Viscosities of HFC-32 and HFC-32/lubricant mixtures

A modified capillary tube method has been used to measure viscosities for HFC32 over a temperature range from -20 to 90°C and a pressure range from 0.1 to 5.3 M Pa, and for the liquid mixtures of HFC-32 with a synthetic polyolester oil at temperatures from 20 to 75°C and oil mass fractions from 0.44 to 1. Estimated uncertainties in the measured viscosities do not exceed ± 1.2 and ± 1.8°% for the pure fluocarbon and the mixtures, respectively. It is found that viscosity isotherms for HFC-32 at subcritical temperatures exhibit a minimum with increasing pressure, with the viscosity decreasing as much as 10% relative to its value at one atmosphere. Correlations are presented for dilute gas viscosities, excess viscosities, and saturated liquid and vapor viscosities. These correlations are shown to lit our data within experimental uncertainties. For HFC-32/lubricant mixtures, a free-volume viscosity model has been applied to correlate the experimental data.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

R32制冷剂

自从1997年京都会议以后, R22和R410a都被认为是需要淘汰的制冷剂,世界各国都在寻找合适的替代制冷剂,并作为重要的任务。 R32被认为是一种有潜力的替代R22与R410a在空调器中使用的制冷剂。本文综述R32替代的可行性和它与R410a的性能比较。     

Two-stage doping of silicon with phosphorus-32 and sulfur-32 isotopes

We describe a principally new approach to obtaining solid sources of sulfur for the two-stage diffusion doping of silicon, which eliminates the surface erosion of wafers. According to the proposed method, ³²P radionuclide is diffused into a near-surface region of silicon in the first (introduction) stage and then converted into ³²S isotope in the second state. It is shown that the samples of silicon doped by this method with ³²S isotope contain deep levels with the ionization energies E _c − 0.13 eV, E _c − 0.25 eV, E _c − 0.37 eV, and E _c − 0.50 eV, which exhibit a donor character and are related to the sulfur impurity. It is established that the diffusion of ³²S isotope into p-Si leads to a change in the type of conduction, while the diffusion of this isotope into n-Si decreases the resistivity of the initial material.     

A 32 x 32 element row-column addressed capacitive micromachined ultrasonic transducer

This paper presents characterization and initial imaging results of a 32 x 32 element two-dimensional capacitive micromachined ultrasonic transducer array. The devices are fabricated using a wafer bonding process in which both the insulation layer and the membrane are user-deposited silicon nitride. The transducers use a row-column addressing scheme to simplify the fabrication process and beamformer. By adjusting the number of rows and columns that are biased, the effective aperture of the transducer can be adjusted. This is significant because it permits imaging in the near-field of the transducer without the use of a lens. The effect on the transmit beam profile is demonstrated. The transducer has a center frequency of 5.9 MHz and a relative bandwidth of 110%. Images of horizontal and vertical wires are taken to demonstrate image resolution. A three-dimensional image of four pin heads is also demonstrated.     

Index to Volume 32

ABSTRACT

Most of the recently developed methods on optimum planning for accelerated life tests (ALT) involve “guessing” values of parameters to be estimated, and substituting such guesses in the proposed solution to obtain the final testing plan. In reality, such guesses may be very different from true values of the parameters, leading to inefficient test plans. To address this problem, we propose a sequential Bayesian strategy for planning of ALTs and a Bayesian estimation procedure for updating the parameter estimates sequentially. The proposed approach is motivated by ALT for polymer composite materials, but are generally applicable to a wide range of testing scenarios. Through the proposed sequential Bayesian design, one can efficiently collect data and then make predictions for the field performance. We use extensive simulations to evaluate the properties of the proposed sequential test planning strategy. We compare the proposed method to various traditional non-sequential optimum designs. Our results show that the proposed strategy is more robust and efficient, as compared to existing non-sequential optimum designs. Supplementary materials for this article are available online.     

A 32 x 32 capacitive micromachined ultrasonic transducer array manufactured in standard CMOS

As ultrasound imagers become increasingly portable and lower cost, breakthroughs in transducer technology will be needed to provide high-resolution, real-time 3-D imaging while maintaining the affordability needed for portable systems. This paper presents a 32 x 32 ultrasound array prototype, manufactured using a CMUT-in-CMOS approach whereby ultrasonic transducer elements and readout circuits are integrated on a single chip using a standard integrated circuit manufacturing process in a commercial CMOS foundry. Only blanket wet-etch and sealing steps are added to complete the MEMS devices after the CMOS process. This process typically yields better than 99% working elements per array, with less than ±1.5 dB variation in receive sensitivity among the 1024 individually addressable elements. The CMUT pulseecho frequency response is typically centered at 2.1 MHz with a -6 dB fractional bandwidth of 60%, and elements are arranged on a 250 μm hexagonal grid (less than half-wavelength pitch). Multiplexers and CMOS buffers within the array are used to make on-chip routing manageable, reduce the number of physical output leads, and drive the transducer cable. The array has been interfaced to a commercial imager as well as a set of custom transmit and receive electronics, and volumetric images of nylon fishing line targets have been produced.     

Extensometric measuring-computing system 32 IVK-01

This article examines a 32-channel measuring-computing system for measuring dynamic strains, forces, pressures, and temperatures. It discusses the areas of application, structure, composition, main technical specifications, and software of the system.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 49–51, August, 1994.     

R32涡旋式压缩机开发

R32是一种具有巨大应用潜力的制冷剂,但其适用的涡旋式压缩机的开发尚不成熟,尤其是排气温度过高的问题严重影响R32制冷剂的应用。本文指出R32涡旋式压缩机开发的重点与难点,并探讨R32涡旋式压缩机未来的开发方向。     

基于STM32的测力仪设计

本文基于STM32处理器设计了一种体积小、技术先进、质量稳定、价格合理的新型测力仪器.根据测力仪功能和误差精度的需求,从硬件构架和软件设计两方面提出了设计方案.对测力仪系统的数据采集、采样电路、接口、主程序、ADC的配置和使用及远程通讯问题进行了研究.结合测力仪系统组成框图、测力仪数据采集框图、数据采样电路、周期时序图...     

R32和R32/R1234yf混合工质黏度实验测量及模型

本文针对含HFOs类混合制冷剂黏度开展实验和模型研究。采用振动弦法黏度计对R32纯质和R32/R1234yf混合制冷剂黏度进行了实验测量,测量的温度范围分别为263~350 K、263~360 K,压力最高均为30 MPa,实验系统黏度测量的不确定度为2%。本文共获得了177组实验数据,利用得到的实验数据,基于硬球模型分别拟合了R32纯质和R32/R1234yf混合制冷剂黏度方程。R32纯质黏度实验数据与方程的平均绝对偏差为0.28%,最大绝对偏差为0.92%;R32/R1234yf混合工质黏度实验数据与方程的平均绝对偏差为0.69%,最大绝对偏差为2.09%。由此可见,实验数据和黏度模型吻合较好,为R32和R32/R1234yf混合制冷剂的应用研究提供了重要参考依据。     

Crystal growth kinetics in BaOAl2O32SiO2 and SrOAl2O32SiO2 glasses

Crystallization kinetics of BaOAl₂O₃2Si0₂ (BAS) and SrOAl₂O₃2SiO₂ (SAS) glasses in bulk and powderforms have been studied by non-isothermal differential scanning calorimetry (DSC). The crystal growth activation energies were evaluated to be 473 and 451 kJ mol^–1 for bulk samples and 560 and 534 kJ mol^–1 for powder specimens in BAS and SAS glasses, respectively. Development of crystalline phases on thermal treatments of glasses at various temperatures has been followed by powder X-ray diffraction. Powder samples crystallized at lower temperatures than the bulk and the crystallization temperature was lower for SAS glass than BAS. Crystallization in both glasses appeared to be surface nucleated. The high temperature phase hexacelsian, MAl₂Si₂O₈ (M = Ba or Sr), crystallized first by nucleating preferentially on the glass surface. Also, monoclinic celsian does not nucleate directly in the glass, but is formed at higher temperatures from the transformation of the metastable hexagonal phase. In SAS the transformation to monoclinic celsian occurred rapidly after 1 h at 1100 °C. In contrast, in BAS this transformation is sluggish and difficult and did not go to completion even after 10 h heat treatment at 1400 °C. The crystal growth morphologies in the glasses have been observed by optical microscopy. Some of the physical properties of the two glasses are also reported.     

R32与POE或PVE润滑油混合物的物性计算模型与分析

准确计算制冷剂-润滑油混合物的热力性能是分析和评价润滑油对压缩机性能影响的基础。根据厂家提供的实验数据,利用显式拟合关联式法和经验公式修正,本文分别给出了R32/POE和R32/PVE混合物工质对的物性计算模型,同时用相同的方法给出了R410A/POE的混合物溶解度与黏度计算模型来进行对比,模型对物性参数的预测值与厂家提供的实验数据的偏差均在5%以内,为压缩机优化设计及性能分析提供了准确、可靠的热力学模型。此外,在GX工况下对比分析了混合物溶解度随温度、压力的变化及混合物黏度随溶解度、温度、压力的变化,并对混合物的物性做了比较分析,对于制冷剂R32,PVE润滑油较POE润滑油更适用于;而对于润滑油POE,R32与POE的混合性较R410A与POE的混合性好。