Scaled experiment and numerical study on the effect of a novel makeup air system on smoke control in atrium fires

In the field of fire safety engineering, makeup air systems design for atriums is always a concern for researchers and engineers. A novel makeup air system integrating breathing zone and underfloor air supply (BUMS) was applied in the investigated atrium in this study. However, the flow rates proportional relationship of makeup air required for effective smoke control on each floor remains unclear. Scaled experiments and numerical simulations were carried out to address this problem in this study. The results show that the BUMS effectively controlled temperature, followed by visibility, with minimal impact on carbon monoxide (CO) concentrations. When the flow rate of makeup air was equal on each floor, the sizes of the safe evacuation passageways created by the BUMS on the third and fourth floors were not conducive to the safe evacuation of personnel. Based on the proportion of the CO concentration of each floor under natural ventilation, distribution proportions of makeup air flow rate were obtained. The effective action area was used to help determine the upper limit flow rate ratio for each floor. Calculation results revealed that when the flow rate distribution proportion for the first to fourth floors was 15%, 27%, 28% and 30%, respectively, the smoke control effectiveness has been improved. These findings are expected are expected to provide a theoretical basis for designing makeup air systems in atrium and large-space buildings.