Numerical Simulation Of Thermal Hydraulic Performance In Electric Heating Core Simulator

Reactor safety is the precondition for using nuclear energy, and ensuring the safety of the reactor is the basic principle of reactor design and operation. The reactor thermal hydraulic is an important research content in the study of reactor safety. Electric heating core simulation device is a simplified experimental device, which is used for studying the reactor thermal hydraulic characteristics. In this thesis, numerical simulation method is used for researching the thermal hydraulic characteristics in this experimental equipment. The purpose of the study in this paper is to grasp the thermal hydraulic characteristics of the experimental device and to guide the following thermal-hydraulic experiments. Meanwhile, the calculation results will be used for analyzing this experimental device structure design. If the structure design is unreasonable, an optimization scheme will be put forward to.In the paper, PRO/E software is adopted to establish the calculation model, ICEM software is applied to generate mesh, and FLUENT software is selected to carry out the calculation. According to the simulation results, flow filed characteristics in downcomer and lower plenum in this experimental device are studied. From the calculation results, we can analyze the current sharing performance of the uniform flow orifice and support plate, obtain the core inlet flow distribution. We can also learn the coolant flow field and temperature field characteristics in the core and the characteristics of heating rod outer wall temperature distribution. We could grasp the basic hydraulic characteristics of the device by comparing the calculation results of design discharge condition and high flow condition. We could clearly understand the thermal characteristics of experimental device under different heating mode and choose the best modality of heating by comparing the calculation results of uniform heating condition and axial cosine heating condition.The calculation results of the two conditions which are used for studying the hydraulic characteristics show that the coolant flow distribution in the downcomer is not uneven, and the eddy in the lower plenum is more intense and the flow field is more complex with the increase of flow rate. The larger the inlet flow rate is, the greater the impact of the flow field in the lower plenum on the fluid in the outlet zone of the downcomer is. Part of the fluid in the lower plenum will enter the downcomer under the inertia effect, and then changes the flow distribution on the outlet cross-section of the downcomer. The property of the uniform orifice plate is affected seriously by the vortexes in the lower plenum, and the uniform orifice plate performance is unqualified. In the two conditions, the non-uniform degree of coolant flow distribution in the core entrance is still large by the joint action of uniform orifice plate and support plate. The results show that the rod bundle channel is too large, so the fluid velocity is too small. In the core, the fluid mainly flow in the axial of the channel except zones below the support plate and the location of outlet pipe of the coolant. That's because these zones exist transverse flow and fluid mixing.The calculation results of the two conditions which are used for studying the thermal characteristics show that the temperature distribution in the core is uneven and there is a large temperature gradient between heat rods and fluid near the wall. It shows that temperature is much lower in the center of the core, while it is much higher in the core edge. If the total heating power is the same, the maximum temperature of the coolant in cosine heating condition is lower than that in uniform heating condition. In the uniform heating condition,the highest coolant temperature and highest wall temperature of the heated rod are both located in the stagnant area above the hot leg. While in the cosine heating condition,the highest coolant temperature is located in the outlet pipe zone; in the middle of rod the wall temperature, which has a wide range, is higher than other zone of the rod. Through the above comparisons we can know that the axial cosine heating mode is more suitable than the uniform heating mode for the present experiment, and the uniform heating mode is more suitable for the optimized experimental device using the improved scheme.