Coupled heat and mass transfer analysis of NH<Subscript>3</Subscript>-H<Subscript>2</Subscript>O falling film absorption on inner tube surface with low solution flow rates

NH₃-H₂O falling film absorption usually takes place with low solution flow rate in real absorption refrigeration system. An experimental study of inner vertical absorption is carried out for the consideration of air-cooling absorber. Variable working conditions are tested to evaluate the heat and mass transfer performances.The traditional evaluation method based on log-mean-temperature（concentration） difference is criticized for its lack of theoretical basis while simultaneous heat and mass transfer process occurs. A new method proposed by Kim and Infante Ferreira is modified to evaluate the experimental results with reasonable assumptions. The method is based on the derivation of coupled heat and mass transfer differential equations of NH₃-H₂O absorption process.The analysis of the same experimental data shows that the new method realizes better consistency with smaller error, especially in heat transfer aspect. Heat and mass transfer performance is enhanced with the increase of solution Reynolds number. Sub-cooling of inlet weak solution also has positive influence on the absorption process,which should be evaluated by the new method correctly. Two correlations are developed to evaluate both Nusselt and Sherwood numbers for the design of air-cooling absorber.     

Preparation of benzene adsorption materials using waste activated alumina

A new type of benzene adsorption material was prepared by using the airtight heat treatment method. This method can directly transform the organic impurities of the activated alumina waste into carbon with adsorption capability. The microstructure and carbon content of materials were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), BET (Brunauer Emmett Teller) surface area analysis and elemental analysis. The influences of heat treatment temperature on the properties of the composite materials were discussed. The benzene adsorption capability of the material was investigated. The experimental results show that the optimal heat treatment process condition is airtight heating at 400°C for 2 h. The resulting sample has carbon mass fraction of 3.57%, specific surface area of 234.70m²/g, pore volume of 0.41m³/g, and average pore size of 6.59 nm. The samples show excellent benzene adsorption capability with an adsorption rate of 21.80%.     

水中呋吗唑酮的固定相光催化氧化

以高压汞灯为光源、负载在海砂上的ＴｉＯ２为催化剂，采用敞口固定床型光催化反应器对水中难降解的呋吗唑酮（ＦＴＤ）进行了固定相光催化氧化实验．结果表明，反应速率可用Ｌａｎｇｍｕｉｒ－Ｈｉｎｓｈｅｌｗｏｏｄ方程描述，与光分解相比，光催化氧化的突出优点是矿化程度高，相同光辐射条件下反应１００ｍｉｎ，０．１０ｍｍｏｌ／Ｌ的ＦＴＤ水溶液经光催化氧化后ＴＯＣ的去除率为８９．１％，而经光分解后ＴＯＣ的去除率仅为２８．８％；在反应体系中投加少量臭氧或过氧化氢可以显著提高ＦＴＤ的氧化效率，说明光催化氧化可以兼容Ｏ３／ＵＶ、Ｈ２Ｏ２／ＵＶ等光激发氧化工艺．探讨了充氧、ＦＴＤ浓度及ｐＨ等对光催化氧化过程的影响．     

热压自然通风室内污染物浓度演变特性

为探究热压自然通风向稳态发展过程室内气态污染物的迁移规律,对不同高度处污染物浓度演化进行了分析.首先结合预测热分层瞬时变化的非均匀三层模型,针对室内不同的下层污染物混合特性,建立了均匀混合和纯置换两种热压自然通风室内污染物输送模型;其次,采用4阶龙格-库塔(Runge-Kutta)方法迭代求解,得到了通风过程室内污染物...     

活性碳纤维负载TiO_2去除低浓度甲醛气体的实验研究

利用自制的光催化气体反应系统,模拟有限密闭空间特殊环境,以甲醛气体为代表,用溶胶凝胶法制得不同配比的TiO2并负载在活性碳纤维上,将其放入马弗炉中在不同温度下煅烧,最后测试其对甲醛的去除效率,且研究了活性炭纤维负载TiO2作为整体材料对甲醛的去除动力学方程.结果表明,冰醋酸、无水乙醇、去离子水和煅烧温度对去除效果的影响是交互的,理想配比下两小时去除率可达78.89%;活性炭纤维负载TiO2作为整体材料对低浓度甲醛的去除满足动力学方程ρA=m0+(ρ0A-m0)exp(-Kt);自制材料对甲醛的去除量为4 357.78mg/(h×m2),稳定性为78.3%.     

Phase transitions relating to the pozzolanic activity of electrolytic manganese residue during calcination

Electrolytic manganese residue（EMR） is generated from electrolytic manganese metal（EMM） industry, and its disposal is currently a serious problem in China.The EMR were calcined in the interval 100—900℃to enhance their pozzolanic activity and characterized by the differential thermal analysis-thermogravimetry（TGDTA）, X-ray diffraction（XRD）,infra-red（IR） and chemical analysis techniques with the aim to correlate phase transitions and structural features with the pozzolanic activity of calcined EMR.Prom the phase analysis and compressive strength results,it is found that the EMR calcined within 700—800℃had the best pozzolanic activity due to the decomposition of poorly-crystallized CaSO₄ under the reducing ambient created by the decomposition of（NH₄）₂SO₄.The appearance of reactive CaO mainly contributes to the good pozzolanic activity of EMR calcined within 700—800℃.The crystallinity of Mn₃CO₄ increases leading an unfavourable effect on the pozzolanic behaviour of EMR calcined at 900℃.The developed pozzolanic material containing 30%（mass fraction） EMR possesses compressive strength properties at a level similar to 42.5^# normal Portland cement,in the range of 41.5—50.5 MPa.Besides,leaching results show that EMR blend cement pastes have excellent effect on the solidification of heavy metals.     

Ag/BaTiO3的制备及光催化性能

采用光催化还原法、浸渍法和水热法分别制备了Ag/BaTiO3催化剂.通过X-射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见吸收光谱(UV-vis)等手段对改性后的催化剂进行表征,考察了掺杂Ag的不同制备方法、催化剂的载Ag量对催化剂光催化活性的影响.实验结果表明,改性后的BaTiO3对亚甲基蓝染料溶液的光催化降解能力有明显提高,采用光催化还原法制备的Ag/BaTiO3催化剂催化活性最高,载Ag量为1.0％的Ag/BaTiO3对亚甲基蓝的降解效果最好,紫外光照射4h后降解率为95％.     

Ag／BaTiO3的制备及光催化性能

采用光催化还原法、浸渍法和水热法分别制备了Ag／BaTiO3催化剂．通过X-射线衍射（XRD）、扫描电子显微镜（SEM）、紫外-可见吸收光谱（UV—vis）等手段对改性后的催化剂进行表征,考察了掺杂Ag的不同制备方法、催化剂的载Ag量对催化剂光催化活性的影响．实验结果表明,改性后的BaTiO3对亚甲基蓝染料溶液的光催化降解能力有明显提高,采用光催化还原法制备的Ag／BaTiO3催化剂催化活性最高,载Ag量为1．0％的Ag／BaTiO3对亚甲基蓝的降解效果最好,紫外光照射4h后降解率为95％．     

Quantitative phase analysis of the calcium silicate slag as the residue of extracting alumina from high-alumina fly ash

Calcium silicate slag is the residue of process of pre-desilication alkali lime sintering applied in the high-alumina fly ash to extract the alumina. The quantitative phase analysis (QPA) of the calcium silicate slag has been performed by the Rietveld method based on the powder X-ray diffraction (XRD) with the aid of noncommercial software GSAS-EXPGUI. A known weight of crystalline internal standard (10% CaF₂) was added to the calcium silicate slag to calculate the fraction of amorphous phase and other crystalline phases on an absolute basis. Besides, the calcium silicate slag was characterized by X-ray fluorescence (XRF) and thermo gravimetric (TG) differential scanning calorimetry (DSC) to test the QPA results and investigate its other characters. Finally, the results show that the amorphous fraction is 17.5% (hereinafter, the percentages refer to the mass fraction), and the major crystalline phases detected in the calcium silicate slag consist of 23.5% Beta-Ca2SiO₄, 10.0% bredigite, 10.3% Ca₃Al₂O₆ (C₃A) and 21.6% CaCO₃.     

Research on reduction of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> by biomass sawdust

The research on biomass reduction of Fe₂O₃ was carried out by using sawdust as reductant. The direct reducing agents in the biomass magnetization process were determined by comparing various biomass pyrolysis products with the reduction degree (divalent iron content in total iron), reduction temperature range and valence change of Fe₂O₃ in the reduction process. The microstructure variation of Fe₂O₃ at different stages was also analyzed by scanning electron microscopy (SEM). Nonisothermal thermogravimetric analysis (TGA) was applied to explore the thermal reduction process. The results show that the direct reducing substances in the biomass reaction with Fe₂O₃ are H₂ and bio-oil, and the reduction process can be divided into two steps: biomass pyrolyzing to release H₂ and bio-oil, and reductive volatiles reacting with Fe₂O₃. The two steps are relatively independent. The kinetic of the reduction reaction follows a first-order reaction kinetic model, with 88.99 kJ/mol activation energy and 9.55 × 10⁸ min^?1 frequency factor.     

Optimal Total Vehicle Pollutants Emission Quantity Based on Link Traffic Capacity Constraints

With the growing of vehicles ownership, the vehicular exhaust emissions have become major sources of air pollution in cities. In this paper, the pollutants, carbon monoxide (CO), nitrogen oxides (NO_x), and hydrocarbon (HC) are considered as evaluation factors. On the basis of the relation between the emission factors and vehicle's velocity and the relation amongst three parameters (Volume, Speed, and Density) of traffic flow, we have designed a model. This calculates the total quantity of pollutants emission from vehicles based on speed, proportion of vehicle types, and traffic volume. Using the theory of nonlinear programming, we have formed an optimal model in which the link capacity is one main constraint and the minimum of the total quantity of pollutants emission is the goal and designed its algorithm solution. The aim of our research is to find a method to control the quantity of traffic pollutants emission through adjusting and controlling the composition of vehicle types, and then the traffic volume and vehicle's running speed indirectly. Finally, the feasibility of the model is justified through a practical example.     

行人在城市道路环境中污染物暴露研究

城市道路作为行人活动的重要场所,其空气质量与人体健康密切相关,而空气污染物对人体健康的影响与人体实际暴露水平有着密切联系. 本文根据污染物暴露的相关概念,分析了城市道路环境下污染物由机动车排放源到人体的过程和行人污染物暴露的影响因素,对比总结了国内外污染物暴露的研究方法及适用性,结合城市道路污染物浓度的分布特点和交通流量变化的峰值特性,根据利兹市的道路污染物排放数据,探讨了行人在不同时段的污染物暴露水平.     

Analysis of Pollutant Exposure of Pedestrian in Urban Street

As an important place of pedestrian activities, the air quality of urban street is closely related to the human health, and the effects of air pollutants on human health have a close contact with the actual level of exposure. According to the concept of exposure, the paper analyzes the process of the exhaust pollutants from vehicles to pedestrians and the influencing factors under the urban traffic environment, and compares the research method of the pollutants exposure at home and abroad. Combined with the distribution characteristics of pollutants concentration and the peak feature of traffic flow in urban street, the paper also discusses the level of pollutant exposure of pedestrian in different time on the basis of the data of pollutant emission in Leeds City.     

CdIn_2S_4光催化降解亚甲基蓝的试验

以CdIn2S4为光催化剂,钨灯模拟可见光,探讨其对活性染料亚甲基蓝的光催化降解过程.考察了光照时间、催化剂用量、亚甲基蓝的初始浓度、反应体系的pH值和温度以及光强对光催化过程的影响.结果表明：对于4mg/L的亚甲基蓝溶液,200W钨灯照射下,CdIn2S4的用量为0.04g/L,pH为3.0,1.5h内其降解率可达97.83%.温度对反应影响很小.     

Friction and cutting properties of hot-filament chemical vapor deposition micro- and fine-grained diamond coated silicon nitride inserts

The micro-crystalline diamond (MCD) and fine-grained diamond (FGD) films are deposited on commercial silicon nitride inserts by the hot-filament chemical vapor deposition (HFCVD) method. The friction and cutting properties of as-deposited MCD and FGD films coated silicon nitride (Si₃N₄) inserts are comparatively investigated in this study. The scanning electron microscopy (SEM) and Raman spectroscopy are adopted to study the characterization of the deposited diamond films. The friction tests are conducted on a ball-on-plate type reciprocating friction tester in ambient air using Co-cemented tungsten carbide (WC-Co), Si₃N₄ and ball-bearing steel (BBS) balls as the mating materials of the diamond films. For sliding against WC-Co, Si₃N₄ and BBS, the FGD film presents lower friction coefficients than the MCD film. However, after sliding against Si₃N₄, the FGD film is subject to more severe wear than the MCD film. The cutting performance of as-deposited MCD and FGD coated Si₃N₄ inserts is examined in dry turning glass fiber reinforced plastics (GFRP) composite materials, comparing with the uncoated Si₃N₄ insert. The results indicate that the lifetime of Si₃N₄ inserts can be prolonged by depositing the MCD or FGD film on them and the FGD coated insert shows longer cutting lifetime than the MCD coated one.     

基于离散事件模拟沥青路面施工对环境的影响

为了降低沥青路面施工过程中能耗及温室气体和污染物排放, 建立了基于离散事件模拟的沥青路面施工环境影响计算模型, 利用概率分布函数和逻辑语句将施工步骤抽象化, 应用图形化离散事件模拟软件构建了沥青路面施工离散事件模型, 将Nonroad计算模型植入, 进行了不同温室气体和污染物的动态计算, 并对比了不同施工情况的模拟排放结果。分析结果表明: 运料车将沥青混合料运输至摊铺现场的过程为沥青路面施工的主要能耗源, 为总能耗的44%, 摊铺过程与运料车返回过程的能源消耗分别为总能耗的32%、12%;温室气体与污染物排放的主要施工步骤为运输和摊铺过程, 占排放总量的50%以上; 摊铺与压实过程产生的排放物主要为NO_x, 运输过程产生的排放物主要为CO₂; 对施工工艺进行调整, 使用不间断摊铺施工会明显减少NO_x的排放, 减排量约为15%;在施工设备方面, 适当增大摊铺设备的容量会减少CO₂和HC的排放, 前者减排量约为25%, 后者约为17%。可见, 基于离散事件模拟沥青路面施工环境影响计算模型, 可量化沥青路面施工过程的能耗及温室气体和污染物排放, 优化沥青路面施工技术方案。      

有机固体废物好氧堆肥反应器的设计

针对目前商品化的堆肥反应器较少,且个别应用的反应器亦存在着反应物料多混合不均匀、易产生臭气等问题,设计了一种带有搅拌齿和吸附层的有机固体废物堆肥反应器。该反应器主体材料用有机玻璃或不锈钢制成,可装堆料100 L。该装置包括保温层、集气层、吸附填料层、进气缓冲层、旋转轴、搅拌齿、进气管、排液管、出料口、排气口、活动盖连接及由保温层内壁包容的空间所构成的堆肥仓。实际进行厨余垃圾堆肥时,平均通风量应为68.19 m3/d;气体流量计的最大量程应为0.15 m3/min;风机应提供的风量为8.4 m3/h,全压为2×103Pa。反应器搅拌轴的直径为30 mm,变速器输出轴的轴径取15 mm,搅拌齿的外径取25 cm,搅拌轴的有效高度为57 cm,搅拌设备的电机额定功率为3.0 kW。该装置具有能使反应物料混合均匀、避免产生臭气等的潜在优点。     

Experimental Study of the Controlling Characteristics of Inverter-Driven Multi-type Air Conditioner

The controlling algorithm was studied for the inverter-driven multi-type air conditioner using electronic expansion valve (EEV) in outdoor unit. The performance of inverter-driven air conditioner with two different units was investigated by varying the outdoor ambient temperature and compressor speed. Based on the test results, the effect of EEV opening on the indoor unit exit superheat was discussed. For the specified outdoor ambient temperature scope and the EEV opening, the superheats of indoor units decrease with the outdoor ambient temperature rising. Improper distribution of refrigerant into each indoor unit will causes excessive superheat difference between two indoor units. Suggestions were then given for the controlling of the superheat.     

Grain refining mechanism of carbon inoculation on Mg-Al alloy

The processing parameters and refining mechanism of Mg-Al alloy treated with a newly developed carbon inoculant under different conditions were investigated experimentally in this work. Results show that the finest ??-Mg grain in AZ91D alloy can be obtained after processing at about 740°C, and the average grain size of ??-Mg grain decreases from about 180.4 to 85.6 ??m by adding mass fraction w _in = 1% inoculant into melt. However, no evident refinement was achieved with excessive inoculant for Mn-free Mg-9Al alloy. Scanning electron microscope (SEM) photo, energy dispersive spectroscopy (EDS) analysis on the Mn-contained intermediate phase and differential scanning calorimetry (DSC) results indicate that Mn element plays an important role in the heterogeneous nucleation of ??-Mg grain. In the early stage of solidification, Al-Mn-C compound particles formed on the surface of Al₄C₃ nano-particles should be the potential nuclei for primary ??-Mg and probably responsible for the grain refinement achieved in the carbon inoculation process.     

Microstructure and hardness of Ni-xSi alloys

The microstructure and hardness of conventionally solidified Ni-xSi (x = 21.4%, 22%, 24%, 26%) alloys were investigated. The solidification microstructures of different Ni-Si alloys were observed by optical microscope (OM) and scanning electron microscope (SEM) and the phase composition was indentified under the help of energy dispersive X-ray (EDX) analysis. The macro- and micro-hardness of the Ni-Si alloys at room temperature were also examined. The experimental results indicated that both the microstructure and hardness closely depended on the Si content. Due to the vast formation of primary ??-Ni₃₁Si₁₂ phase, the hardness of Ni-26.0%Si alloy was significantly improved compared with that of Ni-21.4%Si eutectic alloy. However, the fracture toughness was greatly weakened simultaneously. The (?? ₁-Ni₃Si+??-Ni₃₁Si₁₂) lamellar eutectoid structure formed in the primary ??-Ni₃₁Si₁₂ phase exhibited better ductility than single ??-Ni₃₁Si₁₂ phase at the cost of relatively small hardness reduction.