Analysis Of Flow And Heat Transfer Characteristics Of The Thermal Insulation Structure Of Nuclear Main Pump

Thermal insulation structure(TIS)of nuclear main pump can ensure that the water guide bearing and a bearing seal smooth operation at a lower temperature environment and guide the cooling water to the water guide bearing for cooling and lubrication.In the TIS,the cooling water has played a role in cooling and heat insulation.On the one hand,the cooling water takes away a lot of heat from the TIS to ensure that the temperature inside the TIS does not rise too high.On the other hand,cooling water also play the effect of insulation,preventing the heat of the external environment into the TIS.The control of the flow of cooling water,trade off its thermal conductivity and heat insulation capacity,is conducive to long-term stable operation of the TIS.According to the theory of computational fluid mechanics,the conjugate heat transfer model of TIS is established.The flow field,temperature field and pressure field of different inlet flow are calculated to analyze the influence of different inlet flow on the heat transfer of the heat insulation device.The results show that with the increase of inlet flow rate,the heat insulation capacity of the TIS is also enhanced,and the temperature of the whole TIS tends to decrease.The flow and heat transfer of the TIS of nuclear main pump is very complicated.A plurality of locations of the flow path is connected by a discrete tube distributed in a circumferential direction.Accurate flow analysis of the entire device requires a three-dimensional fine calculation model,which is time-consuming for model meshing and computation.In order to meet the needs of the design and structural optimization of the initial stage of the design,a temperature field approximation method is proposed for TIS containing the circumferential discrete pipelines;witch is based on the equivalent area of through-flow and the equivalent circumferential speed.Compare the results of flow field,temperature field and pressure field.The result of the approximate analysis model is the same as that of the three-dimensional real model.It is suitable to use the approximate analysis model to obtain the result of fluid flow and heat transfer at the early stage of TIS design.An approximate analysis model is used to analyze the size of the throttling gap and the rotational speed of the rotation axis.The results show: The circulating flow increases with the size of the throttling gap.When the circulating flow rate is small,the inlet temperature of the water guide bearing decreases with the increase of the circulating flow rate;when the circulating flow reaches a certain value,the circulating flow has little effect on the inlet temperature of the water guide bearing.