The Visible Research On The Steam Generator Based On A Scaled Experimental Facility

The function of the steam generator(SG)is as heat equipment to transform the main circuit heat to the secondary circuit,make it produce saturated steam to supply the dynamic equipment in the secondary circuit.As the primary loop heat sink for nuclear reactor under normal operating conditions,the secure operation and efficient heat transfer of SG is critical for the the safety of nuclear power plant.However,Because of the giant volum,complex structural,the two-phase flow and boiling heat transfer on secondary side of SG are very complex.For now,the two-phase flow and the mesh problem need to be improved on the numerical simulation.Previous experiments have focused on the syudy of thermal parameters in the local range.Due to the high temperature and high pressure environment of real SG makes it difficult to observe the flow pattern.In order to improve the reliability of SG,such as structural design,operation scheme,etc.,the flow and heat thransfer characteristics of SG need to be researched under operation conditions.This paper is based on the flow pattern of steam generator' secondary side,according to the similarity principle,a visible steam generator experimental faculty was designed and built.Using the PIV device and high speed camera to get the flow pattern of the two-phase flow in the secondary side.The distribution of temperature field in the secondary side were obtained by using the thermocouples.Through the experimental study,the flow phenomena that have not been reported on the secondary side of the SG have been revealed,that is the strong cavity flow in the U-bend region and the transverse flow phenomenon in the straight pipe section.Moreover,we compared the four different feed water ratios(respectively are 1:1,2:3,3:7,1:4 of the cold and hot side's feed water ratio)under the same power condition and got the different flow field distribution.Finding that with the increase of the degree of non-uniform feed water,the temperature field distribution in the subcooled region became uniform,and the phenomenon of cavity flow on the secondary side was reduced.In addition,we added a clapboard in the middle of the U-tubes,then,the phenomenon of two-phase cross flow on the top region has been reduced by this clapboard.According to the experimental results under different conditions,we present two guidelines for thermal design of SG.Guideline 1:The 1:4 ratio of the feed water can effectively reduce the non-uniformity on the flow field and the temperature field.Guideline 2: A clapboard which is arranged in the middle of the U-bend area can effectively block the cavity flow.The two guidelines has important value for reducing the cavity flow of the U-bend area and reducing the flow induced vibration of the heat transfer tube of SG.