In this work,the utilization of lattice Boltzmann method(LBM)in the simulation of coupled conduction and radiation heat transfer in composite materials is studied.The novel D3Q30-LBM and D3Q38-LBM models are proposed ...In this work,the utilization of lattice Boltzmann method(LBM)in the simulation of coupled conduction and radiation heat transfer in composite materials is studied.The novel D3Q30-LBM and D3Q38-LBM models are proposed for the simulation of radiative transfer equation(RTE).The LBM-LBM model,coupled finite volume method(FVM)and LBM are compared with the coupled FVM and discrete ordinate method(DOM)for 2D and 3D simulations.The results show that the original D3Q26-LBM is insufficient for the simulation of radiation,and both the D3Q30-LBM and D3Q38-LBM are close to the DOM for the RTE.The LBM can have large errors in the simulation of heat conduction when the relaxation time is large.Thus,its application in the composite materials is limited when the ratio between thermal conductivities of different components is large.The models with LBM for RTE can be more efficient than the FVM-DOM for the simulation of conduction-radiation heat transfer in composite materials.The FVM-D3Q30-LBM model is suggested because of its accuracy and efficiency.展开更多
During the operation of alkaline direct liquid fuel cells,the alkaline electrolyte is usually needed in the anode electrode to accelerate the electrochemical reaction kinetics of the liquid fuel.However,the crossover ...During the operation of alkaline direct liquid fuel cells,the alkaline electrolyte is usually needed in the anode electrode to accelerate the electrochemical reaction kinetics of the liquid fuel.However,the crossover of the alkaline solution in the anode through the anion exchange membrane to the cathode can increase the transfer resistance of the oxygen in the cathode.In order to reduce the crossover of the alkaline solution,the diffusion process of the alkaline solution in the anion exchange membrane needs to be fully understood.In this work,interface models of anion exchange membrane-alkaline electrolytes are established based on the cell structure of the quaternary ammonium polysulfone(QAPS)membrane to simulate the dynamic process of the alkaline solution in the membrane.The effect of the type and the concentration of the alkaline solution on the transportation of the metal ions and OH^-in the membrane are studied.The results show that the agglomeration of Na+is formed more easily than K^+in the interface model.Because of the strong interaction of Na^+on OH^-,OH^-ions appear to be concentrated,resulting in that the diffusion coefficients of the metal ion and OH^-in the in Na^+solution are lower than those in the K^+solution.In addition,with the raised concentration of electrolyte solution,the aggregation degrees of the metal ions and OH^-can be increased,which means an enlarged mass transfer resistance of the components.Furthermore,by adding a polytetrafluoroethylene(PTFE)layer on the QAPS membrane,the distribution of metal ions tends to be concentrated,and the number of hydrophilic channels in the QAPS membrane is reduced,which significantly increases the alkali resistance of the anion exchange membrane.展开更多
文摘In this work,the utilization of lattice Boltzmann method(LBM)in the simulation of coupled conduction and radiation heat transfer in composite materials is studied.The novel D3Q30-LBM and D3Q38-LBM models are proposed for the simulation of radiative transfer equation(RTE).The LBM-LBM model,coupled finite volume method(FVM)and LBM are compared with the coupled FVM and discrete ordinate method(DOM)for 2D and 3D simulations.The results show that the original D3Q26-LBM is insufficient for the simulation of radiation,and both the D3Q30-LBM and D3Q38-LBM are close to the DOM for the RTE.The LBM can have large errors in the simulation of heat conduction when the relaxation time is large.Thus,its application in the composite materials is limited when the ratio between thermal conductivities of different components is large.The models with LBM for RTE can be more efficient than the FVM-DOM for the simulation of conduction-radiation heat transfer in composite materials.The FVM-D3Q30-LBM model is suggested because of its accuracy and efficiency.
基金The work was supported by the National Natural Science Foundation of China(Grant Nos.51806165,51906186).
文摘During the operation of alkaline direct liquid fuel cells,the alkaline electrolyte is usually needed in the anode electrode to accelerate the electrochemical reaction kinetics of the liquid fuel.However,the crossover of the alkaline solution in the anode through the anion exchange membrane to the cathode can increase the transfer resistance of the oxygen in the cathode.In order to reduce the crossover of the alkaline solution,the diffusion process of the alkaline solution in the anion exchange membrane needs to be fully understood.In this work,interface models of anion exchange membrane-alkaline electrolytes are established based on the cell structure of the quaternary ammonium polysulfone(QAPS)membrane to simulate the dynamic process of the alkaline solution in the membrane.The effect of the type and the concentration of the alkaline solution on the transportation of the metal ions and OH^-in the membrane are studied.The results show that the agglomeration of Na+is formed more easily than K^+in the interface model.Because of the strong interaction of Na^+on OH^-,OH^-ions appear to be concentrated,resulting in that the diffusion coefficients of the metal ion and OH^-in the in Na^+solution are lower than those in the K^+solution.In addition,with the raised concentration of electrolyte solution,the aggregation degrees of the metal ions and OH^-can be increased,which means an enlarged mass transfer resistance of the components.Furthermore,by adding a polytetrafluoroethylene(PTFE)layer on the QAPS membrane,the distribution of metal ions tends to be concentrated,and the number of hydrophilic channels in the QAPS membrane is reduced,which significantly increases the alkali resistance of the anion exchange membrane.
