Study on the Influence of Different Momentum Ratios on Cold and Hot Fluid Mixing and Thermal Stress in T-Tube

Abstract In order to study the mixing process of cold and hot fluids in T-tubes with different momentum ratios and its influence on the thermal stress of the tubes, the large eddy simulation (LES) method was used to calculate the temperature fluctuations of the tube wall and tube fluids under different momentum ratios. Then, the thermal fluid–structure coupling calculation is carried out, and the influence rule of different momentum ratios on the thermal stress of T-tube is obtained. The results show that there are two reasons for the greater stress at the joint of the main branch pipe. On the one hand, under the same temperature difference, the larger the momentum ratio, the longer the downstream length, the smaller the temperature gradient, and therefore the smaller the temperature fluctuation, so there will be no huge thermal stress. On the other hand, the case 1 condition has the largest temperature difference compared to the other conditions in this study. The joint action of the two makes the thermal stress of the T-shaped tube reach the maximum under the case 1. Therefore, in order to ensure the safe operation of the nuclear power system and reduce the thermal stress of the pipeline, the momentum ratio of the main branch pipe fluid in the pipeline should be increased as much as possible, and the temperature difference between the cold and hot fluids should be reduced.