制冷工质HFC-134a热力学性质计算模型

根据国外有关资料,对比分析了HFC-134a两组基于MH方程的热力学性质参数方程,优化组合出较为精确的HFC-134a热力学性质计算模型,推导了相应的焓熵计算公式,用Visual Fortran 5.0编程计算了所得模型的部分焓熵值,验证了该模型的准确性,在常见的制冷空调工程实用工作温度和压力范围内有良好的计算精度,全部计算公式均适用于工程设计应用.     

并联机床的动力学特性对加工精度影响的分析

为了提高并联机床的加工精度,分析了并联机床的动力学特性对加工精度的影响。根据牛顿—欧拉方程,得到并联机床的动力学方程,解得连杆的驱动力;根据杆件轴向伸长量与受力之间的关系,得到连杆的长度误差;以无长度误差的连杆长度为优化目标,用优化的方法,得到动平台的位姿,并与连杆有长度误差时动平台的位姿比较,得动平台的位姿误差;根据刀具在动平台坐标系中位置,得刀具加工位置误差及对被加工零件精度的影响。结果表明：并联机床连杆的长度误差,引起刀具加工位置误差,使被加工零件产生形位误差和尺寸误差;并联机床电主轴偏心引起连杆的长度误差的扰动,产生刀具加工位置的扰动误差,影响被加工零件的表面粗糙度。     

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。     

R134a单元式风冷冷风机组冷凝器设计

单元式风冷冷风空调机组普遍采用波纹翅片管冷凝器。对冷凝器进行设计的关键是确定制冷工质在铜管内的冷凝换热系数及空气在翅片侧的表面换热系数，同时也需要考虑空气流过冷凝器的压降，以便选择风机。采用数学模型及换热关联式计算相关参数，在此基础上对R134a单元式风冷冷风空调机组的冷凝器进行设计。     

Spatial and energy distributions of particles sputtered from NiPd single crystals

Molecular dynamic simulation has been used to study the sputtering of NiPd single-crystal disordered compounds. Spatial distributions, as well as the energy of Ni and Pd particles sputtered from the NiPd (001) face have been investigated, for Ar bombarding ions of energies E₀ ranging from 0.1 keV to 5 keV, incident at different angles. The results have shown a predominant exit both of Ni and Pd atoms near the same close-packed directions, in contrast to what is observed for ordered binary compounds. For unchanged composition of the surface, the emission of Ni in the <011> close-packed directions is significantly greater than the emission of Pd. When the composition of top layers was changed, however, the opposite is observed and the exit of Pd prevails. Energy dependence and energy spectra of sputtered components have been analysed as well as the origin and the number of the generation of ejected particles. The observed trends are explained by the particular behaviour of correlated collisions in single crystals.     

Performance of ejector cooling systems using low ecological impact refrigerants

The theoretical behaviour of an ejector cooling system, using as working fluids propane, butane, isobutane, R152a and R134a, is obtained. The ejector works as a thermo-compressor that is simulated with a validated one-dimensional mathematical model, whose errors are lower than 6%. For a system unitary cooling capacity, a parametric study is carried out varying the generation, condensation and evaporation temperatures. From the obtained data, a complete analysis of the system performance can be achieved when the ejector and system operation parameters are considered. The best performance corresponds to the system using propane, because has the highest system coefficient of performance and its ejector has the maximum entrainment ratio value, the least area ratio value and the highest efficiency value. The considered generation temperature ranging from 70 °C to 95 °C is appropriate for low-grade energy sources assisting thermal cooling systems. After this system performance, come those in which R152a and R134a are employed, with isobutane and butane at the end. The obtained results represent potential design points of an efficient ejector cooling system operation, because to each combination of the above mentioned temperatures corresponds one and only one ejector geometry.     

异丁烷(R600a)饱和蒸气压的实验研究

利用改进的Burnett法PvTx实验台,精确测量了66组R600a饱和蒸气压实验数据.温度测量范围为253-393 K,压力测量范围为73-2833 kPa;温度测量偏差不大于±10 mK,压力测量偏差不大于±870 Pa.提出了一个新的R600a饱和蒸气压方程,方程适用温度范围为120 K到临界温度,与已有实验数据进行了比较,还计算得到了R600a的正常沸点和偏心因子值.     

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.     

Predicting remnant lifetime of high-temperature materials by a resistance degradation model

Abstract

Lifetime and remnant life of engineering materials at high temperature has been analyzed based on a resistance degradation model. It can be demonstrated that the lifetime includes two time processes: resistance degradation process before crack initiation and crack growth process after the crack initiation. Traditional lifetime prediction, via the crack growth model, was found to involve the paradox that the lifetime is in proportion to the initial crack size. Whereas, experiments of static fatigue using glass sheet specimens did not confirm this proportional relationship. For a smooth sample, fracture resistance depends on the strength of the material, so a strength degradation model was used to estimate the lifetime zone between an upper and lower bound. It is defined that the material fails when the residual strength decline to the working stress or deformation reaches a designed limit. It is concluded that the quantity of lifetime mainly depends on the rate of resistance degradation for a brittle component under applied load. Thus, lifetime prediction is simulated as a simple relationship between distance, rate and time, in which the distance is known, the rate can be obtained from experiments and then the lifetime can be calculated.     

A Self-Similar Solution of Navier–Stokes and Energy Equations for Rotating Flows between a Cone and a Disk

A laminar flow and heat transfer are investigated in a gap between a disk and a cone which touches the disk by its apex. Group analysis is used to reduce the Navier–Stokes and energy equations to a self-similar form which enables one to derive their exact numerical solution. Calculations are performed for cases of cone rotation with a stationary disk, disk rotation with a stationary cone, and simultaneous rotation of the disk and cone at different velocities for several values of the exponent in the power-law radial distribution of the disk temperature and Prandtl number of 0.71. The calculation results for the case of cone rotation with a stationary disk agree well with the known experimental data.     

R134a单元式风冷冷风空调机蒸发器设计

以理论模型为基础，对R134a单元式风冷冷风机组翅片管式蒸发器进行设计。应用管内流动沸腾换热模型仿真分析R134a的质量流量对沸腾换热的影响，利用外掠翅片管束换热关联式计算管外翅片侧表面换热系数，进而得出翅片管蒸发器总传热系数，利用计算结果进行设计。     

空间任意方位面对面平行度误差的测定

本文按照面对面平行度误差的定义，在机器坐标系建立空间任意方位被测零件的面对面平行度误差评定的数学模型，并采用有效集法快速、简便地求得最优解，为坐标测量机上实现最小条件评定面对面平行误差开辟了一条有效途径     

与臭氧安全工质R134a互溶的润滑油特性的理论分析及试验

根据制冷剂与润滑油互溶的理论基础分析了与R134a相兼容的润滑油的特性，指出酯类润滑油POEs作为R134a配对的润滑油更为合适；给出R134a系统用润滑油的指标；最后对酯类润滑油与R134a的互溶性做了试验研究，证明R134a与酯类润滑油的互溶性很好。     

A New Method for Liquid Viscosity Measurements: Inclined-Tube Viscometry

In this article, a method which can be used to measure the viscosity of liquids with an inclined tube at high pressures and for low-boiling substances is described. The measurement equation was established. The measuring methods for two unknown parameters which are in the measurement equation are presented, and a viscosity measurement system was designed and constructed, which consists of an experimental cell, an inclination-angle control subsystem, a constant temperature subsystem, and a data collection and process subsystem. At atmospheric pressure, the kinematic viscosity of pure water was measured at temperatures from 273.15 K to 333.15 K to demonstrate the performance of the apparatus. The results show that the absolute average relative deviation is 0.84% in comparison with reliable literature values. The kinematic viscosity of saturated liquid R134a and R600a were also measured at temperatures from 273.15 K to 295.15 K and 273.15 K to 300.15 K, respectively, and the corresponding absolute average relative deviations are 1.04% and 1.02% in comparison with reliable literature values. These experimental results demonstrate the performance of the apparatus, while providing estimates of the uncertainty and reliability of the experimental system.     

R600a制冷剂用新型冷冻机油的研制

利用新疆环烷基原油资源,采用高压加氢组合工艺新技术生产的基础油,通过原料筛选、优化调合比例及添加剂复配后,研制出满足用户要求的适用于R600a制冷剂的全封闭冷冻机油。研究表明,该冷冻机油解决了与R600a制冷剂相溶性及其与制冷剂共存时的热一化学稳定性、抗磨性能等问题。目前已成功通过压缩机台架试验。     

近共沸制冷剂R134a/R290的研究

当R134a的质量在55%～65%之间时,R134a/R290混合物是近共沸混合物.它可以作为R22的替代制冷剂,并具有优秀的循环性能.这种制冷剂用在空调器中是安全的,并有可能采用矿物油或者烷基苯作为润滑油.     

Pairwise combination of methods of detecting radiation sources

The pairwise combination of methods for radio measurements when detecting radiation sources is considered. The statistical parameters of two-dimensional detection with a linear resolving limit are investigated and it is shown that it is possible to achieve a considerable reduction in the probability of missing a radiation source when using such a combination of detection methods. __________ Translated from Izmeritel'naya Tekhnika, No. 8, pp. 68–73, 2008.     

二甲醚作为中高温热泵工质的性能分析

对二甲醚（DME）作为中高温热泵工质的热工性能进行计算与分析,与传统热泵工质R22,R134a及自然工质R600a进行对比,并对变工况（冷凝温度75～95℃,固定循环温升45℃）进行理论计算。计算结果表明,DME制热性能参数与R134a接近,但COP值高于R134a,单位容积制热量在高温工况下具有更出色的性能。而且DME的GWP与ODP值均接近零,可作为绿色环保替代工质直接充注至R134a热泵系统,并可应用于中高温环境。     

Measurements of the viscosity of refrigerants in the vapor phase

Measurements of the viscosity of refrigerants R124, R125, R134a, and R152a in the vapor phase are presented. The measurements, performed in a new vibrating-wire instrument, cover a temperature range from 273 to 333 K from about atmospheric pressure up to below the saturation pressure. The uncertainty of the reported values is estimated to be better than ±1%. Comparison with measurements of other investigators reveals a lack of reliable data in the vapor region for these compounds. Paper presented at the Fourth Asian Thermophysical Properties Conference., September 5–8, 1995, Tokyo, Japan.     

Thermal conductivity of a wide range of alternative refrigerants measured with an improved guarded hot-plate apparatus

The thermal conductivity of the refrigerants R22, R123, R134a, R142b, R143a, and R152a has been determined as a function of temperature in the range from 300 to 460 K. Measurements were carried out at atmospheric pressure with an improved guarded hot-plate apparatus. The width of the instrument's gas layer and the temperature difference across the metering section were varied to detect any stray heat transfer. Radiation correction factors were derived from IR absorption spectra. The uncertainty of the measurements is estimated to be 2% at a standard deviation of less than 0.1%. All values are correlated with respect to temperature in the range covered. The equations are found to represent the results with average deviations of 1%. Our data sets are compared with corresponding hot wire results. In contrast to the generally preferred hot wire technique, with its possible electrical and chemical interactions between the wire and the polar refrigerant, there are no such difficulties using a guarded hot-plate apparatus. Our data sets may thus contribute to the discussions on discrepancies in thermal conductivity values from various authors using hot wire as one particular method.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, USA.