| AMTEC (Alkali Metal Thermal To Electric Converter) is a promising technology for converting heat energy to electric energy directly. It is characterized by high conversion efficiency, no moving parts and low maintenance requirements. Multi-level Capillary Artery Evaporator (MCAV) is one of most important components of the AMTEC. The working fluid absorbs heat energy and vaporizes in the MCAV ,and the capillary force forces the working fluid to move from the low pressure domains to the high pressure domains. So the MCAV properties will seriously affect the AMTEC performance.A axisymmetric two-dimensional mathematical model has been developed based on Dacy's law to simulate the Working fluid flow, heat transfer and phase change phenomena in the MCAV.Source terms have been added in the Continuity equation,Momentum equation and Energy equation to simulate the processes of mass, momentum and energy transfer in the phase change. And the Phase Field Method has been used to track liquid-vapor interface. In this paper,it has not only analyzed the wetting angle on the impact of numerical simulation results, but also studied the heat heat flux, inlet temperature,capillary pump materials and capillary diameters on the capillary pump performance.The simulation results shows that with the increase in heat flux, vapor-liquid interface has the trend to move within the capillary pump, and mass flow is correspondingly improved. However, there is a certain heat flux limit, an overall failure of capillary pump will happen if beyond this limit. As the inlet temperature increases, phase-change interface is also penetrated inside the pump, but a small increase in mass flow. To avoid large fluctuations in the system, it can change the MCAV inlet temperature to adjust the pump performance. In this paper, three different materials capillary pump also has been considered, which are molybdenum, nickel and titanium.The results shows that the material has little impact on phase-change interface location ,but it will seriously affect the MCAV transport capacity because of the different heat transfer coefficients. Finally, the paper shows that MCAV has a higher transmission capacity compared with the single-level capillary pump. |
