“非回流式水幕消防电梯井”在建筑设计中的可行性

消防电梯外侧采用防火分隔水幕系统,用来对空间进行防火分隔,以阻止火势蔓延扩大,起着防火墙的作用。消防电梯内侧采用防护冷却水幕系统,消防水幕衰减火灾热辐射,降低火场温度,提高电梯井的隔热效率,降低电梯金属外壳吸收热量,"非回流"的水体将带走大量的热量,维持电梯轿厢内温度。保护电线电源。     

Assessment of pollutant dispersion from rooftop stacks: ASHRAE,ADMS and wind tunnel simulation

The prediction of downwind concentration of effluents from stack located on top of buildings is important. Most current dispersion models assess the pollutant concentration at distances away from the building. It is important to study pollutant dispersion within the recirculation zone of the building, since studies have shown that effluents released from rooftop stacks have a tendency to re-enter the building through intakes located on the roof. These effects get more pronounced with the influence of RoofTop Structures (RTS). This paper presents a comparative study of the Atmospheric Dispersion Modelling System (ADMS), American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE 2003 and 2007 versions) and wind tunnel results. Four different cases involving a low-rise and high-rise building for stack heights (h_s) ranging from 1 m to 7 m, exhaust momentum ratios (M) ranging from 1 to 5 and wind direction (θ) of 0° and 45°, have been studied for neutral atmospheric stability conditions. In this regard the effect of RTS has also been examined by using wind tunnel, ADMS and ASHRAE models. ADMS yields higher dilutions near the stack at θ = 0° and cannot model the effect of RTS. Wind tunnel data compare well with ASHRAE 2003 at M = 5 for the low-rise building, but generally predict higher dilutions for the high-rise building. ASHRAE 2003 predicts lower dilutions than ADMS for the high-rise building, while ASHRAE 2007 yields very low dilutions for all cases, suggesting a need to reassess its suitability for practical design.     

Investigation of entrainment and thermal properties of a cryogenic dense-gas cloud using optical measurement techniques

Cryogenic dense-gas clouds have been investigated in a heavy-gas channel under controlled source and ambient conditions. Advantage is taken from new, non-intrusive optical measurement techniques (e.g. image correlation velocimetry, ICV, and background oriented Schlieren, BOS) providing detailed pictures of the temperature and velocity field in relevant regions of the cloud. The ice particles in the cloud, formed by nucleation, represent a natural seeding to be used as tracers, which have the advantage of behaving passively. Two layers can be identified in a cryogenic gas cloud: a lower cold layer, which is visible due to the presence of ice particles, and an invisible upper layer, where the ice particles have melted, mostly due to heat addition by air entrainment into the upper layer. A two-layer model has been applied to a generic element of the cloud, where detailed experimental data regarding velocity and temperature are available. Thermal- and dilution behaviour can be interpreted by means of the model which is presented in detail. A global entrainment parameter is deduced allowing a simple comparison with existing experimental information obtained by other traditional experimental techniques. The numerical values of the present entrainment parameter agree well with the correlations proposed by other authors. Thermal effects, such as heat transfer from the ground, appear to be very important. In addition, the visible height of the cloud can be predicted in relative good agreement with the experimental observations, by means of a thermal balance including the phase transition of the ice particles.     

如何控制贫化率,提高矿石品位

控制贫化率要有相应的措施和方法,良好的计划和计算机系统是降低贫化率,提高品位的有效手段。     

Effects of nitrogen dilution for coal synthetic gas fuel on the flame stability and NOx formation

Experimental studies were conducted to investigate the flame stability and the thermal/fuel NOx formation characteristics of the low calorific value (LCV) coal derived gas fuel. Synthetic LCV fuel gas was produced by mixing carbon monoxide, hydrogen and ammonia on the basis that the thermal input of the syngas fuel into a burner is identical to that of natural gas. The syngas mixture was fed to and burnt on flat flame burner. With the variation of the equivalence ratio for specific syngas fuel, flame behaviors were observed to identify the flame instability due to blow-off or flash-back and to define stable combustion range. Measurements of NOx content in exhaust gas were made to compare the thermal and the fuel NOx emissions from the LCV syngas combustion with those of the natural gas. In addition, the nitrogen dilution of the LCV syngas was attempted as an NOx reduction technique, and its effects on NOx emission and flame stability were investigated. This work was presented at the 7 ^th Korea-China Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, July 25–28, 2008.     

Laminar burning velocities and flame instabilities of diluted H2/CO/air mixtures under different hydrogen fractions

An experimental study was conducted using outwardly propagating flame to evaluate the laminar burning velocity and flame intrinsic instability of diluted H₂/CO/air mixtures. The laminar burning velocity of H₂/CO/air mixtures diluted with CO₂ and N₂ was measured at lean equivalence ratios with different dilution fractions and hydrogen fractions at 0.1 MPa; two fitting formulas are proposed to express the laminar burning velocity in our experimental scope. The flame instability was evaluated for diluted H₂/CO/air mixtures under different hydrogen fractions at 0.3 MPa and room temperature. As the H₂ fraction in H₂/CO mixtures was more than 50%, the flame became more unstable with the decrease in equivalence ratio; however, the flame became more stable with the decrease in equivalence ratio when the hydrogen fraction was low. The flame instability of 70%H₂/30%CO premixed flames hardly changed with increasing dilution fraction. However, the flames became more stable with increasing dilution fraction for 30%H₂/70%CO premixed flames. The variation in cellular instability was analyzed, and the effects of hydrogen fraction, equivalence ratio, and dilution fraction on diffusive-thermal and hydrodynamic instabilities were discussed.     

遗传算法在低贫化放矿中的应用

采用无底柱分段崩落采矿法，国内外一直采用截止品位放矿法来控制出矿。低贫化放矿提高出矿品位，降低废石混入。用遗传算法确定最低贫化率，且归纳出检验矿山能否实施低贫化放矿的经验公式，在梅山铁矿实际应用中取得较好效果。     

Operation of a TES microcalorimeter cooled by a compact liquid-helium-free He-He dilution refrigerator directly coupled to a Gifford-McMahon cooler

A superconducting transition edge thermosensor (TES) microcalorimeter was irradiated with LX-ray photons emitted by an ²⁴¹Am source maintained at an operating temperature of 120 mK using a compact liquid-helium-free ³He-⁴He dilution refrigerator directly coupled to a Gifford-McMahon (GM) cooler. The first and second stages of the GM cooler were directly coupled to the first and second pre-cool heat exchangers of a stick shaped dilution unit through copper plates in a vacuum chamber. The helium-free dilution refrigerator provided a cooling power of 20 μW at 100 mK. Detection signals of LX-ray photons emitted by the ²⁴¹Am source were observed by operating the TES microcalorimeter in a severe noise environment induced by the mechanical vibrations of the GM cooler.     

Effect of diluent size on the performance of a micro-scale fixed bed multiphase reactor in up flow and down flow modes of operation

The comparative behaviors of a micro-scale fixed bed multiphase reactor in up flow and down flow modes of operation were studied for hydrodesulfurization of atmospheric gas oil over a commercial catalyst. The experiments for the two modes of operation were conducted for a wide range of diluent size and other process variables such as liquid hourly space velocity and hydrogen/gas oil ratio. The results showed that the down flow mode of operation using 0.19 mm size of diluent could be used for generating reliable and meaningful data. On the other hand, the use of up flow mode of operation is restricted only for higher space velocities even while using 0.19 mm size of diluent. The results also indicated that the performance of the up flow mode of operation was poor at higher hydrogen/gas oil ratio. This change in performance is pronounced when higher size of diluent was used with the catalyst. In contrary, the hydrogen/gas oil ratio had minimum effect on the performance of the reactor for down flow mode of operation.     

送粉激光熔覆界面特性及熔覆层稀释率

通过调整扫描速度、送粉速率、熔覆材料颗粒度进行单道送粉激光熔覆试验 ,借助显微组织分析、扫描电子显微分析、透射电子显微分析 ,研究了工艺参数对送粉式激光熔覆层与基体间结合界面形态及界面附近组织结构的影响规律 :工艺参数对熔覆层稀释率的影响作用 ,提出熔覆层界面附近局部稀释率的概念