基于汽车尾气余热回收的温差发电系统的理论研究

发布时间：2018-10-14 19:01

【摘要】：能源是社会发展的推动力,是人类赖以生存的基础,随着工业化的快速发展,能源的需求量也大大增加。我国是世界上第一大汽车生产和消费国,汽车是生活中非常普及的交通工具,但其燃料燃烧所产生的能量仅有少部分用于驱动车辆运行,不能被有效利用的能量中更是有一部分以尾气形式直接排放到大气中,造成巨大的能源浪费和环境污染。温差发电技术是利用半导体材料的塞贝克效应直接将热能转换成电能的一种技术,具有经济环保、寿命长等优点,在当前节能减排的号召下,温差发电技术在低品位能源的回收利用中发挥着重要的作用。本文就是利用温差发电的基本原理,对汽车尾气中的余热能进行回收和再利用。由于现有的汽车尾气温差电技术在热量传递过程中热损失比较大,导致温差发电器的输出功率和热电转换效率还比较低,根据传热学理论,增加换热面积可起到强化传热的作用,并且考虑到相变换热导热稳定、热阻小的特性,可以为发电器提供稳定热源,优化发电器性能。基于上述原理本文设计了一种充有相变工质的半导体温差发电器结构,建立了以汽车尾气为热源的发电器数学模型,并模拟计算了该结构的输出性能。结果表明,在尾气温度相同的情况下,增大相变换热结构的吸放热端面积比可有效达到强化传热的目的,实现整体输出功率和热电转换效率的提高。但随着尾气温度的升高,优化效果逐渐减弱,所以应该针对不同的尾气温度范围选择相适应的相变工质对传热进行强化。增大尾气流量同样可起到强化传热的作用,且尾气流量越大,相变换热结构对发电器输出性能的优化作用越不明显。同样还计算了发电器自身几何参数对输出性能的影响,得出输出功率随发电器长度的增加存在一个峰值,而热电转换效率则不断减小。增大冷凝段高度会使输出功率先增加后减小,且峰值点对应的冷凝段高度随发电器长度的增加而减小,随蒸发段管数的增加而增加。而热电转换效率随冷凝段高度增加而降低,随蒸发段管数的增加而升高。本文通过对发电器工作性能的研究,总结了输出功率、热电转换效率随尾气温度、流量、发电器几何参数的变化规律,指出了目前研究方面的不足,提出了改进建议,并展望了课题后续的研究计划。
[Abstract]:Energy is the driving force of social development and the basis of human survival. With the rapid development of industrialization, the demand for energy has increased greatly. Our country is the largest automobile production and consumption country in the world, the automobile is a very popular means of transportation in daily life, but only a small part of the energy generated by the burning of its fuel is used to drive the vehicle running. Some of the energy which can not be effectively used is discharged directly into the atmosphere in the form of tail gas, which results in huge energy waste and environmental pollution. Thermoelectric power generation technology is a kind of technology which directly converts heat energy into electric energy by using the Seebeck effect of semiconductor materials. It has the advantages of economic and environmental protection, long life, etc., under the current call of energy saving and emission reduction, Thermoelectric technology plays an important role in the recovery and utilization of low-grade energy. In this paper, the waste heat energy in automobile exhaust is recovered and reused by the basic principle of thermoelectric power generation. Due to the large heat loss in the heat transfer process of the existing thermoelectric technology of automobile exhaust gas, the output power and thermoelectric conversion efficiency of the thermoelectric generator are still relatively low, according to the theory of heat transfer, Increasing the heat transfer area can enhance the heat transfer, and considering the characteristics of stable phase change heat transfer and low thermal resistance, it can provide a stable heat source for the generator and optimize the performance of the generator. Based on the above principle, a structure of semiconductor thermoelectric generator filled with phase change working fluid is designed, and the mathematical model of generator with automobile exhaust as heat source is established, and the output performance of the structure is simulated and calculated. The results show that when the tail gas temperature is the same, the heat transfer enhancement can be achieved by increasing the area ratio of the end-to-end of the phase change heat transfer structure, and the overall output power and the efficiency of thermoelectric conversion can be improved. However, with the increase of tail gas temperature, the optimization effect is gradually weakened, so the heat transfer should be strengthened according to different range of exhaust gas temperature. Increasing tail gas flow can also enhance heat transfer, and the larger the tail gas flow, the less the optimization effect of phase change heat transfer structure on the output performance of generator. The effect of generator geometry parameters on output performance is also calculated. It is concluded that there is a peak value of output power with the increase of generator length, while the thermoelectric conversion efficiency decreases continuously. With the increase of condensing section height, the output power will first increase and then decrease, and the condensing section height corresponding to the peak point will decrease with the increase of generator length and increase with the increase of the number of tubes in the evaporation section. However, the efficiency of thermoelectric conversion decreases with the increase of condensation height and increases with the increase of the number of tubes in evaporation section. In this paper, the variation of output power and thermoelectric conversion efficiency with tail gas temperature, flow rate and generator geometry parameters are summarized through the research on the performance of generator, and the shortcomings of current research are pointed out, and some suggestions for improvement are put forward. The future research plan is also prospected.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM913

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