Investigation On Ventilation Characteristics And Optimization Of Roof Solar Chimney Driven By Solar And Wind Energy

With the rapid development of economy and the improvement of people’s living standard,the proportion of the building energy consumption in the total social energy consumption is increasing.Facing the double challenges of energy crisis and environmental pollution,many countries are developing and utilizing renewable energy for building energy conservation.Solar chimney is a method to enhance natural ventilation in buildings to realize the indoor cooling or heating.It is an effective way of building energy conservation,which raise great interests.The coupling of the heat and wind pressure is very important for the characteristic of the roof solar chimney.In view of this,The theoretical analysis of the roof solar chimney driven by solar and wind energy was performed;the mathematical and physical model of a roof solar chimney,which regarding radiation,convection and conduction,were established;Three-dimensional numerical simulations were carried out to study the ventilation performance of the roof solar chimney driven by solar and wind energy;a novel roof solar chimney equipped baffle with multi-hole was proposed and the ventilation performance of the new solar chimney were investigated.The major contents and findings are as follows.(1)The mathematical and physical model of a roof solar chimney,which regarding radiation,convection and conduction,were established.The computational region for wind pressure was proposed and the computational meshes were generated.(2)Three-dimensional numerical simulations were performed regarding the coupling of the heat and wind pressure.The effect of the solar chimney width,length,angle,outdoor wind velocity and solar radiation for the ventilation performance was studied and analyzed.The temperature and the velocity field were attained and the coupling mechanism of the heat and wind pressure was revealed.(3)The result shows that in a certain intensity of solar radiation and wind speed,the roof solar chimney ventilation increases with the width,the angle and length;the larger the width,the ventilation volume growth rate becomes smaller.The outdoor wind speed for 0.5m/s conditions,solar chimney width changes from 0.3m to 0.9m,ventilation increasing rate decreases from 20%to 11%with the width increasing;when the outdoor wind speed is small,the effect of the angle to the roof solar chimney ventilation is more obvious.(4)In the geometric parameters and operating conditions of this study,the leading role on the ventilation channel is hot pressing.When the Ra number is small,the heat conduction is dominant,the Ra number is large,the convection heat transfer is dominant;ventilation performance of outdoor wind pressure on roof solar chimney has gain effect,when the outdoor wind speed change from 0.5m/s to 3m/s,the ventilation increase from 11%to 27%.(5)Double channel roof solar chimney with interpolation perforated plate was proposed to optimize the structure form through the absorbing material.Through three-dimension numerical simulation about its potion characteristics,the results show that when perforated plate is arranged in the middle of-the solar chimney and forms two channels,the heating effect in the middle channels and enhancing of the disturbance of channel intermediate heat promotes the flow speed and enhances the natural ventilation to the chimney channel.(6)The calculation results show that under the coupling effects of wind and thermal pressure with the structure of interpolation porous plate,wind pressure has a gain effect on thermal pressure;when the width and angle of the roof solar chimney is larger,the more obvious the porous plate to improve ventilation;when open porosity of the plate is 63%,the ventilation is increases by 57%.