In large space buildings, nozzle is usually used for ventilation and air conditioning. A secondary airflow-relay system is proposed for situations that building span is larger than the primary jet flow range. A field measurement was conducted to investigate the performance of primary airflow nozzle and secondary jet fan system; a computational fluid dynamics model was built up to research the secondary airflow velocity and relative location of primary and secondary terminal on the ventilation performance. The performance of different computational fluid dynamics turbulence models in predicting the primary jet trajectory path was evaluated by comparing predicted result with field measurements. The temperature field predicted by computational fluid dynamics method was also validated by experimentally measured vertical temperature distribution data in certain measurement points. Various indices including Air Diffusion Performance Index, percentage dissatisfied, and coefficient of variation of temperature and velocity at breathing level were used to quantitatively evaluate the ventilation performance of different configurations. It is found that re-normalization group k-epsilon turbulence model gives the best overall prediction on the primary air nozzle jet trajectory path and field temperature distribution. In a certain large space building utilizing secondary airflow system, the relative location of primary and secondary equipment and air velocity should be properly specified in order to improve the ventilation performance of a large space building. The secondary airflow-relay may potentially increase the cooling energy consumption as indicated by computational fluid dynamics result.
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