R134a／R23A动复叠制冷循环的试验研究

在分析自动复叠制冷循环特点和R134a／R23混合工质特性的基础上，搭建了试验台进行了循环特性的研究。在一系列合理简化的基础上对试验结果进行了分析，并给出了循环系统中各点参数的计算结果和制冷循环的空问压焓图。     

制冷剂R290的国内研究进展

对国内制冷剂R290作为R22替代工质的研究进展进行回顾,首先从热力学特性角度说明R290替代R22的可行性,并对R290在家用空调器等方面替代R22的理论分析和试验研究方面的进展进行陈述,进而对R290在复叠式制冷循环以及自行复叠制冷循环中的理论和试验研究进行论述。指出虽然R290在国内还未得到推广使用,但用来替代R22具有一定的可行性。     

R22/R23自动复叠制冷循环的特性研究

通过一个两级自动复叠制冷循环系统来研究R22/R23混合工质的循环特性,在一系列合理简化的基础上讨论了其组分的充注比例和循环比例的关系,分析了循环比例的计算方法,并给出了循环系统中各点参数的计算结果和空间压焓图.     

R22、R404A与R407F制冷剂压缩机性能对比

分析R22、R404A与R407F制冷剂的物理性质,并采用涡旋压缩机进行试验测试。结果表明:在高温应用上,R22、R404A和R407F制冷能力数值相近,R407F制冷系数比R22、R404A稍低;而在低温应用上,R407F制冷能力、制冷系数比R22、R404A都低。     

R290直接接触冷凝制冷循环性能分析对比

本文分析了R290直接接触冷凝(DCC)制冷循环的性能,并与R290常规单级压缩制冷循环的热力性能进行对比,得出:在最佳主循环冷凝温度下,R290直接接触冷凝制冷循环可获得最大性能系数和最低冷凝器热负荷。主循环过冷液体的过冷度增大,最优性能系数降低、最低冷凝器热负荷增加、蒸发器的制冷剂质量流量减少,同时,获得最优性能系数和最低冷凝器热负荷的最佳主循环冷凝温度升高。当蒸发温度为-15～-6℃,R290直接接触冷凝制冷循环相比R290单级压缩制冷循环的性能系数提高了7.5%～14.9%,冷间供冷设备蒸发器的制冷剂质量流量减少了26.5%～36.7%,冷凝器热负荷减少了1.5%～3.7%。结果表明R290直接接触冷凝制冷循环具有很好的发展前景。     

R744/R600及R744/R600a混合工质热泵循环性能研究

基于换热器中的传热窄点温差的限制,对R744/R600及R744/R600a在所研究的工况范围内分别替代传统制冷剂R22的亚临界热泵循环特性分别进行了计算分析.结果表明:R744/R600和R744/R600a具有不同的最优配比,可以使得制热性能系数(COPh)最大;R744/R600及R744/R600a在最优配比下的COPh分别比R22系统增大11.98％和8.24％,分别比纯质R600和R600a大36.43％和36.24％,比跨临界循环R744系统增加7.07％和4.71％.在最优配比下,R744/R600和R744/R600a的冷凝压力低于R22,分别为0.84MPa和1.18MPa;压缩机排气温度也低于R22,在90℃以下.     

R22及其替代物的热物性计算及比较

本文根据R2 2、R12 5的状态方程对空调替代工质R410A热物性进行了计算 ,并对比了R410A与R2 2的热力学性质和理论制冷循环的各项指标。     

R32替代R22制冷系统的分析

为从能量＂质＂的方面揭示R32替代R22的合理性,分别对使用R22和R32作制冷剂的制冷系统,在ARI 520标准的空调工况下进行分析,首先对整个循环系统进行分析,得到系统的效率和冷量,然后分析制冷循环各环节损失的原因,给出各环节的效率、损失和损失系数的计算表达式,并进行计算和比较。分析表明,R32的制冷系统更有利于能量的充分利用,而且主要是压缩环节损失明显减少,说明R32替代R22的可行性。     

采用管壳式冷凝器的R407C制冷机组性能的分析

对R407C在采用管壳式冷凝器的制冷循环中冷凝压力和冷凝温度的确定进行了分析,并对采用R407C和R22为制冷剂的机组性能进行了对比。     

采用R744/R290的自复叠制冷系统热力性质分析

对采用R744/R290混合自然工质的自复叠制冷循环的热力性质进行分析。经过计算,得出了冷凝器压力、蒸发器压力、冷凝器出口温度、蒸发器出口制冷剂的状态、混合工质中R744浓度对系统性能的影响。为今后R744/R290的实验研究和实际应用提供了理论依据,减少了实验的工作量。     

Solubility of R22, R23, R32, R134a,R152a,R125 and R744 refrigerants in water by using equations of state

This paper tries to demonstrate the ability of VPT and CPA equations of state and modified mixing rules for predicting of solubility CHC1F₂ (R22), CHF₃ (R23), CH₂F₂ (R32), C₂H₂F₄ (R134a), C₂H₄F₂ (R152a), C₂HF₅ (R125) and CO₂ (R744) refrigerants in water at different temperatures and pressures. For this purpose, the fugacity of each component in gas and liquid phases is calculated by using VPT and CPA equations of state. Also in this work, the interaction parameters for mixing rules in each mixture are optimized by using two-phase equilibrium data (VL_W). Results of the two-phase flash calculation show good agreement between obtained solubility and the experimental data. The predicted solubility of the selected refrigerants in water agrees with the experimental data with accuracy of about 1.5% and 3.5% by VPT equation of state – modified mixing rule and CPA equation of state – Van der Waals classic mixing rule respectively.     

Exergetic analysis of a vapour compression refrigeration system with R134a, R143a, R152a, R404A, R407C, R410A, R502 and R507A

This communication deals with the exergetic analysis of a vapour compression refrigeration system with selected refrigerants. The various parameters computed are COP and exergetic efficiency in the system. Effects of degree of condenser temperature, evaporator temperature and sub-cooling of condenser outlet, supper-heating of evaporator out let and effectiveness of vapour liquid heat exchanger are also computed and discussed. In this study, it was found that R134a has the better performance in all respect, whereas R407C refrigerant has poor performance.     

Viscosity of refrigerants R12, R113, and R114 and mixtures of R12 + R114 at high pressure

New viscosity measurements for the gaseous and supercritical state of the halogenated hydrocarbons R12, R113, and R114 and binary mixtures of R12 + R114 of different compositions are presented. The measurements were carried out at superheated and supercritical temperatures from 30 to 200° C and in the pressure range from 1 to 80 bar. Viscosity was measured with an oscillating-disk viscometer and the data obtained are relative to the viscosity of nitrogen. The estimated accuracy of the measured results is ±0.6%. The results obtained show that, at subcritical temperatures, the pressure effect on viscosity is negative. This anomalous behaviour is investigated in detail in this work. At atmospheric pressure the viscosity of gas mixtures is almost a linear function of their composition. At high pressure, the residual viscosities - ₀ of both the pure components and the mixtures were used to follow a single relationship versus the residual reduced density _r0.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Viscosity of Gaseous R404A, R407C, R410A, and R507

This paper presents new measurements of the viscosity of gaseous R404A (52 wt% R143a, 44 wt% R125, 4 wt% R134a), R407C (23 wt% R32, 25 wt% R125, 52 wt% R143a), R410A (50 wt% R32, 50 wt% R125), and R507 (50 wt% R143a, 50 wt% R125). These mixtures are recommended as substitutes for the refrigerants R22, R502, and R13B1. Measurements were carried out in an oscillating-disk viscometer. The obtained values of the viscosity are relative to the viscosity of nitrogen. The experiments were performed at atmospheric pressure over the temperature range 297 to 403 K. and near the saturation line up to pressures of 0.6 P _crit. The estimated uncertainty of the reported viscosities are ±0.5% for the viscosities at atmospheric pressure and ± 1% along the saturation line, being limited by the accuracy of the available vapor pressure and density data. The experimental viscosities at atmospheric pressure are employed to determine the intermolecular potential parameters, and , which provide the optimum representation of the data with the aid of the extended law of corresponding states developed by Kestin et al. A comparison of the experimental viscosity data with the values calculated by REFPROP, both at atmospheric pressure and along the saturation line, is presented.     

Energy performance evaluation of R1234yf,R1234ze(E), R600a,R290 and R152a as low-GWP R134a alternatives

In 2014, the Directive 517/2014 was introduced by European Parliament to reduce the use of high-GWP greenhouse gases in the European area in order to limit global climate change in accordance with the objectives marked by the EU Research and Innovation programme Horizon 2020. These restrictions affect the large majority of artificial refrigerants among which R134a is included due to its relatively high GWP₁₀₀ (1301). The widely used of R134a in the refrigeration and air conditioning fields reveals the need to identify new low-GWP alternatives. Accordingly, in this work five low-GWP R134a possible choices have been tested and compared in an identical refrigerating facility equipped with a hermetic compressor, under the same operating conditions.The refrigerants used in this analysis are: R290 and R600a (HCs); R134a and R152a (HFCs), and finally, R1234yf and R1234ze(E) (HFOs). All of them have been assayed without changes in the facility, that is, as direct drop-ins. The results obtained from the experimental tests are presented and commented in this work from the energetic point of view.     

Flow-boiling of R22, R134a, R507, R404A and R410A inside a smooth horizontal tube

Flow boiling heat transfer coefficients of R22, R134a, R507, R404A and R410A inside a smooth horizontal tube (6 mm I.D., 6 m length) were measured at a refrigerant mass flux of about 360 kg/m² s varying the evaporating pressure within the range 3–12 bar, with heat fluxes within the range 11–21 kW/m². The experimental data are discussed in terms of the heat transfer coefficients as a function of the vapour quality. The experimental results clearly show that the heat transfer coefficients of R134a are always higher than those pertaining to R22 (from a minimum of +6 to a maximum of +45%).     

Measurements of the surface tension for R290, R600a and R290/R600a mixture

The surface tensions of R290, R600a and R290/R600a mixture have been measured by the modified differential capillary-rise method. Twenty-two data points for R290 and 21 data points for R600a were obtained in the temperature range between 273 K and 354 K, and 43 data points for R290/R600a mixture on three isotherms of 278 K, 300 K and 320 K were obtained. The experimental uncertainties of temperature and surface tension are estimated to be within 20 mK and 0.2 mN m⁻¹, respectively. Surface tension correlations as a function of temperature for pure R290 and R600a were formulated in the temperature range between 253 K and critical temperature, and the correlation as a function of the composition for R290/R600a mixture was discussed at 278 K, 300 K and 320 K. It is found that the surface tension for R290/R600a mixture can be reproduced by the simple mixing rule by mole fraction with the correlations of both pure components.     

Measurements of the thermal conductivity of liquid R32, R124, R125, and R141b

This paper reports measurements of the thermal conductivity of refrigerants R32, R124, R125, and R141b in the liquid phase. The measurements, covering a temperature range from 253 to 334 K and pressure up to 20 MPa, have been performed in a transient hotwire instrument employing two anodized tantalum wires. The uncertainty of the present thermal-conductivity data is estimated to be ±0.5%. The experimental data have been represented by polynomial functions of temperature and pressure for the purposes of interpolation. A comparison with other recent measurements is also included.     

Viscosity of R134a, R32, And R125 at Saturation

This paper reports the results of the measurement of the viscosity of R134a close to the saturation line in the vapor phase. The new measurements were carried out in a vibrating-wire viscometer specially constructed for the purpose, and the results have an accuracy of ±2%. In addition, the opportunity is taken to present a reevaluation of earlier measurements along the saturation line of the viscosity of R32 and R125. Improved equations of state for these fluids are now available and can be employed to generate improved values for the viscosity.