共查询到19条相似文献,搜索用时 750 毫秒
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本文通过分析三管伴随保温输油管线的传热特征,推导出保温层厚度与单位管长年总分摊费用之间的关系式,并采用0.618法求最优保温层经济厚度。 相似文献
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保温对于节能关系重大,关键是在设计施工中选好保温材料,作好保护层。本文对几种保温材料的性能、特点作了介绍,对几种保护层的施工方法作了比较,并给出了保温层厚度的计算实例。 相似文献
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文章利用有限元软件建立数值模型,研究了不同结构层厚度组合下路面的力学响应,计算了不同结构参数的路面临界降雨强度,并讨论了结构参数对新型双层排水沥青路面排水性能的影响,得到如下结论:(1)不同排水层和防水层的厚度组合工况下路面结构的整体受力情况相同,排水层和防水层的厚度组合对新型双层排水沥青路面在车辆荷载作用下的力学响应特性影响很小;(2)影响新型双层排水沥青路面排水能力的因素由强至弱分别为上层空隙率、横坡、下层空隙率、上层厚度,在上层空隙率为20.0%、横坡为6.0%、下层空隙率为20.0%、上层厚度为4.5 cm的工况下,新型双层排水沥青路面的临界降雨强度最大,达到了7.56×10-6 m/s。 相似文献
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随着寒区公路隧道的不断增多,寒区隧道的保温问题也受到广泛重视。为了分析计算此类隧道施工过程中的温度场,验证寒区隧道保温设计的必要性,确定保温设计的经济性和有效性,文章以某市西山隧道为背景,结合东北冻土的热力性质特点,利用大型有限元计算程序Ansys,对寒区隧道进行了模拟分析,并且将计算的理论数据与实际测定的数据进行对比,分析隧道开挖后围岩温度场的分布、初期支护以及二次衬砌的温度变化过程,对隧道保温效果进行评定。数据对比表明,将保温层设置在二次衬砌外侧是比较合理的,但在东北寒区,对于断面半径达7m的大断面隧道,仅使用40 mm厚的PU硬质聚氨酯泡沫板作为保温材料是不合理的。为使设计经济合理,保温材料在径向上可以采用不同的厚度。 相似文献
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从传热学基础理论出发,运用对流传热实验关联式,计算了膨胀节导流筒与烟气、膨胀节外表面与周围环境的对流换热系数,同时以等效辐射换热系数来简化辐射换热,并且对波纹管与隔热层之间的烟气夹层及波纹管与保温层之间的空气夹层的传热方式进行了分析,综合考虑了对流和辐射传热,得出了烟气夹层和空气夹层的当量热导率。采用ANSYS实现几何建模、网格化、加载和求解的自动进行,得出了膨胀节在模拟工况下的温度场分布;研究了结构设计参数的变化对波纹管工作温度的影响,为膨胀节的设计提供了参考依据,以保证膨胀节在管网中安全运行。 相似文献
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寒冷地区隧道温度、渗流规律与冻害预防 总被引:1,自引:0,他引:1
根据试验隧道的温度和水流量测试成果,得出了寒冷季节隧道水流量和隧道衬砌后浅层围岩温度随时间的变化规律。预防隧道冻害应有系统观念,一味提高隧道内温度或衬砌壁后温度未必有利于问题的解决。在试验隧道中采用了冻害综合防治措施,即:(1)加强拱顶围岩注浆;(2)选用低温柔性好的防水板;(3)喷射混凝土表面降糙;(4)采用LV法铺设防水层;(5)施工缝设置可排水止水带;(6)采用直接通至中央排水管的环向排水管并进行局部保温;(7)在衬砌下隅角背后设置保温层;(8)在衬砌壁后预埋电热带穿线管等,取得了良好的综合防冻效果。 相似文献
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为保障海上终端装卸船海底热油管道安全经济运行,引入了国外始于深海油气田开发的流动保障的概念,建立了海底热油管道的水力、热力模型.为了提高计算的准确性,在建立热力模型时,采用变化的比热容进行计算,考虑了含蜡原油结晶潜热的影响;建立水力模型时,考虑了含蜡原油在管内流动的温降过程是蜡结晶的相变过程,采用了分段计算方法.同时,... 相似文献
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This paper presents a novel methodology to control urban traffic noise under the constraint of environmental capacity. Considering the upper limits of noise control zones as the major bottleneck to control the maximum traffic flow is a new idea. The urban road network traffic is the mutual or joint behavior of public self-selection and management decisions, so is a typical double decision optimization problem.The proposed methodology incorporates theoretically model specifications. Traffic noise calculation model and traffic assignment model for O–D matrix are integrated based on bi-level programming method which follows an iterated process to obtain the optimal solution. The upper level resolves the question of how to sustain the maximum traffic flow with noise capacity threshold in a feasible road network. The user equilibrium method is adopted in the lower layer to resolve the O–D traffic assignment.The methodology has been applied to study area of QingDao, China. In this illustrative case, the noise pollution level values of optimal solution could satisfy the urban environmental noise capacity constraints. Moreover, the optimal solution was intelligently adjusted rather than simply reducing the value below a certain threshold. The results indicate that the proposed methodology is feasible and effective, and it can provide a reference for a sustainable development and noise control management of the urban traffic. 相似文献
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We analyze the double moral hazard problem at the joint venture type airport–airline vertical relationship, where two parties both contribute efforts to the joint venture but neither of them can see the other’s efforts. With the continuous-time stochastic dynamic programming model, we show that by the de-centralized utility maximizations of two parties under very strict conditions, i.e., optimal efforts’ cost being negligible and their risk averse parameters both asymptotically approaching to zero, the vertical contract could be agreed as the optimal sharing rule, which is the linear function of the final state with the slope being the product of their productivity difference and uncertainty (diffusion rate) level index.If both parties’ productivities are same, or the diffusion rate of the underlying process is unity, optimal linear sharing rule do not depend on the final state. If their conditions not dependent on final state are symmetric as well, then risk sharing disappears completely. In numerical examples, we illustrate the complex impact of uncertainty increase and end-of-period load factor improvement on the optimal sharing rule, and the relatively simple impact on total utility levels. 相似文献