【作者】 陈曦；

【导师】 朱家骅；

【作者基本信息】 四川大学 ， 化学工程， 2006， 博士

【摘要】 利用低位废热节能降耗、减少环境热污染是当前清洁生产技术领域的开发热点之一。决定其经济性的关键是废热的有效利用率，因此需要特别的措施克服低位能传热推动力小的不利因素，最大限度地减少不可逆损失。本文以热力学第二定律为基础，从热力学熵产分析和温度场熵分析两个不同的角度，定量地研究了流动及传热体系的不可逆程度，揭示影响传热推动力的因素。对评价流动及传热体系的热力学完善程度，改进传热系统的热力性能有一定的应用价值。从热力学第二定律出发，根据Prigogine在非平衡态热力学过程及“熵产生”概念基础上完成的任意体系的熵产表达式推广应用于降膜蒸发过程熵产分析，并得到管内降膜蒸发的熵产计算式。引入单位熵产数得到管内降膜蒸发的单位熵产计算式，并在Reynolds数大于1450（C_pμ/λ）^1.06（0.5-0.25ω）^-1情况下得到单位熵产数和雷诺数之间以及单位熵产数和膜径比之间的定量关系，根据数值计算结果揭示了如下规律：①降膜蒸发过程熵产随流体的雷诺数增加先降低再增大，存在最小熵产数，对应的雷诺数为最佳雷诺数Re_opt，此区域为最佳工况区；②降膜蒸发过程熵产随降膜管内液膜厚度减小先降低再增大，也存在最小熵产数，最佳膜径比ω_opt对应的区域也是最佳工况区。为验证以上理论分析模型，本文进行了DAP湿线尾气脱湿—磷酸降膜蒸发的现场实验，获得了长周期运行条件下的实验数据。以30％的磷酸稀溶液为工质，通过Φ30×2×6000传热管内磷酸降膜蒸发实验数据对比，理论分析的模型与实验结果吻合良好，表明本文熵产计算式可以表达降膜蒸发过程的熵产规律，对过程强化过程传热和提高传热效率具有实际应用价值。从玻尔兹曼定律和信息熵的理论出发，以物理场熵的概念为基础，本文定义了温度场熵的概念。并根据物理场熵的计算方法推导出了温度场熵的计算公式。通过与热力学熵的比较可知尽管两者在反映的层次和反映的方式上不同，但是热力学熵产分析和温度场熵都是空间温度梯度的积分表达，二者均能根据温度场的温度分布反映传热推动力的损耗以及流动及传热体系的不可逆程度，因而具有一致性。将此公式应用于矩形散热翅片的研究中，根据翅片表面温度分布函数，计算出翅片表面的温度场熵。并通过其反映的所需传热推动力大小和不可逆程度的定量地描述矩形散热翅片的热力学性能。本文同时研究了翅片自身的特性参数对温度场熵的影响，研究表明在一定的范围内，翅片表面的温度场熵与翅片的导热系数和厚度成反比，与翅片长度成正比。根据矩形翅片热效的计算公式，引入钢、镉和铝三种材质热效的文献数据，得到热效随导热系数、厚度和长度变化的曲线。与温度场熵随翅片自身特性参数的变化趋势相比较可知，矩形散热翅片的温度场熵与其热效一样，不仅能对翅片的热力学性能进行定量描述，而且对优化热力系统设计具有一定的指导意义。通过本文的研究表明熵产分析可以表达流动及传热体系的热力学完善程度，并且得到了现场实验验证。温度场熵理论也能分析和表达流动及传热体系的热力学性能，所获得的结果为改进体系的传热推动力小的不利因素及提高热力系统的传热效率提供了理论依据。更多还原

【Abstract】 Using the low position waste heat energy to reduce environment thermal pollution is one new field of technology development on clean production. Deciding its economic key is the using efficiency of waste heat energy. It needs special methods to overcome the disadvantage factor: lacking driving force for heat transfer of low potential energy, in order that the irreversible loss of system can be furthest reduced. Based on the second law of thermodynamics, the article focuses on two sides: thermodynamics entropy analyzes and temperature field entropy. According to researches on system irreversible loss for heat transfer and fluxion, it finds out the influence factors of driving force for heat transfer. It is valuable to assess the thermodynamics perfect degree of heat transfer and fluxion system and improve thermal performance of heat transfer system.According to the open system entropy production expression, depended on the"entropy production" conception and non-equilibrium state for thermodynamics process which had been demonstrated by Prigogin with the second law of thermodynamics, the analysis method of entropy generation is applied to thermal analysis of falling film evaporation. Through the introduction of unit entropy generation number it can be deduced the mathematical formula of unit entropy generation number in the tube of falling film evaporation. On the condition of Re>1450（C_pμ/λ）^-1.06（0.5-0.25ω）^-1, it obtains the relationships between unit entropy production number and the Reynold’s number or theδ/R which obeys the following rules according to the numerical value calculating result:（1） In the tube of falling film evaporation process, entropy generation reduces firstly along with the increasing of fluid Reynold’s number, then increases. There exists minimum unit entropy generation number which corresponds Re_opt, and this point is optimal working point;（2） Entropy generation complies the similar rule along with the reducing ofωlike Re. There also exists minimum unit entropy generation number which correspondsω_opt.In order to confirm the theoretical analysis model, the industrial experiment of DAP tail gas partial condensation combined with phosphoric acid falling film flow evaporation was carried out, and experimental data could be collected under long-term work conditions. Taking 30% phosphoric acid dilute solution as the working substance, it is proved that the theoretical analysis model and the experimental result tallies good through the empirical datum contrast of falling film flow evaporation experiment in theΦ30×2×6000 pipe that the phosphoric acid passing on. This mathematical formula can express the entropy generation rule in falling film evaporation process, and it has the actual applications for strengthening the force for the heat transfer process and enhancing the thermodynamic efficiency.On researches of Boltzmann law and information entropy theory, this article defined the temperature field entropy concept based on the definition of physical field entropy, and deduced the normal calculating formula about temperature field entropy. Compared with thermodynamics entropy, the analysis on thermodynamics entropy generation and the application on temperature field entropy are coherence, though they are different in levels and methods. Both of them can reflect the irreversible dissipation of driving force for heat transfer and fluxion.This formula can be applied in the thermal research of rectangular fin radiator to calculate the temperature field entropy according to the fin radiator temperature distribution function. It can quantitively express the irreversible loss of rectangular fin radiator for heat transfer by the irreversible dissipation of driving force in process. This article has also studied the influence factors to temperature field entropy. In the certain scope, a quantitative relationship is deduced that temperature field entropy is proportional with heat conduction coefficient and thickness or it is inverse proportional with length.According to formula of fin efficiency, we obtained the working curves ofηvs. L andηvs.σat different materials: steel, cadmium and aluminum. Compared with the change tendency of temperature field entropy along with the fin radiator characteristic parameter, it may be known that the temperature field entropy of rectangular fin radiation can not only reflect system’s thermodynamics capability but also find out the change mechanism of fin efficiency. It is valuable for the actual application to optimize thermal system design.The results of the study can be summarized as the following: the entropy generation analysis may express the irreversible dissipation of driving force and the thermodynamics perfect degree of heat transfer and fluxion system which was proved by experimental data like as the temperature field entropy. According to these obtaining conclusions it is useful for heat transfer and fluxion system to improve the using ratio of driving force and to enhance heat transfer efficiency.更多还原