【作者】 刘庆伟；

【导师】 尹洪超；

【作者基本信息】 大连理工大学 ， 热能工程， 2012， 硕士

【摘要】 传统单级氨水吸收式制冷公用工程消耗大,性能系数低,双级氨水吸收式制冷设备多,体积大,钢材消耗多,结构比较复杂,国内一些学者提出了单级氨水吸收式制冷GAX循环以提高系统性能系数,但是该GAX循环需要有较高的热源温度,在低温热源下受到限制,不能利用较低焓值的低温余热。本文在前人研究的基础上,分别从热力学第一定律和热力学第二定律的角度分析低温余热型氨水吸收式制冷HGAX循环,建立其数学模型,讨论系统工况,初始状态参数变化对循环性能的影响。分析总结出HGAX循环在低温余热回收利用中的基本原理和主要优势,以实现低温余热的高效回收利用。本文根据Schulz的氨水溶液饱和气相和饱和液相的状态方程式,分析氨一水工质对的热力学性质,运用vb软件编制计算氨水热力性质的计算程序。通过计算表明该状态方程的计算结果比较接近相关文献中的实验结果。论文通过对低温余热型氨水吸收式制冷HGAX循环理论分析,建立其数学模型,编制计算机程序计算各状态点热力学参数以及各设备的热负荷等,进而计算该系统的热平衡和性能系数。根据HGAX循环状态参数计算结果,进行HGAX循环的性能分析,分别分析发生温度、制冷温度、冷却水温度、中间压力对循环性能的影响,并与传统GAX循环,一般单级循环、中压双效复叠吸收式制冷循环作对比。分析得出HGAX循环在回收低温余热的方面的性能优势。引入夹点分析法分析氨水吸收式制冷系统,利用该方法能够最大程度的回收系统内部循环热,从而提高了系统的性能系数。并对HGAX循环进行热力学第二定律分析,分别从能量的量的方向和质的方向分析该循环的特性。通过具体的火用分析计算得出GAX循环的火用效率和各设备的无量纲火用损失。更多还原

【Abstract】 Traditional single-stage NH3-H2O absorption refrigeration system consumes a large number of utilities. The cop of of which is low. Two-stage NH3-H2O absorption refrigeration system need more devices, larger volume, more steel consumption than the single-stage system. This is more complicated. In order to improve the cop of the absorption refrigeration system, some domestic scholars have proposed a single-stage ammonia GAX absorption refrigeration cycle. However, the GAX cycle need high temperature heat source. Its cop is low when the heat source temperature is not enough high. That is to say, this will be out of work in condition of low temperature exhaust heat. Under such background, there is of necessity to upgrade the equipment. In this paper, a detailed analysis of the ammonia-water HGAX absorption refrigeration cycle from the viewpoint of the first law of thermodynamics and the second law of thermodynamics respectively on the basis of previous studies,. Then the paper sets up a mathematical model for the cycle, including finding out the suitable working condition and the influence of the initial parameters variables. Finally, the paper comes up with the main advantages of the HGAX cycle and applies the model in practical. The specific works are as follows.The paper studies the thermodynamic properties of the refrigerant, according to ammonia water solution saturated vapor and saturated liquid state equation. Then write computational programs of ammonia water thermodynamic properties by VB software. The results accord well with the literature conclusion.The paper establishment a mathematical model of the HGAX cycle and preparation of a computer program to calculate the thermodynamic parameters of each state point and the heat load of each device based on the basic principles of the ammonia water absorption refrigeration cycle, and calculate the heat balance and the cop of the system. According to the status parameter to analysis the performance of HGAX cycle, the heat source temperature, the refrigeration temperature, the cooling water temperature and the intermediate pressure have a significant effect on the cop of the cycle. We compared the cycle with the conventional GAX cycle, general single-stage cycle and the middle pressure double-effect cascade cycle. Even on the low temperature heat source, the coefficient of performance of the HGAX cycle is significantly higher than the traditional cycle. This paper introduces pinch point analysis to analyze the NH3-H2O absorption refrigeration system. The method can recover maximum internal heat form the streams. So using the new method to analyze the NH3-H2O absorption refrigeration system could increase its cop.In this paper the GAX and HGAX absorption refrigeration cycles are studied and compared from the viewpoint of both first and second law of thermodynamics. Exergy analyses were performed in order to calculate the total exergy destruction rate within the cycles and also reveal the contribution of different components to the destructions. In order to evaluate the efficiencies of the cycles at different working conditions, particularly from the viewpoint of the second law, parametric studies were also performed.更多还原