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Condensation Process (condensation + process)
Selected AbstractsNumerical investigation of the effect of inlet condition on self-excited oscillation of wet steam flow in a supersonic turbine cascade,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009Wu Xiaoming Abstract Self-excited oscillation can be induced due to the interaction between condensation process and local transonic condition in condensing flow, which is an important problem in wet steam turbine. With an Eulerian/Eulerian numerical model, the self-excited oscillation of wet steam flow is investigated in a supersonic turbine cascade. Owing to supercritical heat addition to the subsonic flow in the convergent part of the cascade, the oscillation frequency decreases with increased inlet supercooling. Mass flow rate increases in the oscillating flow due to the greater supersaturation in condensation process, while the increase will be suppressed with the flow oscillation. Higher inlet supercooling leads to the fact that the condensation process moves upstream and the loss increases. Moreover, some predictions of oscillation effects on outflow angle and aerodynamic force are also presented. Finally, heterogeneous condensations with inlet wetness and periodic inlet conditions, as a result of the interference between stator and rotor, are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] The Planck,Benzinger thermal work function in the condensation of water vaporINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2006Paul W. Chun Abstract Based on the Planck,Benzinger thermal work function using Chun's method, the innate temperature-invariant enthalpy at 0 K, ,H0(T0), for the condensation of water vapor as well as the dimer, trimer, tetramer, and pentamer form in the vapor phase, was determined to be 0.447 kcal mol,1 for vapor, 1.127 for the dimer, 0.555 for the trimer, 0.236 for the tetramer, and 0.079 kcal mol,1 for the pentamer using ,G(T) data reported by Kell et al. in 1968 and Kell and McLaurin in 1969. These results suggest that the predominant dimeric form is the most stable of these n -mers. Using Nemethy and Scheraga's 1962 data for the Helmholtz free energy of liquid water, the value of ,H0(T0) was determined to be 1.21 kcal mol,1. This is very close to the value for the energy of the hydrogen bond EH of 1.32 kcal mol,1 reported by Nemethy and Scheraga, using statistical thermodynamics. It seems clear that very little energy is required for interconversion between the hypothetical supercooled water vapor and glassy water at 0 K. A hypothetical supercooled water vapor at 0 K is apparently almost as highly associated as glassy water at that temperature, suggesting a dynamic equilibrium between vapor and liquid. This water vapor condensation is highly similar in its thermodynamic behavior to that of sequence-specific pairwise (dipeptide) hydrophobic interaction, except that the negative Gibbs free energy change minimum at ,Ts,, the thermal setpoint for vapor condensation, where T,S = 0, occurs at a considerably lower temperature, 270 K (below 0°C) compared with ,350 K. The temperature of condensation ,Tcond, at which ,G(T) = 0, where water vapor begins to condense, was found to be 383 K. In the case of a sequence-specific pairwise hydrophobic interaction, the melting temperature, ,Tm,, where ,G(Tm) = 0 was found to be 460 K. Only between two temperature limits, ,Th, = 99 K and ,Tcond, = 383 K, where ,G(Tcond) = 0, is the net chemical driving force favorable for polymorphism of glassy water and hypothetical supercooled water vapor. Analysis of the water vapor condensation process based on the Planck,Benzinger thermal work function confirms that a thermodynamic molecular switch occurs at 10 K, wherein a change of sign in [,Cp(T)]cond leads to a true negative minimum in the Gibbs free energy of vapor condensation, and hence a maximum in the related equilibrium constant, Kcond. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Morphological changes of sperm nuclei during spermatogenesis in the brown alga Cystoseira hakodatensis (Fucales, Phaeophyceae)PHYCOLOGICAL RESEARCH, Issue 2 2003Shinya Yoshikawa SUMMARY Morphological changes and chromatin condensation of sperm nuclei were observed during spermatogenesis in the fucalean brown alga Cystoseira hakodatensis (Yendo) Fensholt. Ultrastructural studies have shown that the mature spermatozoid has an elongated and concave nucleus with condensed chromatin. The morphological changes and the chromatin condensation process during spermatogenesis was observed. Nuclear size decreased in two stages during spermatogenesis. During the first stage, spherical nuclei decreased in size as they were undergoing meiotic divisions and the subsequent mitoses within the antheridium. During the second stage, the morphological transformation from a spherical into an elongated nucleus occurred. Afterwards, chromatin condensed at the periphery in each nucleus, and chromatin-free regions were observed in the center of the nucleus. These chromatin-free regions in the center of nucleus were compressed by the peripheral chromatin-condensed region. As the result, the elongated and concave nucleus of the mature sperm consisted of uniformly well-condensed chromatin. [source] Carboxyl terminated polyamide 12 chain extension by reactive extrusion using a dioxazoline coupling agent.POLYMER ENGINEERING & SCIENCE, Issue 12 2002Part II: Effects of extrusion conditions Condensation reactions between a carboxyl terminated polyamide 12 and a dioxazoline carried out by reactive extrusion have been characterized in the first part of this study. In the present paper, we focus on the influence of extrusion conditions on reaction progress. Influences of screw profile, screw speed, barrel temperature and feed rate have been established. The use of a flow computation software permitted confirmation of the importance of thermal and mechanical degradations in the condensation process. [source] New aspects of unsaturated polyester resin synthesis.POLYMER INTERNATIONAL, Issue 5 2003Part 2. Abstract The distribution of unsaturations in the prepolymer of a typical unsaturated polyester (UP) resin (maleic anhydride, phthalic anhydride and 1,2-propylene glycol) has been shown to influence the kinetics of the cure process with styrene monomer. Segments containing double bonds in close proximity appear to lower the reactivity of the resin due to steric hindrance, as indicated by the fact that the rate of cure and the final degree of cure, measured by differential scanning calorimetry (DSC), increase as the average sequence length (SL) of maleic units decreases. This implies that the reactivity of UP resins may be improved by synthesis of prepolymers with certain reactant sequence-length distributions. The copolymer formed by the melt condensation process of maleic anhydride, phthalic anhydride and 1,2-propylene glycol in the absence of a transesterification catalyst has a non-random structure with a tendency towards blockiness. This was established using 1H NMR analysis in tandem with deterministic and Monte Carlo modelling techniques. Copyright © 2003 Society of Chemical Industry [source] Formation, growth mechanism and packing sequences of binary alloy cluster anions from laser ablation of mixtures of lead and transition metalsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2003Xia Zhang By using laser ablation of the mixtures of a transition metal (M: Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag) plus lead, M/Pb binary cluster anions were observed except for Zn, and the number of transition metal atoms contained in the binary clusters is at most 4. This behavior is different from that reported previously for M/Ge binary clusters. The experiments indicate that it is also very difficult to form Al/Pb clusters. The distribution patterns of M/Pb binary alloy cluster anions are remarkably similar to those of pure Pb clusters, consistent with a formation mechanism in which transition metal atoms are sequentially attached to [Mx,1Pby], clusters and thus form [MxPby], clusters by a simple condensation process. As the number of transition metal atoms increases, the intensities of binary clusters gradually decrease. It is proposed that [MPb4], and [MPb5], cluster anions might be the unit building blocks of M/Pb binary cluster anions, and the layer packing sequences for magic clusters are predicted on this basis. The [MxPby], binary clusters containing 13 atoms (x,+,y,=,13; x,,,0) are proposed to have an icosahedral structure. Copyright © 2003 John Wiley & Sons, Ltd. [source] Reduction of Active Elastase Concentration by Means of Immobilized Inhibitors: A Novel Therapeutic ApproachBIOTECHNOLOGY PROGRESS, Issue 3 2004Valentina Grano The inhibitory power of three different active Nylon membranes, separately loaded with three different protease inhibitors, was studied with the aim of reducing the increased elastase concentration occurring during hemodialysis or extracorporeal blood circulation in patients undergoing cardiopulmonary bypass. Chemical grafting was carried out to make the inert Nylon membrane suitable for the immobilization of the inhibitors. The behavior of immobilized ,1 -antitrypsin, bovine pancreatic trypsin inhibitor (BPTI), or elastatinal was separately studied. ,1 -Antitrypsin and BPTI were covalently immobilized by means of a diazotization process, whereas elastatinal was covalently attached via a condensation process mediated by glutaraldehyde. The inhibitory power of each membrane type was studied as a function of the amount of immobilized inhibitor and temperature. All active membranes have shown good inhibitory power. The most efficient membrane was that loaded with ,1 -antitrypsin, the less efficient that with BPTI. [source] Vapor Condensation Heat Transfer in a Thermoplate Heat ExchangerCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2007J. Mitrovic Abstract The heat transfer and pressure drop in a thermoplate heat exchanger operating as a condenser have been investigated experimentally. In order to separate the heat transfer resistances in the condensation process, the single phase forced convection has been studied using distilled water and Marlotherm oil in the thermoplate and correlations developed for the Nusselt number and the friction factor. For the condensation experiments, an apparatus has been constructed comprising two identical condensers composed of the same thermoplate type as employed in the single phase experiments. Isopropanol is used as a test fluid at pressures below atmospheric pressure. The heat transfer resistances in the condensation experiments are separated and expressions for the condensation heat transfer and pressure drop are developed with the aid of the results obtained in the single phase studies. [source] | ||||||||||||||||