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Z. Ning C.S. Cheung Y. Lu M.A. Liu W.T. Hung 《Atmospheric environment (Oxford, England : 1994)》2005,39(40):7880-7893
The aim of the work presented here is to study experimentally and numerically the dispersion characteristics of vehicular exhaust plume at an idle condition in an idealized and simplified environment. The gaseous and particulate concentrations in the exhaust plume of three idling motor vehicles were measured in an isolated environment under calm weather conditions. Despite the difference in the initial concentrations, the pollutants decayed exponentially in all directions.The CFD code PHOENICS 3.3, with the k–ε eddy dissipation sub-model, was used for the numerical simulation. The simulated results match very well with the experimental results close to the source of emission but decay to the ambient concentrations much slower. The effects of the initial emission concentration, exit velocity, exit direction and crosswind intensity have been investigated parametrically. The initial pollutant concentration will increase the local concentrations but the pattern of dispersion remains the same. The exit velocity will increase the momentum of the jet, resulting in a deeper penetration downstream. The exit angle has a stronger influence on pollutant dispersion than both initial pollutant concentration and exit velocity. When the exit angle is 15°, the pollutants tend to spread on the ground region. Crosswind shows a significant effect on the dispersion of the exhaust plume also. It will divert the plume to disperse in the same direction of the wind with limited penetration in the downstream direction. 相似文献
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A study of using dual membrane technologies, microfiltration (MF) and reverse osmosis (RO), for reclaiming blowdown of the cooling tower was conducted at ZJK power plant, Hebei province, China. The study shows that the combined MF-RO system can effectively reduce water consumption in the power industry. The results indicate that MF process is capable of producing a filtrate suitable for RO treatment and achieving a silt density index (SDI) less than 2, turbidity of 0.2 NTU. The water quality of RO effluent is very good with an average conductivity of about 40 micros/cm and rejection of 98%. The product water is suitable for injection into the cooling tower to counteract with cooling water intrusion. After adopting this system, water-saving effectiveness as expressed in terms of cycles of concentration could be increased from 2.5-2.8 times to 5 times. 相似文献
748.
超声波强化污水厌氧生物处理综述 总被引:1,自引:0,他引:1
通过对超声波辐射促进微生物活性以及超声波强化污水好氧生物处理、厌氧污泥减量化处理等作用机制的分析研究,探讨将超声波应用于强化污水厌氧生物处理的可行性.同时对超声波强化污水厌氧生物处理的应用前景进行了展望. 相似文献
749.
Aqueous solubilities of four non-ortho and eight mono-ortho substituted PCBs were determined using a generator-column technique followed by subsequent off-line GC/ECD analysis of the aqueous solutions. The method is based on pumping water through a column containing glass beads coated with the congener being studied and has been used to measure solubilities at room temperature. The method circumvents many of the experimental difficulties encountered with the traditional shake-flask system. Aqueous solubility of 3,3′,4,4′-tetrachlorobiphenyl determined by this procedure is compared with data obtained from the shake-flask method and the computational method. The precision of replicate measurements is better than ±6.5%. Aqueous solubilities determined for 12 congeners ranged from 6.07 × 10−11 to 4.47 × −9 mol/L and generally decreased with molecular weight and increased with degree of ortho-chlorine substitution within a molecular-weight class. 相似文献
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Selected organonitrogen, organophosphorus and organochlorine pesticides have been determined in precipitation samples collected at 10 sites in the Gdańsk region (northern Poland) over a period of one year (1998). Compounds which were detected most often included simazine (0.11-5.80 ng/l), fenitrothion (0.1-2.10 ng/l), chlorfenvinfos (0.1-1.30 ng/l), gamma-HCH (0.012-5.06 ng/l), heptachlor epoxide (0.05-3.28 ng/l) and aldrin (0.02-3.28 ng/l). The pesticide concentrations in precipitation samples revealed seasonal fluctuations, with higher concentrations observed during the application periods (June and July). The concentrations observed were also affected by the inflow of polluted air masses from the southwest. The total pesticide concentration in the precipitation samples was strongly related to the abundance of green areas in the vicinity of the sampling sites. A weak correlation was also found between the total concentration of organonitrogen and organophosphorus pesticides, and the total concentration of organochlorine pesticides in the samples collected. 相似文献