Investigation On The First-order Phase Transition Thermomagnetic Power Generation Material MnFe(P,Si) And The Design Of A New Type Of Thermomagnetic Generator

In the world today, electricity is mainly supplied by thermal power, wind power, solar energy and nuclear power, and thermal power holds the dominant position. However, the efficiency of traditional thermal power is about 35%—40%; small portion of the residual energy supply to the city heating and most of the residual energy is lost as waste heat. Moreover, most of the industrial productions also produce large amounts of non recyclable waste heat. If this part of the industrial waste heat can be used for power generation, it is not only in line with the national policy about low-carbon energy, energy conservation and energy re-use, but also has important scientific significance for the efficient use of national resources. While, the thermomagnetic power generation is a new type of power generation model which can directly convert thermal energy into electrical energy. Combining thermomagnetic power generation with existing power generation mode and industrial production would greatly improve the energy utilization, and could even aspire to replace the existing thermal power generation model, and improve the efficiency of power generation.The main content of this paper are as follows:1. The ball-milling technique and solid-state reaction method were used for the preparation of first-order phase transition compound MnFe(P,Si), the phase transition and magnetocaloric effect in this system were studied. The results show that the MnFe(P,Si) compound exhibits Fe2P type hexagonal structure with space group P 62m, and there exist little amount of second-phase of Fe3Si or Fe5Si3 in some of these compounds. MnFeo.9Po.5Sio.5 exhibit single phase and undergoes ferromagnetic-to-paramagnetic and paramagnetic-to-ferromagnetic transition at Ttw= 330 K and Ttc= 318 K, respectively. The thermal hysteresis of this compound is AThys= 12 K. The phase transition is completed in 10 K when heating and cooling, which indicates that the phase transition is first order phase transition. The maximal magnetic entropy change is determined to be-ΔSmax= 18.6 J/(kgK) in the external magnetic field of 0 - 1.5 T. The maximum specific heat capacity is Cp= 1571 J/kgK (heating) and 1447 J/kgK (cooling). So, we can infer that MnFe0.9P0.5Si0.5 compound meets the demand of thermal power generation, which is a candidate material for thermal magnetic power generation with good thermomagnetic power generation performance. See Chapter fourth for details.2. A thermomagnetic generator is designed and manufactured. The prototype is composed of three parts, which are water supply and filtration system, integrated circuit control system and thermomagnetic power generation system. Compared with the previous generation equipment, it substantially increased the working space of the sample, take full advantage of the magnetic field provided by the permanent magnet. Many improvements also have been made to the water supply system. Automatic cycle control of prototype system has been realized by integrated circuit and made a great innovation on design of the sample room and so on. Then put the sample from Bilige, Yujiang Liu and Zhongshen Liu into the thermomagnetic generator which I designed to test the power generation. See Chapter fifth for details.Conclusions:After repeated experiments, it is found that the thermal magnetic power generation is feasible. The power generation current can be expressed by I=-R/μ0NS dt/dMV. Therefore, it is as far as possible to reduce the total resistance of the coil R and increase the cross sectional area of the coil perpendicular to the direction of the magnetic field S by constantly increasing the number of turns of the coil N. Certainly, the most important is to improve the phase transformation efficiency of the sample itself, and ensures that the Curie temperature Tc is in the proper range, increase the change rate of magnetization (?)t/(?)MV-and then increase the power generation current. Moreover, improve the mechanical properties of the samples to ensure that the samples can work continuously and efficiently.At last, although the research on thermomagnetic power generation is still in the embryonic stage, but with the rapid development of various fields of science, also with the indefatigable efforts of many Physics researchers, I believe that the thermomagnetic power generation will leave an indelible mark in the history.