微粒污垢的特性分析

利用微粒污垢的一个预测模型 ,结合实验结果 ,研究了管壳式换热器管内微粒污垢的积聚特性。考察了颗粒质量分数、颗粒直径和流体速度对渐近污垢热阻的影响。提出了大、中。

弧线管微粒污垢特性的实验研究

微粒污垢的沉积造成换热面流动阻力增大,传热效率降低,腐蚀加剧。文中通过不同流速和微粒浓度下微粒污垢的加速实验,得到了弧线管微粒污垢渐近热阻值和诱导期;同时,用数值方法模拟了弧线管的内部流场和壁面剪切力。结果表明:弧线管微粒污垢的渐近热阻值和诱导期与微粒浓度和流速有关,流速增大、微粒浓度降低,其诱导期延长,渐近污垢热阻减小。而且,在清洁状态、析晶污垢和微粒污垢状态下,弧线管比对应光管都具有良好的传热和阻垢性能,其主要原因是由于弧线管内部流场和壁面剪切力周期性变化所引起的。

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。

颗粒性质对颗粒污垢成垢影响的数值模拟研究

为了探究颗粒性质对换热面上颗粒污垢成垢过程的影响,本文建立了颗粒污垢沉积和剥蚀模型,采用计算流体力学(computational fluid dynamics,CFD)方法,借助Fluent软件,对不同颗粒性质条件下颗粒污垢的沉积过程进行了数值模拟。结果显示,颗粒污垢热阻先增加后平稳,一段时间后达到一个渐近值。随着颗粒密度的增大,结垢速率逐渐减缓,但由于物性参数不同,污垢热阻值呈现不同的变化规律;随着颗粒粒径的增大,结垢速率逐渐减缓,污垢热阻渐近值随之增大;随着颗粒浓度的增大,结垢速率逐渐加快,污垢热阻渐近值也随之增大。由数值模拟结果可知,减小颗粒浓度和粒径可减缓结垢速率,减小污垢热阻渐近值;颗粒种类对污垢热阻的影响较大。该方法对研究污水中多种颗粒沉积规律具有重要意义。

Experimental study on fouling characteristics and influence factors of spiral-grooved tube

In this paper,we carried out a series of experiments on fouling characteristics of 6 kinds of spiral-grooved tubes to investigate the impact of hardness,temperature and structure parameters of cold water on fouling characteristics of spiral-grooved tube.Experimental results showed that when cold-water temperature decreased,fouling resistance of spiral-grooved tube also decreased.Asymptotic fouling resistance increased accompanied with increase of cold-water hardness.However,the asymptotic fouling resistance appeared to reduce when hardness increased to some extent.Geometric parameters of spiral-grooved tubes had remarkable effect on fouling resistance,which showed a tendency of decrease with increase of groove depth and decrease of pitch.In this study,the minimum asymptotic fouling resistance was observed in the spiral-grooved tube with small pitch and large groove depth.