Numerical analysis of thermal comfort and air freshness generated by a multi-cone diffuser with and without lobed inserts

Abstract

In this work, a numerical investigation using Ansys Fluent software is performed to study the flow pattern, the indoor thermal comfort, and the air freshness generated in a full-scale ventilated office room occupied by a sitting occupant. The performance of a multi-cone ceiling diffuser equipped with lobed inserts is assessed and compared with a traditional multi-cone ceiling diffuser. The indoor thermal comfort is evaluated using the predicted percentage of dissatisfaction (PPD) and the draft rate (DR) indicators. To assess the air freshness inside the office room, the mean age of air (MAA) is evaluated. After validating the simulation, the effect of the supply flow rate on the airflow pattern, the thermal comfort, and the air freshness, are investigated. Velocity contours show that recirculation zones in the domain result from the interaction between the supplied air and the thermal plume above the occupant's head. The statistical analysis of PPD and DR reveals that - depending on the supply flow rate - lobed inserts reduce the thermal dissatisfaction and the draft effect in the occupied zone. However, in terms of MAA, the lobed inserts reduce the air freshness slightly in the vicinity of the occupant's head.