Investigation Of The Factors Influencing The Indoor Thermal Environment Of An Impinging Jet Ventilation Room In Heating Mode With Cold Air Infiltration

Impinging jet ventilation(IJV) is a novel strategy for building ventilation which combined the advantages of mixing ventilation(MV) and displacement ventilation(DV). The IJV can be used for both room cooling in summer and space heating in winter, thus it is different from the traditional building ventilation methods. As a new strategy for room ventilation, few works has been performed for evaluating it performances, so it is important to explore the indoor thermal environment and thermal comfort when the IJV is used for room heating.In a room without evident cold air infiltration, the IJV system can overcome the disadvantages of the MV which exhibits significant vertical thermal stratification, i.e. the temperature at the floor is lower than that near the ceiling region. But in a room with uncontroled cold air infiltration, few studies can be found on the heating performance of IJVs. Therefore, a series of measurements under different heights of the outlet and supply air parameters are carried out to investigate the airflow and the temperature distribution in such a room with cold air penetration. The results indicate that advantage of small temperature gradient in the IJV rooms is evidently weakened due to the cold air infiltration. The temperature contrast between the ankle and head levels is greater than 3?C under different heights of supply inlet, this causes the uncomfortable feeling indoors. With the gradually increasing of the height of warm air inlet, the temperature contrast between the ankle and head rises and the phenomenon of temperature stratification become more obvious, while there is no significant draft sensation. When the supply velocity is increased, the temperature gradient decreases and heating energy efficiency can be improved significantly. Meanwhile, the risk of draft may be reduced. Therefore, an appropriate low outlet’s height and relatively high supply velocity should be adopted in the IJV system when it is used for room heating with significant cold air infiltration for the purpose of indoor thermal comfort.