Study On Indoor Air Movement Of Up-supply Down-return Supply By 2DPIV

With the development of people's living standard,it has been focused more and more on the demand of indoor air quality and thermal comfort which is closely related to the indoor air flow.Indoor air flow is generally very complex turbulent flow which makes it difficult to obtain accurate measurement results with the traditional singlepoint contact measuring method.In this paper,the particle image velocimetry(PIV) is introduced as an effective tool for measurement of the whole-field instantaneous velocity vectors of the flow field of air conditioning room.In this paper,the effect of different air supply velocities,obstacle positions and thermal source intensity on the air flow velocity and temperature field of the model room was studied.The 2DPIV ventilation system was build.The model room,of which the size was 600mm×300mm×340mm(L×W×H),had a non-isothermal up-supply down-retum air supply.The particle image velocimetry(PIV) is used to measure the temperature field and the two-dimension flow field of the two cross sections of which one was at Z=150mm(the middle place of the model room) and the other at Y=110mm. Related softwares were used to display the whole flow field and obtain the data.And the energy utilization coefficient and the nonuniformity coefficient were analysed in this paper.The study shows that:1.In the vertical cross-section which was at Z=150mm,when obstacle position and heat source intensity set,the entrainment of jet flow to the air in the model room was intensified as the supply air velocity increased from 0.9m/s to 1.5m/s.The main vortex area in the model room enlarged and its central place moved to the exhaust as the air flow velocity increased.In the dimensionless axial velocity variation diagram of the jet flow with a height of 275mm,all the curves had the same changing trend when X/L＜0.8.In the velocity diagram of supply air flow with a height of 45mm,when X/L＜0.3, the air flow velocity decreased sharply as the value of X/L increased.The best uniformity of velocity distribution was obtained when V=0.9 m/s.The variation of obstacle position dramaticlly changed the distribution of the flow field in the model room.The main effect was as follows:the size of the biggest vortex area in the return flow zone,the central position of the vortex and the variation of velocity distribution.The size of the biggest vortex area in the return flow zone decreased gradually and its central place had a tendency of moving against the return air inlet as the obstacle position changed from 150mm to 450mm.The increase of the heat source intensity did not change the air distribution of the flow field of the jet flow area.In the heat source intensity contrastive figure(Y=45mm), in the area where 0.4