【作者】 张悦；

【导师】 陈金灿；

【作者基本信息】 厦门大学 ， 理论物理， 2007， 博士

【摘要】 有限时间热力学是现代热力学的一个重要分支,主要研究非平衡系统在有限时间中的能流和熵流的规律。它在开发新能源,发展新技术,保护生态环境等方面都具有重要意义。有限时间热力学可以被应用到许多研究领域,特别在热力学循环的优化设计方面已取得大量研究成果。而布雷顿循环是当今能源转换领域里的支柱型循环系统,具有重要的实际应用价值。本论文分为两个部分,第一部分运用有限时间热力学理论,围绕布雷顿循环的几种不同模型进行分析研究,所得结果为布雷顿循环的优化设计提供了理论依据。第二部分,对两种典型的布朗马达模型作了分析研究,得出了一些有意义的结果。在第一部分,研究了以理想气体为工质的布雷顿制冷循环和动力循环的性能特性,考虑绝热过程和各换热过程中的不可逆因素,对无回热和回热式布雷顿循环的性能进行分析比较,阐明了采用回热过程的优越性,确定了回热器参数适用的范围。建立了以量子费米气体3He为工质的回热式量子不可逆布雷顿制冷循环。对循环的回热特征和性能特性进行了研究,综合分析了绝热过程不可逆性和量子简并性对循环性能的影响,确定了费米布雷顿制冷循环正常运行的压强比界限。对几种有趣的情况做了详细讨论。建立了以顺磁盐为工质的二级磁化布雷顿制冷模型,从顺磁盐的热力学性质出发,导出了重要性能参数的表达式,如输入功,制冷量,性能系数等。分析了中间磁化过程,回热过程以及不可逆绝热过程对循环性能的影响,对循环的制冷率和制冷系数进行了优化分析,确定了循环的优化工作区域以及工质的最优状态参数。建立了一类太阳能驱动热机的广义循环模型,它涵盖了太阳能驱动卡诺,布雷顿,布雷森等热机系统。详细分析了各种不可逆因素对循环性能的影响,包括有限时间热传递,不同传热规律,热漏,热机内部不可逆性等因素。在给定太阳能供热率情况下,以总效率为目标函数对太阳能热机系统的性能进行了优化分析,确定了太阳能热机系统的最佳工作状态。在第二部分,介绍了布朗马达(布朗微热机)的背景知识与研究现状。分析了两种典型布朗马达模型的运行机制。在第一个模型中,热驱动的布朗微热机的空间不对称周期势场可以和不同的热源接触,计算结果表明由动能引起的布朗微热机和热源之间的热交换是不可逆的,效率不能达到卡诺效率。在第二个模型中,布朗马达的不对称周期性势场的温度随时振荡,振荡的时间结构影响粒子定向输运,所得结果表明方形波的振荡结构并不总是最利于粒子的定向输运。更多还原

【Abstract】 Finite-time thermodynamics is a new important branch of the modern thermodynamics. It is mainly used to investigate the laws of energy and entropy flows of non-equilibrium systems in finite time. It is of very important significance for exploiting new energy resources, developing new technologies, protecting natural resources and so on. Finite-time thermodynamics has been applied in many research fields. Especially, a lot of important achievements in the optimal design of thermodynamic cycles have been obtained. The Brayton cycle is the backbone of power cycle systems in the present energy conversion fields, and consequently, has important value in the practical applications.This thesis is composed by two parts. In the first part, the performance of the several models of the Brayton cycle is investigated by using Finite-time thermodynamics and the results obtained here may provide some theoretical basis for the optimal design of the Brayton cycle. In the second part, the two typical models of the Brownian motor are studied and some significant results are obtained.In the first part, the performance characteristics of the Brayton refrigerator and heat engine using the ideal gas as the working substance are investigated, in which the irreversible effects in the adiabatic and other heat-transfer processes are considered. The performance of the Brayton cycle with regeneration and without regeneration is compared. The advantages of using the regenerator are expounded. The reasonable ranges of the parameters in the regenerator are determined. An irreversible model of the Brayton refrigeration cycle working with an ideal Fermi gas 3He is established. The characteristics of regeneration and performance of the cycle are revealed. The influence of quantum degeneracy of the gas and the irreversibility in the adiabatic processes on its performance is analyzed comprehensively. The minimum pressure ratio of the cycle is determined. Some special cases are discussed. A cycle model of two-stage magnetization Brayton refrigerators using a paramagnetic material as the working substance is established. On the basis of the thermodynamic properties of a paramagnetic material, the expressions of some important parameters such as the work input, the refrigeration load and the coefficient of performance (COP) are derived. The influence of the inter-magnetization processes, regeneration processes and the irreversibility in the adiabatic processes on the performance of the cycle is discussed. The refrigeration load and the COP of the cycle are optimized, and the optimally operating region of the cycle and the optimal working parameters are determined. The unified cycle model of a class of solar-driven heat engines is presented. This model may include Carnot cycle, Brayton cycle, Braysson cycle,and so on. Several irreversible effects on the performance of the cycle system are taken into account, which include finite time heat transfer, different heat transfer laws, the heat loss, the internal irreversibilities of the heat engine, and so on. When the heat-supplying rate of the system is given, the performance of the cycle model is optimized by using the overall efficiency of the system as the object function, and consequently, the optimally working states of the solar-driven heat engine system are determined.In second part, the background and research status of Brownian motors are introduced and the operating mechanisms of two typical Brownian motor models are investigated. In the first model, a thermal Brownian micro heat engine is set up, in which the periodic potential is spatially asymmetric and contacted with the alternately changed hot and cold reservoirs. The results obtained show that the heat flow via the kinetic energy of the particles is always irreversible and its efficiency cannot approach the Carnot efficiency. In the second model, the temperature of periodic potential is periodically oscillating and the time structure of oscillation will affect the directed transport of Brownian particles. It is found that the temporal symmetric temperature oscillation may not be the best choice for the directed transport.更多还原