基于工质物性的热力循环性能探索  

The performance of thermodynamic cycles based on the properties of working fluids

作　　者：苏文 赵力 邓帅 

机构地区：[1]天津大学机械工程学院中低温热能高效利用教育部重点实验室,天津300072

出　　处：《科学通报》2018年第2期232-240,共9页Chinese Science Bulletin

基　　金：国家自然科学基金(51476110)资助

摘　　要：工质作为热力循环实现能量转换不可或缺的载体,其物性直接决定了循环性能的高低.为探究工质物性对热力循环的性能影响,首先采用立方型状态方程计算了实际工质的剩余性质,并根据理想气体的热力性质推导了任意状态下工质的热力学参数,进而得到了等容过程、等压过程、等温过程及绝热过程中能量的表达式.在此基础上,针对4个动力正循环,即卡诺循环、朗肯循环、布雷顿循环及斯特林循环,分别推导了循环输出功及效率的表达式,分析了循环性能与温度、工质物性之间的关系.针对工程应用中热力循环完善度偏低的问题,基于状态方程及循环温熵图探索了面向工质特性的热力循环性能极限,为热力循环的实际运行及优化设计提供了理论参考.With the increase of global energy demand,themodynamic cycles,such as Rankine cycle,refrigeration or heat pump,have been widely employed to generate work or transfer heat.Since these cycles generally consist of a linked sequence of state points with physical properties variables,the physical properties of working fluid are essential to the cycle analysis.They directly determine the design of components,the cycle performance,the cycle stability and safety.However,in the thermodynamic analysis,the determination of cycle performance and the calculation of required physical properties are usually seperated.The thermodynamic peroperties of working fluids are often obtained from the complex experimental equations,so that the relationship between the cycle performance and the working fluids has not been established yet.What＇s more,due to the fact that Carnot efficiency doesn＇t contain detailed information on the properties of working fluids,a nature idea emerges how to derive the efficiency limit under the constraint of working fluids.Thus,in this work,the influences of thermodynamic properties on power cycles are investigated and the limiting efficiencys are proposed.In order to derive the cycle performances from the physical properties of working fluids,a general cubic equation of state is employed to obtain the residual properties,such as residual enthalpy,residual entropy and residual internal energy.Thereafter,on the basis of the properties of ideal gas,thermodynamic parameters of working fluids at any state are determined.According to the thermodynamic general relationships,the required heat is obtained for four classical processes,namely isochoric,isobaric,isothermal and isentropic processes.Based on the derived expressions,the output work and cycle efficiency are obtained for power cycles including Carnot cycle,Rankine cycle,Brayton cycle and Sterling cycle.The relationship between the cycle performance and the temperature,the properties of working fluids is developed.As a theoretical upper bound of cycle ef

关 键 词：热力循环 工质物性 性能极限 状态方程 剩余性质 

分 类 号：TK123[动力工程及工程热物理—工程热物理]