R134a：制冷剂的最佳选择

外层空间臭氧层的耗损受到全球普遍关注,自从这一现象首次披露以来,空调制冷行业发生了巨大的变化。例如,多数离心冷冻设备制造商都在试图采用对大气无害的制冷剂,一些厂商采用螺杆压缩机代替离心压缩机。无论如何,使用无害制冷剂的新设备终将取代全球成千上万套旧式制冷装置。     

船用冷藏装置以R134a替代R12作为制冷剂的研究

本文对制冷装置中以R134a替代R12作为制冷剂的运行及需要解决的问题作了分析，通过计算，得出结论认为，在船用制冷装置中用R134a替代R12是可行的，并给出了替换过程中要采取的措施。     

混合制冷剂R1234yf/R134a PVTx性质的实验研究

为了获得混合制冷剂R1234yf/R134a的热物性数据,本文利用Burnett法为基础搭建的高精度PVTx实验台,在温度为268~323 K时,测定了质量分数为55%/45%,50%/50%和45%/55%混合制冷剂R1234yf/R134a的PVT性质,最终拟合了三种不同配比的混合工质的气态维里方程,方程和实验数据具有较高的重合度。     

机械冷藏车R134a替代R12的试验研究

对铁路冷藏车R134a替代R12进行了相关的试验研究。通过模拟计算、试验数据整理、图形化处理,并对照理论计算的结果。试验表明,采集获得的数据与理论计算有很好的符合。R12多应用于冷冻冷藏设备,用R134a替代后,基本的热力参数都和R12系统接近,但设备的制冷性能会有小幅的下降,制冷量将减少15％左右。对于安全性要求高和易泄露的场合,R134a是R12的最佳替代物。     

R32／R134a混合工质泄漏对系统性能的影响

HCFC- 2 2 ( R2 2 )作为一种长“寿命”的氯氟烃制冷剂 ,含有 0 .0 5 5的 ODP值和 16 0 0的GWP值 ,将会长时间破坏臭氧层和造成全球变暖 ,影响大气环境。国际大气环保公约规定在2 0 30年 1月 1日禁止销售和使用 HCFC,欧美和日本等发达国家已经将禁止使用时间表大大提前 ,R2 2的替代十分紧迫 ,美国杜邦公司、ICI公司和联信公司等等相继推出了 R2 2的替代制冷剂。目前国际上倾向于采用混合工质替代 R2 2 ,然而混合工质除共沸物外 ,均因其组成物质的沸点不同而导致气相与液相成分不同。因此 ,在制冷器具中 ,由于制冷剂的泄漏 ,导致制…     

R134a臣卧式螺旋管内流动沸腾换热特性实验研究

对R134a在水平直管和螺旋管内的沸腾换热特性进行了实验研究.在三个不同的蒸发温度(5℃、10℃和20℃),工质R134a的质量流量范围为100～400kg/(m~2·s)和干度范围为0.1～0.8的条件下,实验得到了R134a在水平直管和螺旋管内的沸腾换热系数随其质量流量和干度的变化关系,将水平直管和螺旋管内的沸腾换热特性数据进行了比较,结果显示,在实验条件下,卧式螺旋管的传热系数比直管的平均增加13.7%.     

R134a制冷剂在微通道中的相变传热特性实验

设计了一个可控制制冷剂流量、压力和温度等实验工况的微通道换热器相变流动与换热的可视化实验平台,对R134a制冷剂流经微通道换热器进行了冷凝换热实验研究.试验测量了小质量流率下的R134a制冷剂在多个饱和状态工况下的冷凝换热性能,涉及质量流量、进出口压力和温度等参数.实验分析了传热系数与雷诺数的关系,与Koyama的关联式预测比较接近.分析了摩擦系数随雷诺数的变化,与H L MO和Wu＆Little方程计算得到的数值相近.     

Experimental and theoretical study on flow condensation with non-azeotropic refrigerant mixtures of R32/R134a

Experiments on flow condensation have been conducted with both pure R32, R134a and their mixtures inside a tube (10 m long, 6 mm ID), with a mass flux of 131–369 kg m⁻²s⁻¹ and average condensation temperature of 23–40°C. The experimental heat transfer coefficients are compared with those predicted from correlations. The maximum mean heat transfer coefficient reduction (from a linear interpolation of the single component values) occurs at a concentration of roughly 30% R32 for the same mass flux basis, and is approximately 20% at Gr = 190 kg m⁻²s⁻¹, 16% at Gr = 300 kg m⁻²s⁻¹. Non-ideal properties of the mixture have a certain, but relatively small, influence on the degradation. Among others, temperature and concentration gradients, slip, etc. are also causes of heat transfer degradation.     

一种新型高效传热铜管的冷凝传热性能实验研究

建立无润滑油实验台，以R22。R134a和R410A为工质。测试新型铜管Turbo-DWT和常规内螺纹铜管Turbo—A的冷凝传热性能，并进行比较。从实验数据可知。新管型Turbo-DWT的冷凝传热系数高于Turbo-A约42％，且压降低于Turbo-A约65％（R134a）。三种制冷荆相比，R22的传热系数最高，R410A的压降最小。Turbo-DWT是一种更高效的冷凝传热管，且适用于各种冷媒。     

R22饱和蒸汽在C-S水平管外凝结换热的实验研究

以R22为工质在套管式冷凝器中对C-S水平管在饱和蒸汽状态下冷凝传热的性能进行实验研究，得出凝结换热系数与表面张力及蒸汽流速之间的关系，并拟合出其实验关系式。     

An experimental study on condensation of refrigerant R134a in a multi-port extruded tube

In the present study, the local characteristics of pressure drop and heat transfer are investigated experimentally for the condensation of pure refrigerant R134a in two kinds of 865 mm long multi-port extruded tubes having eight channels in 1.11 mm hydraulic diameter and 19 channels in 0.80 mm hydraulic diameter. The pressure drop is measured at an interval of 191 mm through small pressure measuring ports. The local heat transfer rate is measured in every subsection of 75 mm in effective cooling length using heat flux sensors. It is found that the experimental data of frictional pressure drop agree with the correlation of Mishima and Hibiki [Trans. JMSE (B) 61 (1995) 99], while the correlations of Chisholm and Laird [Trans. ASME 80 (1958) 227], Soliman et al. [Trans. ASME, Ser. C 90 (1998) 267], and Haraguchi et al. [Trans. JSME (B) 60 (1994) 239], overpredict. As a trial, the data of local heat transfer coefficient are also compared with correlations of Moser et al. [J. Heat Transfer 120 (1998) 410] and Haraguchi et al. [Trans. JSME (B) 60 (1994) 245]. The data of high mass velocity agree with the correlation of Moser et al., while those of low mass velocity show different trends. The correlation of Haraguchi et al. shows the trend similar to the data when the shear stress in their correlation is estimated using the correlation of Mishima and Hibiki.     

Condensation heat transfer of binary refrigerant mixtures of R22 and R114 inside a horizontal tube with internal spiral grooves

An experimental study of the condensation of pure and mixed refrigerants of R22 and R114 inside a spirally grooved horizontal copper tube has been carried out. A double-tube counterflow condenser in the pressure range 3–21 bar and at a mass flow-rate 26–70 kg h⁻¹ was used. The axial distributions of refrigerant, tube wall and cooling water temperatures, wall heat flux density and vapour quality are shown graphically. The variation of tube wall temperature around the circumference of the tube is also shown. The local Nusselt number depends on the molar fraction, whereas the average Nusselt number can be correlated by an equation which is modified from a previously established equation for pure refrigerants inside a horizontal smooth tube. The frictional pressure drop evaluated is correlated well by the Lockhart-Martinelli parameters and is independent of the concentration of the mixture.     

混合工质水平管内流动凝结换热研究进展

从实验和模型两个方面,综述了国外对混合工质在水平光管和强化管内流动凝结换热的研究。对多种公开发表的混合工质凝结换热关联式的适用性和准确性进行了讨论。同时,指出了现有研究方法和研究内容的不足,以及应进一步深入研究之处。     

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.     

水平细管管内凝结换热系数的数值模拟

对3种管径（2mm,4mm和6mm）的水平细圆管管内流动凝结换热特性进行研究。采用通用CFD软件Fluent6．3中的Mixture模型,结合UDF编程对物理模型进行数值求解。数值计算结果表明,小尺寸条件下管内凝结换热的规律不同于常规尺寸管道。随着管径的逐渐减小,重力对凝结的影响逐渐减小,气液面切应力、液体表面张力的作用加强。细管凝结过程的局部换热系数远远大于Nusselt的理论解。     

R134a通过短管流动的试验研究

短管机构在汽车空调、家用空调和热泵系统中得到越来越广泛的应用。目前，关于提供通过短管机构ＣＦＣ替代物性能研究方面的数据很少。本文给出了ＣＦＣ替代物Ｒ１３４ａ通过短管机构的流动特性试验研究。在很宽的操作条件下，通过试验研究了Ｒ１３４ａ流过短管机构的性能参数变化。长径比在７￣２０范围内，冷凝温度为３５℃￣５４℃时，过冷度可达１３．９℃，短管入口干度可达１０％左右。对进入短管的两相流和过冷液体性能进行了