Equivalent Homogeneous Strength Design Of The Plate-fin Heat Exchanger

The Plate-fin heat exchanger(PFHE)with a high efficiency of heat exchange and compact structure is regarded as the promising heat exchange component in the high temperature gas-cooled reactor(HTGR)or other application areas.However,due to the complexity of plate-fin structure,the full-scale high temperature strength design code of PFHE has not been established yet under the service environment of high temperature,pressure and cyclic thermal stress.This paper has established the high temperature strength design method of PFHE based on equivalent homogeneous method.Analytical model of equivalent homogenized constants is derived and then verified.Besides,influences of dimension parameters on these equivalent homogenized constants are discussed.Additionally,equivalent homogeneous strength design application example of PFHE is analyzed.And,the main content and conclusions of this paper are as following:(1)Combined with ASME Section III Subsection NH,the high temperature strength design method of PFHE is established based on the equivalent homogenized method.The tensile tests of short time at room and high temperature,creep and fatigue tests are conducted.It finds that the facture mode contains two categories:facture along the brazed seam and facture from the brazed fillet.Considering the manufacturing quality of plate-fin structure,the stain and stress magnification factors are defined and the value of them are calculated.(2)The analytical model of equivalent homogenized mechanical constants of plate-fin structure is derived by equivalent method and then verified by finite element analysis and experimental.The results of analytical model show a good agreement with that of finite element analysis.As for the calculation results of elastic modulus E_y,it finds that only the fin parallelled to Y-direction can influence the deformation in Y-direction.The result of equivalent elastic modulus E_z shows a good agreement with that of finite element analysis.However,the results of finite element analysis and analytical model are a little higher than those of experimental.The tensile deformation is the dominate deformation mechanism of fins and the the difference caused by neglecting bending can satisfy the demand for engineering application.Influences of dimensional parameters of plate-fin structure on the analytical model of equivalent homogenized constants are discussed.It shows that these equivalent homogenized constants are highly dependent on dimensional parameters.(3)The analytical model of equivalent homogenized thermophysical constants of plate-fin structure is derived.Influences of dimensional parameters of plate-fin structure on the analytical model of equivalent homogenized thermophysical constants are discussed.It shows that these equivalent homogenized thermophysical constants are highly dependent on dimensional parameters.(4)Based on equivalent homogenized constants of plate-fin structure,the homogeneous finite element analysis model and the classical model of PFHE are established in order to validate the homogenized method.It shows that the homogenized method can well predict the macroscopic property of plate-fin structure and enormously reduce the computational time.The equivalent homogeneous strength application example of PFHE is analyzed,and the result of full-scale design is proved to satisfy design criteria for primary stress and creep-fatigue lifetime.