雙效溴化鋰吸收式冰水機之熱力經濟學最適化設計

Thermoeconomic Optimization of Double-Effect LiBr Absorption Chillers

楊尚達(Shang-Da Yang)

指導教授 ： 鄭智成

國立臺北科技大學/工程學院/化學工程研究所/碩士(2013年)

摘要

本研究針對雙效平行型與串聯型溴化鋰吸收式冰水機進行熱力學分析與熱力經濟學最適化設計。首先根據系統中各個熱交換器單元質量守恆、能量守恆與狀態方程式建立雙效溴化鋰吸收式冰水機的數學模式，然後以此模式對雙效吸收式冰水機做熱力學分析，計算每個單元中的不可逆性和能量損失情況，並探討整個雙效吸收式冰水系統性能係數(COP)及可用能效率的影響。
最後以熱力經濟學的概念對雙效吸收式冰水機進行最適化設計，此方法即為結構法。結構法結合了熱力學上的考量以及經濟學上的最適化，其優點為個別單元能夠獨立進行最適化，不必同時考慮整體系統的最適化，同時藉由結構係數的導入，可導出計算冰水機系統中各個單元最適化熱交換器面積方程式。最後以此最適化面積討論系統重要設計參數(循環比、溴化鋰濃溶液濃度及分配比)對性能係數、可用能效率、不可逆性及成本上的影響。模擬結果顯示，經過最適化設計後，雙效溴化鋰吸收式冰水機的年總成本和性能係數都會獲得改善，而能量損失的變化情形則與系統年總操作時間有關，可用能效率會隨年總操作時間之增加而提升。

關鍵字

雙效溴化鋰吸收式冰水機 ； 不可逆性 ； 性能係數(COP) ； 可用能效率 ； 熱力經濟學 ； 最適化設計 ； 結構法

並列摘要

This study presents the thermodynamic analysis and thermoeconomic optimization of double-effect (parallel-type and series-type) lithium bromide (LiBr) absorption chillers. The mathematical model of double-effect LiBr absorption chillers is first established based on mass balance relations, energy balance relations, and constitutive state equations of each heat exchanger unit. Then, this study analyzes the thermodynamic properties of the double-effect absorption chiller, and calculates the irreversibility and energy loss of each unit. The effects of the coefficient of performance (COP) and exergy efficiency are investigated.
This study conducts the optimum design of the double-effect absorption chiller using a thermoeconomic method, known as the structural method. This method not only takes the thermodynamic considerations into account but also considers the economic optimization. The advantage of using the structural method for thermoeconomic optimization is that the various elements of the system can be optimized on their own. A simple equation to calculate the optimum area of each heat exchanger can be derived by introducing the coefficient of structural bond (CSB). The effects of important design parameters of the system (solution circulation ratio, LiBr concentration and distribution ratio) on the coefficient of performance (COP), exergy efficiency, irreversibility and total annual cost are investigated. Simulation results show that the total annual cost and the COP are improved after the optimization. The condition of energy loss depends on the annual operation time so that the exergy efficiency is improved for an increasing annual operation time.

並列關鍵字

double-effect lithium bromide absorption chiller ； irreversibility ； coefficient of performance ； exergy efficiency ； thermoeconomic ； optimization ； structural method

參考文獻

8. 林志謙，溴化鋰吸收式冰水機的熱力學分析與熱力經濟學最適化設計，碩士論文，臺北科技大學化學工程研究所，臺北，2011。

15. M-T. Ke, Absorption chiller, National Taipei University of Technology Department of Energy and Refrigerating Air-Conditioning Engineering.

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