Disturbance effect is one of the important factors for wind damage to large cooling towers.Existing studies on the wind-induced interference of cooling tower groups are aimed at the same size and the lack of wind-indu...Disturbance effect is one of the important factors for wind damage to large cooling towers.Existing studies on the wind-induced interference of cooling tower groups are aimed at the same size and the lack of wind-induced interference effects between cooling towers of different sizes.With the background of the additional cooling tower project at Shandong Luxi Power Plant in China,the rigid body pressure wind tunnel test is carried out to obtain 194 conditions for the three combinations of the existing four-tower combination(small size),the new two-tower combination(large size)and the six-tower combination surface wind pressure distribution.Numerical simulation of the surrounding flow field of the cooling tower group with the most unfavorable interference condition of the six-tower combination is conducted using the computational fluid dynamics(CFD)method.Based on this,the characteristics of the average and pulsating wind pressure distribution of the cooling tower surface under the six-tower combination are mainly studied,and the load interference coefficients of the large-sized cooling tower and the small-sized cooling tower under the three tower group combinations are compared.The velocity flow field and vorticity changes around the cooling tower group at unfavorable wind angles are analyzed,and the wind-induced interference mechanism between cooling tower groups of different sizes is mainly refined.Research shows that the interference effect between such cooling tower groups of different sizes is much larger than that of cooling tower groups of the same size,which is specifically manifested as the enhancement effect of small-sized cooling towers and the shielding effect of large-sized cooling towers.The interference coefficient of large-sized cooling tower groups increases by 28%,and the interference coefficient of small-sized cooling tower groups decreases by 6.4%.The airflow acceleration caused by the pinch effect between small-sized cooling tower groups has an adverse effect on large-sized cooling towers and can significantly increase the magnitude of local wind load.The shielding effect of large-sized cooling towers can reduce the overall wind load of small-sized cooling towers.The research conclusions can provide the basis of wind load value design for wind resistance design of such large cooling tower addition projects.展开更多
The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this stud...The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its application in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment performance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54% in comparison with the conventional system(constant air volume with reheat system). In respect of condensation risk, it was found that the annual frequency of occurrence of condensation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parameters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed.展开更多
[Objective]To explore the best T.sinensis processing technology.[Method]The T.sinensis was treated by hot wind drying,freeze drying and blanching,and the contents of ascorbic acid,total phenolics and nitrite were dete...[Objective]To explore the best T.sinensis processing technology.[Method]The T.sinensis was treated by hot wind drying,freeze drying and blanching,and the contents of ascorbic acid,total phenolics and nitrite were determined respectively before and after the treatment to be a standard to evaluate the influence of different processing methods on the quality of T.sinensis.[Result]Both drying and blanching produced certain impact on the contents of all three components,among which the content of ascorbic acid was slightly influenced by vacuum freeze drying and short-time blanching,but greatly affected by long-time blanching and hot wind drying;the loss rate of polyphenols was above 60% when the hot wind drying,freeze drying and blanching lasted for more than 5 min,while it experienced little change under short-time blanching;hot wind drying and blanching may greatly reduce the content of nitrite,however,the vacuum freeze drying even improved the content,which would produce adverse impact on food safety.[Conclusion]Short-time blanching is the best method to process T.sinensis,it can effectively reduce its content of nitrite and retain the nutrients.展开更多
基金supported in part by the National Natural Science Foundations(Nos. 51878351, U1733129,51761165022)the Outstanding Youth Fund of Jiangsu Natural Science Foundation(No. BK20160083).
文摘Disturbance effect is one of the important factors for wind damage to large cooling towers.Existing studies on the wind-induced interference of cooling tower groups are aimed at the same size and the lack of wind-induced interference effects between cooling towers of different sizes.With the background of the additional cooling tower project at Shandong Luxi Power Plant in China,the rigid body pressure wind tunnel test is carried out to obtain 194 conditions for the three combinations of the existing four-tower combination(small size),the new two-tower combination(large size)and the six-tower combination surface wind pressure distribution.Numerical simulation of the surrounding flow field of the cooling tower group with the most unfavorable interference condition of the six-tower combination is conducted using the computational fluid dynamics(CFD)method.Based on this,the characteristics of the average and pulsating wind pressure distribution of the cooling tower surface under the six-tower combination are mainly studied,and the load interference coefficients of the large-sized cooling tower and the small-sized cooling tower under the three tower group combinations are compared.The velocity flow field and vorticity changes around the cooling tower group at unfavorable wind angles are analyzed,and the wind-induced interference mechanism between cooling tower groups of different sizes is mainly refined.Research shows that the interference effect between such cooling tower groups of different sizes is much larger than that of cooling tower groups of the same size,which is specifically manifested as the enhancement effect of small-sized cooling towers and the shielding effect of large-sized cooling towers.The interference coefficient of large-sized cooling tower groups increases by 28%,and the interference coefficient of small-sized cooling tower groups decreases by 6.4%.The airflow acceleration caused by the pinch effect between small-sized cooling tower groups has an adverse effect on large-sized cooling towers and can significantly increase the magnitude of local wind load.The shielding effect of large-sized cooling towers can reduce the overall wind load of small-sized cooling towers.The research conclusions can provide the basis of wind load value design for wind resistance design of such large cooling tower addition projects.
基金Supported by Competitive Earmarked Research Grant of Hong Kong Government(CERG No.522709)
文摘The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its application in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment performance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54% in comparison with the conventional system(constant air volume with reheat system). In respect of condensation risk, it was found that the annual frequency of occurrence of condensation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parameters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed.
基金Supported by National Natural Science Foundation(30771510)
文摘[Objective]To explore the best T.sinensis processing technology.[Method]The T.sinensis was treated by hot wind drying,freeze drying and blanching,and the contents of ascorbic acid,total phenolics and nitrite were determined respectively before and after the treatment to be a standard to evaluate the influence of different processing methods on the quality of T.sinensis.[Result]Both drying and blanching produced certain impact on the contents of all three components,among which the content of ascorbic acid was slightly influenced by vacuum freeze drying and short-time blanching,but greatly affected by long-time blanching and hot wind drying;the loss rate of polyphenols was above 60% when the hot wind drying,freeze drying and blanching lasted for more than 5 min,while it experienced little change under short-time blanching;hot wind drying and blanching may greatly reduce the content of nitrite,however,the vacuum freeze drying even improved the content,which would produce adverse impact on food safety.[Conclusion]Short-time blanching is the best method to process T.sinensis,it can effectively reduce its content of nitrite and retain the nutrients.
