Thermal comfort and energy performance of a low-mixing ceiling-mounted personalized ventilator system

This paper studies the performance of an integrated ceiling diffuser and personalized ventilator coaxial nozzle system to localize the air conditioning and fresh air needs around the occupants. The coaxial nozzle minimizes air entrainment between the fresh air stream and the room air and allows effective delivery of clean air. A detailed 3D CFD model is coupled to a bioheat model to improve prediction of the microenvironment conditions around the human and the associated local and overall thermal comfort. Subjective assessments were carried out with 10 human participants who were given the chance to undergo three different experimental runs individually and cast their votes about thermal comfort. The 30 samples obtained experimentally were within ±20% of the predicted numerical values especially for the upper body parts. Extensive simulations were performed to assess the effect of nozzle supply temperature and flow rate on the performance of the cooling system and on occupant comfort. The localized air conditioning system reduced the energy consumption by up to 34% when compared with conventional mixing systems providing the same level of thermal comfort.

► A low-mixing ceiling-mounted nozzle integrated with a diffuser was modeled.
► The CFD model was coupled with a bioheat model predicting human thermal response.
► No local thermal draft was reported by the subjects.
► Thermal comfort conditions equivalent to those obtained with mixing systems were observed.
► The system provided energy savings up to 34% when compared to mixing systems.