三元混合物的爆炸极限实验

参照国标GB/12474-90的有关规定,设计了一套测试可燃气体爆炸极限的实验装置。系统地测量了三元混合物R290+R152a+R134的爆炸极限,积累了爆炸极限数据,绘制了爆炸极限曲线。混合物的临界爆炸比(CFR),随着R290/R152a体积比的增大而增大。     

HCFC22替代用制冷剂混合物性能

本文将14种由R32、R125、R134a、R152a、R290（丙烷）和R1270（丙烯）等构成的制冷剂混合物在试验热泵上进行试验,以替代家用空调器中常和的HCFC22。该热泵能力为3．5kW,其蒸发器和冷凝器以不涂为传热介质（HTF）,并采和逆流型。所有试验中的HTF温度均固定在ARI试验工况A的数值。试验结果表明：由R32、R125和R134a构成的三元制冷剂混合物给出的性能系数（COP）和能力比HCFC22大4－5％。在其同时,由R125、R1134a和R152a构成的三元制冷剂混合物的COP和能力均低于HCFC22。R32／R134a二元制冷剂混合物的COP比HCFC22高7％,而R290／R134a二元共沸制冷剂的COP和能力均提高3－4％。所试验的制冷剂混合物压缩机排气温度均比HCFC22低得多,表明制冷剂事物系统可靠性和寿命均更高。最后,采用吸气一液体热交换器（SLHX）的试验结果表明,SLHX在用于空调器时须特别注意,因为其影响随制冷剂而定。     

新型替代制冷剂HFC-32爆炸极限影响因素研究

本文利用可燃性气体爆炸极限测定实验台研究了温度、相对湿度、阻燃剂对HFC-32爆炸极限的影响。结果表明:在-5~55℃范围之内,升高温度会促使HFC-32爆炸上限逐渐增大,其爆炸下限逐渐减少,拓宽了HFC-32的爆炸区间;当相对湿度低于60%时,增大相对湿度会导致HFC-32爆炸下限稍微增大,其爆炸上限稍微减少,当相对湿度由60%逐渐增至87%时,其爆炸上限急剧减少,直至爆炸极限范围消失;添加CF_3I或HFC-134a阻燃剂可促使HFC-32爆炸极限范围减少,而且CF_3I的阻燃效果优于HFC-134a,当CF_3I/HFC-32体积比由0增至1或HFC-134a/HFC-32体积比由0增至10时,两种混合气的爆炸范围最终都减少为0。研究结果为抑制HFC-32燃烧提供了重要的理论依据。     

全卤代烃对可燃制冷剂燃烧极限的抑制性研究（英文）

依据国标GB/T12474-90,对7组二元混合物的燃烧极限进行了实验测量,分别是丙烷/三氟碘甲烷、丙烷/四氟甲烷、1,1-二氟乙烷/四氟甲烷、甲烷/六氟乙烷、1,1-二氟乙烷/三氟碘甲烷、乙烷/三氟碘甲烷和甲烷/三氟碘甲烷。所有测量都在大气压力和室温条件下进行,测量不确定度低于0.27 mol%。通过对已经修正过的Le Chatelier的预测模型进一步的修改和开发,并用新的模型预测了全卤代烃对可燃的混合物制冷剂燃烧极限的抑制性。通过分析预测结果和实验数据,发现改进后的公式能够很好地拟合经过全卤代烃稀释后的可燃制冷剂的燃烧极限实验数据。     

制冷剂R161燃烧抑制试验研究

采用球形瓶法和柱形管法进行R161的燃烧极限和燃烧速度研究,并分别以R22,R134a和R125等不燃制冷剂为阻燃剂,研究其对R161的燃烧抑制情况。一方面,考查R22／R161,R134a／R161和R125／R161混合工质不同摩尔比、不同空气含量下的燃烧极限,获得各体系的燃烧范围和临界抑爆比;另一方面,考查各混合工质不同摩尔比、不同化学当量比下的燃烧速度,获得各体系的2L燃烧等级临界配比。从而为开发零ODP,低GWP的新型环保制冷剂提供重要的燃烧安全特性数据。     

R32/R134a混合制冷剂扩散吸收制冷系统实验研究

在国内外扩散吸收制冷研究现状的基础上,分别采用R32、R134a和R32/R134a混合物为制冷剂,DMF(N,N-二甲基甲酰胺)为吸收剂,Ar为扩散气体,对扩散吸收制冷系统进行了性能研究,探究了混合制冷剂配比以及加热功率对系统制冷效果的影响。实验结果显示,R32/R134a混合制冷剂的制冷效果要优于R32或R134a纯制冷剂,且在不同的组分浓度和不同的加热量下,制冷效果不同,存在较好的R32浓度范围。     

混合制冷剂R134a/R600a应用于冰箱的研究

对于R134a/R600a组成的混合制冷剂,当R134a的质量百分比在75%～95%之间时,可以形成一种近共沸混合物.本文介绍了这种近共沸混合制冷剂的性质,理论分析并实验验证了它作为R12的替代制冷剂的循环性能,并对它采用烷基苯或者矿物油作为润滑油时的制冷系统回油性能进行了实验研究.     

R134a与R410A在空调工况下的性能比较

传统制冷剂R22的替代已是大势所趋.本文着重对R22的替代制冷剂R134a与R410A的传热、阻力压降特性进行实验比较研究,认为R410A在传热、阻力压降特性方面比R134a优良,作为R22的替代制冷剂,R410A应比R134a更有竞争力.     

环丙烷热力性能的理论分析与实验研究

通过对RC270、R600a及R134a三种制冷剂热力性能的理论研究,对比分析表明RC270的单位容积制冷量比R600a大144.5%,比R134a大33.8%,其性能系数COP比R600a高出5.9%,比R134a高出9.7%;同时,针对家用冷藏冷冻箱BCD-228,根据国家标准的相关要求,对家用冷藏冷冻箱分别使用RC270、R134a两种制冷剂的制冷循环性能进行了实验研究,实验结果表明,RC270比R134a节能4.7%,能效指数降低2.9%,研究结果对RC270新型制冷剂推广应用具有一定的参考价值。     

R-134a在水平直管和螺旋管内凝结换热特性的实验研究

对替代制冷剂R-134a在水平直管和螺旋管内的凝结换热特性进行了实验研究。在三个不同的冷凝温度（35℃、40℃和45℃）、制冷剂R-1Ma的质量流量变化范围为100-400kg／（m^2·s）和制冷剂的干度范围为0．1-0．8的条件下,实验得到了R-134a在水平直管和螺旋管内的凝结换热系数随R—134a的质量流量和干度的变化关系,并将水平直管和螺旋管内的凝结换热特性数据进行了对比。实验结果表明,R-134a在螺旋管内的凝结换热系数比直管的大4％。13．8％。     

Lower Flammability Limit of Difluoromethane and Percolation Theory

Measurements of flammability limits by the ASTM E 681 method are believed to be affected by vessel size. In order to investigate the effect of volume on measured lower flammability limits in air, experimental measurements of the lower flammability limit of difluoromethane (R-32) are made at 21°C using 3, 5, 12, and 20 L vessels. A spark ignition source is used with the voltage adjusted to the value where dielectric breakdown just begins to occur (approximately 7–12 kV). The results demonstrated a higher concentration for the lower flammability limit for the vessels smaller than 5 L suggesting that wall effects quench the flame propagation. The lower flammability limit for vessels with a 5 L or greater volume are in good agreement with those obtained in earlier investigations. For 5 L and larger vessels the lower flammability limits systematically shift to higher concentrations of difluoromethane with increasing vessel size which is consistent with a percolation model for spatial flame propagation. Extrapolation of the data to infinite vessel size using a percolation model yielded a lower flammability limit of 15.2 vol.%. The results are consistent with the work of Richard for refrigerant mixtures, R134a/R152a and R125/R152a, in large volume vessels (200 L) where effects of vessel walls are negligible.     

含R290混合物用于家用空调冷媒的性能研究

对含R290的共沸混合工质用于替猪八戒R22的可行性进行了研究.理论计算结果表明,共沸混合物除了具有优良的热物理性能之外,容积制冷量亦有所提高,有可能成为R22的替代物;对这几种工质的可燃性进行了评估,认为其用于家用空调节器器是安全的.     

Research on the flammable characteristics of fluoroethane (R161) and its binary blends

As one of the potential new generation refrigerants, R161 possesses the suitable thermodynamic properties and small climate change effects, but it is flammable. This paper contributed to its fundamental flammable characteristics theoretically and experimentally. Firstly, its flames were researched under various testing conditions. Then influences of temperature and vessel dimensions on the flammability limits of R161 were tested and analyzed. The results indicated that the lower flammability limits of R161 increased with the decrease of temperature while its upper flammability limits reduced oppositely, when initial temperature varied from 55 °C to −5 °C. Thirdly, a method was proposed to estimate the refrigerants' flammability limits, which concerned three impact parameters, the gas concentration, bond dissociation energies and enthalpy variations. Finally, the flame suppression effects of 1,1,1,2,3,3,3-heptafluoropropane (R227ea), trifluoroiodomethane (R13I1), and trans-1,3,3,3-tetrafluoropropene (R1234ze) to R161 were tested, and the critical flammability ratios (CFR) of some inhibitors to R161 were obtained.     

Performances d'une machine tritherme à éjecteur utilisant des mélanges de fluides frigorigènesPerformance analysis of a jet cooling system using refrigerant mixtures

The optimisation of a jet cooling system using refrigerant mixtures as substitutes of pure refrigerants has been investigated. A steady-state simulation program, for given temperatures of the sources, integrating simple models of each component has been developed. A Peng-Robinson equation of state assuming equality of the fugacities of the two phases was used to model the thermodynamic properties of the vapour and liquid-vapour equilibrium. The refrigerants investigated in this study are: the pure refrigerants R142b, R152a, RC318, R124, R134a, R22 and the binary refrigerants R22/RC318, R22/R142b, R22/R124, R22/R152a, R22/R134a, R134a/R142b, R152a/R142b and R134a/R152a. Results show that the use of a binary mixture does not always increase the performance of system. Generally, when the mixture is strongly zeotropic (e.g.: R22/RC318), the cooling efficiency of the system decreases. However, when the mixture is mildly zeotropic (e.g. R134a/R142b) or almost azeotropic (e.g. R134a/R152a), efficiency and energetic efficiency increase.     

R1234yf整车汽车空调泄漏扩散研究

新能源电动汽车热管理系统与传统乘用车不同,对采用热泵空调系统并利用液冷冷却电池的新能源电动汽车,制冷剂充注量比传统汽车空调增加了400～800 g.若使用可燃制冷剂,泄漏扩散至乘员舱,燃烧风险将增大.本文通过数值模拟对R1234yf制冷剂在蒸发器破损泄漏随送风进入乘员舱后的浓度变化过程和最高浓度进行了动态监测.结果表明...     

Prediction of in-tube condensation heat transfer characteristics of binary refrigerant mixtures

This study presents a prediction model for the condensation heat transfer characteristics of binary zeotropic refrigerant mixtures inside horizontal smooth tubes. In this model, both the vapor-side and liquid-side mass transfers are considered, and the high flux mass transfer correction factor is used to evaluate mass transfer coefficients. The model was applied to the binary zeotropic refrigerant mixture R134a/R123, which has a large temperature glide. Calculation results showed that the heat transfer degradation of R134a/R123 due to gradients in the mass fraction and temperature is considerable, and depends on the mass fraction of the more volatile component and the vapor mass quality of the refrigerant mixture. By comparison with experimental data, incorporating the present finite mass transfer model for the liquid film side into the calculation algorithm was shown to reasonably well predict the condensation heat transfer coefficients of binary refrigerant mixtures with the mean deviation of about 10.3%. In the present calculations, however, it was also found that the high flux mass transfer correction factor had only a slight effect on the condensation heat transfer.     

可燃制冷剂R32室内空调器泄漏扩散特性的实验研究

制冷剂R32具有良好的环保特性和热工性能,但其可燃性限制了它的应用推广,因此需要对R32的安全性进行分析。实验研究了分体壁挂式空调用制冷剂R32在空调运行时,蒸发器不同泄漏位置和不同泄漏速度对室内R32浓度分布的影响,得出R32在空调运行时的泄漏扩散特性。研究表明:可燃性制冷剂R32在室内机蒸发器处发生泄漏时,泄漏过程可分为快速泄漏阶段和低速泄漏阶段;蒸发器出口泄漏比蒸发器入口泄漏危险性高;仅在蒸发器出口大流量泄漏时,室内机附近区域R32浓度最大值为16.79%,超过可燃下限(14.4%)16.6%。可燃浓度持续了22 s,存在着火的可能性,但概率较低;排风作用对各测点的浓度衰减影响强烈,可有效降低室内R32的浓度。     

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.     

Performance des mélanges de frigorigènes utilisés pour remplacer le HCFC22

In this study, 14 refrigerant mixtures composed of R32, R125, R134a, R152a, R290 (propane) and R1270 (propylene) were tested in a breadboard heat pump in an attempt to substitute HCFC22 used in residential air-conditioners. The heat pump was of 3.5 kW capacity with water as the heat transfer fluid (HTF) in the evaporator and condenser that are in a counter current flow configuration. All tests were conducted with the HTF temperatures fixed to those found in the ARI test A condition. Test results show that ternary mixtures composed of R32, R125, and R134a have a 4–5% higher coefficient of performance (COP) and capacity than HCFC22. On the other hand, ternary mixtures containing R125, R134a and R152a have both lower COPs and capacities than HCFC22. R32/R134a binary mixtures show a 7% increase in COP with the similar capacity to that of HCFC22 while R290/R134a azeotrope shows a 3–4% increases in both COP and capacity. The compressor discharge temperatures of the mixtures tested are much lower than those of HCFC22, indicating that these mixtures would offer better system reliability and longer life time than HCFC22. Finally, test results with a suction line heat exchanger (SLHX) indicate that SLHX must be used with special care in air-conditioners since its effect is fluid dependent.