管壳式换热器污垢热阻分析及数值模拟研究

Analysis and Numerical Simulation of Fouling Heat Resistance of Shell-and-Tube Heat Exchanger

选取一常用的管壳式换热器为研究对象,管程壳程介质分别为常温循环水与高温减顶气。在操作工况下研究了管程内外污垢的对流和热传导热阻,分别建立了无污垢、管内有污垢、管外有污垢和管内外均有污垢等4种情形下的有限元计算模型,在ANSYS Workbench平台进行了瞬态热分析数值模拟,得到了管程内外污垢对换热器热通量和温度分布的影响规律。研究表明:污垢不能降低管内、外的对流换热系数,但污垢显著增大了换热器管程内外的热传导热阻。由于管材与污垢导热系数的差别较大,有污垢的管道一侧的温度梯度较大。无污垢管程热通量值比有污垢管程热通量值高出数倍甚至一个数量级。

In this study,a commonly used shell-and-tube heat exchanger was selected as the research object.The mediums inside and outside the tube were medium-temperature circulating water and high-temperature capping gas respectively.The problems of convection and heat conduction and thermal resistance of the fouling inside and outside the tube were studied under operating conditions.On this basis,the finite element calculation models were established in four situations,such as no fouling,fouling inside the tube,fouling outside the tube,and fouling inside and outside the tube.The numerical simulation of transient thermal analysis was carried out on ANSYS Workbench platform,and the influence law of fouling inside and outside the tube on the heat flux and temperature distribution of the heat exchanger was obtained.It is found that fouling cannot reduce the convective heat transfer coefficient inside and outside the tube,but the presence of fouling significantly increases the heat conduction and thermal resistance inside and outside the tube of the heat exchanger.Due to the large difference between the thermal conductivity of the tube and the fouling,the temperature gradient on the side of the tube with the fouling is large.The heat flux value of the non-fouling tube side is several times or even an order of magnitude higher than the heat flux value of the fouling tube side.