Investigation Of The Factors Influencing The Performances Of Impinging Jet Ventilation Systems In A Heating Mode

Impinging jet ventilation (IJV) system is believed to be beneficial for obtaining both highventilation efficiency and energy efficiency, it combines advantages of both displacementventilation (DV) and mixing ventilation (MV), i.e., it can be used for both room cooling insummer and space heating in winter, and thus it has been used gradually in the past decade.In a phytotron, conducts a series of experiments to study the heating effects with IJV and MVunder different air supply conditions respectively. Analyses the influences of air supply velocityand temperature on thermal environment in heating room with two ventilation modes, andcompares indoor thermal comfort. The results indicate that the vertical temperature gradient in anIJV room is slighter than that in a MV room, because the downward air flow of the IJV helps indistributing the warm air down to lower levels. The temperature stratification is less sensitive todifferent supply air states in an IJV room than in a MV, and thus it has a significant impact ondecreasing building’s heating energy consumption. In addition, the velocity is higher in lower partnear the nozzle in the IJV, which could lead to a higher draught risk very close to the floor than ina MV room, the experimental results show that the thermal environment is acceptable in theoccupied zone of an IJV room in the whole test range.In addition, the warm air supplied by the nozzle of the IJV, which is used for room heating,has significant effects on the flow pattern in rooms when it moves as a free jet, for the directionsof the thermal buoyancy and the momentum force are opposite. Meanwhile, the length of the freejet is mainly determined by the height of supply air inlet.The aim of the present study is to investigate the distributions of indoor air velocity andtemperature under two heights of supply inlet. The experiment results show that the height of theinlet only affects the reduction of the air temperature close to the floor, the influence of the heighton the vertical distribution of indoor temperature is negligible. The height of the inlet also has astrong effect on the air distributions in the rooms. The air velocity is decreased near the floor andincreased in the zone far away above the floor with the increase of the inlet height.. Due to thetemperature is high near the inlet when the supply height is low, the lower supply height results inthe lower level of draft.