二元物系HFC125/HFC152a的热力学性质研究

1引言二元混合工质HFC125／HFC152a臭氧破坏势为零，具有替代CFCs的潜力，也是我们所建议的三元代用混合工质HFC32／HFC125／HFC152a的二元子物系【‘」之一。迄今尚未见到关于该物系的热力学性质研究报导，本文对其进行PVTX实验研究、状态方程与混合规则关联和热力学性质计算。2实验实验在定容式PVTx实验装置上进行，测量精度为laTD528inK、IAPD51·4PPa、卜对训三0．1％和卜叫刮刀1％，采用直接观察法测量泡露点的温度和压力附加认定误差分别不超过50inK和4kPa［‘］。HFC125为美国杜邦公司提供，经天津大学分析中心分析…     

Non-Uniform Onset of Nucleate Flow Boiling of R-134a Inside a Glass Minichannel

The present work is an experimental investigation of the incipient boiling of R134a inside a circular glass minichannel mounted horizontally and equipped with a series of transparent indium tin oxide heaters. The effects of heat flux input levels and refrigerant mass fluxes on the onset nucleate boiling process and on the saturated boiling heat transfer rate are quantitatively explored. The flow pattern visualizations, carried on by means of a high-speed camera, show that the nucleation process is oddly non-uniform: the first vapor bubbles are always generated on the upper side of the tube and lead to a first wall temperature drop. A further increase in the heat flux values results in an increased wall superheat until bubble nucleation also originates on the lower side of the tube, causing a second wall temperature drop. Finally, at higher heat input levels, the boiling process becomes uniformly distributed on the inner tube surface. This phenomenon occurred also after a 180° rotation of the glass tube, and, after a critical analysis of the potential origins, it remains presently unexplained. An evaluation of heat transfer coefficients for low vapor quality regimes is finally presented.     

纳米粒子对矿物油/HFC体系制冷系统特性影响的研究

本文简要介绍了纳米粒子对矿物基冷冻机油/HFC体系相溶性与饱和性的作用机理及相关模型,实验研究了r型二氧化钛纳米粒子对矿物基冷冻机油与HFC类工质的相溶性、含油工质体系的饱和特性及采用矿物油/HFC体系的制冷系统特性的影响.     

Chemical Sensors and Microinstrumentation

The ¹H NMR spectra of racemic (erythro) methoxamine free base, 1, 1-(1-aminoethyl)-2,5-dimethoxybenzenemethanol, have been studied at or near ambient temperatures in CDCl₃ or CD₃CN with the added chiral lanthanide shift reagent (LSR), tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato] europium (III), 2. Spectrometers operating at 60, 200 and 300 MHz were employed; some COSY spectra were acquired to support assignments. Enantiomeric shift differences (Δ Δ Δ) were observed for several nuclei of 1 with added 2 in either CDCl₃ or CD₃CN and an “anomalous” (upfield) shift was seen for the NCH signal. A high degree of signal broadening was seen for runs with either solvent, and surprising similarity was found for the slopes in plots of chemical shift versus [2]/[1] molar ratios for the different nuclei of 1 whether the hydrogen bond donor solvent (CDCl₃) or the hydrogen bond acceptor solvent (CD₃CN) was used. Together with the anomalous shift noted above, these results are interpreted as consistent with strong bidentate chelation of 2 by 1.     

1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Methastyridone, 2,2-Dimethyl-5-(2-Phenylethenyl)-4-Oxazolidinone

Abstract

The 60 MHz ¹H NMR spectra of methastyridone, 2,2-dimethyl-5-(2-phenylethenyl)-4-oxazolidinone, 1, have been studied at 28° in CDCl₃ solution with the achiral reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, Eu(FOD)₃, and the chiral reagent tris[3-(heptafluoropropylhydroxy-methylene)-d?camphorato]europium(III), 3, Eu(HFC)₃.     

NMR Studies of Drugs. Application of a Chiral Lanthanide Shift Reagent for Potential Direct Determination of Enantiomeric Excess of Methsuximide

The 200 MHz ¹H NMR Spectra of methsuximide, 1,3-dimethy1-3-ogebt1-2,5-otrrikudubeduibem 1, havebeen studied in CDC13 solution with the chiral reagent, tris[3-(heptafluoropropy1-hydroxymethylene)-d-camphorato] europium (III), 2, Eu(HFC)3. Substantial lanthanide-induced shifts are seen. In addition, significant enantiomeric shift differences are observed for several of the nuclei of 1. With a 2:1 molar ratio near 1.0, the CCH3 and NCH3 signals show nearly baseline resolution between the peaks from each enantiomer, providing excellent potential for direct determinations of enantiomeric excess of samples of 1. As little as 2% of a minor enatiomer should be readily detectable.     

NMR Studies of Drugs. Phensuximide. 1H and 13C NMR Methods with Chiral Solvating Agents and Lanthanide Shift Reagents

NMR spectra of the racemic anticonvulsant, phensuximide, 1, in CDCl₃ solution, have been studied with additives to explore methods for potential direct determination of enantiomeric excess (% ee). Proton studies at 200 MHz with the chiral solvating agent (CSA) (-)-2,2,2-trifluoro-1- (9-recommended for ee analysis due to uncertainties of contributions to the NCH₃ from the CH₂ proton absorptions.     

NMR Studies of Agricultural Compounds. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Herbicide,Diclofop Methyl

The 60 MHz H NMR spectra for the herbicide, diclofop methyl, 1, have been studied in CDCl₃ solution at 28±1° with the added achiral lanthanide shift reagent (LSR) tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), Eu (FOD)₃, 2, and with the chiral LSRs, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III)₃, Eu(HFC)₃, 3, and tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorato]europium(III), Eu(FACAM)₃, 4. Both 2 and 3 produced substantial lanthanide-induced shifts (LIS) consistent with predominant LSR binding at the ester carbonyl. Much smaller LIS magnitudes were observed with 4. Modest enantiomeric shift differences (ΔΔδ) were elicited with 3 for the OCH₃ and the CCH₃ resonances of 1. The former signal appears to offer greatest potential for the direct determination of enantiomeric excess of samples of 1, with 3:1 molar ratios ca. 0.3–0.4 resulting in valley heights as low as 33% of the average peak heights of the OCH₃ signals of the two enantiomers.     

NMR Studies of Agricultural Compounds. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Herbicide,Fenoxaprop-Ethyl

The 200 MHz H NMR spectra of the herbicide, fenoxaprop-ethyl, 1, have been studied in CDCl₃ solution at ambient temperatures as the racemic ester free base with the added chiral lanthanide shift reagent (LSR), tris [3 - (heptafluoropropylhydroxymethylene) - (+) - camphorato]europium(III), Eu(HFC)₃, 2, with some additional runs using the achiral LSR, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), Eu(FOD)₃, 3, for supplemental spectral simplification. With 2, definite enantiomeric shift differences (ΔΔδ) were observed only for the CH₃CH₂O resonance. Although increased spectral complexity for the CH₂O signal was seen with added 2, this could have resulted from anisochrony of the diastereotopic protons, H_a and H_b, of this methylene group rather than true ΔΔδ, since the achiral 3 led to near-baseline separation between the CH_aH_bO signals. Lanthanide-induced shift (LIS) magnitudes were interpreted as consistent with predominant LSR binding at the ester carbonyl.     

变温工况下可燃制冷剂的爆炸极限

鉴于当前紧迫的HCFCs淘汰形势,很多学者针对替代潜力较大的HFC161和HC1150的热力性质、循环性能以及常温下可燃性等进行了研究,然而针对变温工况下上述可燃制冷剂爆炸极限影响规律的研究却极为少见.为此,本课题组建立了一套由上位机自动控制的可燃气体爆炸极限测试系统,并对HFC161和HC1150在-3～55,℃范围内的爆炸极限进行了试验研究.结果表明:在一定的温度范围内,温度升高会使不可燃的混合气体出现热激化现象,而成为可燃可爆状态.当环境温度由-3,℃升高到55,℃时,HFC161和HC1150的爆炸极限范围分别增加了1.42%、4.59%.低温对制冷剂爆炸极限有较明显的抑制作用;2种工质的燃爆特性的温度敏感区大约位于10～40,℃区间,当温度高于40,℃或低于10,℃时,温度对制冷剂可燃上、下限的影响均减弱.试验结果和变化规律为可燃制冷剂在变温工况下的安全应用奠定了基础.