【作者】 许雄文；

【导师】 韩凤琴； 刘金平；

【作者基本信息】 华南理工大学 ， 电站系统及其控制， 2012， 博士

【摘要】 非共沸混合工质制冷在超低温领域应用广泛，对其研究具有深刻的理论和现实意义。混合工质的两相流动将引起当地工质浓度与流动浓度的偏移。本文以两相流动守恒方程为基础，推导并求解当地浓度偏移的数学模型，通过丙烷/异丁烷混合工质J-T制冷机的蒸发器蒸发过程实验对求解结果进行验证；分析其数学模型，本文还得到了两相流动过程中当地浓度的偏移规律。由于两相流动的浓度偏移，制冷循环中循环工质浓度将不同于充注工质浓度，循环工质中重组分浓度偏低而轻组分偏高。另外，在自复叠制冷循环中，J-T节流阀开度变化也会引起循环工质浓度的变化，本文对其进行了近似模拟和分析并在实验中进行了验证。为提高自复叠循环的效率，本文对自复叠循环各换热过程进行了详细分析，并近似计算得出了其理想换热过程；根据自复叠循环的热源温度变化过程，得到了自复叠大温差制冷系统所需的工质特性；最后对大温度滑移的三元混合工质R41/R125/R124混合工质应用于自复叠大温差热泵和自复叠直热式热泵热水器进行浓度和压力优化。混合冷剂组分浓度及运行压力对天然气液化流程运行的安全性及经济性影响很大。为此，本文提出了基于Aspen plus流程模拟，遗传算法智能寻优的优化方法，对SMR混合工质天然气液化流程冷剂组分和运行压力进行了优化。在得到的优化方案的基础上，分析了运行参数对各设计变量变化的敏感度和优化参数下运行系统对环境变化的适应度。另外，本文还对SMR流程不同工况下的运行参数进行优化。首先，在不改变运行压力的前提下，对不同环境下的SMR流程进行冷剂浓度优化，并使优化的冷剂组分浓度对其进冷箱温度（T2）进行线性拟合，得到了（-20~40℃）之间不同工质进冷箱温度下冷剂浓度及其线性回归函数。而当天然气液化负荷变化时，在已知采用的离心压缩机参数的前提下，保持冷剂浓度不变，对不同液化负荷下的运行压力和离心压缩机转速进行优化，并拟合得到离心压缩机转速对液化负荷的二次回归函数。Aspen plus模拟结果表明，以上的拟合函数在对应的工况下都具有较高的运行效率。天然气液化流程的变冷剂浓度分析对于其流程设计和季节性变工况运行具有很好的指导意义，但是，使冷剂浓度根据环境温度进行实时变化并不能轻易实现。鉴于此，本文最后研究了采用纯工质循环预冷混合工质循环深冷的天然气液化流程，调节纯工质预冷循环来适应环境的变化，从而保证混合工质深冷循环稳定运行。这种流程综合利用了纯工质制冷循环的变工况调节性能稳定和混合工质大温差制冷循环效率高的特点。文中分析了其节能的理论基础，并计算分析了其改造投资效益及回收年限。更多还原

【Abstract】 Non-azeotropic refrigeration is widely used in the cryogenic field, of which study is ofinterest from an academic as well as a practical point of view.In the refrigeration cycle, gas-liquid flow with phase transition is inevitable. Intwo-phase flow of mixed working fluid, there will be a difference between local compositionand circulating composition, i.e. composition shift. Based on conservation equations, themathematical model of the composition shift was set up and solved. The result calculated withpropane/I-butane binary mixture was verified by the experiment in the evaporator of arefrigerator. Plus, the composition shift principle was gotten by the analysis from themathematical model. The composition shift makes the difference between the circulatingcomposition and charged composition in a refrigerator. The flowing refrigerant contains somemore low-boiling-point components and some less high-boiling-point components.Additionally, in the auto cascade refrigeration (ACR) process, the variation of J-T valvesopening also causes the change of the circulating composition of refrigerant. This paperapproximately simulated the ACR system, then analyzed and experimentally verified thecirculated composition variation responding to the alteration of the opening of valves.In order to improve the efficiency of ACR system, the causes of low efficiency in ACRexperiment were analyzed, and the ACR process running with the ideal heat transfer processeswas obtained. Then, based on the characters of temperature variation of heat source, thedemands for the properties of mixed refrigerant were analyzed and listed. At last, thecomposition and operating pressures were optimized for the one-stage ACR heat pumpsoperated with large temperature difference using R41/R125/R124ternary-componentsmixture as refrigerant.The refrigerating processes a none-azeotropic as working fluid shares a significantpart in liquefaction field. To optimize the refrigeration process using multi-componentsnon-azeotropic mixture, this paper proposed a new optimization process which applies thecommercial simulation software Aspen plus to simulate the process and searches theoptimal solution using Genetic Algorithm (GA). It was applied to optimize the SMR LNGprocess’s refrigerant composition and running pressures in this paper. In addition, theperformances’ sensitivity to each optimized variable and the solution adaption to theenvironment change were studied. When ambient condition alters, the operating pressureswere fixed, the mixed-refrigerant compositions were optimized under different inlet temperatures of the cold box (T2) and performed linear regression. When the liquefaction loadalters, the refrigerant composition was fixed, the operating pressures were optimized. Thenthe corresponding rotate speeds of centrifugal compressor were calculated and quadraticallyregressed with the liquefaction load.Of course, it is impossible to make the refrigerant composition timely alters as theambient condition changes. Therefore, at last of this paper, the LNG process containingprecooling pure refrigerant cycle and deep-cooling mixed refrigerant cycle was proposed. Itcan adjust the precooling load to adapt the change of ambient condition and sequentially keepthe stability of mixed refrigerant cycle. The process synthesizes the stability of purerefrigerant cycle in load adjustment and high efficiency of mixed refrigerant cycle. Thetheoretical basis of energy saving was proposed and the payback time of the innovation investwas analyzed.更多还原