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.     

R407C用于变浓度热泵系统的实验研究

提出将R407C用于新型变浓度容量调节热泵系统中,对三元混合物进行了标定分析,并进行了固定工况下变浓度稳态实验与变工况下定浓度与变浓度稳态性能对比实验研究.实验结果表明,固定工况下制热量、制冷系数和耗功均随着低沸点质量分数的增加而增加;定工况下蒸发器进口温度为-6.5℃时容量调节范围为12％.R407C变工况变浓度调节后可以比原混合物很好地控制制热量随着蒸发器进口温度的降低而降低,并且节省系统耗功,可避免蒸发器进口温度过高引起的压缩机耗功过大的问题.     

R161/R13I1/R32混合物替代R22的理论分析

选用R161/R134a//R32和R161/R13I1/R32三元混合工质作为R22的替代制冷剂,分析其在不同工况下的制冷循环热力性能和可燃性,并与R22、R407C和R410A进行比较。结果表明所选的R161/R134a/R32混合物和R161/R13I1/R32混合物均具有作为R22替代物的潜力,并且R161/R13I1/R32混合物的GWP值远低于R32、且不可燃,优势更加明显。     

应用于热泵热水器的工质性能对比研究

从热泵热水器的原理和基本理论循环出发，分别对R22、R134a、R407C和R417a四种工质进行理论计算和对比分析，以便对热泵热水器的设计提供一定的参考。结果表明，四种工质中R134a和R417a最具推广价值，其结果还有待实验进行进一步论证。     

R417a在热泵热水系统中替代R22的实验研究

在热泵热水系统中，对新混合工质R417a进行了理论制冷循环分析和灌注式替代R22的循环性能对比试验研究，结果表明混合工质R417a的制热量稍低于R22，但性能系数COP、压缩机排气温度和功耗等循环性能指标均优于R22，实验过程中R417a工质性能稳定，运行正常，不需更换润滑油。     

R134a／R123自然复叠式热泵系统浓度配比分析

冷热源温度和混合工质浓度配比都会影响自然复叠式热泵系统的热力性能,提出了迭代式定步长搜索法,对80~95"12冷凝温度和0~20℃蒸发温度区间内的R134a/R123自然复叠式热泵系统进行了浓度配比优化计算和分析,得出计算温度区间内任意冷热源温度组合条件下的系统最佳充注浓度.结果表明,在每一组冷热源温度条件下,存在一个最优的混合工质浓度配比对应于系统最大COP值.浓度配比优化可提高自然复叠式热泵循环的热力性能,在最优COP对应的浓度配比条件下,自然复叠式热泵系统的压比较低.     

以R32为工质的准二级压缩热泵系统实验研究

为研究以R32为工质的准二级压缩热泵系统的循环性能,搭建了以R32为工质的热泵实验系统并进行相关研究.研究结果表明,在冷凝温度40℃,蒸发温度在-10～-5℃时,用R32的准二级压缩热泵系统与采用相同工质的单级系统相比,排气温度降低10～20℃,并能控制在130℃以内,保证了机组的安全运行;制热量提高了12％,制热COPh随中间补气压力的不同而高于或低于单级压缩系统,相对补气压力的适宜值范围为0.9～1.1.     

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。     

R32/R1234yf混合工质热泵循环性能分析

在热泵热水器的名义工况下,对R32/R1234yf混合工质热泵循环性能进行计算分析。结果表明:R32/R1234yf的最优质量配比为60/40,使制热性能系数达到最大值4.727,较R22系统增大8.64%;在最优质量配比下,R32/R1234yf系统的单位容积制热量、单位质量制热量和冷凝压力均比R22系统大,但其压比和排气温度均低于R22系统。     

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。     

Formation Conditions of Clathrates Between HFC Alternative Refrigerants and Water

There are two promising candidates as alternative refrigerants for air-conditioners and heat pumps. The first is R407C, which is composed of HFC-32 (23 mass%), HFC-125 (25 mass%), and HFC-134a (52 mass%). The second is R410A, which is composed of HFC-32 (50 mass%) and HFC-125 (50 mass%). In this study, formation conditions of clathrate compounds between water and HFC alternative refrigerants such as HFC-32, HFC-125, HFC-134a, and their mixtures, R407C and R410A, were investigated. Phase diagrams of clathrates of these HFC alternative refrigerants and their mixtures were determined. From the phase diagrams, the critical decomposition temperature and the critical decomposition pressure were determined. The relationship between the critical decomposition points for the clathrates of HFC-32, HFC-125, HFC-134a, R410A, and R407C were studied. It is found that R407C and R410A form clathrate compounds with water under the evaporating temperature condition in the refrigeration cycle of air-conditioners and heat pumps.     

R22替代工质回热循环的性能分析

R22的替代工质的制冷性能通常比R22差，采用回热循环是改善循环性能的一种方法，但是增加回热器会带来成本的增加，而且不同的制冷剂在回热循环中的COP及容积制冷量的变化也是不同的。针对上述问题，分析回热循环的特性和6种制冷剂（R290，R1270，R134a／R1270（0．45／0．55），R134a／R290（0．6／0．4），R407C和R410A）在回热循环中的容积制冷量和COP的变化特点。研究结果表明，R134a,／R1270，R290和R134a／R290系统使用回热器后，性能改善较大，R410A系统只有在高冷凝温度、高过热度时才有必要使用回热器，其余替代工质系统使用回热器，其系统性能改善不明显。     

Flow condensation heat transfer coefficients of R22, R134a, R407C, and R410A inside plain and microfin tubes

Flow condensation heat transfer coefficients (HTCs) of R22, R134a, R407C, and R410A inside horizontal plain and microfin tubes of 9.52 mm outside diameter and 1 m length were measured at the condensation temperature of 40 °C with mass fluxes of 100, 200, and 300 kg m⁻² s⁻¹ and a heat flux of 7.7–7.9 kW m⁻². For a plain tube, HTCs of R134a and R410A were similar to those of R22 while HTCs of R407C are 11–15% lower than those of R22. For a microfin tube, HTCs of R134a were similar to those of R22 while HTCs of R407C and R410A were 23–53% and 10–21% lower than those of R22. For a plain tube, our correlation agreed well with the present data for all refrigerants exhibiting a mean deviation of 11.6%. Finally, HTCs of a microfin tube were 2–3 times higher than those of a plain tube and the heat transfer enhancement factor decreased as the mass flux increased for all refrigerants tested.     

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.     

The surface tension of HFC refrigerants and mixtures

The surface tension of the refrigerants R32, R125, R134a, R143a and R152a, as well as the binary refrigerant mixtures R32-R125, R32-R134a, R125-R134a, R125-R143a, R125- R152a, R143a-R134a and R134a-R152a, and the commercially available ternary mixtures R404A and R407C was measured across the temperature range from −50 to 60°C using a measuring unit based on the capillary rise method. Different formulations for calculation of the surface tension of the binary and ternary mixtures on the basis of the surface tension of the pure refrigerants were tested. With an approach based on mass proportions in the mixture, a good correspondence between the measured and calculated values was achieved.     

Viscosity of Alternative Refrigerants R407C and R407E in the Vapor Phase from 298.15 to 423.15 K

This paper presents new measurements of the viscosity of gaseous R407C (23 mass% HFC-32, 25 mass% HFC-125, 52 mass% HFC-143a) and R407E (25 mass% HFC-32, 15 mass% HFC-125, 60 mass% HFC-143a). The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K. The densities of these two fluid mixtures were calculated with the equation-of-state model in REFPROP. The viscosity at normal pressures was analyzed with the extended law of corresponding states developed by Kestin et al., and the scaling parameters needed in the analysis were obtained from our previous studies for the viscosity of the binary mixtures consisting of HFC-32, HFC-125, and HFC-134a. The modified Enskog theory developed by Vesovic and Wakeham (V-W method) was applied to predict the viscosity for the ternary gaseous HFC mixtures under pressure. As for the calculation of pseudo-radial distribution functions in mixtures, a method based on the equation of state for hard-sphere fluid mixtures proposed by Carnahan-Starling was applied. It was found that the V-W method can predict the viscosity of R407C and R407E without any additional parameters for the ternary mixture.     

降低R32压缩机排气温度的方法

作为下一代制冷剂替代物,R32 由于其GWP值较低、热工性能好,正在受到瞩目.但是正因为其容积制冷量大、热工效率高,R32 与其他制冷剂相比具有压缩机排气温度高的特点.解决这个问题成为一项将 R32 实际应用到环境负荷小、高能效而且成本比较低的空调系统,并推广到世界市场的重要技术课题.本文将阐述利用膨胀阀控制压缩机吸气干度,同时使用 R32 专用的润滑油来降低排气温度,以解决这个问题的方法.     

R407C在巴士空调的应用

本文根据R407C的特性分析结合我们的实验数据,分析了R407C应用于巴士空调时的制冷量、能效比、换热效率、对环境的影响、应用于巴士空调时的系统变化,以及与R134a的比较。     

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。     

R404A和R407A冷冻涡旋式压缩机性能比较

对制冷剂R404A与R407A的热物理特性进行比较,探讨R407A应用于冷冻涡旋式压缩机的可行性,并对这2种制冷剂涡旋式压缩机进行测试,根据容积效率、等熵效率、排气温度、压缩机电流等参数的比较分析,为R407A涡旋式压缩机的开发提供参考依据。