入口温度对换热器污垢热阻的影响及其修正

为提高污垢热阻测量精度,在分析污垢热阻温差监测法的基础上,研究了循环冷却水入口温度对换热器污垢热阻的影响。通过对污垢热阻测量模型参数进行推算,利用最小二乘法原理对污垢热阻数据进行处理,确定了在线测量污垢热阻的修正方法。修正前污垢热阻数据表明了循环冷却水入口温度与换热器污垢热阻之间呈反比例的关系。针对无垢和有垢两种情况,分别对污垢热阻测量模型进行了修正,结果表明:对于某电厂现场数据和实验室数据,修正效果均使污垢热阻测量值更加准确,证明了修正公式的可靠性。     

板式换热器以松花江水为冷却水条件下的污垢特性

为研究板式换热器在天然水下的污垢特性,实验采用BR0.015F型板式换热器,研究了其在不同的流速和温度下的污垢特性,用扫描电镜观察了已经结垢的换热表面。结果表明：此板式换热器松花江水的污垢类型为渐进型且不存在诱导期,随着流速的增大污垢热阻降低的幅度减小。冷却水温度在27.5～28.5 ℃时污垢热阻较大,温度升高污垢热阻降低;换热表面的混合污垢成片的附着于换热面,有少量的难溶盐析出的晶体生成。     

PTFE管在生活污水中的换热特性研究

研究了浸泡在生活污水中的PTFE管和铝塑管的污垢生长特性和换热性能。根据污垢热阻变化曲线总结出污垢在塑料换热器上生长特性,污垢的生长过程可分为三个阶段:生长阶段,过渡阶段和振荡阶段。通过分析和比较PTFE管和铝塑管的污垢热阻和换热系数,说明了PTFE管在抑制污垢生长和传热性能都优于铝塑管,PTFE材质更适合于污水热能回收系统中。     

Ca~(2+)环境下板式换热器微生物污垢特性

为了研究Ca2+环境下微生物的污垢特性,通过人工配比方法加入Ca Cl2与铁细菌,对板式换热器循环冷却水系统在不同温度、速度和铁细菌浓度下的污垢特性进行了实验研究。结果表明:在Ca2+环境下污垢热阻高于纯铁细菌污垢热阻,且温度越高污垢热阻渐近值越小,流体速度越大污垢热阻渐近值越小,铁细菌浓度越大污垢热阻渐近值越大。     

板式换热器冷却水污垢热阻预测的偏最小二乘回归法

搭建板式换热器冷却水污垢热阻实验台,测得不同时间、流速和温度下天然循环冷却水（松花江水）中铁离子、氯离子、细菌总数、pH值、溶解氧、浊度、电导率等水质参数,随机取一组实验的水质参数作为输入变量,建立换热器冷却水污垢热阻预测的偏最小二乘回归模型,对板式换热器的污垢热阻进行预测。整个实验过程中,热水进口温度为43.5～44.5℃,冷却水进口温度为21.5～22.5℃,流速为0.104 m·s-1,当温度和流速发生变化时,则重新采取数据。经过计算,确立本模型应提取4个潜变量,由此建立了板式换热器冷却水污垢热阻预测模型。预测结果和实验结果最大相对误差在5.11%以内。结果表明偏最小二乘回归算法的污垢模型预测精度高,所建预测模型是合理可行的。     

板式换热器铁细菌生物污垢特性的实验分析

为探讨铁细菌在板式换热器里的污垢规律,对不同流速、温度及浓度下铁细菌在板式换热器内的污垢特性进行了实验研究。结果表明：随着流速的增加,铁细菌的污垢热阻渐近值逐渐减小;随着温度的升高,铁细菌的结垢诱导期明显缩短,结垢速率加快,污垢热阻的渐近值呈减小的趋势;而随着浓度的增加,污垢热阻值呈现明显的增长。     

板式换热器铁细菌生物污垢特性的实验分析

为探讨铁细菌在板式换热器里的污垢规律,对不同流速、温度及浓度下铁细菌在板式换热器内的污垢特性进行了实验研究。结果表明:随着流速的增加,铁细菌的污垢热阻渐近值逐渐减小;随着温度的升高,铁细菌的结垢诱导期明显缩短,结垢速率加快,污垢热阻的渐近值呈减小的趋势;而随着浓度的增加,污垢热阻值呈现明显的增长。     

管壳式蒸汽换热器污垢热阻的影响

在炼油厂的许多装置中,使用蒸汽作为热源加热工艺介质十分普遍,在管壳式蒸汽换热器设计中存在的污垢热阻对换热能力的影响有时被设计人员忽略。本文通过工程实例来阐述污垢热阻对换热器换热能力以及凝结水温度的影响,在需要精确控制被加热介质一侧的换热场合,由于能量守恒以及换热平衡的双重制约,蒸汽的流量以及凝结水温度并不能随意控制,而是与污垢热阻一一对应的。如果换热器选型时选择过大的换热器,很可能导致公用工程介质的出口温度偏离设计值较大,存在隐患,所以换热器的选型过于保守是不良的设计习惯。     

管壳式蒸汽换热器污垢热阻的影响

在炼油厂的许多装置中,使用蒸汽作为热源加热工艺介质十分普遍,在管壳式蒸汽换热器设计中存在的污垢热阻对换热能力的影响有时被设计人员忽略.本文通过工程实例来阐述污垢热阻对换热器换热能力以及凝结水温度的影响,在需要精确控制被加热介质一侧的换热场合,由于能量守恒以及换热平衡的双重制约,蒸汽的流量以及凝结水温度并不能随意控制,而是与污垢热阻一一对应的.如果换热器选型时选择过大的换热器,很可能导致公用工程介质的出口温度偏离设计值较大,存在隐患,所以换热器的选型过于保守是不良的设计习惯.     

海水板式换热器微生物污垢特性的实验研究

海洋生物附着及低速海流等因素直接影响海水换热器换热效果。为研究海水板式换热器的污垢特性,本文采用自行设计的板式换热器实验装置,通过富集培养并分离出硫酸盐还原菌（SRB）,使其附着海水板式换热器设备,并利用扫描电镜及热阻试验台,实验研究了附着污垢层的形成、生长及其换热特性,并对低流速海流环境下换热器的污垢热阻特性进行了对比实验。实验结果表明：污垢层的形成在不同时期其形貌和特征不同。能谱分析显示其组成的元素主要为C、H、O、Ca,是由各种有机物和悬浮颗粒组成。在诱导期后,污垢热阻符合渐进污垢增长模型,1 m/s以内的低流速下污垢热阻随流速增大而增大。     

Heat Exchanger Network synthesis with Detailed Heat Exchanger Design

Pressure drop and fouling are important issues in heat exchanger network synthesis, which are usually neglected. Heat exchangers were designed in detail during the heat exchanger network synthesis, and pressure drop and fouling effects were taken into account. Pinch analysis combined with exergoeconomic analysis was used for determining optimal minimum approach temperature (ΔT_min) for heat exchanger network synthesis. Exergy consumption of heat transfer in HENs was calculated using a subsection integral on balanced composite curves. The heat transfer coefficients of all heat exchangers in the network were calculated iteratively to meet the requirements of optimal area and allowable pressure drops. The proposed method was applied to an industrial case. Numerical results indicate the importance of the detailed design of heat exchangers in HENs synthesis.     

Investigation of Scale Formation in Heat Exchangers of Phosphoric Acid Evaporator Plants

The primary problem in concentrating phosphoric acid is due to fouling on the tube‐side of the heat exchangers of the evaporator units. Scaling on the heat transfer surfaces occurs because of high supersaturation of phosphoric acid liquor with respect to calcium sulphate. A review of the existing literature reveals that no information is available on heat transfer and on crystallization fouling of industrial phosphoric acid solutions. In this investigation, the solubility of different calcium sulphate types in phosphoric acid solution was studied and its dependency on acid concentration and temperature was investigated. A large number of fouling experiments were carried out in a side‐stream of a phosphoric acid plant at different flow velocities, surface temperatures and concentrations to determine the mechanisms, which control the deposition process. After identifying the effects of operational parameters on the deposition process, a model was developed for prediction of fouling resistances. The reaction of calcium sulphate crystallization followed a second order rate with respect to the supersaturation. The activation energy evaluated for the surface reaction of the deposit formation was found to be 57 kJ/mol. The predicted fouling resistances were compared with the experimental data. Quantitative and qualitative agreement between measured and predicted fouling rates is good.     

Constrained thermohydraulic optimization of the flow rate distribution in crude preheat trains

Crude preheat trains are heat exchanger networks which heat the crude oil stream in the petroleum distillation using hot product streams and pumparounds. The final heating step is executed in a furnace. The thermal efficiency of this process is strongly dependent on the crude preheat train performance, and, during the refinery operation, the heat load of the exchangers may decrease due to fouling. Associated to the reduction of the thermal effectiveness of the heat exchangers, fouling also causes an increase of the flow resistances along the thermal equipment. A potential approach to mitigate this problem is based on the optimization of the distribution of the flow rates in the crude preheat train for maximizing the final crude temperature. In this context, this paper presents a constrained nonlinear programming formulation for this task. The equality constraints encompass mass, energy and mechanical energy balances and heat exchanger equations for describing the thermal and hydraulic behavior of the system. The performance of the proposed approach is explored using two examples, a simple network and a crude preheat train based on a real Brazilian refinery.     

型板换热器的传热性能和阻力降特性研究

研究一种新型高效型板换热器 ,对型板换热器的传热特性及阻力降性能等进行了实验研究。通过研究发现 ,型板换热器的传热系数比列管式换热器的传热系数高 5 0 %～ 10 0 % ,阻力降值比传统的列管式换热器低 ,与型板内流体流速的 1 4 4次方成正比     

一项评价污垢对换热器传热性能影响的指标

以热力学第二定律为基础 ,提出了一项评价污垢对换热器传热性能影响的指标———单位传热量的熵增率 ,讨论了洁净状态下的传热单元数Ntuo、冷热流体热容率比R、冗余面积a等参数对换热器在考虑污垢时的传热性能的影响 ,并把不同流型换热器的评价结果进行了比较     

Heat exchanger fouling by olefin-kerosene mixtures

Fouling resistances of solutions of olefins in kerosene were measured on a hot wire probe and an annular probe operating in parallel at liquid temperatures of about 80°C and heat fluxes from 180-350 kW/m². Straight chain terminal olefins, octene-1 and decene-1 showed little fouling, whereas hexadecene-1, and the cyclic olefins 4-vinyl-cyclohexene, indene and dicyclopentadiene all showed marked fouling. The effects of heat flux, air versus nitrogen saturation, and the presence of an inhibitor were determined. The probable mechanism of fouling is discussed.     

微型换热器研究进展

介绍了微型换热器的特点、材料及形式。理论研究表明电子冷却微型换热器存在最佳外形尺寸 ,并给出了一个简单的求解方法。还对微型换热器的冷却方式及其应用研究做了综述     

An experimental study of the air-side particulate fouling in fin-and-tube heat exchangers of air conditioners

An experimental study was conducted to investigate the chronological performance variation such as pressure drop across a heat exchanger and cooling capacity due to the air-side particulate fouling of fin-and-tube heat exchangers for air conditioner evaporators used. Thirty samples of air conditioners used in the field such as inns, restaurants, and offices are collected in chronological order of use. This study was intended to provide factual long-term fouling data under actual operating conditions. It was found that the important parameters to influence the fouling of heat exchangers are the concentration and size of indoor pollutants, the filter efficiency, the hydrophilicity of fin surfaces, fin spacing, and the structure of fins. The pressure drop of heat exchangers increases from year to year due to the deposition of indoor pollutants larger than 1 Μm in size and increases up to 44% in the samples used for 7 years. Also, the air-side particulate fouling degrades the cooling capacity by 10-15% in the samples used for 7 years.     

折流杆换热器抗振性能的分析

对折流杆换热器抗振性能进行剖析,指出折流杆换热器的抗流体诱导振动性能取决于壳程流体流场的基本性质,而不在于其对管子的支承方式。进而指出折流杆换热器的抗振缺陷,并提出了相应的防振措施。     

振荡流热管研究现状及在干燥系统中的应用研究

对振荡流热管及振荡流热管换热器研究现状进行了分析,并时振荡流热管换热器用于干燥余热回收系统进行了研究。结果表明,自激振荡流热管是一种高效的传热元件,利用这种热管研制出的高效换热器完全适用于干燥尾气的余热回收。