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。     

气凝胶绝热毡用于火电厂高温管道保温的设计研究

提出了气凝胶绝热毡新型保温材料的两种保温方案,并将其与常规保温方案对比,研究了不同方案的保温厚度、散热损失和经济性.结果表明,气凝胶绝热毡新型保温材料用于电厂高温管道保温时,可显著减小保温厚度和散热损失.对于鄂州电厂2×1000 MW主蒸汽管道而言,保温厚度由300 mm降低到200 mm,散热损失发电功率减少约15 ...     

聚氨酯预制直埋保温管道散热损失研究

针对聚氨酯预制直埋保温管道散热损失开展实验与数值模拟研究。通过实验测试了聚氨酯预制直埋保温管道的散热损失,同时对输送介质温度、聚氨酯导热系数、土壤温度及其导热系数进行了测试,对影响聚氨酯预制直埋保温管散热损失的相关因素进行分析。并根据实验数据开展数值模拟研究,分析了不同条件对聚氨酯预制直埋保温管道散热损失的影响。研究结果表明:聚氨酯预制直埋保温管道散热损失随输送介质温度的升高而增加,保温管道周围土壤温度与保温管道径向距离成反比,聚氨酯保温材料导热系数对保温管道的散热损失影响较大,土壤导热系数在1.082-1.561 W/m·K时,土壤导热系数与保温管道散热损失成正比,但对保温管道散热损失产生影响较小。     

塔式光热电站系统保温和电伴热设计及选型

在塔式光热电站中，为了减少设备和管道的散热损失，需在电站的设备和管道上设置电伴热以弥补这部分散热损失，以保证设备和管道内的熔盐不凝结。给出了保温和电伴热的设计原则，并以国内某塔式光热电站过热器为研究对象，计算得到多组保温和电伴热设计选型方案，并根据保温厚度和电伴热功率确定了最佳的经济方案。     

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.     

热网管道保温与热化发电之间的相互关系分析

热网管道的保温设计，尤其是长距离热风管道的保温设计，对热网管道设计成功与否显得十分重要。而热电厂供热参数的高低不仅与经济发电相关，更主要的是跟热网的保温、散热损失有关。一般热能工程设计手册中，仅有经济厚度等计算方法介绍，而没有考虑保温散热损失对热化发电的影响。这对集中供热来说是合理的，但对于热电联产来说，似乎有点欠缺。本文试图通过实例分析计算，来说明保温厚度、散热损失、热化发电的相互关系。以期重视热网管道的保温设计、施工，正确处理经济厚度与热化发电的联系，进一步降低消耗，节约能源。     

大庆采油五厂埋地输油管的保温优化

针对大庆采油五厂埋地集输管道保温状况进行了现场运行工况测试,计算了其传热系数、散热损失及动力损失,并通过优化设计软件,以年运行费用和年分摊费用之和的最小为目标函数,优化了保温层厚度,进行了效果比较分析。结果表明:总传热系数降低了85.9%,压降降低了6%,温差降低了81.8%,热流密度降低了91.7%,保温层折旧费用升高了9%,散热损失费用降低了88.8%,动力费用降低了7%,总费用降低了77.8%,每年节约78.6万元,保温层折旧费用通过优化设计后有所提高,但却大大降低了散热损失费用。     

上海石化蒸汽输热管道的实测与评价

通过对上海市石油化工股份有限公司公用事业公司蒸汽输热管道的测试,详细说明了测试方法、散热损失的计算方法.以其中16号管为例,对测试数据进行分析,说明各种测试情况下散热损失的变化情况,并结合管道保温情况综合分析各因素对管道散热损失的影响,从而为蒸汽输热管道的建设和评价及节能改造提供建议和依据.     

蒸汽管道保温技术改造取得成效

衢州化学工业公司年生产用汽量为3.32×10~(15)J,生产用汽由热电厂统一供应,蒸汽外管道(Φ57mm以上)总长11.5km.原保温材料为水泥珍珠岩,围护材料为石棉水泥抹面.为了大幅度降低蒸汽外管道散热损失,节约能源,缓和供汽紧张局面,提高经济效益,在化工部及浙江省计经委的帮助指导下,我公司制订了保温技术改造规划及方针目标,运用了优化设计手段,优选出了最佳的保温隔热材料及围护材料,设计了最佳     

基于牛顿法考虑热价波动的管道保温厚度计算

为了快速计算考虑市场热价波动的管道保温厚度,基于牛顿法编制软件求解管道保温厚度的隐函数。在经济、控制散热损失和控制外表面温度原则下,分别获得了相应的保温厚度,并将其与文献案例进行对比。对比表明:软件计算结果正确可靠;在三种原则下,软件圆整厚度与国标图集厚度吻合。引入热价波动因素后,软件计算速度快,计算结果更准确。在实际工程中加以利用,能提高工作效率。     

保温管道优化程序的建立及优化界面设计

本文介绍了保温管道优化设计方案，优化程序的组成及计算方法，优化界面的构成及实现的功能。     

供热管道保温材料的选择及经济保温层厚度计算

合理选择供热管道的保温材料及经济保温层厚度,对减少管道在输送热媒过程中的散热损失,降低工程造价尤为重要。本文根据国家现行标准和有关规定,对热网保温材料的选择、经济保温层厚度的简便计算方法进行了阐述。为工程实践中在管道保温方面,达到节能降耗,节约投资的目的提供参考。     

稠油地面蒸汽管线热力参数影响及保温厚度优化

提高蒸汽注汽品质和优化保温层厚度是改善地面蒸汽管线热力输运、实现稠油高效开采的关键。建立了油田地面蒸汽管线热力参数计算模型和保温层厚度经济性分析模型,基于分段微元方法求解沿程蒸汽干度、热损等特性参数,分析了锅炉出口蒸汽参数和注汽流量的影响规律,并结合经济厚度法的计算原理优化了保温层厚度。结果表明：提高锅炉出口蒸汽温度和压力,沿程蒸汽干度降低速度变快,沿程热损增加变快,与锅炉出口蒸汽温度313 oC,压力10.2 MPa相比,其热损最大增加11.15%;增加注汽流量,蒸汽干度提升且随管线沿程降幅缩小,等梯度注汽流量差下,高注汽流量时蒸汽干度降幅较小,其降幅为3.58%;经济厚度为0.33m时,其热损费用同比原有厚度可降低68.22%。     

Economic and environmental impacts of insulation in district heating pipelines

The determination of optimum thickness of insulation is often applied to energy technologies and building projects. In this study, the energy, economic and environmental evaluations of thermal insulation in district heating pipeline are discussed. The optimum insulation thickness, energy saving over a lifetime of 10 years, payback period and emissions of CO₂, CO and SO₂ are calculated for nominal pipe sizes and fuel types based on heating loads in Afyonkarahisar/Turkey. The life cycle cost analysis is used to determine the optimum thickness of the pipeline material in order to take into account the change in inflation that directly affect both the cost of pipeline material and fuels depending on fuel type. The results show that the highest value of optimum insulation thickness, energy savings, emissions and the lowest payback period are reached for a nominal pipe size of 200 mm. About three times more energy saving results by making 200 mm nominal pipe instead of 50 mm. Considering the economical and environmental advantages, the geothermal energy is a better choice and then fuel-oil. When thermal insulation is done in a district heating pipeline, there will be a significant reduction of 21% in the amount of CO₂ emitted to the atmosphere.     

Two-dimensional thermal analysis of liquid hydrogen tank insulation

Liquid hydrogen (LH₂) storage has the advantage of high volumetric energy density, while boil-off losses constitute a major disadvantage. To minimize the losses, complicated insulation techniques are necessary. In general, Multi Layer Insulation (MLI) and a Vapor-Cooled Shield (VCS) are used together in LH₂ tanks. In the design of an LH₂ tank with VCS, the main goal is to find the optimum location for the VCS in order to minimize heat leakage. In this study, a 2D thermal model is developed by considering the temperature dependencies of the thermal conductivity and heat capacity of hydrogen gas. The developed model is used to analyze the effects of model considerations on heat leakage predictions. Furthermore, heat leakage in insulation of LH₂ tanks with single and double VCS is analyzed for an automobile application, and the optimum locations of the VCS for minimization of heat leakage are determined for both cases.     

管路保温节能的计算方法研究

推导出单层和双层保温层最适宜厚度的计算公式,介绍了合理选择和布置双层绝热材料以使保温费用最低的方法。     

Comparative performance investigation of integrated collector‐storage solar water heaters with various heat loss reduction strategies

A detailed comparative assessment is reported on the thermal performance of integrated collector‐storage (ICS) solar water heaters with various strategies for reducing top heat losses. The objective of this investigation is to assess and compare heat loss reduction strategies. The shape of ICS solar water heater considered in present investigation is rectangular. The thermal performance of the solar water heater is evaluated and analyzed for the following cases: (1) single glass cover without night insulation; (2) single glass cover with night insulation; (3) double glass cover without night insulation; (4) transparent insulation with single glass cover; and (5) insulating baffle plate with single glass cover. Energy balances are developed for each case and solved using a finite difference technique. The numerical assessment of the system performance is performed for a typical July day in Toronto. Each strategy is observed to be beneficial, reducing top heat losses, and improving system performance. The greatest performance enhancements are observed for the water heater with a single glass cover and night insulation and for the system with a double glass cover and without night insulation. Copyright © 2010 John Wiley & Sons, Ltd.     

一种新的热力管道及其保温层设计方法

利用热经济学的基本原理，对热力管道内介质的输送过程进行了分析，得到了热力管道的年总费用方程，分析了热力管道管径和保温层厚度等因素对年总费用的影响，提出了一种热力管道及其保温层的新的设计方法－同步设计法；从降低输送介质年总费用的角度出发，得到了最佳管径和最佳保温层厚度的计算公式，其结果可供工程设计参考。     

Adjustable insulation for enhancing the performance of phase change materials in buildings

The energy savings of a building roof integrated with a phase change material (PCM) and different insulation strategies are presented in this paper. The proposed roof structure includes a concrete slab with a PCM layer and an air cavity insulation, which can be adjusted according to certain strategies. The adjustable insulation is devised to enable a reduced total heat gain throughout 24 h in summer days, thereby improving the performance of the PCM. The heat gain/loss through the roof with the PCM layer and adjustable insulation is compared with that of the roof with the PCM layer and fixed insulation during a typical year in Hangzhou, China. The effects and optimization of the melting temperature of the PCM are also explored. The simulation results show that, overall, the adjustable insulation can reduce the daily heat flux through the roof by approximately 20% compared with the conventional fixed insulation.     

回填土质对埋地热油管道传热影响的研究

针对不同导热系数的土样回填管沟,忽略管道轴向温降建立二维非稳态传热模型,环境温度采用周期性边界条件。利用有限容积法,对方程进行离散,数值模拟了管道投产第一年内正常运行非稳态传热过程,同时应用"焓-多孔度"技术,并考虑原油凝固潜热对温降的影响,数值模拟了管道停输非稳态温降过程。结果表明:采用导热系数相对较小的土质回填管沟,管壁及保温层外壁热流密度明显减小,而且回填区温度较高散热较慢,由计算的安全停输时间可知,回填土质导热系数越小安全停输时间越长,模拟结果符合实际。