Decoupled thermal–hydraulic analysis of an air-cooled separated heat pipe for spent fuel pools under natural convection

An investigation of the decoupled thermal–hydraulic analysis of a separated heat pipe spent fuel pool passive cooling system(SFS)is essential for practical engineering applications.Based on the principles of thermal and mass balance,this study decoupled the heat transfer processes in the SFS.In accordance with the decoupling conditions,we modeled the spent fuel pool of the CAP1400 pressurized water reactor in Weihai and used computational fluid dynamics to explore the heat dissipation capacity of the SFS under different air temperatures and wind speeds.The results show that the air-cooled separated heat pipe radiator achieved optimal performance at an air temperature of 10℃ or wind speed of 8 m/s.Fitted equations for the equivalent thermal conductivity of the separated heat pipes with the wind speed and air temperature we obtained according to the thermal resistance network model.This study is instructive for the actual operation of an SFS.

Analytical solution for the time-fractional heat conduction equation in spherical coordinate system by the method of variable separation

In this paper,using the fractional Fourier law,we obtain the fractional heat conduction equation with a time-fractional derivative in the spherical coordinate system.The method of variable separation is used to solve the timefractional heat conduction equation.The Caputo fractional derivative of the order 0 〈 α≤ 1 is used.The solution is presented in terms of the Mittag-Leffler functions.Numerical results are illustrated graphically for various values of fractional derivative.

Combustion Synthesized Porous Body of Fe_3O_4/Al System by Controlled Microwave Heating and Heating Behavior of the Products

Microwave-induced substitutional combustion reaction was utilized to fabricate porous ceramic composite from Fe_3O_4/Al powder mixtures.The porous composite body was obtained by controlling the combustion reaction progress in a 2.45 GHz single mode applicator.Prior to the fabrication of the porous body,heating behavior of the powder mixtures were studied in the separated electric(E)and magnetic(H)fields.In addition,heating ability of the microwave fabricated porous product was also investigated.Fe_3O_4 powder can be heated up easily in both maximum H and E field, but a better heating was observed in the maximum H field.Regardless of the mixtures ratio(mixing compositions), maximum H field shows better heating characteristics.In E-field heating,temperature of the Fe_3O_4 samples decreased sharply when Al powder was added.However,the same phenomenon was not observed in the maximum H field heating. Thus,fabrication of the porous composite body was carrying out in maximum H field.Through an adequate control of the reaction progress,products with a porous structure consisting of well-distributed metal particles in the alumina and/or hercynite matrix were obtained.Consequently,heating of the fabricated porous composite body was also been successfully carried out in the maximum H field.Product phases and microstructure were the main factors influencing the heating ability of the porous composite body.

Direct TEM Observation of Phase Separation and Crystallization in Cu_(45)Zr_(45)Ag_(10)Metallic Glass

The structural evolution of Cu_（45）Zr_（45）Ag_（10） metallic glass was investigated by in situ transmission electron microscopy heating experiments. The relationship between phase separation and crystallization was elucidated. Nucleation and growth-controlled nanoscale phase separation at early stage were seen to impede nanocrystallization, while a coarser phase separation via aggregation of Ag-rich nanospheres was found to promote the precipitation of Cu-rich nanocrystals.Coupling of composition and dynamics heterogeneities was supposed to play a key role during phase separation preceding crystallization.