Optimal Design And Fresh Air Treatment Scheme For Residential Buildings

With the rapid development of urbanization and economy,outdoor air condition is decreasing year by year.In a particular season,haze has become a common phenomenon,which poses serious threat to people's health.Indoor air quality is not optimistic due to outdoor air pollution becomes more and more serious.The fresh air exchanger gradually attracts people's attention for their requirement of high quality living environment.It can not only dilute the concentration of indoor pollutants,but also increase the indoor oxygen content and reduce the happening of "sick building syndrome".Based on the principle of healthy and energy conservation,this study employed numerical simulation and experimental test to optimize the design,put forward fresh air treatment schemes on the fresh air exchanger of the residential buildings.This study used Airpak software to perform numerical simulation of the flow field,air age,CO2 concentration and PMV-PPD distribution under four different air supply rates,such as 60m3/h,120m3/h,180m3/h and 240m3/h.A structure of dual valve was designed to control the internal circulation,to decide the installation position using CFD method,and the effects of the valve opening degree and air supply rate on the return air capacity were also simulated.Fresh air exchanger test bench was set up to measure the relationship between air volume and voltage,and the return air capacity under different valve opening degree and air supply rate.In addition,this research applied CFD method to simulate the internal steady flow field under three different air supply grilles,and calculate the sound pressure distribution on the wall of the warehouse body,and the suitable sound insulation and noise reducing measure were found through the calculation of discrete noise of spiral air distribution structure.Thus,the appropriate noise reduction measures were selected.The results are as follows:(1)The larger the fresh air volume is in the building,the lower the mean air age is.Since the pollutant concentration has been decreased,the air quality has been increased.Therefore,people feel much more comfortable.The CO2 concentration in the bedroom is much higher than that in living room,and the air age has been increased gradually along the air flow direction.Air quality in the area far away from the fresh air exchanger is worse than those near the exchanger.The upper air age generally is lower than the down area.The results show that the installation location,the fresh air volume and the direction of air supply are the main factors that influence the distribution of the indoor flow field.(2)In order to determine the installation position of the circulating valve in the fresh air exchanger,the value is set at 160 mm above the circulating cabinet bottom surface.When the distance is 160 mm,the air volume is 82.32m3/h,the air of which in the exhaust passage passes into the fresh air channel uniformly through the return valve.Return air volume gradually increases when the valve is set in the following order,i.e.,exhaust valve fully open and return valve one-third open,exhaust valve half open and return valve two-thirds open,exhaust valve fully open and return valve fully open,exhaust valve a half open and return valve one-third open,exhaust valve fully open and return valve two-thirds open,exhaust valve a half open and return valve fully open.When the exhaust valves a half open and return valve fully open,the maximum volume of return air,is 82.33m3/h;while exhaust valve fully open and return valve one-third open,the minimum volume of return air,is 32.93m3/h.The effect of the change of the return valve opening on the return air volume is greater than that of the exhaust valve opening,and the return air volume of the return valve increases linearly with the air supply volume.Considering the indoor pollutants concentration and the difference temperature of indoor and outdoor,the design of the fresh air exchanger internal circulation process control scheme is determined.(3)The experimental results show that the maximum volume of return air is 180m3/h and the maximum volume of exhaust air is 120m3/h,the error value is 10.51m3/h with comparison to the simulation value.The effect of the change of the return valve opening on the return air volume is greater than that of the exhaust valve opening.Additionally,different air supply under the return air return air volume is tested,and the error value is 10.89m3/h with comparison to the simulation value.The error is caused by the model,the production process,the experiment,and the reason of error is analyzed,which can provide the improvement scheme for the manufacturer of the fresh air exchanger.To analyze the fresh air exchanger energy-saving performance.The results show that the fresh air exchanger is saving more energy,which has internal circulation process.(4)The maximal sound pressure and mean sound pressure of the circular spiral grille are smaller than those of circular grille and rectangular grille.The maximal sound pressure of circular spiral grille is 10.19 dB,which is 52% smaller than that of the circular grille.In addition,the average sound pressure is 4.46 d B,which is 66.7% smaller than that of the rectangular grille.Therefore,it turns out that circular spiral grille is the most optimal structure.The peak monitoring points of the fresh air exchanger on the silo wall appears in the range of 0 to 250 Hz,when the range is beyond 250 Hz,the sound pressure level decreases with the frequency,and the sound pressure value at the upper area of the air outlet of the fresh air blower is generally lower than that of the down area.The results show that the simulation results are consistent with theoretical results,indicating that simulation results are valid.