功熵与功(火用)

类似于克劳修斯采用由3个等温过程和3个绝热过程组成的可逆热转功循环,建立热向功转换与热量从高温向低温转换的等价定律,并导出克劳修斯等式和熵的方法.本文采用由3个等压过程和3个等容过程组成的可逆功转热循环,建立了功向热转换与功量从高压向低压转换的等价定律,导出了逆循环等式和功熵,并推广至任意可逆的逆循环.系统的体积就是功熵,它是逆循环的核心物理量.类似于(火用)的定义和表达式,定义了新的物理量——功(火用),并借助于逆p-V循环导得了它的表达式.而后阐明了功熵和功(火用)的物理意义,并与热熵和热(火用)的物理意义进行对比.最后介绍了它们在可逆过程性能分析中的应用.

压缩机等熵功的精确计算方法

压缩机的效率是衡量其完善性的重要指标,压缩机的等熵功是计算效率的一个基本参数,因此需要给出精确计算值。本文根据等熵过程始态、终态熵相等的原则,提出了一个计算往复活塞压缩机等熵过程理论循环功的精确计算方法,应用该方法可以提高压缩机效率的计算精度。该方法还可以方便地编制计算机程序。通过实例,对文中提出的精确计算方法和常用的压缩机等熵功计算方法的计算结果进行了比较,并对两者的差别进行了分析。

致冷机的功－熵关系及其应用

在不同热源情况下，对致冷机应用整个系统熵的变化改写热力学第一定律的形式，得到相应的功－熵关系，并讨论了它的一些简单应用．

空气源热泵系统换热器及机组性能的实验研究

基于现有的实验测试平台,实验分析了质流密度、干度、风速、翅片形状、蒸发温度、冷凝温度等实验变量对空气源热泵系统性能的影响规律。经实验验证:强化管内换热特性均优于光滑管,在冷凝换热实验中,管内换热系数与质流密度、干度均成正相关,而在沸腾换热实验中,管内换热系数随干度的增加呈现先增大后减小的变化趋势;3种不同翅型换热器,其换热特性优劣顺序为桥片型翅片换热器、百叶窗型翅片换热器、波纹型翅片换热器,而对于同一翅型换热器,空气侧换热系数与风速呈正相关、与翅片间距呈负相关;工况环境主要通过影响压缩机吸排气饱和压力影响机组性能,即压缩机压缩比的增加导致等熵耗功的增大,进而使系统性能降低。

Properties of Fuzzy Entropy Based on the Shape Change of Membership Function

Modification of a fuzzy partition often leads to the change of fuzziness of a fuzzy system. Researches on the change of fuzzy entropy of a fuzzy set, responding to shape alteration of membership function, therefore, play a significant role in analysis of the change of fuzziness of a fuzzy system because a fuzzy partition consists of a set of fuzzy sets which satisfy some special constraints. This paper has shown several results about entropy changes of a fuzzy set. First, the entropies of two same type of fuzzy sets have a constant proportional relationship which depends on the ratio of the sizes of their support intervals. Second, as for Triangular Fuzzy Numbers （TFNs）, the entropies of any two TFNs which can not be always the same type, also, have a constant proportional relationship which depends on the ratio of the sizes of their support intervals. Hence, any two TFNs with the same sizes of support intervals have the same entropies. Third, concerning two Triangular Fuzzy Sets （TFSs） with same sizes of support intervals and different heights, the relationship of their entropies lies on their height. Finally, we point it out a mistake that Chen＇s assertion that the entropy of resultant fuzzy set of elevation operation is directly to that of the original one while elevation factor just acts as a propartional factor. These results should contribute to the analysis and design of a fuzzy system.

Maximum-entropy clustering algorithm and its global convergence analysis

Constructing a batch of differentiable entropy functions touniformly approximate an objective function by means of the maximum-entropy principle, a new clustering algorithm, called maximum-entropy clustering algorithm, is proposed based on optimization theory. This algorithm is a soft generalization of the hard C-means algorithm and possesses global convergence. Its relations with other clustering algorithms are discussed.

Zero dissipation limit to a Riemann solution consisting of two shock waves for the 1D compressible isentropic Navier-Stokes equations

We investigate the zero dissipation limit problem of the one-dimensional compressible isentropic Navier-Stokes equations with Riemann initial data in the case of the composite wave of two shock waves. It is shown that the unique solution to the Navier-Stokes equations exists for all time, and converges to the Riemann solution to the corresponding Euler equations with the same Riemann initial data uniformly on the set away from the shocks, as the viscosity vanishes. In contrast to previous related works, where either the composite wave is absent or the effects of initial layers are ignored, this gives the first mathematical justification of this limit for the compressible isentropic Navier-Stokes equations in the presence of both composite wave and initial layers. Our method of proof consists of a scaling argument, the construction of the approximate solution and delicate energy estimates.

Optimization of heat transfer and heat-work conversion based on generalized heat transfer law

Examples of heat transfer and heat-work conversion are optimized with entropy generation and entransy loss,respectively based on the generalized heat transfer law in this paper.The applicability of entropy generation and entransy loss evaluation in these optimization problems is analyzed and discussed.The results show that the entransy loss rate reduces to the entransy dissipation rate in heat transfer processes,and that the entransy loss evaluation is effective for heat transfer optimization.However,the maximum heat transfer rate does not correspond to the minimum entropy generation rate with prescribed heat transfer temperature difference,which indicates that the entropy generation minimization is not always appropriate to heat transfer optimization.For heat-work conversion processes,the maximum entransy loss rate and the minimum entropy generation rate both correspond to the maximum output power,and they are both appropriate to the optimization of the heat-work conversion processes discussed in this paper.

Power output analyses and optimizations of the Stirling cycle

Based on the finite time thermodynamics theory,the entransy theory and the entropy theory,the Stirling cycles under different conditions are analyzed and optimized with the maximum output power as the target in this paper.The applicability of entransy loss(EL),entransy dissipation(ED),entropy generation(EG),entropy generation number(EGN) and modified entropy generation number(MEGN) to the system optimization is investigated.The results show that the maximum EL rate corresponds to the maximum power output of the cycle working under the infinite heat reservoirs whose temperatures are prescribed,while the minimum EG rate and the extremum ED rate do not.For the Stirling cycle working under the finite heat reservoirs provided by the hot and cold streams whose inlet temperatures and the heat capacity flow rates are prescribed,the maximum EL rate,the minimum EG rate,the minimum EGN and the minimum MEGN all correspond to the maximum power output,but the extremum ED rate does not.When the heat capacity flow rate of the hot stream increases,the power output,the EL rate,the EG rate and the ED rate increase monotonously,while the EGN and the MEGN decrease first and then increase.The EL has best consistency in the power output optimizations of the Stirling cycles discussed in this paper.

On λ-Power Distributional n-Chaos

For each real number λ∈ [0, 1], λ-power distributional chaos has been in- troduced and studied via Furstenberg families recently. The chaoticity gets stronger and stronger as A varies from 1 to 0, where 1-power distributional chaos is exactly the usual distributional chaos. As a generalization of distributional n-chaos,λ-power distributional n-chaos is defined similarly. Lots of classic results on distributional chaos can be improved to be the versions of λ-power distributional n-chaos accordingly. A practical method for distinguishing 0-power distributional n-chaos is given. A transitive system is constructed to be 0-power distributionally n-chaotic but without any distributionally （n ＋ 1）-scrambled tuples. For each λ∈ [0, 1], ）,-power distributional n-chaos can still appear in minimal systems with zero topological entropy.