Investigation On The Effect Of Building Size On Collision Jet Ventilation And Mixed Ventilation Heating Under Cold Wind Intrusion Conditions Donghua University

In recent years,along with the rapid development of China's economy,people's living standards have also been continuously improved,and people's requirements for indoor air quality are also getting higher and higher.The air supply method plays a decisive role in the quality of indoor air.Reasonable air supply method can not only meet the requirements of human thermal comfort,but also reduce the energy consumption of air conditioners and achieve energy saving goals.At present,the commonly used air supply modes are divided into two types: Mixing ventilation(MV)and displacement ventilation(DV).MV can be used for both summer cooling and winter heating,but it has the disadvantages of low ventilation efficiency and poor indoor air quality.DV can achieve both energy savings and good air quality goals,but it cannot be used for winter heating because the air supply speed is too low.Therefore,it is urgent to seek a new type of ventilation.Impinging jet ventilation(IJV)is a new type of ventilation.The principle is that the high-momentum fresh air is sprayed vertically downward from the air supply port,and the momentum is attenuated after hitting the ground,and then spreads to a wide extent along the floor surface.Therefore,from the principle,IJV is similar to DV when it is cooled,which can provide better air quality and reduce the energy consumption of building cooling.At the same time,the air supply speed of the IJV is relatively large,so that the hot air flow during heating can overcome the floating force to reach the indoor working area,and then mix with the indoor air from bottom to top.Therefore,IJV not only overcomes the defect that MV is difficult to send hot air directly into the lower part of the room,but also avoids the defect that DV can not be used for winter heating.It is a new type of ventilation with great application potential.Many tall public buildings,because the outer door at the entrance of the building will be frequently opened,when the winter heating,the outside cold wind invades the room and sinks to the ground,which has a greater impact on the indoor thermal environment and greatly increases the heating energy consumption.In the case of collision jet hot air heating,the hot air directly sent to the ground can effectively resist the intrusion of outdoor cold air.However,at present,most researches on IJV focus on cooling conditions,and there are few studies on heating conditions,and only a few scholars have studied the impact of cold wind intrusion on IJV heating rooms,and more consideration of cold air intrusion to indoor heat.The average effect of environmental impact is almost unrelated to its dynamic characteristics.Therefore,this paper mainly uses the numerical simulation method to study the dynamic influence of building size on the indoor temperature field and flow field of IJV and MV heating and ventilation room under the condition of cold wind intrusion.In addition,this paper compares the impact of IJV and MV on the indoor temperature field and flow field in the case of cold wind intrusion,and propose the possibility of improving the heating effect.The results show that the temperature of the indoor room of IJV and MV heating will fluctuate after the cold wind invades the room,but compared with MV,IJV can effectively resist the influence of cold wind intrusion,the indoor vertical temperature difference is small,and the heating energy utilization rate is high.By comparing the heating effects of IJV and MV heating in different building sizes,IJV is more suitable for tall space buildings than MV.In addition,the indoor heating effect can be improved by increasing the air blowing speed of the MV.