Investigation of inter-zonal heat transfer in large space buildings based on similarity: Comparison of two stratified air-conditioning systems

Abstract Stratified air-conditioning (STRAC) has been deployed in large space buildings to achieve vertical thermal stratification with significant energy-saving potential. This research focuses on two typical STRAC systems: floor-level sidewall air-supply system (FSAS) and nozzle sidewall air-supply system (NSAS). By employing experiment and CFD methods, airflow pattern and heat transfer between the unoccupied and occupied zone under the two air supply systems are investigated in a reduced-scale laboratory. The geometric models of the prototype building, with a geometrical scaling factor of 4:1, are established according to similarity principles and studied by CFD simulation. The results demonstrate that the two scales have similar indoor thermal performances. The numerical simulation results of the prototype building provide and compare commonly used inter-zonal heat transfer coefficients of actual large space buildings with the two typical STRAC systems. For FSAS, heat conduction caused by temperature gradient dominates the inter-zonal heat transfer. In NSAS, both heat conduction due to temperature gradient and heat convection due to airflow contributes equally to this heat transfer. The inter-zonal heat transfer coefficient Cb is affected by the airflow pattern and zonal division, and closely associated with local turbulence intensity.