This work presents a numerical simulation employing the computational fluid dynamic (CFD) approach using the commercial ANSYS FLUENT software to evaluate the thermal comfort, airflow pattern, and temperature distribution in an office room occupied by a seated occupant. The purpose of the study is to assess the performance of swirl-lobed ceiling diffusers equipped with inclined lobes inserted at various angles. A detailed experimental study was carried out to validate these numerical simulations for conventional diffuser (CD) configuration with an inlet airflow rate of \(Q_{s}=\) 200 m \(^{3}\) /h. The predictions are performed using the SST ( \(k-\omega\) ) turbulent model. Subsequently, the airflow characteristics and temperature performance were evaluated and compared for different diffuser configurations: with normal inserted lobes (LD), inclined inserted lobes at 19 degrees (LD1), and 35 degrees (LD2). Thermal comfort was assessed using the percentage of predicted dissatisfaction (PPD) and draft rate (DR) indices. The velocity contours were investigated to illustrate recirculation zones created by the interaction of the airflow and the occupant’s thermal plume at head level. The inclined lobe diffuser configurations provided better thermal comfort than the CD by at least 5% and −20% in terms of DR and PPD indices, respectively. However, the LD1 case provides better air diffusion and lower temperature in the occupied zone than both the LD2 and LD cases, providing a very refreshing sensation to the occupant with PMV \(= -\) 0.13 than LD2 and LD cases that provide PMV of −0.23 and −0.17 respectively, in other words, providing better indoor ventilation. The mean velocity in the region around the diffuser in the LD1 case was 25% lower than in the CD case and almost 49% higher than in the LD case, while being nearly equal to the LD2 case generating more vortices than the other lobed cases.
