改进保温厚度计算方法的探讨(二)

四、保温层实用厚度的计算方法 1.制订校正系数的导则 (1)节能性。制订保温层理论厚度的校正系数必须首先考虑减少散热损失;并保证在任何地区、任何工况下的长期使用年限内,保温层的散热损失都能符合GB4272的规定。 (2)经济性。将保温层的理论厚度按照不同工况,即保温对象对企业生产的不同功用,从保温后能耗的节省中抽出一小部     

工艺配管的保温厚度计算

<正>在计算输送高温流体的配管的保温层厚度时,其流体的温度降或管道散热量与保温层厚度的关系可由下式计算(请参见图1):一般,在已知保温层厚度,求温度降或散热量时,可直接从式(1)或式(2)计算得出,显然很简单。但是,如果给定温度降或散热量反过来求保温层厚度时,则需用试差法来进行计算,这样就麻烦多了。     

保温层厚度的计算方法

在进行保温设计时,首先要确定保温层的厚度。根据不同的保温目的,保温层厚度可采用不同的方法计算,如表面温度法、允许散热损失法、热平衡法等。按照《设备及管道保温技术通则(国家标准GB4272—84)》规定,为减少保温结构散热损失的保温层厚度,应按“经济厚度”的方法计算。所谓经济厚度,是指保温后的年散热损失费用和投资的年分摊费用之和为最小值时保温层的计算厚     

保温层临界厚度的确定

1前言在化工生产中，当设备及管路在高于或低于周围环境的温度下操作时，常需要保温。通常所采取的保温措施是在设备或管路的外壁上包保温性能好的固体材料作为保温层。一般认为，热损失随保温层厚度的增加而减少。笔者运用数学方法对传热过程进行分析，证明只有当保温层厚度大于某一临界值时，增加保温层的厚度才能减少热损失。而当保温层的厚度小于该临界值时，不仅不能减少热损失，反而会使热损失增加。2热损失与保温层厚度间的关系对保温层的传热如图1所示。对管内流体与环境空气问列传热速率方程式，得：式中L管长，（m）ti、to管内流…     

玻璃熔窑碹顶保温不当造成的玻璃质量事故分析

熔窑碹顶保温可显著提高熔窑的热效率，但保温层过厚时，保温层下层温度较高，若高于所选用的保温材料的熔融温度将会造成比较严重的问题。通过对实际发生的质量事故机理的分析和研究，提示玻璃从业人员在进行窑炉保温设计和施工时，应注意保温层厚度与保温材料性能的关系，防止保温材料熔融而侵蚀主体材料造成损失。     

一种计算油罐保温层经济厚度的简易方法

从经济学的角度利用油罐热损失的基本公式,以没有加保温层所造成的热量损失的情况和加设保温层之后的情况对比,构造出确定保温层最优经济厚度的数学表达式,对其进行适当的处理得出其公式。     

水泥厂保温层经济厚度影响因素探讨

本文以圆筒与平面的保温层经济厚度为研究对象,分析了影响层经济厚度的敏感度的10种因素,得出量化影响规律.研究表明,圆筒和平面保温层经济厚度的计算结果误差与管径及保温层经济厚度都有关系,当管道外径为1000mm（GB/T 8175-2008中之规定）时,二者的相对误差范围在5％～38.6％之间,保温层经济厚度＜200mm时的相对误差在20％以内;热能价格、运行时间、年利率、偿还年限、风速对保温层经济厚度影响不大;但在进行水泥厂保温层经济厚度设计时,必须考虑流体温度、管道外径、环境温度、保温层导热系数以及保温层单位投资价格的影响,进行优化设计.     

寒冷地区除尘器保温层厚度的计算

寒冷地区的除尘器若保温层厚度不够,可能导致工作异常,而其保温层厚度是根据公式计算的。因此,对有关计算公式进行讨论分析,合理确定除尘器的保温层厚度十分必要。1除尘器的传热过程讨论保温层厚度的计算,首先要分析除尘器的传热过程。由于除尘器多为平壁或直径大于2m的筒体,因     

埋地管道总传热系数影响因素研究

利用软件对不同管径的埋地管道总传热系数的因素进行计算,确定管道保温层厚度、保温层传热系数、管道埋深、土壤导热系数因素对管道总传热系数均产生影响,且管径越大,影响越大。管道总传热随管道保温层厚度、管道埋深增大而减小,随管道保温层系数、土壤导热系数增大而增大。各因素的影响程度由大到小依次为：保温层导热系数、保温层厚度、土壤导热系数、土壤埋深。     

架空热油管道保温层厚度计算

建立了管道保温计算的数学模型,通过具体实例,用计算机编程得出大量数据,通过origin8.0软件绘出保温层厚度分别与保温效率、管道总传热系数、保温层表面温度和沿程温降的关系图,不仅直观地体现了保温层厚度对管道传热的影响以及变化趋势,还可以从图中查出任意厚度下的保温情况,为求解热油管道保温层厚度提供一种新方法。     

激光测厚技术在液晶玻璃基板生产中的应用

在液晶玻璃生产过程中,采用激光测厚技术不仅可以大幅度提高玻璃基板品质厚度的测量频率,实现每片基板玻璃厚度一次测量;同时也能反映玻璃基板品质厚度实时的真实性,加快厚度异常对策效率,而且能有力的推动我国光电产业技术及玻璃基板品质的提升。以玻璃基板厚度为研究对象,对激光测厚系统在液晶玻璃基板中的应用进行分析。     

Effect of Bond Thickness on Fracture Behaviour in Adhesive Joints

To study the effects of bond thickness on the fracture behaviour of adhesive joints, experimental investigation and finite element analysis have been carried out for compact tension (CT) and double-cantilever-beam (DCB) specimens with different bond thickness. Fractography and fracture toughness exhibited apparent variations with bond thickness. Numerical results indicate that the crack tip stress fields are affected by bond thickness due to the restriction of plastic deformation by the adherends. At the same J level, a higher opening stress was observed in the joint with a smaller bond thickness (h). Beyond the crack tip region, a self-similar stress field can be described by the normalized loading parameter, J/hσ₀. The relationship between J and crack tip opening displacement, δ, is dependent on the bond thickness. The strong dependence of toughness upon bond thickness is a result of the competition between two different fracture mechanisms. For small bond thickness, toughness is linearly proportional to bond thickness due to the high constraint. After reaching a critical bond thickness, the toughness decreases with further increase of bond thickness due to the rapid opening (blunting) of the crack tip with loading. A simple model has been proposed to predict the variation of toughness with bond thickness.     

煤液化装置管件及阀门的腐蚀监控措施

详细介绍超声波测厚在煤液化装置的运用,对煤液化装置测厚的布点原则、管理方法、数据处理以及重点部位等进行了详细阐述。     

The study of domain walls in Pb3(PO4)2 ferroelastic crystals

A ferroelastic domain between two domain walls do not have arbitrary thickness. There can be a minimum thickness which satisfies the geometrical boundary condition. In our study we suggest the possible minimum thickness of domain between two domain walls. The calculated thickness is compared with the observed thickness by TEM.     

离心机转鼓壁厚的影响因素及参数关系图

离心机转鼓壁厚的计算中,通过影响壁厚各因素大小变化的分析,找出各影响因素变化,对转鼓壁厚影响的程度和关系,并用图线对这些关系进行表述,即参数关系当量图表示,从而通过图线清楚地了解各因素对壁厚的影响情况,以确定适当的转鼓壁厚。     

光学膜保温性能的研究

研究了光学干涉膜对光的选择性,分析了其厚度对最大反射峰的影响。采用自制的隔热效果测试装置对干涉膜的隔热效果进行了测定。研究表明干涉膜反射光的波长范围主要由其厚度决定,随着光学厚度的增加,主要反射光波波长位置逐渐从较短区域向较长区域迁移;在红外灯照射下干涉膜和空白玻璃之间的温差最高可达2.4℃。     

Influence of Layer Thickness on Cohesive Properties of an Epoxy-Based Adhesive—An Experimental Study

Cohesive laws are determined for different layer thicknesses of an engineering adhesive. The shape of the cohesive law depends on the adhesive layer thickness. Of the two parameters of the cohesive law—the fracture energy and the strength—the fracture energy is more sensitive to thickness variation than the strength. The fracture energy in peel mode (Mode I) increases monotonically as the thickness is increased from 0.1 to about 1.0 mm. At an adhesive thickness of 1.5 mm, the fracture energy is slightly lower than for a 1.0 mm adhesive thickness, indicating a maximum between 1.0 and 1.5 mm. In shear mode (Mode II), the thickness dependence is not as strong, but an increasing trend in fracture energy with increasing adhesive thickness is evident. A slight decrease in strength with increasing adhesive thickness is found in both loading modes.     

中空吹塑成型机壁厚控制系统的发展

叙述中空吹塑成型机壁厚控制系统及中空吹塑成型机的发展状况,重点对其壁厚控制器的发展进行介绍,并通过对国内外壁厚控制器现状的比较,归纳出壁厚控制器的发展趋势,最后提出我国壁厚控制系统的发展对策。     

Effect of Bond Thickness on Fracture Behaviour in Adhesive Joints

To study the effects of bond thickness on the fracture behaviour of adhesive joints, experimental investigation and finite element analysis have been carried out for compact tension (CT) and double-cantilever-beam (DCB) specimens with different bond thickness. Fractography and fracture toughness exhibited apparent variations with bond thickness. Numerical results indicate that the crack tip stress fields are affected by bond thickness due to the restriction of plastic deformation by the adherends. At the same J level, a higher opening stress was observed in the joint with a smaller bond thickness (h). Beyond the crack tip region, a self-similar stress field can be described by the normalized loading parameter, J/hσ₀. The relationship between J and crack tip opening displacement, δ, is dependent on the bond thickness. The strong dependence of toughness upon bond thickness is a result of the competition between two different fracture mechanisms. For small bond thickness, toughness is linearly proportional to bond thickness due to the high constraint. After reaching a critical bond thickness, the toughness decreases with further increase of bond thickness due to the rapid opening (blunting) of the crack tip with loading. A simple model has been proposed to predict the variation of toughness with bond thickness.     

Influence of panel/back thickness on impact damage behavior of alumina/aluminum armors

Using modified SHPB device, damage behaviors of alumina/aluminum armors under impact load were studied. The influences of panel/back thickness on the target damage characteristics were investigated. The transmitted stress wave increased and the reflected stress wave decreased distinctly with the increase of back thickness, while the panel thickness variation had little influence on the stress wave propagation features. The vertex angle of ceramic inverted cone increased with the increase of back thickness and decrease of panel thickness, but the number of radial cracks reduced with the increase of back thickness and the decrease of panel thickness. Furthermore, the failure mechanism of the ceramic panels, including the cone and radial cracks formation mechanism was analyzed. A “composite beam” model has been established to estimate the local bending stress. The model calculation showed that the local bending stress is related to the panel thickness, back thickness and the panel/back moduli ratio.