Application of Finite-Time Thermodynamics and Exergy Method to Refrigeration Systems

• Main Authors: Yih-Feng Su, 蘇益豐
• Other Authors: Chao-Kuang Chen
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/47086220575086026628

博士 === 國立成功大學 === 機械工程學系碩博士班 === 93 === Abstract 　Exergetic efficiency optimization that combines finite-time thermodynamics theory and exergy concept has been applied to an irreversible Carnot refrigeration system, an irreversible Brayton refrigeration system, an irreversible inter-cooled refrigeration system and a two-stage irreversible combined refrigeration system. Multi- irreversiblities considered in these systems include finite rate heat transfer, internal dissipation of the working fluid and heat leak between heat reservoirs. Exergetic efficiency defined as the ratio of rate of exergy output to rate of exergy input of the system is proposed as the objective function to be optimized. The goal of exergetic efficiency optimization is to maximize the objective function. These maximum values of the exergetic efficiency can be determined analytically. The corresponding optimum values of parameters of these systems are obtained simultaneously. These parameters of the system can be effective and important design criteria while evaluating the performance of these refrigeration systems. The influences of design parameters of the system on the maximum exergetic efficiency are discussed. The appropriation of using exergetic efficiency as objective function is discussed. Moreover, in the research of irreversible Carnot and Brayton refrigeration systems, the allocation of a fixed total thermal conductance between the two heat exchangers is discussed using numerical calculation. The results of optimum allocation are also obtained.