Passive Control Strategy for Mixing Ventilation in Heating and Cooling Modes Using Lobed Inserts

Mixing ventilation is commonly used to control thermal comfort in a room by means of air jets. The jet diffusers should distribute the fresh air and energy, for heating or cooling, in the entire occupied zone. Therefore, the design of the diffusers must aim, beyond aesthetic aspect, the ability to provide a good mixing between the jet and the ambient air. Enhancement of jet mixing with the ambient air by means of lobed inserts into a diffuser, was recently proposed in an European patent, as a promising and low-cost solution for improving the performance of HVAC systems. In this paper, an experimental investigation on thermal comfort generated by a classical multi-cone ceiling-mounted diffuser is proposed. Its performance is compared with the same diffuser equipped with lobed inserts. A simplified heated manikin simulates the presence of a human body in the test room. Thermal comfort was analyzed based on traditional pointwise measuring probes and on the standard ISO 7730. It is revealed that the thermal comfort was significantly improved using the lobed diffuser compared to the conventional one, without increase of pressure drop and sound pressure levels.