Critical parameters for HFC134a, HFC32 and HFC125

The vapour-liquid coexistence curves near the critical point for HFC134a (CF₃CH₂F: 1,1,1,2-tetrafluoroethane), HFC32 (CH₂F₂: difluoromethane) and HFC125 (CHF₂CF₃: pentafluoroethane) have been measured by visual observation of the meniscus disappearance. Three sets of 17 experimental results for the saturated liquid or vapour densities for HFC134a, HFC32 and HFC125 have been obtained in the reduced temperature range T/T_c > 0.96 and in the reduced density range 0.4 < ρ/ρ_c < 1.7. From these measurements, the critical temperature and the critical density for these HFCs have been determined in consideration of the meniscus disappearance level as well as the intensity of the critical opalescence. The critical pressure has been calculated by the extrapolation of the vapour-pressure correlation. The uncertainties of the critical temperature, critical density and critical pressure are estimated to be within ± 10 mK, ± 5 kg m⁻³ and ± 9 kPa, respectively.     

In the Mi(d)st Of

It's in the air. The first thing that the term atmosphere evokes is in the air, the intangibility of air. A gaseous layer enveloping the planet, a zone where clouds move about, atmosphere is the invisible shroud around each object emanating (such is the meaning that the word has taken on over time) a sort of fragrance or warmth. Atmosphere is created by the particular subject matter or place – it is given off from it – and corresponds to it like a sort of spirit that floats around, revealing, betraying a certain essence of the place or subject matter, but remaining ever visible. Michel Orsoni, ‘Point of view: A question of atmosphere’, 1998¹. Copyright © 2008 John Wiley & Sons, Ltd.     

A thermodynamic analysis of refrigerants: Possibilities and tradeoffs for Low-GWP refrigerants

We explore the possibilities for refrigerants having low global warming potential (GWP). A set of about 1200 candidate fluids is identified from more than 56 000 small molecules examined by applying screening criteria to estimates for GWP, flammability, stability, toxicity, and critical temperature. Methodologies for this screening have been presented in earlier works and are summarized here. The fluids with critical temperatures between 300 K and 400 K (i.e., those that could be used in current types of equipment with minor modifications) number 62. The fluids include halogenated olefins; compounds containing oxygen, nitrogen, or sulfur; as well as carbon dioxide. We discuss the tradeoffs presented by these 62 candidates, considering their thermodynamic properties and their stability and toxicity characteristics. No fluid is ideal in all regards—all have one or more negative attributes: poor thermodynamic properties, toxicity, chemical instability, low to moderate flammability, or very high operating pressures.     

Kinetic,electronic properties and conductivity studies of （（12Z）N-（5Z）-1-bromo-5-（phenylimino）-1H-pyrrol-2（5H）-ylidene benzenmine {ArN（CNBrCCHCH）NAr} （Ar = C6H5）

Kinetic and conductivity of new Schiff bases compounds such （（12Z）N-（5Z）-1-bromo-5-（phenylimino）-1H- pyrrol-2（5 H）-ylidene）benzenamine {ArN（CNBrCCHCH）NAr} （Ar = C6H5） incorporating the chelating diamino has been studied in this paper and was found a second order of this reaction. Electronic Properties using hyperchem program study has been improved for this compound such angel and bond distance, and then this compound was defining as electric conductivity and did prove to be useful for conduclively compound.     

Computationally efficient model for refrigeration compressor gas dynamics

In this paper a computationally efficient steady state model for a typical refrigeration reciprocating compressor is proposed. The plenum cavity is modelled using the acoustic plane wave theory, while the compression process is modelled as a one-dimensional gas dynamics equation. Valve dynamic models, based on a single vibration mode approximation, are coupled with the gas dynamics equation and acoustic plenum models. The steady-state solution of the resultant coupled non-linear equations are posed as a boundary value problem and solved using Warner's algorithm. The Warner's algorithm applied to compressor simulation is shown to be computationally more efficient as compared to conventional techniques such as shooting methods. Comparisons are based on the number of iterations and time taken for convergence. Effect of operating conditions on the overall compressor performance is also investigated.     

Vapour–liquid equilibrium data for the difluoromethane+1,1,1,2,3,3,3-heptafluoropropane system at temperatures from 283.20 to 343.38 K and pressures up to 4.5 MPa

Isothermal vapour–liquid equilibrium data for the difluoromethane (R32)-1,1,1,2,3,3,3-Heptafluoropropane (R227ea) binary system are presented at 283.20, 303.21, 323.21 and 343.38 K and pressures up to 4.5 MPa. The experimental method, used for this work, is of the static-analytic type. It takes advantage of mobile pneumatic capillary samplers (Rolsi™, Armines’ patent) developed in our laboratory. The four P, x, y isothermal data have been represented with the Soave–Redlich–Kwong (SRK) equation of state and the MHV1 rules involving the NRTL model.     

Inhibition de l'action phototoxique du bergaptène par des filtres UV-A

Il est bien acquis que le 5-méthoxypsoralène (5-MOP, bergaptène) contenu dans l'essence de bergamote exerce plusieurs actions biologiques à la suite d'irradiation en lumière UV-longue (UV-A, λ > 320 nm). Cette étude a eu pour but de vérifier si la réponse phototoxique, déclenchée chez le cobaye à la suite d'application cutanée de 5-MOP suivie par rayonnement UV, peut être réduite ou même annulée par l'application simultanée de substances absorbant les rayons UV-A. Les solutions photosensibilisatrices employées étaient (a) une solution alcoolique de 5-MOP, (b) de l'essence de bergamote diluée, et (c) un parfum expérimental. Parmi les filtres qui ont été essayés, deux dérivés du dibenzoylméthane se sont révelés particulièrement efficaces. On a observé que l'activité protectrice de ces filtres augmente de façon significative lorsqu'ils sont dissous dans l'essence de bergamote, ou dans le parfum, par rapport à l'activité demontrée dans la solution alcoolique de 5-MOP. Un dérivé du distirylbiphényle possédant un maximum d'absorption à 350 nm s'est révelé particulièrement actif.
Inhibition of bergaptene toxicity by UV-A filters     

An experimental investigation and modelling of the viscosity refrigerant/oil solutions

This paper presents experimental data for the viscosity of solutions of refrigerant R600a (isobutane) with mineral compressor oils Azmol, Reniso WF 15A, and R245fa (1,1,1,3,3-pentafluoropropane) with polyolester compressor oil Planetelf ACD 100 FY on the saturation line. The experimental data were obtained for solution of R600a with mineral compressor oil Azmol in the temperature range from 294.7 to 338.1 K and the concentration range 0.04399 ≤ w_R ≤ 0.3651, the solution of R600a with mineral compressor oil Reniso WF 15A at the temperatures from 285.8 to 348.4 K and the concentration range 0.03364 ≤ w_R ≤ 0.2911, the solution of R245fa with polyolester compressor oil Planetelf ACD 100 FY at the temperatures from 309 to 348.2 and the concentration range 0.06390 ≤ w_R ≤ 0.3845. The viscosity was measured using a rolling ball method. The method for prediction of the dynamic viscosity for refrigerant/oil solutions is reported.     

20世纪初中国女子美术留学教育

众所周知,20世纪前期在中国历史上出现了规模宏大的留学热潮。其中,女子留学研习美术,是中国近现代美术教育史上一个不可忽视的现象。她们或留学日本,或留学欧美,主动引进传播西方美术,为中国美术走向多元化、中西兼容的开放时代立下了不朽的功绩。