Design and preparation of aluminum alloy with high thermal conductivity based on CALPHAD and first-principles calculation

To obtain the aluminum alloy with high thermal and mechanical properties,the effects of alloying elements and the second phases on the thermal conductivity of Al alloys were investigated by CALPHAD and first-principles calculation,respectively.The properties of the second phases,including Young's modulus,Poisson's ratio and minimum thermal conductivity,were systematically studied.Results show that the ranking order of the effects of the alloying elements on the thermal conductivity is Mg>Cu>Fe>Si,and for Al-12Si alloys,the mathematical model of the relationship between the alloying elements and the thermal conductivity can be expressed as λ=ax^(2)-bx+c when the second phase precipitates in the matrix.All kinds of ternary phases of Al-Fe-Si have higher deformation resistance,rigidity,theoretical hardness,Debye temperature and thermal conductivity than the other phases which possibly exist in the Al-12Si alloys.Based on the guidance of CALPHAD and first-principles calculation,the optimized chemical composition of Al alloy with high conductivity is Al-11.5Si-0.4Fe-0.2Mg(wt.%)with a thermal conductivity of 137.50 W·m^(-1)·K^(-1)and a hardness of 81.3 HBW.

Design and Performance Analysis of a Modified Vacuum Single Basin Solar Still

Water is essential to life. The origin and continuation of mankind is based on water. The supply of drinking water is an important problem for the developing countries. Among the non-conventional methods to desalinate brackish water or seawater, is solar distillation. The solar still is the most economical way to accomplish this objective. Tamilnadu lies in the high solar radiation band and the vast solar potential can be utilized to convert saline water to potable water. The sun’s energy heats water to the point of evaporation. When water evaporates, water vapour rises leaving the impurities like salts, heavy metals and condensate on the underside of the glass cover. Sunlight has the advantage of zero fuel cost but it requires more space and generally more equipment. Solar distillation has low yield, but safe and pure supplies of water in remote areas. In this context, the design modification of a single basin solar still has been discussed to improve the solar still performance through increasing the production rate of distilled water. The attempts are also made to increase the productivity of water by using different absorbing materials, depths of water, heat storage medium and also by providing low pressure inside the still basin. They greatly improve the rate of evaporation and hence the rate of condensation on the cooler surface. The theoretical results agree well with the experimental ones.

Adaptive Thermal Comfort in Brazilian Schools by Building Performance Simulation (BPS)

Building performance simulation (BPS) is a crucial tool towards the design of projects better adapted its climatic context. In this sense, the objective of this research is to evaluate a method of thermal comfort analysis of schools in three Brazilian cities using BPS. The methodological procedures involved a literature review, in which the simulation tool and analysis method were chosen. Following simulations with the software DesignBuilder were performed using as study case a standard school typology designed by the General Coordination of Educational Infrastructure (CODIN/FNDE). This article evaluates its percentage occupied comfort hours in 3 reference cities: Cuiabá-MT, Brasília-DF, and Curitiba-PR. The results show respectively, for the cities of Curitiba, Brasília and Cuiabá, percentages of comfort hours of 76%, 70%, and 23%. The research states that the project must have different strategies for different climates. Finally, this article recommends this method should be applied to other cities and buildings.

Theoretical design and experimental verification of high-entropy carbide ablative resistant coating

Composition design of high-entropy carbides is a topic of great scientific interest for the hot-end parts in the aerospace field.A novel theoretical method through an inverse composition design route,i.e.initially ensuring the oxide scale with excellent anti-ablation stability,is proposed to improve the ablation resistance of the highentropy carbide coatings.In this work,the(Hf_(0.36)Zr_(0.24)Ti_(0.1)Sc_(0.1)Y_(0.1)La_(0.1))C1-δ(HEC)coatings were prepared by the inverse design concept and verified by the ablation resistance experiment.The linear ablation rate of the HEC coatings is
1.45μm/s,only 4.78%of the pristine HfC coatings after the oxyacetylene ablation at 4.18 MW/m2.The HEC possesses higher toughness with a higher Pugh's ratio of 1.55 in comparison with HfC(1.30).The in-situ formed dense(Hf_(0.36)Zr_(0.24)Ti_(0.1)Sc_(0.1)Y_(0.1)La_(0.1))O2-δoxide scale during ablation benefits to improve the anti-ablation performance attributed to its high structural adaptability with a lattice constant change not exceeding 0.19%at 2000-2300℃.The current investigation demonstrates the effectiveness of the inverse theoretical design,providing a novel optimization approach for ablation protection of high-entropy carbide coatings.

Structural design and thermal performance simulation of shade roof of double-slope greenhouse for mushroom-vegetable cultivation

A new type of roof structure was developed for the shade room in a double-slope greenhouse used for mushroom-vegetable planting.A simulation model was developed to evaluate the thermal performance of the new roof with an insulation thickness of 0.12 m in Beijing,China.The results showed that(1)the indoor air temperature of the shade room with the newly implemented shade roof was 2.7℃-4.9℃ higher than that of an ordinary shade room during the winter months;(2)The indoor air temperature of the solar room adjacent to the shade room with the new roof was higher than that of the ordinary solar room and the minimum indoor air temperature of the solar room was increased 1.9℃ at winter night;(3)the indoor temperature of the shade room with the new roof design was 2℃-4℃ lower than that of the ordinary shade room during the summer months;(4)Under factory production conditions,which were conducted in a controlled environment to promote the annual growth of the edible fungus,the heating energy consumption of the shade room after the implementation of the new roof structure was reduced by 69.3%,the amounted to total energy savings of 61.3% per year.The new roof structure provided a significant improvement in the thermal environment compared to an ordinary shade room,improved the vegetable growth in the winter,and also significantly reduced the energy consumption and production costs.

Integration system research and development for three-dimensional laser scanning information visualization in goaf

An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.

Satellite Constellation Configuration Design with Rapid Performance Calculation and Ordinal Optimization

Satellite constellation configuration design is a complicated and time-consuming simulation optimization problem. In this paper, a new method called the rapid method for satellite constellation performance calculation is developed by the Hermite interpolation technique to reduce the computing complication and time. The constellation configuration optimization model is established on the basis of the rapid performance calculation. To reduce the search space and enhance the optimization efficiency, this paper presents a new constellation optimization strategy based on the ordinal optimization （00） theory and expands the algorithm realization for constellation optimization including precise and crude models, ordered performance curves, selection rules and selected subsets. Two experiments about navigation constellation and space based surveillance system （SBSS） are carried out and the analysis of simulation results indicates that the ordinal optimization for satellite constellation configuration design is effective.

Finishing Effect on Warmth Property of Cotton/Kapok Blended Knitted Fabric

Nowadays,more and more natural or functional fibers are being investigated due to their utilization in thermal underwear.Kapok fiber is one of the natural cellulosic fibers whose source is the kapok plant. It has hollow body and sealed tail,which exhibits desirable features required for functional textiles of this nature. In this study,cotton / kapok( 80 /20 by mass) blended yarn with two types of yarn size 18. 5 and 14. 8 tex,respectively are knitted into plain stitches. The fabrics are undergone with an optimal preparation plan according to orthogonal design. Then,after dyeing and softening,fabric properties including thermal and water-vapour resistances, wicking property, pilling behaviour, and surface morphology,are tested and scrutinized for their candidacy for thermal underwear. The results showed that cotton / kapok blended fabrics have good thermal resistance which is significantly higher than those of cotton / modal blended fabrics,and the same water vapour resistance compared with cotton / modal blended fabrics which are normally used as underwear. Cotton / modal blended knitted fabrics has better pilling grade than cotton / kapok blended fabrics. Meanwhile, the cotton / kapok blends fabrics have good wicking property. Collectively,it was concluded that cotton / kapok blended fabric was appropriate for thermal underwear. However,the main limitation of these fabrics is their pilling properties.

Predication of 3-D Viscous Flowfield of a Centrifugal Impeller

A three-dimensional viscous code has been developed to solve Reynolds-averaged Navier-Stokes equations. The governing equations in finite volume form are solved by two-step Runge-Kutta scheme with implicit residual smoothing. The eddy viscous is obtained using the Baldwin-Lomax model. A prediction of the 3-D turbulent flow and the performance in the “all-over controlled vortex distribution” centrifugal impeller with a vaneless diffuser has been made for the compressor at design and off-design condition. The predicted effi-ciency is a little higher than the experiment data. These results suggest that the present calculation code is able to determine the flow development in the impeller and also the turbulence model in the centrifugal im-peller should be improved.

运用KCS Initial Design软件包进行总体性能计算

本文讨论了如何将ＫＣＳＩｎｉｔｉａｌＤｅｓｉｇｎ 的几个模块贯穿使用，使之应用于船舶总体性能计算，着重介绍了ＳＰＡＣＥ和ＣＡＬＣ两个核心模块。

基于Design-Expert的UHPC强度及收缩率计算模型研究

为实现关键配比参数调整下超高性能混凝土(UHPC)的性能指标控制并得到各性能之间的相互影响规律,利用软件Design-Expert分析了UHPC的主要性能影响因素,基于主要因素对鮑罗米(Bolomy)公式进行了修正,建立了关于UHPC抗压强度、收缩率的计算模型。结果表明:对UHPC抗压强度、收缩率影响较大的三个配比因素分别为水胶比、胶砂比、粉煤灰掺量;基于主要影响因素,利用Design-Expert对UHPC配合比进行了优化,得到了抗压强度≥176 MPa,且收缩率≤320μm·m-1的UHPC试件;通过主要影响因素构建了Bolomy抗压强度及收缩率计算模型,并由计算数据与实验数据对比分析可知,修正后的Bolomy计算模型,可准确反映出抗压强度及收缩率与各主要影响因素之间的关系。

Thermo-Dynamical Analysis on Electricity-Generation Subsystem of CAES Power Plant

Besides pumped hydropower, Compressed Air Energy Storage (CAES) is the other solution for large energy storage capacity. It can balance fluctuations in supply and demand of electricity. CAES is essential part of smart power grids. Linked with the flow structure and dynamic characteristic of electricity generation subsystem and its components, a simulation model is proposed. Thermo-dynamical performance on off-design conditions have been analyzed with constant air mass flux and constant gas combustion temperature. Some simulation diagrams of curve are plotted too. The contrast of varied operation mode thermal performance is made between CAES power plant and simple gas turbine power plant.

船用金属氢化物储氢技术研究综述

金属氢化物储氢是一种基于化学吸收原理的氢气储存方法,具有高体积储氢密度和高安全性的特点,在船舶储氢领域的应用潜力备受关注。在此背景下,对于金属氢化物储氢技术在船舶上的应用,有着材料性能、反应器性能、热管理系统、成本等一系列有待研究的问题。首先,对金属氢化物储氢技术进行归纳,总结梳理金属氢化物的工作原理及材料性能方面的研究进展,并介绍金属氢化物在船舶上的应用情况;然后,结合氢能船舶的应用环境及需求,分析金属氢化物储氢技术在船舶上应用的技术、经济可行性,并以满足氢能船舶对氢气储量和放氢速率要求为目标,介绍船用金属氢化物储氢系统的研究,包括储氢系统性能研究、储氢反应器结构、反应器结构优化、耦合船舶燃料电池的热管理系统和储氢系统设计思路;最后,结合上述研究内容,对船用金属氢化物储氢系统的研究方向进行总结与展望。

主跨160m铁路网状体系拱桥设计参数影响研究

为研究铁路网状体系拱桥的结构受力性能,以某主跨160 m双线铁路网状体系拱桥为研究背景,采用有限元方法,建立桥梁结构的三维空间仿真分析模型,对比吊杆根数、吊杆倾角、拱肋倾角和矢跨比4种设计参数对桥梁静力性能的影响,讨论结构位移、轴力、弯矩、应力等响应的变化规律。结果表明:吊杆根数的增大能减小活载引起的桥梁竖向位移,但拱圈压应力有所增大;桥梁的最大拉应力和最大压应力均随着吊杆倾角的减小而增大,最大压应力出现在拱肋拱脚位置,吊杆倾角为40°和50°时,吊杆所受拉应力大于钢材容许应力,吊杆倾角大于50°时,梁端短吊杆受压;随着拱肋倾角增大,拱桥拉应力近乎线性增大,压应力有所减小;矢跨比越大,活载作用下跨中挠度越小,桥梁最大轴力和弯矩有一定程度减小,吊杆受到的拉应力也越大,矢跨比为0.14~0.20时,拱桥最小应力绝对值随着矢跨比的增大而减小,而当矢跨比从0.20增大至0.22时,最小应力绝对值则显著增大。

超临界二氧化碳离心压缩机气动设计与性能分析研究进展

超临界二氧化碳(supercritical carbon dioxide,SCO_(2))Brayton循环具有效率高、结构紧凑等优点,在能源动力系统中有着良好的应用前景。离心压缩机作为该循环系统的重要部件,因其运行范围广、单级压比大、效率高等优点同样在能源、动力及化工行业得到广泛的应用。气动设计与性能分析是所有压缩机工作的基础,其包含一维气动设计与分析及全三维CFD(computational fluid dynamics)数值分析等关键部分。相对于传统离心压缩机,近临界点特殊的工质物性为SCO_(2)离心压缩机设计与分析带来了新的挑战。通过对近期相关文献的探讨,综述了SCO_(2)离心压缩机的设计方法以及相关学者的性能分析实验,着重介绍了一维设计方法和三维流动分析中的影响因素,并在综合分析后提出了关于SCO_(2)离心压缩机的设计和性能分析的研究重点。

基于改进多点支撑骨架状态模型的热再生沥青混合料配合比设计

由于就地热再生旧料(Reclaimed asphalt pavement,RAP)的异同性,目前还没有对设计热再生沥青混合料的最合适方法达成共识。因此,通常基于符合高速公路法规中马歇尔沥青混合料设计方法进行设计,这并不能保证充分地利用RAP且需要大量的时间和劳动成本。本工作通过改进多点支撑骨架状态模型提出了一种热再生沥青混合料配合比的设计方法,设计了四种不同RAP掺量下的热再生沥青混合料;然后通过高温车辙试验、浸水马歇尔试验、冻融劈裂试验、小梁弯曲试验和间接拉伸疲劳试验测试不同RAP掺量下的新方法设计的高温稳定性、水稳定性、低温抗裂性和疲劳耐久性等路用性能,并与沥青玛蹄脂(Stone mastic asphalt,SMA)热再生沥青混合料进行对比。结果表明:新方法设计热再生沥青混合料的高温稳定性较SMA提升了10%左右;水稳定性增强了1%~2%;而低温抗裂性有些许的下降,但仍满足规范要求;在RAP掺量小于40%时,新方法设计的热再生沥青的疲劳寿命和SMA相当,当RAP掺量大于40%时,新方法设计的热再生沥青疲劳寿命显著降低;因此确定了新方法设计的最大粒径为16 mm的热再生沥青混合料的最佳RAP掺量为40%左右。

夏热冬冷地区动态传热保温设计室外典型气象参数确定方法

GB50176-2016《民用建筑热工设计规范》中围护结构外墙保温设计采用稳态方法,但夏热冬冷地区由于特有的建筑运行模式,使外墙传热方向发生逆转,故稳态方法难以满足冬季室内热环境水平提升的实际需求。提出一种基于动态传热的冬季外墙保温设计室外计算温度确定方法,探究室外干球温度和太阳辐射逐时波动的最不利组合,将保温设计的目标由“日”提升到“时”。基于典型城市2007-2017年逐时气象数据,以外墙内表面温度的累计不保证天数作为热工设计指标,将累计不保证天数恰好不为0(指各朝向外墙内表面温度低于室内基本热舒适条件下所能允许温差的天数)时作为典型日挑选的依据,并将典型日出现频率最高的日期作为室外计算温度选取的依据,获得冬季保温设计典型日,并获得了典型日计算时长的影响。可为夏热冬冷地区围护结构外墙保温设计室外计算参数的挑选提供理论支撑。

基于插片散热器的某功放单元设计

设计一款可在室内机房环境条件下工作,总热耗约为2700 W,结构紧凑、散热方式简单、散热效果良好,可安装在19寸机柜内的功放单元。依据该功放单元工作原理、内部器件布局、热耗,综合考虑散热与结构要求,设计一种采用组合插片散热器强迫风冷的方案。通过功放模块和电源分组固定安装在分层的3个插片散热器上,同时与设备侧壁形成完整的风道的方式,实现了功放单元的强迫风冷散热;并对该设备进行了热传导与散热理论计算,同时运用仿真软件建立模型,进行数值分析。数值仿真结果显示,该功放单元正常工作热交换达到平衡状态时,功放模块外壳最高温度为64.2℃,满足设计要求。通过实物样机验证了该功放单元基于组合插片散热器结构设计方案的可行性,以及计算、仿真方法的合理性、正确性。

碳化材料的烧蚀性能参数辨识方法

针对碳化材料烧蚀性能参数测量难度大的问题,对基于优化算法的烧蚀性能参数辨识方法进行了研究。根据一维连续模型描述碳化烧蚀材料的内部热响应情况,与公开试验数据进行对比验证,各测量点计算误差均小于15%。采用基函数表征法对材料碳化前后的比热容和导热率进行表征,基函数选取为切比雪夫多项式。根据PICA材料的温度测试试验数据,对材料的热解动力学参数和基函数的待定系数采用遗传算法进行辨识,将辨识得到的材料烧蚀性能参数代入一维连续模型中进行计算,与验证工况下的试验数据进行比对,计算得到的温度曲线平均相对误差小于10%。

基于相变蓄冷技术的冷库供冷系统性能分析

针对现有冷库能耗高的问题,本研究提出了一种基于相变蓄冷技术的冷库供冷系统,通过在电价较低的谷电时段利用蓄冷设备储存冷量,在电价较高的尖电时段释放冷量。对系统冷负荷、蓄冷量、相变材料的用量及流量等关键参数进行了设计计算,并开展了系统运行性能分析。结果表明,与传统风冷直冷型冷库系统相比,该系统在尖峰时段的日均用电量降低了88.6%,高峰时段降低了81.9%,日均用电量节能率高达18.69%,同时日均电费成本降低了46.72%。此外,压缩机的日均启停次数减少了72.48%,系统运行的稳定性得到了改善,有效延长了设备的使用寿命,降低了维护成本,在增强系统稳定性、降低能耗和运行成本方面具有明显优势。