Basic Research On Alkali Metal Thermal-to-Electric Converter With NaK Working Fluid

Alkali Metal Thermal-to-Electric Converter (AMTEC) is a new type of energy converting device of high power density, high efficiency, non-pollution, non-noise and high reliability, which could be suitable for many kinds of heat resources and converts heat energy into electric energy directly.In this thesis, the research progress of AMTEC all over the world was reviewed, the significance of research on NaK-AMTEC was described.The evaluation of electrical characteristics of AMTEC was one of the several important tasks in this thesis. Firstly, the electromotive forces of Na-AMTEC K-AMTEC and NaK-AMTEC were calculated. Secondly, in the category of electrochemical thermodynamics, the electrical and energetic characteristics of NaK-AMTEC, such as output voltage, electrode power density and thermal-to-electric converting efficiency were deduced and compared with Na-AMTEC as well as K-AMTEC. In addition, from the viewpoint of electrochemical kinetics, the electrode polarizing process of AMTEC and its effect on the AMTEC performance were discussed.Parasitical thermal radiation loss is one of the main factors which greatly influences the thermal-to-electric convening efficiency of AMTEC. In order to evaluate the influence of the thermal radiation from outer surface of BASE tube on the thermal-to-electric converting efficiency of AMTEC, a simplified model was used to calculate the net thermal radiation quantities from outer surface of BASE tube in AMTEC with different layer numbers of heat shields.In order to make experimental research on NaK-AMTEC, the methods and technical skills of active brazing were investigated for joining of NaK-BASE tube with a - Al2O3 transition section and a - Al2O3 transition section with metal flange. And, the preparation processing of porous electrode film was studied also.On the basis of solving above problems, the experimental research on NaK-AMTEC cell was conducted. The damage of BASE tube was analyzed, the possible ways to solve this problem were suggested.In the appendixes, the thermophysical properties of three kinds of working fluidof AMTEC (sodium, potassium, and sodium-potassium alloy), the methods and technical skills for preparation of three corresponding beta " alumina solid electrolytes (Na-BASE, K-BASE and NaK-BASE) as well as their ionic and electronic conducting characteristics and electrode materials of AMTEC were described.