Effect of opening diffuser and return vent location on air quality, thermal comfort and energy saving in desk displacement ventilation (DDV) system

Many investigations have recently been performed on return vent height and indicate that having 1.3 m distance from the floor is the optimized height for it. In this article, the effect of distance between opening diffuser and return vent on air quality, thermal comfort and energy saving was investigated. According to the results, by increasing the distance between opening and return vent up to 5 m, the return vent could be placed near the floor at height of 0.6 m without any unacceptable consequence in indices. Therefore in this case, energy saving of 15.8% could be achieved rather than 8%, 10.9% and 15.2% in other cases. However, the air quality was lower compared to the other cases. In the case having better air quality and more thermal comfort with acceptable energy saving of 15.2%, the opening and return vent were relocated at maximum distance between them (5 meters) and return vent was placed at the suggested height of 1.3 m from the floor, which was found to be the optimum scenario.