列表法计算发电厂蒸汽管道双层保温经济厚度

发电厂蒸气管道采用双层保温材料可以降低保温投资成本,改善保温结构并延长其使用寿命。双层保温材料经济厚度的计算是一个复杂过程,本文根据经济厚度原理,采用列表法计算了发电厂蒸汽管道双层保温结构的经济厚度。     

电站管道的防冻保温计算与布置

严寒地区的电站管道在冬季面临着冻结和爆管的危险,因此需要全面考虑管道的防冻保温设计。介绍保温层计算和电伴热计算的物理模型和计算方法,并采用Visual Studio(C#)进行了算法的实现。结果表明:保温效果不会随着保温层厚度的增加而无限增大,小管道必须辅以伴热来确保不会结冻,所需加热带的长度需要综合考虑加热带和保温层两者的经济性来选取。指出合理的管道防冻保温布置能够在实现经济性的同时保证电站在冬季安全稳定的运行。     

太阳能热水装置上下水管道的防冻与解冻试验研究

根据目前太阳能热水装置上下水管道现行的防冻与解冻技术的不足,提出新的管道保温结构,从另一个角度出发进行一些基础性对比实验。     

集中供热管道保温厚度优化计算方法探讨

本文从供热管道保温投资效益的角度提出了优化保温层厚度的概念。结合国家最新的保温计算规范,探讨了利用计算机编程优化计算保温层厚度的计算方法,给出了计算机编程计算的计算步骤。这不仅对规划和设计供热管道最佳保温层厚度具有指导意义,而且为利用计算机编程评价供热管道保温的投资经济性和节能效果提供了方向。     

保温结构热工缺陷对管道散热的影响研究

由于施工质量、外力破损、保温材料性能等多方面原因,管道保温结构存在不同程度的热工缺陷。热工缺陷的存在导致保温结构局部外表面温度过高,散热损失过大,对整条管线热损失有一定影响。而目前所进行的管道保温效果测试与评价工作很少考虑保温结构热工缺陷的影响,导致管线散热损失计算存在一定偏差。本文介绍了管道保温结构热工缺陷位置散热损失测试与计算方法,并提出热工缺陷散热附加系数来衡量热工缺陷对管道散热损失的影响,为今后研究保温结构热工缺陷散热损失提供方法指导。     

基于Start-Prot的低温水管道改造应力计算及温降研究

随着长输热力管道项目普及,设计人员需要关注管道直径与管道厚度值,管道的应力分析应受到广泛关注。管道的管径越大,管道保温投资越大,保温层厚度的计算越发重要。基于Start-Prof软件计算9 000 km管道项目的应力,从而确定优化方案;根据《城镇供热直埋热水管道技术规程》（CJJ/T 81—2013）对保温厚度进行计算、校核,研究低温水改造时由热水管道保温厚度发生改变引起的温降。     

基于煤粉管道散热计算的锅炉经济性与耗差分析

以630MW锅炉为例对煤粉管道保温前后散热损失进行计算,保温后散热损失大幅降低,经济性可观;中国南方火电锅炉煤粉管道有必要保温,节能减排意义重大;对不同环境温度下煤粉管道保温前后发电煤耗变化量进行计算并提出拟合曲线,结果表明,发电煤耗变化量与环境温度成直线线性关系,线性公式有效指导不同环境温度下的耗差计算.     

技术市场

技术市场ＪＱＮ双泡洗高效保温板一、简介该产品以聚苯乙烯废弃泡沫塑料为原料，既适用于住宅建筑、公共场所办公楼建筑的外墙复合保温、屋面保温、隔热；也适用于冷库、暖房、活动房、临时工棚的维护建筑，还可用于防冻管道等异型构件，具有广泛的应用前景。北京经贸委办...     

保温管道经济评估的优化设计模型

本文介绍了保温管道经济评估优化设计方案和三个优化设计模型。包括保温管道的单双层结构和最佳保温材料的优化选取,最佳保温层厚度的设计计算。优化设计模型中的传热模型采用管道分段求解方式,管道散热损失的计算分成水平管和竖直管两种,并考虑了支架的散热损失。保温管道的经济模型分为单层结构和双层结构两种。     

室外蒸汽管道泄水阀防冻装置的应用及节能

一、前言 吉林化学工业公司电石厂位于祖国东北吉林省,是大型化工企业。其生产和采暖用架空蒸汽管道遍布整个厂区,泄水阀门多达120个。泄水阀的防冻方法是使阀门靠近蒸汽管道,阀门上部的泄水管长度仅170～180mm,并在泄水管和阀门外面做保温层,借助蒸汽管道的热量来达到阀门在冬季不结冻的目的。但尽管如此,每年冬季都会出现由于少数阀门保温质量差些或保温层破损而未及时发现,在严寒的季节出现阀门冻裂而大量跑蒸汽的现象,只好在严寒季节开启泄水阀使其保持少量排汽状态,以维持泄水阀不冻。鉴于上述情况,根据吉林省冶金设计院在《室外热力泄水阀、排气阀的防冻设计》一文的介绍,结合本厂的具体情况,制作出一种蒸汽管道泄水阀防冻装置,并付诸实用。经过1990年末开始的漫长的严寒冬季的考验,证实了该装置实用效果良好,在装置未做保温层的情况下,阀门一直未结冻。 二、防冻原理     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

Contents in Volume 23,2014

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Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.