Finite time thermodynamics study and exergetic analysis of ammonia-water absorption systems.
Finite time thermodynamics study and exergetic analysis of ammonia-water absorption systems.
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DOI：
10.1016/j.ijthermalsci.2010.02.005
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发表时间：
2010-07
影响因子：
4.5
通讯作者：
B. L. Lostec;J. Millette;N. Galanis
中科院分区：
文献类型：
--
作者：
B. L. Lostec;J. Millette;N. Galanis
本文介绍了在稳态条件下使用氨水混合物运行的单级吸收机的优化研究。假设蒸发器中的功率、进入四个外部热交换器的外部流体的温度以及这些热交换器的有效性和泵的效率是固定的。结果包括总热导 UAtotas 的最小值以及相应的平均内部温度、整体不可逆性和一系列性能系数 (COP) 值的火能效率。它们表明存在 COP 的三个最佳值：第一个最小化 UAtot，第二个最小化整体不可逆性，第三个最大化火能效率。他们还表明，这三个 COP 值低于最大 COP，这对应于内部和外部温度趋向于一个共同值。还评估了各种参数对热交换器的最小热导和相应的火用效率的影响。从放热的角度来看，降低解吸器和蒸发器的温度并提高冷凝器和吸收器的参数值是有意义的。然而，如果希望保持恒定的 COP，这些变化必须伴随着总 UA 的显着增加。工作流体和溶液之间的内部热交换器提高了吸收装置的总体火用效率和性能系数。
This paper presents an optimization study of a single stage absorption machine operating with an ammonia–water mixture under steady state conditions. The power in the evaporator, the temperatures of the external fluids entering the four external heat exchangers as well as the effectiveness of these heat exchangers and the efficiency of the pump are assumed fixed. The results include the minimum value of the total thermal conductance UAtotas well as the corresponding mean internal temperatures, overall irreversibility and exergetic efficiency for a range of values of the coefficient of performance (COP). They show the existence of three optimum values of the COP: the first minimises UAtot, the second minimises the overall irreversibility and the third maximises the exergetic efficiency. They also show that these three COP values are lower than the maximum COP which corresponds to the convergence of the internal and external temperatures towards a common value. The influence of various parameters on the minimum thermal conductance of the heat exchangers and on the corresponding exergy efficiency has also been evaluated. From an exergetic viewpoint it is interesting to reduce the temperature at the desorber and at the evaporator and to raise the values of that parameter at the condenser and the absorber. However these changes must be accompanied by an important increase in the total UA if it is desired to conserve a constant COP. The internal heat exchangers between the working fluid and the solution improve both the overall exergy efficiency and the coefficient of performance of the absorption apparatus.