Numerical Simulation Of Thermal Performance Of AMTEC

The Alkali Metal Thermal to Electricity Converter(AMTEC) is a new energy convertion technology. The capillary artery evaporato(rCAV) of AMTEC is one of the most critical components,it is a kind of porous media,it provides impetus for fluid in AMTEC with the capillary force produced by the evaporation of liquid on the interface of liquid and gas.The performance of AMTEC was determined by the temperature of BASE,the pressure drop between the two sides of BASE and the mass flux.Heat and mass transfer of fluid when flowing in AMTEC has an important effect on the performance of AMTEC.This dissertation investigated the heat and mass transfer in AMTEC by numerical simulation,a three-dimensional model was employed to solve this problem.The main work consists of two parts(:1)analysed the performance of the CAV in AMTEC,track the interface between liquid and gas, the evaporation process in CAV was simulated with FLUENT software package by using it's User Define Function(UDF);(2)analysed the output performance of AMTEC,BASE was treated as porous media to simulate the pressure drop between the two sides of it,the endothermic process while thermal converting to electric at BASE zone was also solved by UDF,an energy source program compiled by UDF was used here,the heat flux was associate with the temperature of BASE,the pressure drop between the two sides of BASE and the mass flux of the whole system.Radiation in low pressure chamber was calculated by DO model in FLUENT.This dissertation studied the effect of hot end temperature,cold end temperature and the mass flux on the position of the interface between liquid and gas ,the volume fraction of gas at the exit of CAV and the output performance of AMTEC in detail.As a result,the temperature field,pressure field,volume fraction field and density field under various condition were obtained,and the relation between output performance and these parameters were also shown.Numerical results show that in a range of parameters,CAV is in the stage of funicular evaporation,and is devided into three zones:liquid zone, two-phase zone and gas zone.The closer it stands to the heat wall,the greater temperature gradient is,so the more intense the evaporation is.With the increasing of temperature in hot end and cold end,phase change interface moves towards capillary wick,with the increasing of mass flux it moves towards the high pressure chamber.There are limits to parameters in AMTEC,system will fail to work if some parameters beyond the limits.The output power increases while the hot end temperature or mass flux increases,and it reduces with the increase of cold end temperature.The efficiency of AMTEC increases while the mass flux increase,and reduces with the increase of hot end temperature or the reduction of the cold end temperature.