一种四级自动复叠制冷系统混合工质组分选取及配比研究

对于多级自动复叠制冷系统,混合制冷工质的选取和组分配比具有重要的影响作用。针对四级自动复叠制冷系统,运用REFPROP8.0软件建立了混合工质种类选择及其配比研究的理论模拟方法,通过分析比较混合工质的饱和压力、蒸发温度,模拟出混合工质组分和配比：R600a/R23/R14/R740=45/21/19/16,充入该混合工质配比进行实验研究,获得了-150℃的设计柜温。研究表明,该混合工质理论模拟方法,能够有效指导实验研究,取得理想的制冷温度。     

一种五级自动复叠制冷系统的初步试验研究

提出了一种五级自动复叠制冷循环,根据不同的系统采用不同的制冷工质和不同的混合配比,可以获得不同的蒸发温度,分析了非共沸混合工质的组分选取原则并选取了组分,探讨了适用于自动复叠制冷系统混合工质计算的方法,根据要求选择了R22、R23、R14、R740和R728五种制冷工质作为系统循环工质,对混合工质的配比进行了模拟计算,得出了理论模拟最优配比并通过试验研究加以比较确定.     

非共沸混合工质单级压缩回热循环实验研究

针对非共沸混合制冷工质单级压缩回热制冷循环,分析了LHR循环的特点及主要研究问题。根据非共沸混合制冷工质的特性,讨论并选取了适合于-70℃低温冷柜的混合制冷工质R23和R600a。利用制冷工质物性分析软件NIST Refprop 8.0初步研究了不同配比时制冷系统的特性,然后通过实验方法从不同角度分析混合制冷工质的配比对系统性能的影响,最终得到比较合理的混合制冷工质R23/R600a组分比例3:7。同时分析了该配比下制冷压缩机排气温度、压比、低温冷柜内温度等的变化特点,最后对蒸发器的温度变化特性和回热器的温度变化特性进行了总结。     

三级自动复叠系统混合工质配比设计与验证

为了确定应用于三级自动复叠系统的混合工质,说明了混合工质组分确定的方法,并据此为一台设备选取了R134a/R23/R14/R50作为制冷剂。通过提出了一些理想状态假设之后,简化制冷剂在制冷系统中的循环过程。忽视非必须制冷剂R50对系统的影响,认为系统中只有R134a/R23/R14进行制冷循环。利用串联热平衡法计算了各组分的循环流量,以R14的循环量作为对比单位,与实验得出的最佳配比进行比较。通过分析误差原因,指出了在实际设备制造过程中根据计算结果确定混合工质配比的可行性。     

碳氢工质R600a/R1150在低温冰箱中的应用研究

采用碳氢制冷工质R600a/R1150进行实验研究,以低温冰箱为研究对象,对比分析了R600a/R1150与R600a/R23/R14两种混合工质在两级自复叠制冷循环系统中的特性。在不同工况下,对混合工质的几种质量配比进行了对比实验,结果表明,混合工质R600a/R1150在62/38的配比下系统性能最优,此配比下,系统在25℃环境温度下,箱内温度可以达到-80℃,在32℃环境温度下,箱内温度可以达到-77℃。在相同工况下,混合工质R600a/R1150的系统性能优于R600a/R23/R14,前者的箱内温度较后者低约2℃,系统充注量比后者少了36.4%。     

三元混合制冷剂R32+R161+R1234yf气液相平衡实验研究

本文研究了含R1234yf的三元混合制冷剂的气液相平衡性质和模型,利用基于液相单相循环法搭建的气液相平衡实验装置,对温度范围为283.15～323.15 K的三元混合制冷工质R32+R161+R1234yf进行了实验研究,共得到45组实验数据。同时采用Peng-Robinson-Stryjek-Vera(PRSV)状态方程结合Wong-Sandler(WS)混合法则和Non-Random Two-Liquid(NRTL)活度系数模型,在前期工作得到的二元混合工质的模型参数的基础上,对三元混合工质气液相平衡性质进行推算。最后将模型推算结果与实验数据进行对比,结果表明系统压力平均绝对偏差AAD_p为0.34%,系统组分R32和R161的气相摩尔分数平均绝对偏差AAD_y_1和AAD_y_2分别为0.002和0.001。     

一个改进自行复叠制冷循环的实验研究

自行复叠制冷循环以其结构简单、可靠性高、适应性强等特点,在能源、生物、医学和生命科学等领域得到了日益广泛的重视和应用。针对一个改进的自行复叠制冷循环,建立了该制冷循环的实验台,进行了不同配比的二元混合工质和三元混合工质的自行复叠制冷循环性能实验,得出了改进自行复叠制冷循环的降温特性图以及性能系数COP和制冷量与制冷温度的关系。最后比较了二元自行复叠系统与三元自行复叠系统稳态运行参数的优劣。     

三元混合工质用于变容量热泵系统的实验研究

简要回顾并总结了国内外关于变容量热泵系统的研究方向,在新型变浓度热泵试验台上进行了三元混合工质R23/R32/R134a变工况、变浓度等一系列的实验,并对实验结果进行了分析.结果表明:三元混合工质用于变浓度热泵系统时,单质工质之间互相弥补了各自的不足,发挥了各自的优势,在循环性能上以及容量调节方面都表现出很大的优越性;随着冬季室外温度的降低,混合工质在变浓度运行要比定浓度运行能够放缓制热量下降的节奏,表现出更节能的优点.     

两级自动复叠制冷系统的试验研究

建立了一套两级自动复叠制冷系统,采用R22/R23作混合制冷工质,冷柜内温度可达到-65℃;对因混合工质的配比不同而引起的制冷温度、启动状态的变化也进行了试验研究.     

混合工质Linde-Hampson制冷系统的实验研究

搭建了混合工质Linde-Hampson制冷系统,将4种工质R245fa/R600a/R508b/R14按照不同比例混合后进行实验研究。通过优化制冷剂组分得到不同配比下的最低运行温度,分析了最优配比下环境温度对系统运行性能的影响。结果表明:将4种工质按照不同配比进行混合,系统的最低运行温度范围在-45℃~-85℃之间。在环境温度35℃时,混合工质按比例R245fa:R600a:R508b:R14=0.45:0.3:0.18:0.07充注时,系统运行温度可达到-85℃,在此条件下,将环境温度从35℃降低到5℃,系统运行温度则从-85.5℃降低到-89.3℃。     

150K四级自动复叠制冷系统设计

为获得150 K的低温,提出一种四级自动复叠制冷系统的设计,选择R134a/R23/R14/R50非共沸混合工质作制冷剂.通过NIST软件对混合工质热力参数用进行计算,根据文献和经验公式对压缩机、冷凝器、蒸发器、换热器进行计算和选型.     

Liquid Thermal Conductivity of Ternary Mixtures of Difluoromethane (R32), Pentafluoroethane (R125), and 1,1,1,2-Tetrafluoroethane (R134a)1

The thermal conductivities of ternary refrigerant mixtures of difluoromethane (R32), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a) in the liquid phase have been measured by the transient hot-wire method with one bare platinum wire. The experiments were performed in the temperature range of 233 to 323 K and in the pressure range of 2 to 20 MPa at various compositions. The measured data are correlated as a function of temperature, pressure, and composition. From the correlation, we can calculate the thermal conductivity of pure refrigerants and their binary or ternary refrigerant mixtures. The uncertainty of the measurements is estimated to be ±2%.     

HFC-161混合物替代R502的理论研究

提出一种新型制冷剂HFC-161/125/143a(质量百分比10/45/45)用于替代制冷剂R502.新制冷剂环境性能良好,ODP值为0,GWP值为3466,GWP值小于R502及其常用替代制冷剂R404A和R507.采用Refprop软件计算了HFC-161混合物的基本热物理性质,以及低温工况和变工况下的理论循环性能,并与制冷剂R502、R404A、R507的相关数据进行对比.结果表明:新制冷剂的运行压力、压比、COP值、单位容积制冷量与R502相当,温度滑移小于R502常用替代物R404A,是一种性能优良的制冷剂R502的替代物.     

Experimental research on the performance of the diffusion absorption refrigerator with mixed fluoride refrigerants

A diffusion absorption refrigerator (DAR) operating with mixed fluoride refrigerants was built to obtain low refrigerating temperature at low generating temperature. Two groups of mixed fluoride refrigerants, R23/R134a and R23/R32/R134a, were tested experimentally. The N,N-dimethylformamide (DMF) and helium were used as the absorbent and inert gas, respectively. For the DAR with R23/R134a, the refrigerating temperature was not obviously influenced by the concentration of R23 in the mixed refrigerant vapor or the amounts of helium. For the DAR with R23/R32/R134a, an optimal concentration of R32 in the mixed refrigerant vapor and an optimal pressure were both found to achieve the lowest refrigerating temperature which was −28.8 °C at a generating temperature of 106.9 °C, and a refrigerating temperature of −23.7 °C was obtained at an extraordinarily low generating temperature of 83.3 °C. It showed the promising potentials of DAR operating with mixed fluoride refrigerants in applications of low temperature refrigeration and efficient utilization of the low-grade thermal energy.     

Isothermal vapor liquid equilibrium measurements for difluoromethane (R32) + fluoroethane (R161) + trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) ternary mixtures

Difluoromethane (R32) + fluoroethane (R161) + trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) ternary system could be a promising alternative refrigerant mixture. The vapor liquid equilibrium (VLE) data for this system are important for the evaluation of its performance. In this work, the VLE of R32 + R161 + R1234ze(E) were measured for the first time by a quasi-static analytical apparatus over the temperature range of 283.15 to 323.15 K. The ternary system of R32 + R161 + R1234ze(E) is a zeotropic system within the studied temperature range. The Peng–Robinson–Stryjek–Vera (PRSV) equation of state combined with the Wong–Sandler (WS) mixing rule and the non-random two-liquid (NRTL) activity coefficient model was used to predict the ternary VLE data by using the parameters of binary mixtures (R32 + R161, R32 + R1234ze(E) and R161 + R1234ze(E)). The calculated values show excellent agreement with the experimental results. The average absolute deviation (AAD) of pressure is 0.16%. The average absolute deviations of vapor phase mole fractions for R32 and R161 are 0.0021 and 0.0028, respectively.     

R404A单机双级与R404A/R23复叠式制冷系统对比分析

通过建立双级压缩制冷系统和复叠式压缩制冷系统热力学模型,在冷凝温度40℃,蒸发温度为-65℃条件下,分析不同的中间温度对两种制冷系统压缩机轴功率,制冷剂流量以及制冷系数等性能参数的影响,并对两种制冷系统的实际运行费用进行了比较。结果表明:在相同的工况下,双级压缩式压缩机轴功率、R404A制冷剂质量流量低于复叠式;而双级压缩制冷系统COP(制冷性能系数)高于复叠式。在冷凝温度为40℃,蒸发温度为-65℃,中间温度为-14℃时,与复叠式制冷系统相比双级压缩式制冷系统全年运行节能可达13%。理论研究表明在-65℃的超低温工况下,双级压缩式制冷系统更具有优势。     

HFCs混合制冷剂热力性质的研究

为了利用PR方程和Huron-Vidal混合规则对三元混合制冷剂的热力性质进行精确计算,通过对10组二元HFCs混合制冷剂的汽液相平衡实验数据进行热力学关联,得出了相应的NRTL模型参数,由优选得到的过量Gibbs自由能NRTL模型的相互作用系数预测了构成R407C和R404A的三元混合制冷剂R32／R125／R134a以及R125／R143a／R134a的汽液相平衡,结果表明,泡点压力实验值和计算值的算术平均相对偏差小于0．42％,各组分的汽相组成实验值和计算值基本吻合。最后还应用相关热力性质分别对R32／R125和R407C进行了理论制冷循环分析计算并和其他模型的计算结果进行了比较。     

Correlating Thermal-Conductivity Data for Ternary Liquid Mixtures

The performance of several semi-empirical expressions for correlating the temperature, pressure and composition dependence of the thermal conductivity (λ) of pure organic liquids and mixtures was investigated. The temperature and pressure dependence is adequately represented by Chisholm approximants of order (1, 1) or (2, 1) with five and eight adjustable constants, respectively. The fully predictive Vredeveld equation uses mass fractions as the composition variable. It significantly underestimated λ values for the R32 + R125 + R134a ternary refrigerant system. Binary predictive models with one or two adjustable parameters include the quadratic Scheffé polynomial and its corresponding Padé approximant, the cubic “Margules” model and the theoretical Wassiljewa equation. It was found that the Padé (2, 2) approximant and the Wassiljewa equation satisfactorily correlated the extensive ternary mixture data published by Rowley and coworkers. Best results were obtained when the mole fraction was used as a composition variable. The predictive capability of the models was checked using the R32 + R125 + R134a ternary refrigerant system. Combining rules were used for cross parameters such that the temperature and pressure dependence was incorporated via the pure fluid properties. Model parameters were fixed using binary data alone. In this case, the quadratic Scheffé, Padé (2, 2), and Wassiljewa (with temperature- and pressure-independent parameters) all provided satisfactory predictions for ternary mixtures.     

Performance of R170 mixtures as refrigerants for refrigeration at −80 °C temperature range

The refrigeration performance parameters of two binary azeotropic mixtures of R170 + R23 and R170 + R116 and a ternary azeotropic mixture of R170 + R23 + R116 were measured systematically in the low-stage loop of a two-stage cascade system. In addition, the performance of the currently used R508B refrigerant was also measured at similar conditions for comparison. A two-stage cascade refrigeration testing apparatus was designed and assembled, in which an R404A system was used as the high-temperature refrigeration stage. Thermodynamic performance parameters of the low-stage loop such as the coefficient of performance (COP), cooling capacity, and the discharge temperature of these four mixtures were measured at various condensation and evaporating temperatures. The results show that the COP of the R170 + R116 binary mixture is up to 10% higher than that of R508B. These mixtures show good potential as low-temperature stage refrigerants for applications in the ?80 °C temperature range.