混合制冷工质

混合制冷工质ＤＡＤｉｄｉｏｎＮＩＳＴ，ＧａｉｔｈｅｒｓｂｕｒｇＭＤ，ＵＳＡ工业上为了填补由于一些重要的ＣＦＣｓ（如Ｒ１１和Ｒ１２）被取消使用而导致的空白，初步的方法是发展对臭氧层破坏作用较小或没有破坏作用的其它单组分的工质（如ＨＣＦＣ１２３和ＨＦＣ１...     

二元混合工质脉管制冷特性研究

从制冷工质角度，在理论上分析了采用混合工质代替纯质氦以提高脉管制冷机在８０Ｋ温区制冷性能的可能性。初步的分析得到了两组二元混合工质对，一组在８０Ｋ温区附近依旧保持气态，如氦－氖，氦，－氢，氢－氖，另一组在８０Ｋ温区附近处于气液两相，如氦－氮，氢－氮，氖－氮，其中，氮气的摩尔组分小于１０Ｔ。     

小型制冷装置应用混合工质的研究

本文介绍了应用非共沸混合物的小型制冷系统的特性。将不同配比的HFC152a/HCFC22双组分混合工质用于冰箱中。实验室进行的试验表明,以适当配比构成的HFC152a/HCFC22混合工质可用于替代家用制冷设备中的CFC12。     

制冷剂CFC12的一种新三元替代工质HFC152a／HFC125／HFC134a

利用统一循环分析法,对２１种纯质和混合工质制冷循环进行了计算,利用混合工质优势互补原则提出了一种对臭氧层无破坏作用,无毒,不可燃,并具有更轵 新三元混合制冷工质ＨＦＣ１５２ａ／ＨＦＣ１２５／ＨＦＣ１３４ａ。     

HCs替代HCFC22的理论空调循环分析

关联了4种二元碳氢化合物系基于PT状态方程及其混合规则的交互作用参数,对16种HCs纯质和混合物系进行了理论空调循环分析。结果表明HC1270、HC290、HC1270／HC290、HC1270／HC600a、HC290／HC600a等具有在空调系统中替代HCFC22的潜力。     

四元混合工质一次节流制冷实验研究

研究了四元混合工质对一次节流系统制冷性能的影响.从安全性和环境友好两个角度出发,选择了两种不同的四元混合工质作为研究对象,分别记为MR 1和MR 2;通过遗传算法对两种研究对象的最佳摩尔浓度进行了优化;在同等工况的实验系统里对两种研究对象进行了对比研究.通过比较混合工质的节流效应、系统中压缩机的运行参数及箱内温度等方面...     

微型J—T混合工质制冷研究的进展与水平

文章阐述了混合工质制冷的机理与特点，通过图表介绍混合工质制冷研究的一些新进展，对从事微型Ｊ－Ｔ制冷工作的同志有一定的参考价值。     

混合工质节流制冷循环的优化原则及其应用

提出了在混合工质制冷循环优化中应遵循的三条较为合理和切实可行的优化原则。在此基础上，采用定循环运行压比优化方法，在较为合理的外部约束条件下，对二元混合工质循环进行了优化计算，分析了各设计变量对循环性能的影响，并进行了实验验证。     

非共沸混合工质自复叠制冷循环研究进展

系统介绍了自复叠制冷循环的工作原理、发展和主要研究方向,对几种典型的自复叠制冷系统进行了分析比较,介绍了一种带有精馏装置的新型自复叠制冷系统,最后提出了自复叠制冷系统设计需要考虑的一些关键问题。     

引射吸收制冷循环工质对性能比较

三压力引射吸收制冷循环是最新改进的吸收式制冷循环，其制冷性能明显优于传统的吸收式制冷循 。选用ＮＨ３－Ｈ２Ｏ，ＮＨ３－ＬｉＮＯ３，ＮＨ３－ＮａＳＣＮ三工质对水冷空调制冷工况的详细计算，分析了发生温度，吸收温度和冷凝温度，以及蒸发温度对性能系数和泵功的影响。     

Nucleate boiling heat transfer coefficients of mixtures containing HFC32, HFC125, and HFC134a

Nucleate boiling heat transfer coefficients (HTCs) of binary and ternary mixtures composed of HFC32, HFC125, and HFC134a on a horizontal smooth tube of 19.0 mm outside diameter were measured. A cartridge heater was used to generate uniform heat flux on the tube. Data were taken in the order of decreasing heat flux from 80 kW m⁻² to 10 kW m⁻² with an interval of 10 kW m⁻² in the pool temperature at 7 °C. HTCs of nonazeotropic mixtures of HFC32/HFC134a, HFC125/HFC134a, and HFC32/HFC125/HFC134a showed a reduction of HTCs as much as 40% from the ideal values while the near azeotropic mixture of HFC32/HFC125 did not show the reduction. Four of the well known correlations were compared against the present data for binary mixtures. Stephan and Körner's and Schlünder's correlations yielded a good agreement with a deviation of less than 10% but they can not be easily extended to multi-component mixtures of more than three components. A new correlation was developed utilizing only the phase equilibrium data and physical properties. A regression analysis was carried out to account for the reduction of HTCs and the final correlation, which can be easily extended to multi-component mixtures of more than three components, yielded a deviation of 7% for all binary and ternary mixtures.     

二元混合工质HFC32/125绝热指数计算模型分析

绝热指数与定压比热在制冷系统数值分析和计算中极为重要。本文以纯物质的PR状态方程为基础，利用适当的混合法则对绝热指数和定压比热进行理论推导，得出适用于二元混合工质的绝热指数与定压比热方程；对HFC32／125的定压比热分区进行数值拟合，得出定压比热的拟合方程，本文对理论推导和数值拟合的结果进行比较，从而为系统分析和计算提供精确热物理性质方程。     

Study on the Interaction Coefficients in PR Equation with vdW Mixing Rules for HFC and HC Binary Mixtures

The Peng-Robinson equation of state with the van der Waals mixing rules was used to correlate vapor–liquid equilibrium (VLE) data for HFC/HC, HFC/HFC, and HC/HC binary mixtures. The interaction parameter k _ij was obtained for every binary mixture. It was assumed that k _ij has contributions from the two components, and each component has its own constant contribution factor k _i for the mixture, and the values of k _ij indicate the degree in difference of properties between the two components. Therefore, the interaction parameters k _ij is proposed as: k _ij  = k _i  − k _j . The values of the mixing factor k _i for Hydrofluorocarbons (HFCs) and Hydrocarbons (HCs), including propane, isobutane, n-butane, R23, R32, R125, R143a, R134a, R152a, R227ea R236fa, R236ea, and R245fa, were obtained by least-square fitting. In total, 39 refrigerant binary mixtures were analyzed on the basis of this method, and the results showed good agreement with experimental data. The overall average absolute deviations of pressure and vapor mole fraction are 1.3 % and 0.0089, respectively.     

Thermal Conductivity of Binary Refrigerant Mixtures of HFC-32/125 and HFC-32/134a in the Liquid Phase

The liquid thermal conductivity of mixtures of HFC-32/125 and HFC-32/134a was measured using the transient hot-wire apparatus in the temperature ranges from 213 to 293 K and from 193 to 313 K, respectively, in the pressure range from 2 to 30 MPa and with HFC-32 mass fractions of 0.249, 0.500, and 0.750 for each system. The uncertainty of the thermal conductivity was estimated to be ±0.7%. For practical applications, the thermal conductivity data for the two mixtures were represented by a polynomial in temperature, pressure, and mass fraction of HFC-32 with a standard deviation of 1.0%.     

Prediction of the Thermal Conductivity and Viscosity of Binary and Ternary HFC Refrigerant Mixtures

A recently developed scheme, based on considerations of hard-sphere theory, is used for the simultaneous prediction of the thermal conductivity and the viscosity of binary and ternary HFC refrigerant mixtures, consisting of HFC-32, HFC-125, and HFC-134a. In this prediction scheme, the hypothetical molecular parameters of HFC refrigerant mixtures were assumed to be the molar average of the pure component values. The close agreement between the predicted values and the experimental results of thermal conductivity and viscosity demonstrate the predictive power of this scheme.     

Measurements of Saturation Densities in Critical Region and Critical Loci for Binary R-32/125 and R-125/143a Systems

R-32/125 (difluoromethane/pentafluoroethane) and R-125/143a (pentafluoro-ethane/l,l,l-trifluoroethane) binary systems are promising alternative refrigerants to replace conventional refrigerants, i.e., R-22 and R-502. The saturated vapor- and liquid-density data in the critical region of these mixtures were measured using the visual observation of the meniscus disappearance in an optical cell. For the R-32/125 system, 35 saturation density data were measured at three compositions, 10, 35, and 50 mass% R-32. Nineteen saturation density data were also measured for R-125/143a (50/50 mass%). The critical temperatures and densities for these binary refrigerants were determined by taking into consideration the level and location of the meniscus disappearance as well as the intensity of the critical opalescence. Correlations to represent the critical loci of these binary refrigerants for an entire range of compositions have been developed. The experimental uncertainties of the saturation density data are estimated to be within 9 mK in temperature and 0.5 to 5.0 kg · m^–3 in density. The uncertainties of the critical temperature and density are estimated to be within 12 to 14mK and 4 to 8kg · m^–3, respectively.     

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

Thermal conductivities of zeotropic mixtures of R125 (CF₃CHF₂) and R134a (CF₃CH₂F) in the liquid phase are reported. Thermal conductivities have been measured by a transient hot-wire method with one bare platinum wire. Measurements have been carried out in the temperature range of 233 to 323 K and in the pressure range of 2 to 20 MPa. The dependence of thermal conductivity on temperature, pressure, and composition of the binary mixture is presented. Measured thermal conductivity data are correlated as a function of temperature, pressure, and overall composition of the mixture. The uncertainty of our measurements was estimated to be better than 2%.     

Thermal Conductivity of Ternary Refrigerant Mixtures of HFC-32/125/134a in the Liquid Phase

The liquid thermal conductivity of two ternary mixtures of HFC-32/125/134a (23.0/25.0/52.0 and 19.0/43.8/37.2 wt%) was measured using a transient hot-wire instrument in the temperature ranges from 193 to 293 K and from 213 to 293 K, respectively, and in the pressure range from 2 to 30 MPa. The thermal conductivity has an estimated uncertainty of ±0.7%. For engineering purposes, the thermal conductivity data were correlated using a polynomial in temperature and pressure for each mixture with a standard deviation of 0.6%.     

Analysis based on EU Regulation No 517/2014 of new HFC/HFO mixtures as alternatives of high GWP refrigerants in refrigeration and HVAC systems

The EU Regulation No 517/2014 is going to phase-out most of the refrigerants commonly used in refrigeration and air conditioning systems (R134a, R404A and R410A) because of their extended use and their high GWP values. There are very different options to replace them; however, no refrigerant has yet imposed. In this paper we review and analyze the different mixtures proposed by the AHRI as alternative refrigerants to those employed currently. These mixtures are composed by HFC refrigerants: R32, R125, R152a and R134a; and HFO refrigerants: R1234yf and R1234ze(E). It is concluded, from the theoretical analysis, that most of the new HFO/HFC mixtures perform under the HFC analyzed (although some experimental studies show the contrary) and, in most cases, do not meet the GWP restrictions approved by the European normative. Furthermore, some of the mixtures proposed would have problems due to their flammability.     

一种根据热源温度品位自动调节效能的溴化锂吸收式制冷循环

针对一种提出的根据热源温度品位自动调节效能的新型溴化锂-水吸收式制冷循环进行了理论分析,该循环可以平滑调节系统COP和工作范围。循环在单效循环基础上加入一对中压蒸发/吸收器,中压蒸发器的冷量用于冷却进入系统的冷却水。这样降低了吸收器出口稀溶液的浓度,升高了被结晶特性限制的发生温度上限,也降低了循环截止发生温度。通过建立模型直观说明了循环的效率变化以及对循环工作范围的扩大。计算结果表明在32℃和40℃的冷却水温下,新的循环(0.n效循环)可以分别将单效循环发生温度范围扩大2倍和6倍,同时保持0.3~0.75的COP。