容器水力冲砂存在问题及改进措施

本文介绍了容器水力冲砂的原理，分析了冲砂设计中存在的问题，提出了相应的改进措施。

分离器在线除砂工艺改进与智能化应用

某油田三相分离器在线除砂效果差,分离器积砂严重。对分离器除砂机理分析,对于分离器水力除砂系统,不同砂物质均存在临界流化系数,除砂效率遵循指数递减规律。对该油田除砂系统内部设计、参数设置和作业程序等分析后发现,除砂作业工序复杂、工作量大是除砂效果差的主要原因。提出了除砂作业新方法和智能化控制方案,提高了作业效果,降低了作业难度,为分离器除砂提效提供解决思路,有利于分离器在线除砂智能化升级。

An experimental comparison of water based alumina and silica nanofluids heat transfer in laminar flow regime

Experimental investigations were carried out to determine the Al2O3/water and SiO2/water nanofluids flowing through a circular tube. convective heat transfer performance and pressure drop of Measurements show that the addition of small amounts of nano-sized Al2O3 particles to the base fluid increases heat transfer coefficients considerably, while the result for the silica nanofluids contradicts with the alumina nanofluids and this leads to some interesting results. In the case of alumina nanofluids, an average increase of 16% in convective heat transfer coefficient is observed with an average penalty of 28% in pressure drop. Moreover, flow resistance increases significantly compared to the base fluid even at very low concentrations of nanofluids. Finally, measured heat transfer coefficients are compared with predicted ones from the correlation of Shah under the same conditions.

Horizontal gas mixing in rectangular fluidized bed:A novel method for gas dispersion coefficients in various conditions and distributor designs

In a rectangular fluidized bed combustor, the tracer gas is injected continuously into the bed from a point source at the center of the distributor plate. In this study, a general governing equation is formulated for tracer gas dispersion in the bed. An analytical solution is derived to estimate the dispersion coefficients, Dxand Dy, in a horizontal plane. The concentration profiles at different sampling heights with various gas velocities are plotted.Subsequently, to estimate the dispersion coefficients, surface fitting of the obtained analytical solution to the experimental data is performed. The dispersion coefficients obtained from this model are compared with those of a conventional model. Additionally, the effect of walls, bed height and gas injection rate on the dispersion coefficients in a horizontal plane is investigated, and the effect of distributor design on the dispersion coefficients in a horizontal plane is investigated with different tracer positions. It is found that Dxand Dyare nearly equivalent at a lower tracer gas ratio of the injected gas to the total gas flow rate. It is also demonstrated that the effect of bed height on Dxis minor. This model is also able to estimate the dispersion coefficients in the case of a multihorizontal nozzle distributor.

Electrode models in electrical impedance tomography

This paper presents different views on electrode modelling, which include electrode electrochemistry models for modelling the effects of electrode-electrolyte interface, electric field electrode models for modelling electrode geometry, and electrode models for modelling the effects of electrode common mode voltage and double layer capacitance. Taking the full electrode models into consideration in electrical impedance tomography (EIT) will greatly help the optimised approach to a good solution and further understanding of the measurement principle.

A Comparative Study on Heat Transfer Performance of Typical Petrochemical Reactors

The performance of heat transfer is a key issue for reactor design in petrochemical industry. Since the heat transfer in reactors is a complicated process and depends on multiple parameters, the evaluation of the heat transfer performance is usually challenging, and few previous studies gave an overall view of heat exchange performance of different types of reactors. In this review, heat transfer coefficients of two types of petrochemical reactors, including the packed bed and the fluidized bed, were systematically analyzed and compared based on a number of reported correlations. The relationship between heat transfer coefficients and fluid flow velocity in different reactors has been well established, which clearly demonstrates the varying range of their heat transfer coefficients. Heat transfer coefficients of gas-phase packed bed can exceed 200 W/m^2·K, rather than the suggested values(17—89 W/m^2·K) mentioned in the literature. The fluidized bed shows better performance for both two-phase and three-phase beds as compared to the packed bed. Systems with liquid phase also show better heat transfer performance than other phases because of the larger heat capacity of liquid. Thus the industrial three-phase fluidized beds have the best heat transfer performance with an overall heat transfer coefficient of greater than 1 000 W/m^2·K. The heat transfer results provided by this review can afford not only new insights into the heat transfer in typical reactors, but also the basis and guidelines for reactor design and selection.

An Innovative Hullform Design Technique for Low Carbon Shipping

Combining modem Computational Fluid Dynamics （CFD） evaluator with optimization method, a new approach of hullform design for low carbon shipping is presented. Using the approach, the designers may find the minimum of some user-defined objective functions under constrains. An example of the approach application for a surface combatant hull optimization is demonstrated. In the procedure, the Particle Swarm Optimization （PSO） algorithm is adopted for exploring the design space, and the Bezier patch method is chosen to automatically modify the geometry of bulb. The total resistance is assessed by RANS solvers. It＇s shown that the total resistance coefficient of the optimized design is reduced by about 6.6% comparing with the original design. The given combatant design optimization example demonstrates the practicability and superiority of the proposed approach for low carbon shipping.

Climate Change Impacts on Water Resources in Yemen

Climate change impacts on water resources are expected to be significant in Yemen. Efforts have been made to understand the expected changes and develop mitigation possibilities for the expected scenarios for a future sustainable use of resources and mitigation of expected impacts. The paper describes the development of a detailed baseline database and the assessment of climate change and variability impacts on water resources over the 2030, 2050 and 2080 time horizon on a Yemen-wide scale. Based on downscaled Global Climate Model data, a range of scenarios were established, representing potential Mean, Warm ＆ Wet and Hot ＆ Dry conditions as derived by evaluating worst case scenarios from the ensemble of the global models for the specified years. The results of the model include an estimated runoff coefficient, monthly rainfall, runoff, infiltration and evaporation representing the water balance in the different catchments. Analysis of the different evaluated scenarios shows that in the Mid, Warm and Wet scenario the hydrological components are generally higher than in the baseline scenario. For the Hot ＆ Dry scenario, runoff, infiltration and evapotranspiration are decreasing due to the decreasing precipitation and increase in temperature. The relative changes in runoff are strongest.

Column Analyses of Chloride Breakthrough and Lead Retention in Amended Sandy Soils

Stormwater quality design manuals lack scientifically creditable bases for many novel LID （Low-Impact Development） designs presently proposed to meet stormwater runoff management requirements. Potential stormwater pollutant adsorption and infiltration enhancement capabilities of forest-derived by-products （e.g. woodchips, bio-char） provide an opportunity to combine these readily availability materials into stormwater quality designs. On-site stormwater runoff treatment through determination of the soil-water transport and lead （Pb） retention capacity of two sandy soils from Oregon is considered. Using synthetic stormwater （-120 mg CI/L and -5 mg Pb/L） displacement tests in pairs ofABS （Acrylonitrile butadiene styrene） soil columns （75 mm dia by 0.46 m tall） with upward flow （to minimize air entrapment） saturated hydraulic conductivity, chloride dispersion and Pb retention by plain and amended soils is evaluated. Generally, soil amendment incorporation （woodchips, compost or biochar） as compared to an amendment layer resulted in improved hydraulic conductivities as compared to that of the soil alone. Chloride breakthrough curves verified that resident soil-water displacement occurred with 0.9 to 1.6 pore volumes and residence times for most columns were 15-30 minutes. No synthetic stormwater Pb ＂breakthrough＂ within the displaced or replaced soil-water was found, rather most Pb was adsorbed within the first 150 mm of soil.

Cyclic electron flow around photosystem I is required for adaptation to high temperature in a subtropical forest tree, Ficus concinna

Dissipation mechanisms of excess photon energy under high-temperature stress were studied in a subtropical forest tree seedling, Ficus concinna. Net CO2 assimilation rate decreased to 16% of the control after 20 d high-temperature stress, and thus the absorption of photon energy exceeded the energy required for CO2 assimilation. The efficiency of excitation energy capture by open photosystem Ⅱ（PSⅡ） reaction centres （Fv＇/Fm＇） at moderate irradiance, photochemical quenching （qp）, and the quantum yield of PSII electron transport （φPSⅡ） were significantly lower after high-temperature stress. Nevertheless, non-photochemical quenching （qNP） and energy-dependent quenching （qE） were significantly higher under such conditions. The post-irradiation transient of chlorophyll （Chl） fluorescence significantly increased after the turnoff of the actinic light （AL）, and this increase was considerably higher in the 39 ℃-grown seedlings than in the 30 ~C-grown ones. The increased post-irradiation fluorescence points to enhanced cyclic electron transport around PSI under high growth temperature conditions, thus helping to dissipate excess photon energy non-radiatively.

The Heat Transfer Coefficients of the Heating Surface of 300 MWe CFB Boiler

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.

Experimental investigation on heat transfer enhancement of mist/air impingement jet

The heat transfer performance of a mist/air jet impingement on a constant-heat flux surface was experimentally investigated.Two objectives were outlined in the current study.The first objective is to assess the effects of mist/air volumetric flow rate ratio,impinging mode and heat flux on the heat transfer characteristics of free mist/air jet impingement.The second objective is to assess the effect of swirl flow induced by the spinning grinding wheel on the mist/air jet impingement,simulating the heat transfer process on a grinding work-piece surface subjected to the mist/air jet impingement.The results show that the addition of dilute water droplets to air flow results in significant heat transfer enhancement.Once the mist/air ratio is increased to a certain value,the increase of heat transfer with the mist/air ratio becomes slow.For a given mist/air ratio,as the increase of heat flux,the contribution of droplet evaporation to the overall heat transfer is weakened relatively,resulting in a decrease of heat transfer enhancement in comparison to the lower heat flux case.The heat transfer coefficient in the stagnation region for the oblique jet is much lower than the normal mist/air jet impingement,while in the region away from the stagnation,the local heat transfer coefficient for the oblique jet is higher than the normal jet.As regards as the mist/air jet impingement in the vicinity of grinding zone is concerned,when the jet impinging direction is consistent with the rotating direction of rotating disk,the swirl flow induced by the rotating disk could entrain more droplets to enter the jet impinging stagnation zone,which is beneficial to convective heat transfer enhancement.Furthermore,as the rotational speed of disk increases,the temperature deceases in impinging jet stagnation zone.

A climatological comparison of column-integrated water vapor for the third-generation reanalysis datasets

The atmospheric reanalysis datasets have been widely used to understand the variability of atmospheric water va- por on various temporal and spatial scales for climate change research. The difference among a variety of reanalysis datasets, however, causes the uncertainty of corresponding results. In this study, the climatology of atmospheric column-integrated wa- ter vapor for the period from 2000 to 2012 was compared among three latest third-generation atmospheric reanalyses including European Centre for Medium-range Weather Forecasts Interim Re-Analysis （ERA-Interim）, Modem-Era Retrospective Analy- sis for Research and Applications （MERRA）, and Climate Forecast System Reanalysis （CFSR）, while possible explanation on the difference between them was given. The results show that there are significant differences among three datasets in the mul- ti-year global distribution, variation of interannual cycle, long-term trend and so on, though high similarity for principal mode describing the variability of water vapor. Over oceans, the characteristics of long-term CWV variability are similar, whereas the main discrepancy among three datasets is located around the equatorial regions of the Intertropical Convergence Zone, the South Pacific Convergence Zone and warm cloud area, which is related with the difference between reanalysis models for the scheme of convective parameterization, the treatment of warm clouds, and the assimilation of satellite-based observations. Moreover, these CWV products are fairly consistent with observations （satellite-based retrievals） for oceans. On the other hand there are systematic underestimations about 2.5 kg/m2 over lands for all three CWV datasets, compared with radiosonde ob- servations. The difference between models to solve land-atmosphere interaction in complex environment, as well as the pauci- ty in radiosonde observations, leads to significant water vapor gaps in the Amazon Basin of South America, central parts of Africa and some mountainous regions. These results would help better understand the climatology difference among various reanalysis datasets better, and more properly choose water vapor datasets for different research requirements.

Traditional Chinese Medicine for the treatment of influenza: a systematic review and Meta-analysis of randomized controlled trials

OBJECTIVE: To justify the clinical use of Traditional Chinese Medicine(TCM) in the treatment of influenza.METHODS: MEDLINE, EMBASE, Chinese Biomedical Literature Database, China National Knowledge Infrastructure Database, China Science and Technology Journal Database, Wanfang Database and the Cochrane Database of Systematic Reviews were searched from thedate of inception until January 1,2013, for the literature on treatment of influenza with TCM.RESULTS: A total of 7 randomized controlled trials were identified and reviewed. Of these trials, 2 compared a(modified) prescription of TCM with oseltamivir and 5 compared a patent traditional Chinese drug with oseltamivir. Based on the Meta-analysis,compared to oseltamivir, the(modified) prescription had similar effect in defervescence [WMD=5.66, 95% CI(﹣32.02, 43.35), P=0.77] and viral shedding [WMD=﹣ 6.21, 95% CI(﹣84.19, 71.76), P=0.88], and the patent traditional Chinese drug also had similar effect in viral shedding [WMD=﹣ 0.24,95% CI(﹣4.79, 4.31), P=0.92] but more effective in defervescence [WMD=﹣4.65, 95%CI(﹣8.91, ﹣0.38),P=0.03].CONCLUSION: TCM has potential positive effects in the treatment of influenza.