| At present,there are contradictions among ventilation effect,indoor comfort and energy consumption in laboratory rooms,which is mainly manifested as:in order to ensure the safe discharge of indoor pollutants,the huge ventilation required makes indoor comfort poor and building energy consumption high.On the one hand,in order to prevent the pollutants from leaking into the rooms while experiment,ventilation system requires a larger number of air quantity,including not only air output but also air input to maintain indoor micro negative pressure.On the other hand,in hot summer of hot and humid areas,it will affect the indoor comfort if air supply direct sent to laboratories without being conditioned,while getting a large amount of air supply conditioned will consume a lot of energy of air-conditioning,and the utilization of air-conditioning energy rate will be low.This paper analyzes a chemistry laboratory in an experimental building of a university in Guangdong province and designs a divided function“supplemental air-fresh air”ventilation and air-conditioning system which is suitable for the chemistry laboratory,by taking the large number of supply air volume of fume hood-the chemical laboratory main exhaust equipment,as the research object,and the indoor environmental comfort,the effect of indoor pollution control as well as the energy saving benefits as the analysis aspects.And CFD numerical simulation technology is used to analyze the system performance according to the supplemental air ratios of the supplemental air system,the width of the supplemental air inlet and the opening height of the working face of the fume hood.The conclusions are as follows:（1）The supplemental air ratio has a certain influence on the indoor temperature and pollutant concentration of the divided function"supplemental air-fresh air"ventilation and air conditioning system,among which the supplemental air ratio has a more obvious effect on indoor temperature.The higher the supplemental air ratio is,the higher the overall indoor temperature will be,and the more chaotic the temperature distribution will be.When the supplemental air ratio increases from 50%to 80%,the indoor average temperature at z=0.1m,1.2m and 1.7m increases by 1.6K,1.3K and 1.3K,respectively.As to the influence of supplemental air ratio on indoor pollutant concentration,the higher the supplemental air ratio is,the higher the indoor pollutant concentration is.When the supplemental air ratio is 50%,60%,70%and 80%,the indoor average pollutant concentration is 0.003ppm,0.031ppm,0.183ppm and 0.685ppm,respectively.（2）The influence of the width of the supplemental air inlet on indoor temperature is not obvious.The indoor temperature decreases with the increase of the width in the range of0.02m～0.08m,and the temperature drop range is generally below 0.5K.However,the indoor temperature tends to rise when the width is greater than 0.08m.The indoor pollutant concentration decreased significantly with the increase of the width of the supplemental air inlet.The indoor pollutant concentration decreases from 3.776m to 0.183 ppm,0.013 ppm and0.009 ppm,respectively while the width increases from 0.02m to 0.05m,0.08m and 0.1m.（3）In the influence of the opening height of the working face of the fume hood,the indoor temperature increases with the increase of the opening height,and the temperature difference between different heights at each horizontal plane is basically below 0.3K.The indoor pollutant concentration increases with the increase of the opening height of the working face.When the working face opening height is 0.15m,0.3m and 0.5m,the indoor average pollutant concentration is 0.001 ppm,0.08 ppm and 0.183 ppm,respectively.The pollutant concentration levels between different working face opening heights reaches the magnitude of10-3,10-2 and 10-1 respectively,showing that the influence of the opening height on indoor pollutant concentration is obvious,and reducing the working face opening can effectively control the indoor pollutant concentration.In the meantime,orthogonal experimental design is used in this paper in order to explore influence degree of each influence factor on system performance under different evaluation indexes and eventually find out the optimal design scheme of the divided function“supplemental air-fresh air”ventilation and air-conditioning system of the chemistry laboratory in this topic.In this analysis,the influence factors include the supplemental air ratio,the width of the supplemental air inlet and the opening height of the fume hood working face,while the levels of pollutant concentration,indoor environmental comfort and system energy efficiency are respectively regarded as different evaluation indexes.Finally,the following conclusions are drawn:（1）The influence of each factor on indoor comfort and indoor pollutant concentration of the system is basically the same as the indoor temperature distribution and pollutant concentration distribution of the system under different design parameters in CFD numerical simulation analysis.It shows that the influence of parameter change on system performance in numerical simulation is reliable.（2）while taking,the normalized concentration of indoor pollutants,as the pollutant evaluation index,the influences of various factors on system performance are,in order from large to small,the working face opening height,the width of the supplemental air inlet and the supplemental air ratio.At this situation,the optimal design scheme of the system is that the opening height of the working face h=0.15m,the supplemental air ratio b=80%,and the width of the supplemental air inlet d=0.08m.（3）while taking ADPI,indoor air diffusion performance index,as the comfort evaluation index,,the influences of various factors on system performance are,in order from large to small,the supplemental air ratio,the opening height,and the width of the supplemental air inlet.At this situation,the optimal design scheme of the system is that h=0.5m,b=60%,and d=0.02m.（4）while takingη,the energy saving rate of total load of air conditioning,as the energy conservation evaluation index,the influences of various factors on system performance are,in order from large to small,the supplemental air ratio,the opening height,and the width of the supplemental air inlet.At this situation,the optimal design scheme of the system is that h=0.5m,b=80%,and d=0.02m. |
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