Research On Ventilation Performance Of Double Skin Facade

Double skin fa(?)ade(DSF)is a promising enclosure structure due to its unique double skin structure with the property of adapting to the thermal demand of buildings in different seasons,which has attracted much attention and research recently.However,there are still more controversies about its ability to meet the demand for indoor ventilation,especially in hot summer and cold winter regions,where the demand for natural ventilation in the transitional season is high,and whether the double skin fa(?)ade can meet the demand for natural ventilation is still not confirmed.To address this issue,research on the thermal and wind pressure ventilation performance of double skin fa(?)ade was carried out.For one,the solar chimney plume model from the literature is used to calculate the thermal pressure ventilation capacity of double skin fa(?)ade in the transition season.Two representative cities in hot summer and cold winter regions(Hangzhou,where solar energy is available,and Chongqing,where radiation is weak)are selected to analyze the ventilation capacity of the thermal pressure effect of the double skin fa(?)ade.Second,the wind pressure ventilation is actually measured in a double-glazed curtain wall test room in an experimental building,and the wind pressure ventilation performance of the double skin fa(?)ade is studied by comparing the measurement with the traditional window-wall structure room in the same building.Third,human body sensory experiments were conducted simultaneously in the two aforementioned comparison rooms to explore the sense of ventilation,comfort and window opening requirements of the double skin fa(?)ade rooms by subjective comparative evaluation,and finally,computational fluid dynamics CFD simulation technology was used to explore measures to improve indoor ventilation of DSF.The main results are as follows:1.The solar chimney plume model can be used for the optimal design of the double skin fa(?)ade.Theoretical calculations show that double skin fa(?)ade have a better capability in providing fresh air.Whether it belongs to Hangzhou,where solar radiation is available,or Chongqing,where solar radiation is weak,and whether it is in the west or south orientation of the building,a reasonably designed DSF can provide more than4 air changes for the office under the effect of pure thermal pressure ventilation for most of the daytime(70%)during the transition season.In addition,the effects of cavity depth,opening size,and the ability to obtain solar radiation heat on cavity ventilation are integrated and need to be considered in the optimal design to avoid one of these parameters becoming a constraint.In the absence of constraints,the ventilation volume increases with increasing depth,increasing height of the opening and enhancing radiation.When the depth increases to a certain level(beyond the opening height),the opening height can become a constraint.The use of heat-absorbing glass increases the heating capacity of the cavity,which can significantly improve the ventilation capacity of the cavity(28%～69%),and the design should give priority to increasing the heat gain of the cavity.The effect of ambient temperature on cavity ventilation can be ignored,but the temperature difference between indoor and outdoor has a great impact on cavity ventilation.Low outdoor ambient temperature has a strengthening effect on ventilation,while high outdoor temperature has a weakening effect on ventilation.2.Continuous measurement experiments were conducted in DSF rooms and conventional open-window rooms under typical spring weather conditions and natural ventilation.The results of the comparison room measurements showed that the air velocity in the conventional test room was significantly higher than that in the DSF room and the thermal comfort PMV values were slightly better than those in the DSF room under no air conditioning and open windows and doors ventilation in the transition season.The differences in temperature,radiant temperature,and relative humidity between the two rooms were minimal;therefore,the differences in thermal comfort values mainly came from the effects of wind speed.The indoor air velocity in the DSF room was usually below 0.25 m/s during the measurement period,regardless of the outdoor wind speed,while there were more frequent air velocity bursts(>0.8 m/s)in the conventional window-and-wall room.3.The results of the physical sensory experiment showed that the respondents’ comfort in the DSF room was at neutral to average comfort,and the comfort was lower than that felt in the room with window-wall structure,which was consistent with the measurement results.In terms of wind sensation,participants generally felt stronger airflow movement in the conventional open-window room than in the DSF room.More than half of the respondents believed that DSF should have larger openings,mainly for better indoor comfort and secondarily for air quality.However,the number of room air changes provided by DSF thermal pressure ventilation alone was up to four,indicating that there were cases where participants psychologically perceived insufficient air changes in DSF rooms and thus were concerned about indoor air quality and thus comfort ratings.4.CFD simulation study shows that: when the DSF test room top weather station ambient wind speed 3 ～ 4m / s,the wind is due south perpendicular to the double glass curtain wall surface,the indoor room door open,the number of ventilation up to 24 times / hour,but the indoor 1.5 m pedestrian plane height in the work area wind speed is often less than 0.25 m / s;simply increase the inner layer of the double glass curtain wall open window(window wall ratio 1 / 10)Ventilation effect is not significantly improved,if you open the outer layer of the corresponding position of the same size window,indoor ventilation can be increased by nearly double.When the inner layer openings are certain,while increasing the height of the upper and lower openings of the outer layer,indoor ventilation also increases,but the rate of incremental trend is decreasing,increasing the rate of extreme values exist.In addition,keeping the upper and lower openings of the inner and outer layers of the double-glazed curtain wall open through has a good gain effect on indoor ventilation.In summary,the results of the study show that although the double skin fa(?)ade has a good ability to provide fresh air,the physical sensory experiments show that people generally do not rate the indoor comfort and wind sensation of DSF rooms highly.The study used measurement data to confirm that the deficiency of thermal comfort values mainly comes from the effect of wind speed.In order to improve the indoor comfort of DSF,the indoor wind speed and indoor natural ventilation can be increased by optimizing the design of the opening area of the inner and outer skin of the double-skin fa(?)ade.