Study On Analytical Models And Influential Factors Of Thermal Stress In Tube Sheet Of Heavy Duty Heat Exchanger

Conventional method of tube sheet design is based on elastic shell theory, with the perforated plate replaced by the equivalent imperforated plate, using relatively simple formula, curve and charts for the calculations of design. However, these calculations could not get the thermal stress of tube sheet caused by temperature difference. At present, the temperature of the tube sheet surface, and the bulk temperature and the heat transfer film coefficient are assumed to get the temperature fields using the finite element method. Then the thermal stress fields of the tube sheet are obtained. However, the accuracy of the results is concerned by many researchers.Three analytical models are applied to calculate the temperature field of a U-tube heat exchanger using the finite element method. In the three models, the temperature of the tube sheet surface, the bulk temperature and the heat transfer film coefficient, and the fluid-solid coupled heat transfer simulation are assumed, respectively. Then the thermal stress fields of the tube sheet are obtained in the temperature fields calculated above. The results show the effect of different analytical models on the simulation of the thermal stress field, serving as a reference for accurate tube sheet design.In order to study the influence of the structure size and flow characteristics on the thermal stress of tube sheet, the fluid-solid coupled heat transfer simulation are assumed to study the influence of these factors on the temperature fields and the thermal stress fields of the tube sheet. The results show that, with the increasing thickness, temperature gradient in the middle part of the tube sheet reduces, namely temperature changes more quietly, and the total stress of the tube sheet decreases. With the change of the position of import and export, the temperature distribution and the thermal stress in the tube sheet are affected. The change of the flow field could cause the change of the flow field near the tube sheet, the temperature gradient of the tube sheet is increased with the increase of velocity of flow, and then the thermal stress is also increased. With the change of fluid properties, the temperature distribution and the thermal stress in the tube sheet are affected, and it should be concerned adequately in the process of design. These research results provide basis for the optimization design of the tube sheet in the heat exchanger.