新一代制冷剂HFO-1234yf的热物性模型

基于Peng-Robinson通用状态方程,采用基团贡献原理以及多项式拟合方法,建立了符合精度要求的新型LGWP制冷剂HFO-1234yf的热物性模型,并对模型进行了验证,利用数学软件对模型进行编程求解,得到了较为全面的HFO-1234yf制冷剂的热物性数据。将HFO-1234yf制冷剂与R134a及R417A制冷剂的热物性能进行了对比,结果显示HFO-1234yf的饱和蒸汽压力与定压比热容和R134a的表现相似,二者的饱和蒸气压均低于R417A,HFO-1234yf制冷剂与R134a和R417A相比,其饱和状态焓值较低,这将导致HFO-1234y系统运行时的性能系数不高。该模型能为HFO-1234yf制冷剂在汽车空调以及固定式空调制冷设备上的应用提供理论依据。     

新一代制冷剂HFO-1234yf的热物性模型

基于Peng-Robinson通用状态方程,采用基团贡献原理以及多项式拟合方法,建立了符合精度要求的新型LGWP制冷剂HFO-1234yf的热物性模型,并对模型进行了验证,利用数学软件对模型进行编程求解,得到了较为全面的HFO-1234yf制冷剂的热物性数据.将HFO-1234yf制冷剂与R134a及R417A制冷剂的热物性能进行了对比,结果显示HFO-1234yf的饱和蒸汽压力与定压比热容和R134a的表现相似,二者的饱和蒸气压均低于R417A,HFO-1234yf制冷剂与R134a和R417A相比,其饱和状态焓值较低,这将导致HFO-1234y系统运行时的性能系数不高.该模型能为HFO-1234yf制冷剂在汽车空调以及固定式空调制冷设备上的应用提供理论依据.     

新型制冷剂HFO-1234yf/R134a/DME的理论与试验研究

提出一种在汽车空调应用中替代R134a的新型制冷剂HFO-1234yf/R134a/DME。利用数据库REFPROP 9.0,通过自行编制的软件对该制冷剂的热力学性能和循环性能进行理论分析,并在电量热器制冷剂循环性能测试装置上,对R134a和HFO-234yf/R134a/DME进行试验研究。理论与试验研究发现,新型制冷剂的制冷量比R134a略小,循环性能系数(COP)也略低,而排气温度比R134a低12℃左右。该新型制冷剂具有替代R134a的潜在可行性。     

欧盟汽车空调指令对汽车企业的影响分析

欧盟汽车空调指令2006/40/EC要求汽车空调制冷剂GWP值≤150,目前,广泛使用的R134a制冷剂的GWP值为1300,因此,R134a逐渐会被禁用,新型制冷剂HFO-1234yf逐步被推广,取代R134a.重点研究了两种制冷剂的性能差异,替代趋势,及空调指令在欧盟的执行情况,以及国内自主汽车企业的应对措施.     

一种替代HFC-134a的制冷剂混合物

HFO-1234yf/HFO-1234ze(E)/HFE-143a组成的制冷剂混合物,具有良好的环境性能;通过对该混合物的理论循环研究及制冷性能和燃烧性能的试验研究,发现该制冷剂混合物在干空气中不可燃,在65%左右湿度空气中的燃烧等级为2L,制冷量和能效比均优于HFO-1234yf,是具有应用前景的HFC-134a替代物。     

可燃性制冷剂将在汽车空调中使用

美国环境保护部(EPA)宣布同意汽车空调系统中使用HFO-1234yf制冷剂。由于该制冷剂对健康和环境的影响,很多组织对此都持有异议。"美国政府批准了这样一个前景不可预测的物质。HFO-1234yf将会是下一个环境炸弹,正如HCFCs破坏臭氧层     

R1234yf热泵技术综述与潜力分析

为了满足逐步严苛的环保法规要求,R1234yf成为车用热泵制冷剂R134a的热门替代制冷剂之一。本文对R1234yf热泵技术的研究进行了综述与分析,其GWP<1,各方面性质均符合车用热泵系统的工作需求。在传热效果上,R1234yf的沸腾传热性能略优于R134a,且冷凝过程压降比R134a低5%~10%,优于R134a系统。在诸多R1234yf和R134a系统的仿真和实验研究中,R1234yf热泵性能略低于R134a,但可以通过优化零部件、强化补气、改善工况等方式使其与R134a十分接近甚至超越。R1234yf低压饱和压力比R134a高约15%,可以适配更高的压缩机转速,低温下制热性能比R134a更好,且较低的压缩机排气温度使系统工作更为稳定,强化补气的效果也优于R134a。因此,R1234yf在车用热泵中具有较好的工作性能和发展前景,可以作为R134a的替代制冷剂。     

R1234yf汽车空调制冷剂的理论循环性能分析

使用MH-59方程编制R1234yf的热力性质计算程序。在汽车空调制冷工况下,对比R1234yf和R134a的压力比、排气温度、单位质量压缩功、单位质量制冷量、单位质量冷凝负荷、COP、热力完善度、单位体积制冷量及压缩机吸气比容,得出它们随蒸发温度的变化情况。理论循环性能分析表明:R1234yf作为汽车空调制冷剂,在不改变制冷系统设备的前提下可以直接替代R134a,并且可以降低压缩机排气温度。     

一种在汽车空调系统中使用的新制冷剂—HFO-1234yf

本文综述了HFO-1234yf制冷剂的热力性能、燃烧性、毒性和使用性能,分析了它在汽车空调系统中使用的评价。     

第四代制冷剂HFO-1234yf

介绍了2,3,3,3-四氟丙烯(HFO-1234yf)的各种性能、用途以及合成研究进展,HFO-1234yf作为1,1,1,2-四氟乙烷(HFC-134a)的替代品而被应用于移动空调系统,已成为第四代制冷剂。     

Energy analysis of vapor compression refrigeration system using mixture of R134a and LPG as refrigerant

According to Kyoto protocol, R134a must be phased out soon due to its high global warming potential of 1430. In this work, an experimental investigation is carried out with R134a and LPG refrigerant mixture (composed of R134a and LPG in the ratio of 28:72 by weight) as an alternative to R134a in a vapor compression refrigeration system. Performance tests were performed under different evaporator and condenser temperatures with controlled ambient conditions. The results showed that the R134a and LPG refrigerant mixture has a higher coefficient of performance and lower compressor discharge temperature and pull down time as compared to R134a by about 15.1–17.82%, 2.10–13.86% and 1.01–5.90% respectively. Furthermore, the miscibility of R134a/LPG with mineral oil as a lubricant was also found good. In conclusion, the mixing refrigerant R134a/LPG proposed in this study seems to be an appropriate long-term candidate to replace R134a as a new generation refrigerant of VCRS, because of its well environmentally acceptable properties and its favorable refrigeration performances.     

二甲醚作为汽车空调制冷剂的性能研究

本文对二甲醚（DME）用作汽车空调制冷剂的性能与现有汽车空调制冷剂R134a进行了对比。首先比较了二甲醚和R134a的基础热力性质，然后对二甲醚和R134a的汽车空调标准工况和变工况下制冷循环性能进行了详细的理论计算及分析。分析表明：二甲醚的制冷性能与R134a基本相似，而性能系数（COP）却优于R134a。因此，更具环保优势的二甲醚是一种理想的潜在的汽车空调制冷剂。     

神经网络模型在制冷剂物性参数计算中的应用

介绍采用BP，RBF和Elman神经网络计算制冷剂物性参数的方法。以R11，R134a和近共沸混合制冷剂R410A为研究对象，分别建立三种制冷剂的BP，RBF和Elman网络饱和物性参数计算模型。根据该模型由已知温度求各制冷剂在饱和气和饱和液状态下的其他物性参数值，通过与REFPROP软件计算结果进行对比，证明BP，RBF和Elman神经网络物性计算模型具有很高的精度，可以用于物性参数的计算，是一种新的物性计算方法。     

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。     

Experiment and simulation on the performance of an autocascade refrigeration system using carbon dioxide as a refrigerant

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility of keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.

Résumé

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility in keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.     

Thermophysical properties of refrigerant R134a

Experimental results of measurements of the thermodynamic and transport properties of refrigerant R134a are presented for the temperature range 240–400 K and pressures up to 89 bar. The thermal properties of the saturated refrigerant were also determined. The results from this study showed that the dependence of viscosity on temperature near the critical region was nonlinear. This observation shows that errors resulting from using previous literature data for design purposes could vary from about 1.5% at 251 K to 30% at 343 K. A computer (IBM PC) was used to obtain empirical relationships for evaluating the thermophysical properties of R134a based on various sets of independent variables.     

Experimental two-phase heat transfer coefficient and frictional pressure drop inside mini-channels during condensation with R1234yf and R134a

The present paper reports condensing two-phase flow pressure drop gradient and heat transfer coefficient (HTC) inside a mini-channel multiport tube with R1234yf and R134a. Several models available in the literature are used to compare predictions of these two fluids. Experimental data are analysed to get the influence of saturation temperature, mass flux, vapour quality and fluid properties. HTC values of R1234yf seem to be lower than R134a under similar conditions. Two-phase flow pressure drops are also lower in the case of the new refrigerant R1234yf.     

制冷剂充注量对新型换热器汽车空调的影响

为了减少R134a的直接排放,各厂商积极采用新型高效换热器来减少汽车空调系统的充注量.在焓差试验台研究传统汽车空调和采用微通道蒸发器和过冷式冷凝器的汽车空调系统的充注量情况,结果表明新型换热器能够显著降低系统的制冷剂充注量,并且在最佳充注量下,蒸发器能够保证一定的过热度,冷凝器出口有足够的过冷度,使系统运行性能最优.采用新型换热器系统的制冷量提高了18％左右,COP提升了约5％,最佳充注量反而比传统系统小100g,.