments of office spaces utilizing different air conditioning systems, including radiant floor cooling, floor supply air conditioning, and traditional ducted air conditioning systems. This allowed for a detailed quantitative comparison of indoor thermal environmental characteristics and air conditioning loads across various systems, highlighting the specific strengths and weaknesses of each system.