普适定常流内可逆制冷机循环模型的(火用)经济性能优化

用有限时间热力学方法分析工作在恒温热源TH、TL之间内可逆普适制冷机循环模型的(火用)经济性能,导出循环利润率与工质温比、制冷系数与工质温比的关系式,和利润率与制冷系数的特性关系.所得结果包含了内可逆Carnot、Diesel、Otto、Atkinson和Brayton制冷循环的有限时间(火用)经济性能.     

包含五种循环的普适定常流内可逆制冷循环最优性能

用有限时间热力学方法分析了一类普适定常流内可逆制冷机循环,导出了存在传热损失时,由一个吸热过程、一个放热过程和两个绝热过程组成的一类普适的定常流内可逆制冷机循环的制冷率、制冷系数、(火用)损失率、(火用)输出率和生态学性能,并由数值计算分析了循环过程对循环性能的影响特点.所得结果包含了内可逆Carnot、Diesel、Otto、Atkinson和Brayton制冷循环的特性.     

普适定常流内可逆制冷机循环模型的炯经济性能优化

用有限时间热力学方法分析工作在恒温热源TH、TL之间内可逆普适制冷机循环模型的炯经济性能，导出循环利润率与工质温比、制冷系数与工质温比的关系式，和利润率与制冷系数的特性关系。所得结果包含了内可逆Carnot、Diesel、Otto、Atkinson和Brayton制冷循环的有限时间炯经济性能。     

包含七类循环的广义不可逆普适制冷循环最优性能

用有限时间热力学理论和方法分析了热漏、热阻和其它不可逆性对定常流普适制冷循环模型性能的影响,导出了由两个绝热过程、两个等热容吸热过程和两个等热容放热过程组成的不可逆制冷循环的制冷率、制冷系数、炯损失率、炯输出率和生态学性能,并由数值计算分析了循环过程对循环性能的影响特点。所得结是包含了存在热阻、热漏和内不可逆损失的Diesel、Otto、Brayton、Atkinson、Dual、Miller和Camot制冷循环的特性。     

基于有限活塞速度的内可逆卡诺热泵循环性能分析与优化

用有限时间热力学理论和方法研究基于有限活塞速度的内可逆卡诺热泵的循环性能,导出了牛顿传热规律下循环最佳供热率和供热系数与活塞速度比的解析关系式,发现供热率与供热系数呈抛物线关系,存在最大供热率及相应的供热系数,与没有考虑活塞速度影响的内可逆卡诺热泵的供热率与供热系数呈递减关系不同。同时通过数值计算分析了热源温比对最佳关系的影响。分析和优化中考虑了循环周期有无限制两种情况。     

广义不可逆卡诺制冷机的有限时间(火用)经济性能优化

本文研究了牛顿定律系统广义不可逆卡诺制冷机的有限时间[火用]经济性能，导出了存在热阻、热漏和其它内不可逆性时卡诺制冷机的最优利润率解析式以及相应的制冷系数界限，并用数值算例分析了热漏等因素对利润率和[火用]经济性能界限的影响。     

联合制冷循环的优化分析

基于有限时间热力学理论,分析由两个内可逆卡诺制冷循环构成的联合制冷循环的优化性能。首先导出联合循环的制冷率与制冷系数的普遍关系，再由它求出活塞式和定常态流两种联合制冷循环在不同约束条件下的基本优化关系，并作了些有意义的讨论，获得一些对实际联合制冷循环有参考价值的新结论，同时还澄清了有关研究中存在的一些问题。     

联合制冷循环的有限时间热力学

研究由两个内可逆卡诺制冷循环构成的无中间热源的联合制冷循环有限时间热力学最优性能。基于一类较为普遍的物理模型，导出其制冷量与制冷系数间的基本关系，再根据活塞式模型循环和定常流模型循环的基本特征，得到两种模型联合到冷循环的最佳制冷率密度与制冷系数间的关系。对前者，与前人所得结果相同；对后者，获得了一些新的有意义的结论。有关结果还可推广到由两个以上制冷循环构成的联合制令循环。     

卡诺制冷机的最佳利润率与制冷系数间的关系

首次将利润率这一经济指标引入制冷机有限时间热力学研究,导出牛顿定律系统卡诺制冷机的最佳利润率与制冷系数间的关系,并得到了最大利润率时的制冷系数界限。借此,提出了有限时间(火用)经济分析的概念。     

内可逆制冷与泵热循环的特征参数

本文用一对特征参数表征内可逆逆卡诺循环的性能,得到了有限时间条件下,内可逆卡诺制冷和泵热循环的性能参数、制冷率和供热率全息谱以及参数选择的有限时间热力学准则。     

Profit rate performance optimization for a generalized irreversible combined refrigeration cycle

Finite-time exergoeconomic performance of a Newtonian heat transfer law system generalized irreversible combined refrigeration cycle model with finite-rate heat transfer, heat leakage and internal irreversibility is presented in this paper. The operation of the generalized irreversible combined refrigeration cycle is viewed as a production process with exergy as its output. The performance optimization of the cycle is performed by taking profit as the objective. The optimal profit rate, optimal COP (coefficient of performance), as well as the relation between the optimal profit rate and COP of the cycle are derived. The focus of this paper is to obtain the compromise optimization between economics (profit rate) and the energy utilization factor (COP) for the cycle, by searching the optimum COP at maximum profit rate, which is termed as the finite time exergoeconomic performance bound. Moreover, the effects of various factors, including heat leakage, internal irreversibility and the price ratio, on the profit rate performance of the cycle are analysed by detailed numerical examples.     

一类回热式布雷顿制冷循环的有限时间热力学性能

研究了恒温热源条件下具有等熵压缩、膨胀过程的闭式回热式布雷顿制冷循环的有限时间热力学性能。导出循环制冷率、制冷系数与循环压比的关系，由此得到最佳制冷率、制冷系数的特性。     

广义不可逆卡诺热泵的有限时间(火用)经济性能优化

本文研究了牛顿定律系统广义不可逆卡诺热泵的有限时间炯经济性能，导出了存在热阻、热漏和其它内不可逆性时卡诺热泵的最优利润率解析式以及相应的供热系数界限，并用数值算例分析了热漏等因素对利润率和炯经济性能界限的影响。     

The effect of refrigerant combinations on performance of a vapor compression refrigeration system with dedicated mechanical sub-cooling

Performance characteristics due to use of different refrigerant combinations in vapor compression cycles with dedicated mechanical sub-cooling are investigated. For scratch designs, R134a used in both cycles produced the best results in terms of COP, COP gain and relative compressor sizing. In retrofit cases, considering the high sensitivity of COP to the relative size of heat exchangers in the sub-cooler cycle and the low gain in COP obtained due to installation of a dedicated sub-cooling cycle when R717 is the main cycle refrigerant, it seems that dedicated mechanical sub-cooling may be more suited to cycles using R134a as the main cycle refrigerant rather than R717. With R134a as the main cycle refrigerant, no major difference was noted, by changing the sub-cooler cycle refrigerant, in the degradation of the performance parameters such as COP and cooling capacity, due to equal fouling of the heat exchangers.     

R404A直接接触凝结制冷循环的性能分析

提出R404A直接接触凝结换热的制冷循环,分析R404A直接接触凝结制冷循环的热力性能,并与常规双级压缩制冷循环的性能进行对比。得出结论:在一定的冷凝温度、蒸发温度和过冷液体的过冷度下,直接接触凝结制冷循环存在最佳的饱和液体温度,并在此最佳的饱和液体温度下,获得最优的性能和最小的冷凝热负荷,随着过冷液体的过冷度增大和蒸发温度升高,直接接触凝结制冷循环的性能系数增加、冷凝热负荷减少,获得最优性能的最佳饱和液体温度值提高。过冷液体的过冷度为25℃时,直接接触凝结制冷循环的最佳性能系数较双级压缩制冷循环的最佳性能系数提高6.2%。直接接触凝结制冷循环的最小冷凝热负荷较双级压缩制冷循环的最小冷凝热负荷减小1.8%。     

Performance of a finned-tube evaporator optimized for different refrigerants and its effect on system efficiency

This paper presents a comparable evaluation of R600a (isobutane), R290 (propane), R134a, R22, R410A, and R32 in an optimized finned-tube evaporator, and analyzes the impact of evaporator effects on the system coefficient of performance (COP). The study relied on a detailed evaporator model derived from NIST's EVAP-COND simulation package and used the ISHED1 scheme employing a non-Darwinian learnable evolution model for circuitry optimization. In the process, 4500 circuitry designs were generated and evaluated for each refrigerant. The obtained evaporator optimization results were incorporated in a conventional analysis of the vapor compression cycle. For a theoretical cycle analysis without accounting for evaporator effects, the COP spread for the studied refrigerants was as high as 11.7%. For cycle simulations including evaporator effects, the COP of R290 was better than that of R22 by up to 3.5%, while the remaining refrigerants performed approximately within a 2% COP band of the R22 baseline for the two condensing temperatures considered.     

Performance assessment of multistage absorption cycles

The performance potential of 11 multistage, multi-effect absorption cycles is evaluated. They include water-lithium bromide, ammonia-water and cascade configurations. All evaluations are based on air-conditioning applications assuming a 4°C evaporator temperature and a 35°C condenser and absorber temperature. The sensitivity of the performance to the approach temperature in the heat exchanger was studied. Eight cycles were selected for a more detailed simulation. The highest COP at zero approach temperature was obtained for a three-stage water-lithium bromide cycle cascaded with two single-stage ammonia water cycles, while for approach temperatures of 5 K the best COP was obtained for the three-stage water-lithium bromide cycle.     

Performance optimization of an irreversible Carnot refrigerator with finite mass flow rate

The present study develops a theoretical model for the optimization of an irreversible Carnot refrigerator subject to a constraint of finite mass flow rate, which includes internal as well as external irreversibilities. By introducing two dimensionless parameters as indicative of the mass flow rates for the refrigerator, the new model allows detailed analyses on the finite mass flow rate allocation problem of working fluids among the hot- and cold-side heat exchangers of Carnot refrigerators. The analytical solutions of the maximum coefficient of performance (COP) for irreversible Carnot refrigerators are obtained under the equivalent of the finite-flow rate constraint. Furthermore, the influences of major parameters on the maximum COP and the corresponding mass flow rate allocation are examined and shown by numerical examples. The obtained results may provide a theoretical guidance for the optimal design and operation of real refrigerators.