R404A和R407C在水平强化管外的凝结换热实验研究

实验研究了近共沸制冷工质R404A与非共沸制冷工质R407C在水平强化换热管管外的凝结换热性能。采用"Wilson图解法"对实验数据进行处理。结果表明:对于R404A和R407C,强化管外的凝结换热系数随着壁面过冷度的增加而增大,呈现出与纯工质冷凝时不同的变化趋势,这主要是近共沸或非共沸工质凝结过程中,某些组分的凝结会遇到其它组分的凝结气膜热阻所造成的;随着过冷度增加,易挥发组分开始凝结,气膜变薄,冷凝传热系数增大。R407C在强化换热管管外的凝结换热系数比R404A要小70%左右,这是由于R407C的温度滑移较R404A要大,管外形成的凝结扩散气膜造成的影响更大。R407C在高热流密度工况下的换热效果提升明显,故应尽量工作在高热流密度区域。     

R407C组分质量误差对压缩机性能测试——流量计法的影响

对于混合工质R407C,在生产、储存、运输、分馏时其组分HFC-32／HFC-125／HFC-134a浓度难以严格达到23％／25％／52％。针对上述问题,本文讨论了R407C各组分浓度误差小于5％时对压缩机性能实验——流量计法的影响,从而提高测试结果的精度。     

R407C组分质量分数误差对压缩机性能测试-量热器法的影响

对于混合工质R407C，在生产过程中，其组分HFC32／HFC125／HFC134a浓度难以严格达到23％，25％和52％，并且由于试验装置的泄漏，其组分的浓度也会出现偏差。因此针对上述问题，讨论R407C组分质量分数误差≤5％时对压缩机性能测试的影响，从而提高测试精度与测试结果的可信度。     

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。     

R407C组分质量误差对压缩机性能测试——流量计法的影响

对于混合工质R407C,在生产过程中其组分HFC32/HFC125/HFC1348浓度难以严格达到23%/25%/52%,并且由于试验装置的泄露,其组分的浓度也会有所偏差.针对上述问题,讨论了R407C各组分浓度误差小于5%时对压缩机性能实验-流量计法的影响,从而提高测试结果的精度.     

基于小型空调系统的R410a和R407C性能比较

小型空调系统在低温工况下存在无法正常运行或运行效率较低等缺点,为寻找低温工况下制冷工质,本文在焓差实验室对R410a和R407C两种制冷剂在小型空调系统中的不同工况进行了实验测试。通过实验结果分析发现,冬季供热时,R410a的平均COP比R407C高4.1%,夏季制冷时,R407C的平均COP比R410a高7.2%。因此,相对于R407C制冷剂,R410a更适合于热泵低温工况。     

三元混合工质R407C热力参数模型分析

R407C是替代R22的一种极具前景的新工质，采用Peng—Robinson型方程对新工质R407C的热力学性质进行了全面的计算，并根据实验数据拟合出新工质的迁移特性计算公式。根据计算结果给出了新工质R407C的压焓图和温-熵图。计算关联式具有较高的精度，热力学参数计算误差小于l％，迁移特性参数误差小于4％。本文的研究结果为新工质R407C的系统分析和计算提供了准确、可靠的热力学性质和热物理性质分析计算结果。     

三元混合工质R407C热力参数模型分析

R407C是替代R22的一种极具前景的新工质，本文采用Peng-Robinson型方程对新工质R407C的热力学性质进行了全面的计算，并根据实验数据拟合出新工质的迁移特性计算公式。根据计算结果给出了新工质R407C的压焓图和温-熵图。计算关联式具有较高的精度，热力学参数计算误差小于1％，迁移特性参数误差小于4％。本文的研究结果为新工质R407C的系统分析和计算提供了准确、可靠的热力学性质和热物理性质分析计算结果。     

流程布置对R407C冷凝器性能的影响

本文基于传热单元法，建立了冷凝器的分布参数模型。以R407C为工质，运用该模型详细分析了四种不同流程布置两排管冷凝器的换热和流动特性，并与以R22为工质的冷凝器进行了性能比较。结果表明：采用R407C为工质时，四种流程布置中，无论是随着管内冷媒流量的变化，还是随着冷凝器迎风面风速的变化，逆流布置换热效果都是最好，换热量比顺流高约5％-40％，压降比顺流高约3％-10％，其次是错流布置，顺流布置最差。在与以R22为工质的冷凝器性能比较中，无论是随着管内冷媒流量的变化，还是随着迎风面风速的变化，R407C冷凝器换热量都比R22冷凝器高约3％-5％，压降低约5％-10％，是其理想的替代产品。     

R407C替代R22的房间空调器特性研究

在分析比较非共沸混合制冷剂R407C和R22的热力特性的基础上，对R407C替代R22的房间空调器特性进行了实验研究，获得了用R407C直接替代R22时，房间空调器的最佳毛细管长度和最佳充灌量，并对进一步提高R407C房间空调器性能提出了建议。     

一种精馏型油分离器的实验研究

精馏是利用气液混合物中各组分挥发度的差异进行分离.本文研制的精馏型油分离器结合了传统油分离器的分离原理和精馏原理,以塔内恒定压力1000 kPa、入口温度62℃、R134a和PAG的质量比为7:3的进料条件用Aspen软件进行模拟,模拟可得通过精馏过程可除去二元混合物中的润滑油.为验证该油分离器的实际可行性,搭建了测试...     

Composition shift in liquid-recirculation refrigerating systems: an experimental investigation for the pure fluid R134a and the mixture R32/134aChangement de composition dans les systèmes frigorifiques à recirculation de liquide : étude expérimentale du frigorigène pur R134a et d'un mélange de R32+R134a

The ability of zeotropic mixtures with a remarkable temperature glide to operate in liquid-recirculation systems is investigated and the results of an experimental comparison between the performances of the pure fluid R134a and the zeotropic mixture R32/134a (25/75% by mass) are presented. R134a performs slightly better in the liquid-recirculation mode than in the traditional dry-expansion mode; on the other hand, liquid-recirculation configuration has a detrimental effect on the zeotropic mixture's performance. The reason for this detrimental effect is the mixture component separation which occurs at the liquid/vapor separator. The effect of this separation is investigated using gas chromatograph analysis.     

Influence of the expansion device on the performance of a heat pump using R407C under a range of charging conditions

The objective of this study is to investigate the effects of the expansion device on the performance of a water-to-water heat pump using R407C, which has been considered as one of the alternative refrigerants to replace R22 with “soft-optimization”, at various charging conditions. The heat pump applying the expansion devices of a capillary tube and an EEV was tested by varying refrigerant charge amount from −20% to +20% of full charge and changing water temperature entering the condenser from 30 °C to 42 °C, while maintaining water temperature entering the evaporator at 25 °C. The R22 capillary tube system is utilized as a baseline unit for the performance comparison with the R407C system. The performance of the capillary tube system is more sensitive to off-design charge than that of the EEV system. As the refrigerant charge deviates from the full charge, the R407C EEV system shows a much lower degradation of capacity and COP as compared to the R22 and R407C capillary tube systems due to an optimum control of superheat by electronically adjusting the EEV opening. In addition, the R407C EEV system shows more a stable compressor discharge temperature at off-design charge than the R407C capillary tube system.     

Electrostatic separation for multi-size granule of crushed printed circuit board waste using two-roll separator

The electrostatic separation is an effective method for recycle of crushed waste electrical and electronic equipment (WEEE). However, the robustness of the classical roll-type separator is vulnerable because of its sensitivity to variation of granule size. A new "two-roll type corona-electrostatic separator" was built to overcome the limitation of the classical one considering the actual situation of the industrial application which always contains granule with different size. Multi-size granule of crushed printed circuit board (PCB) wastes was used for investigation and the results showed that the efficiency of the separation process was improved by using the new separator. Compared with the process (lower voltage) performed on the old separator, the metal products increased 34% while the middling products reduced 73%, respectively. Compared with the process (higher voltage) performed on the old separator, the metal products increased 22% while the middling products reduced 59%, respectively. In addition, the metal component of the middling products using new machine notably decreased, 33% (new machine) compared with 58% (lower voltage) and 66% (higher voltage). The efficiency of the separation process is enhanced compared with the classical one.     

Experimental investigation of the performance of R22, R407C and R410A in several capillary tubes for air-conditioners

The objective of this study is to present test results and to develop a dimensionless correlation on the basis of the experimental data of adiabatic capillary tubes for R22 and its alternatives, R407C (R32/125/134a, 23/25/52 wt.%) and R410A (R32/125, 50/50 wt.%). Several capillary tubes with different length and inner diameter were selected as test sections. Mass flow rate through the capillary tube was measured for several condensing temperatures and various degrees of subcooling at the inlet of each capillary tube. Experimental conditions for the condensing temperatures were selected as 40, 45 and 50°C, and the degrees of subcooling were adjusted to 1.5, 5 and 10°C. Mass flow rates of R407C and R410A were compared with those of R22 for the same test conditions. The results for straight capillary tubes were also compared with those of coiled capillary tubes. A new correlation based on Buckingham π theorem to predict the mass flow rate through the capillary tubes was presented based on extensive experimental data for R22, R407C and R410A. Dimensionless parameters were chosen considering the effects of tube geometry, capillary tube inlet conditions, and refrigerant properties. Dimensionless correlation predicted experimental data within relative deviations ranging from −12% to +12% for every test condition for R22, R407C and R410A. The predictions by the developed correlation were in good agreement with the results in the open literature.     

Experimental investigation on minichannel parallel flow condenser performance with R22, R410A and R407C

A performance evaluation of minichannel parallel flow (MCPF) condenser in residential/commercial refrigeration system has been carried out in calorimeter room with wind tunnel in this paper. The heat rejection and pressure drop characteristics for heat exchangers were compared using R22, R410A and R407C as working fluids. The experimental results showed that heat rejection of MCPF condenser with R410A was higher than that of R22 and R407C by 15.6~26.3% and 12.3~22.7% under full and partial load conditions, respectively. The refrigerant side pressure drop trend of R410A in MCPF condenser was smaller than that of R22 and R407C under the same mass flow rate.     

Changes in optimal design of a dry-expansion evaporator when replacing R22 with R407C: Différences de configuration optimale pour un évaporateur à détente sèche lors du remplacement du R22 par le R407C

An investigation was made on whether the optimal number of tubes in a dry-expansion evaporator, for a given area or a given cost, will change when R22 is replaced with the non-azeotropic mixture R407C. A comprehensive computer program was used to simulate the tube-and-shell evaporator, under several sets of conditions. The simulations show that there are only small differences between R22 and R407C in the optimal number of tubes. However, the results indicate that one can allow a somewhat higher pressure drop for R407C, and that the number of tubes for a given area therefore can be smaller when R407C is used. For both fluids, the evaporator performance is more sensitive to the optimization for a given cost than for a given area.     

Calculation of thermodynamic properties of R407C and R410A by the Martin–Hou equation of state — part I: theoretical development

A theoretical development of the thermodynamic properties of two mixtures of hydrofluorocarbon (HFC) refrigerants, i.e. R407C and R410A (in the superheated vapour state), is carried out. The modelling is based on the Martin-Hou equation of state, which has long been used for pure hydrofluorocarbons (e.g. R134a) with good results. Since R407C and R410A are very well investigated refrigerants, the analytical procedure here derived concerns with those thermodynamic properties of R407C and R410A (in the superheated state) that are not published in the current specialised literature. They are: compressibility factor, isentropic and isothermal compressibility, volume expansivity, isentropic and isothermal exponent, speed of sound and Joule–Thomson coefficient. These properties may be used as a theoretical basis for research into the optimal HFC-mixture for compressor efficiency and for performing cycle calculations in the vapour-phase region for systems working with R407C and R410A.     

R32/R134a和R407C用于变浓度热泵系统的实验

为了解决R32/R134a应用于变浓度热泵系统存在的排气温度过高问题,提出使用三元混合工质R407C用于该系统中.以R32/R134a和R407C作为工质在变浓度容量调节热泵系统中进行了吸气压力不变时的变浓度实验.实验结果表明,R407C在本系统中变浓度范围低于R32/R134a,但R407C的排气温度和耗功均低于R32/R134a,具有良好的变浓度调节潜力.