This paper proposes a push-pull airflow combined with a top draft hood to conduct local exhaust in a rubber workshop.Field measurements are carried out to investigate the characteristics of the emission source,while n...This paper proposes a push-pull airflow combined with a top draft hood to conduct local exhaust in a rubber workshop.Field measurements are carried out to investigate the characteristics of the emission source,while numerical simulation is performed based on the measurement to test the capture efficiency and to further optimize various parameters including push velocity,hood height and exhaust air rate.Compared with the high-hanging hood,the low-hanging hood can effectively capture the pollutant generated by tyre with lower exhaust air rate.The capture efficiency of the low-hanging hood reaches 98.18%with exhaust air rate of 6000 m^(3)/h and push air velocity of 5m/s.The results indicates that the new ventilation appliance can effectively collect the pollutant at a relatively low exhaust rate.展开更多
Range hood is a local ventilation device applied widely in residential kitchen for maintaining healthy environment. This study firstly defines the direct capture efficiency (DCE) based on the two-zone model in a confi...Range hood is a local ventilation device applied widely in residential kitchen for maintaining healthy environment. This study firstly defines the direct capture efficiency (DCE) based on the two-zone model in a confined kitchen space. A mass flux ratio of the secondary captured pollutant to the entrained pollutant from the room zone is proposed for the determination of DCE, where the distribution coefficient is firstly solved, and then its sensitivity analysis on the DCE is carried out. To validate the mass flux ratio and concisely identify the DCE, a virtual purification method that artificially sets the escaped pollutant to zero, is further applied. Compared with the newly developed DCE, the existing indexes, such as contaminant removal efficiency (CRE), total capture efficiency (TCE), fail to differentiate the direct capture from the total capture. Finally, the effects of such factors as makeup airflow pattern, exhaust flow rate, cooking source temperature and the individual occupied/unoccupied on the DCE are fully studied. It is confirmed that different makeup airflow pattern results in distinguished airflow distribution, which makes a significant difference of more than 30% in DCE. Over 50% increase of DCE can be achieved when the exhaust flow rate is increased from 300 to 600 m3/h. About 30% decrease of DCE is observed with the increased cooking source temperature from 100 to 300 °C, and 10% increase of DCE is appeared in the individual occupied case. This reasonable definition and determination of DCE would help to improve the real capture performance of range hoods.展开更多
文摘This paper proposes a push-pull airflow combined with a top draft hood to conduct local exhaust in a rubber workshop.Field measurements are carried out to investigate the characteristics of the emission source,while numerical simulation is performed based on the measurement to test the capture efficiency and to further optimize various parameters including push velocity,hood height and exhaust air rate.Compared with the high-hanging hood,the low-hanging hood can effectively capture the pollutant generated by tyre with lower exhaust air rate.The capture efficiency of the low-hanging hood reaches 98.18%with exhaust air rate of 6000 m^(3)/h and push air velocity of 5m/s.The results indicates that the new ventilation appliance can effectively collect the pollutant at a relatively low exhaust rate.
文摘Range hood is a local ventilation device applied widely in residential kitchen for maintaining healthy environment. This study firstly defines the direct capture efficiency (DCE) based on the two-zone model in a confined kitchen space. A mass flux ratio of the secondary captured pollutant to the entrained pollutant from the room zone is proposed for the determination of DCE, where the distribution coefficient is firstly solved, and then its sensitivity analysis on the DCE is carried out. To validate the mass flux ratio and concisely identify the DCE, a virtual purification method that artificially sets the escaped pollutant to zero, is further applied. Compared with the newly developed DCE, the existing indexes, such as contaminant removal efficiency (CRE), total capture efficiency (TCE), fail to differentiate the direct capture from the total capture. Finally, the effects of such factors as makeup airflow pattern, exhaust flow rate, cooking source temperature and the individual occupied/unoccupied on the DCE are fully studied. It is confirmed that different makeup airflow pattern results in distinguished airflow distribution, which makes a significant difference of more than 30% in DCE. Over 50% increase of DCE can be achieved when the exhaust flow rate is increased from 300 to 600 m3/h. About 30% decrease of DCE is observed with the increased cooking source temperature from 100 to 300 °C, and 10% increase of DCE is appeared in the individual occupied case. This reasonable definition and determination of DCE would help to improve the real capture performance of range hoods.
