Low-mixing coaxial nozzle for effective personalized ventilation

The aim of this work was to study the performance of a novel coaxial nozzle for personalized ventilation that can be used as an add-on to ceiling diffuser. The coaxial nozzle minimizes air entrainment between the central fresh air stream and the room air. It allows effective delivery of clean air to the breathing zone while the recirculated conditioned air is supplied to the space by the associated ceiling diffuser. Detailed 3-D Computational Fluid Dynamics (CFD) simulations were performed and numerical results on velocity, temperature, and CO 2 concentration fields agreed well with experimentally measured values. The effect of the jet flow rate, temperature, and inclination angle on air quality at the breathing zone of the occupant was then investigated. The proposed coaxial personalized ventilation achieved high air quality in the breathing zone demonstrated by a personal exposure effectiveness of 32% at fresh airflow rate of 10 L s −1 per person. It contributed also to the attainment of temperature differences up to 2℃ between the occupant’s microenvironment and the rest of the room air leading to considerable energy savings compared to the mixed convection air conditioning.