Abstract:

This paper proposed a method to improve the safety of shell and tube heat exchangers by adding a heat insulation layer at the inlet end of the heat exchange tube. Based on the SIMPLE algorithm, the transient change model of end temperature difference of three?dimensional shell and tube heat exchanger was established, and the effects of the changes of insulation thickness and insulation material on the safety of heat exchanger were compared. The results show that the temperature difference between the two sides of the heat exchange tube is significantly reduced when the pipe end insulation layer is installed, regardless of the material of the pipe end insulation layer; The greater the thickness of the insulation layer at the pipe end and the thermal conductivity of the insulation material, the greater the reduction of temperature difference, instantaneous thermal shock stress and temperature difference thermal stress on both sides of the heat exchange tube, and the higher the safety of the heat exchanger; When the thickness of the pipe end insulation layer is 247.5 mm and the thermal conductivity is 2.090 0 W/(m?K), the maximum instantaneous temperature difference on both sides of the heat exchange pipe can be reduced by 10.1%, the maximum temperature difference can be reduced by 12.5% during stable operation, and the instantaneous thermal shock stress and temperature difference thermal stress can be reduced by 10.1% and 12.5%.

Key words: Heat exchanger, Heat insulation layer, Safety, Thermal stress

摘要：

提出了一种通过在换热管入口端加装管端隔热层来提高管壳式换热器安全性的方法。基于SIMPLE算法，建立了三维管壳式换热器的端部温差瞬态变化模型，研究了隔热层厚度、隔热层材质对换热器安全性的影响。结果表明，与无管端隔热层的换热管相比，加装管端隔热层时，不管是加装何种材质的管端隔热层，换热管两侧温差均明显降低；管端隔热层的厚度及隔热层材料的导热系数越大，换热管两侧温差降幅、瞬时热冲击应力及温差热应力降幅越大，换热器的安全性越高；当管端隔热层厚度为247.5 mm、导热系数为2.090 0 W/(m?K)时，换热管两侧最大瞬时温差可降低10.1%，稳定工作时最大温差可降低12.5%，瞬时热冲击应力和温差热应力可分别降低10.1%和12.5%。

关键词: 换热器, 隔热层, 安全性, 热应力