Condensation Behavior Research Articles

Pore diameter effects on phase behavior of a gas condensate in graphitic one-and two-dimensional nanopores

Molecular dynamics (MD) simulations were performed on a hydrocarbon mixture representing a typical gas condensate composed mostly of methane and other small molecules with small fractions of heavier hydrocarbons, representative of mixtures found in tight shale reservoirs. The fluid was examined both in bulk and confined to graphitic nano-scale slits and pores. Numerous widths and diameters of slits and pores respectively were examined under variable pressures at 300 K in order to find conditions in which the fluid at the center of the apertures would not be affected by capillary condensation due to the oil-wet walls. For the bulk fluid, retrograde phase behavior was verified by liquid volumes obtained from Voronoi tessellations. In cases of both one and two-dimensional confinement, for the smallest apertures, heavy molecules aggregated inside the pore space and compression of the gas outside the solid structure lead to decreases in density of the confined fluid. Normal density/pressure relationships were observed for slits having gaps of above 3 nm and pores having diameters above 6 nm. At 70 bar, the minimum gap width at which the fluid could pass through the center of slits without condensation effects was predicted to be 6 nm and the corresponding diameter in pores was predicted to be 8 nm. The models suggest that in nanoscale networks involving pores smaller than these limiting dimensions, capillary condensation should significantly impede transmission of natural gases with similar composition.

Morphology evolution, formation mechanism and adsorption properties of hydrochars prepared by hydrothermal carbonization of corn stalk

Hydrochar spheres were formed by the condensation, polymerization and pyrolysis behavior of hemicellulose, amorphous cellulose and soluble lignin.

Complete Condensation of Zero Range Process in Fitness Networks**Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (SRF for ROCS, SEM) of China, and National Natural Science Foundation of China under Grant No. 11505115

In current paper we study the so-called “complete condensation” of zero range process on the fitness network. It is found that under the high temperature limit, the condensation behavior on the fitness model converges to that of the scale-free network, as expected. However, at some temperatures below the critical temprature of Bose–Einstein condensate phase on the fitness network, the complete condensation occurs as well for some values of δ > δc, which is impossible on scale-free network according to the criterion.

Condensation behaviors and resulting heat transfer performance of nano-engineered copper surfaces

We report the microscopic condensation behaviors and resulting heat transfer performance of scalable Cu-based water repellent surfaces with different wetting characteristics including hydrophobic (HPo), superhydrophobic (SHPo) and oil-infused superhydrophobic (Oil-SHPo). The overall heat transfer coefficient and the heat transfer rate through an individual droplet are investigated on horizontally-placed surfaces using the humidity and temperature controlled high speed microscopy combined with thermal network based model. The results show that the average heat transfer rate through an individual droplet is about an order of magnitude smaller on SHPo than on HPo or Oil-SHPo mainly due to smaller droplet radius and higher contact angle. However the investigated SHPo can provide a high number density of condensates throughout the entire measurement via coalescence-induced jumping, while HPo or Oil-SHPo rapidly loses their number density during the droplet coalescence which makes ​the suggested SHPo a promising condenser for long term use. After ∼300min, the overall heat transfer coefficient of the suggested SHPo becomes ∼60% higher than that of HPo and Oil-SHPo. This work clarifies the heat transfer performance of water repellent condensers with different wetting characteristics, and helps develop optimized condensers.

Catch-bond behavior of DNA condensate under tension**Project supported by the National Natural Science Foundation of China (Grant Nos. 11104341, 11474346, 11274374, and 61275192), the National Key Basic Research Program of China (Grant No. 2013CB837200), and the Mechanobiology Institute at National University of Singapore.

Toroid formation is an important mechanism underlying DNA condensation, which has been investigated extensively by single-molecule experiments in vitro. Here, the de-condensation dynamics of DNA condensates were studied using magnetic tweezers combined with Brownian dynamics simulations. The experimental results revealed a surprising non-monotonic dependence of the unfolding rate on the force applied under strong adhesion conditions, resembling the catch-bond behavior reported in the field of ligand-receptor interactions. Simulation results showed that the different unfolding pathways of DNA condensate under large forces derive from the force-dependent deformation of the DNA toroid, which explains the catch-bond behavior of DNA condensate in the magnetic tweezers experiments. These results challenge the universality of the regular toroidal DNA unwrapping mechanism and provide the most complete description to date of multivalent cation-dependent DNA unwrapping under tension.

Size and morphology manipulation of nickel nanoparticle in inductively coupled thermal plasma synthesis

Nickel nanoparticles for the internal electrode of multi-layer ceramic capacitors have been persistently developed in response to the industrial requirements for volumetric capacitance increases. In this context, the manipulation of particle size and morphology is still critical. In the present study, Ni nanoparticles were synthesized by feeding Ni(OH)2 micro-powder feedstock into argon-hydrogen thermal plasma. The injected micro-powder feedstock was fully vaporized and reduced, owing to the high energy density and reactivity of thermal plasma. In association with particle size and morphology, the mass feed-rate and quenching gas were chosen as the variables affecting condensation behaviors from the viewpoint of characteristic times in a general collision-coalescence model. Particle size and morphology varied significantly from well-dispersed coarse nanoparticles to aggregates of fine primary nanoparticles, according to the process parameters. The process parameters' effects on the synthesized nanoparticle properties were considered. In addition, spherical nanoparticles with internal band-like sub-structures were frequent, particularly for coarse particles. From the transmission electron microscopy study and molecular dynamic simulation, it was proven that the band-like sub-structure is nano-twin, and the twin boundary is stabilized by the spontaneous rotating of colliding particles.

Bose-Einstein condensation and critical behavior of two-component bosonic gases

We study Bose-Einstein condensation (BEC) in three-dimensional two-component bosonic gases, characterizing the universal behaviors of the critical modes arising at the BEC transitions. For this purpose, we use field-theoretical (FT) renormalization-group (RG) methods and perform mean-field and numerical calculations. The FT RG analysis is based on the Landau-Ginzburg-Wilson Phi4 theory with two complex scalar fields which has the same symmetry as the bosonic system. In particular, for identical bosons with exchange Z_2,e symmetry, coupled by effective density-density interactions, the global symmetry is Z_2e X U(1) X U(1). At the BEC transition it may break into Z_2,e X Z_2 X Z_2 when both components condense simultaneously, or to U(1) X Z_2 when only one component condenses. This implies different universality classes for the corresponding critical behaviors. Numerical simulations of the two-component Bose-Hubbard model in the hard-core limit support the RG prediction: when both components condense simultaneously, the critical behavior is controlled by a decoupled XY fixed point, with unusual slowly-decaying scaling corrections arising from the on-site inter-species interaction.

QCD Phase Diagram and the Constant Mass Approximation

Dynamical generation of quark masses in the infrared region of QCD plays an important role to understand the peculiar nature of the physics of hadrons. As it is known, the solution of QCD gap equation for the quark mass function is flat for low momentum, but smoothly evolves to the perturbative behavior at high momentum. In this work, we use an effective truncation of QCD gap equation valid up to 1 GeV, and implement it at finite temperature and chemical potential to understand the QCD phase diagram for chiral symmetry breaking-chiral symmetry restoration, and confinement-deconfinement phase transitions from the Schwinger-Dysin equations point of view. Our effective kernel contains a gluon dressing function with two light quark flavors Nf = 2, with current quark mass 0.0035 GeV. An effective coupling, adjusted to reproduce the behavior of the chiral condensate at finite T complements our truncation. We find the critical end point of the phase diagram located at the temperature TE = 0.1245 GeV and the baryonic chemical potential μEB = 0.211 GeV.

Quark deconfinement and gluon condensate in a weak magnetic field from QCD sum rules

We study QCD finite energy sum rules (FESR) for the axial-vector current correlator in the presence of a magnetic field, in the weak field limit and at zero temperature. We find that the perturbative QCD and the hadronic contribution to the sum rules get explicit magnetic-field-dependent corrections and that these in turn induce a magnetic field dependence on the deconfinement phenomenological parameter ${s}_{0}$ and on the gluon condensate. The leading corrections turn out to be quadratic in the field strength. We find from the dimension $d=2$ first FESR that the magnetic field dependence of ${s}_{0}$ is proportional to the absolute value of the light-quark condensate. Hence, it increases with increasing field strength. This implies that the parameters describing chiral symmetry restoration and deconfinement behave similarly as functions of the magnetic filed. Thus, at zero temperature the magnetic field is a catalyzing agent of both chiral symmetry breaking and confinement. From the dimension $d=4$ second FESR we obtain the behavior of the gluon condensate in the presence of the external magnetic field. This condensate also increases with increasing field strength.

Application of humidity-regulating tray for packaging of mushrooms

Major postharvest challenge of mushroom includes high transpiration rate resulting in rapid weight loss and the risk of water vapour condensation inside the package, which results in accelerated deterioration in quality and decay. Thus, this study investigated the transpiration behaviour of mushroom under various combinations of storage temperature (4, 12 and 20°C) and relative humidity (RH) (76, 86, 96 and 100%) and assessed the impact of salt embedded humidity-regulating tray on humidity and condensation behaviour in mushroom package at 7°C and 85% RH. The impact of humidity-regulating and control-polypropylene (control-PP) trays on condensation and quality of mushroom was evaluated after 6 days. Despite the saturated RH condition, across all temperatures studied, mushrooms stored at 100% RH lost moisture at the rate of 0.03–0.22mgkg−1s−1. Humidity-regulating tray maintained a stable RH (93%) inside the package and it absorbed 4.1g of water vapour within 6days at 7°C and 85% RH storage condition. Humidity-regulating tray better maintained the quality of mushrooms compared to control-PP tray, but it absorbed only 4.1g of water vapour in 6 days which was not enough to prevent water condensation in the package headspace for mushrooms.

Characteristics of Droplet Growth Behavior on Hydrophobic Micro-textured Surfaces

For occurring dropwise condensation, the droplet growth behavior such as single droplet growth, coalescence, and fall-off of large droplets play a major role in regard to condensation heat transfer and water harvesting. The present study visualized the droplet growth behavior of dropwise condensation which might be controlled by the surface tension. We used three copper plate with different hole area fraction (i.e., ϕ=0, 0.148 and 0.439). Surface texturing was conducted by using a μ-computer numerical control (μ-CNC) machine and composed of micro-holes (diameter: 300 μm, depth: 200 μm) with 691 μm, 401 μm pitch. To make the hydrophobic surfaces, the copper surfaces were coated self-assembled monolayer (SAM). From the results, it was found that for only SAM coated surface, random coalescence occurred and affected the droplet growth significantly, whereas for textured SAM coated surfaces, the droplet started to be grown up at the textured holes and coalesced near the holes, indicating that capillary effects might affect the droplet growth mechanism. In particular, the fall-off time at which a coalesced droplet is removed away from the surface increased when the textured surfaces was used, because of surface tension effect increased by the textured holes.

Phase transition in finite density and temperature lattice QCD**Supported by National Natural Science Foundation of China (11335001, 11105153, 11405178), Projects of International Cooperation and Exchanges NSFC (11261130311)

We investigate the behavior of the chiral condensate in lattice QCD at finite temperature and finite chemical potential. The study was done using two flavors of light quarks and with a series of β and ma at the lattice size 24 × 122 × 6. The calculation was done in the Taylor expansion formalism. We are able to calculate the first and second order derivatives of in both isoscalar and isovector channels. With the first derivatives being small, we find that the second derivatives are sizable close to the phase transition and that the magnitude of decreases under the influence of finite chemical potential in both channels.

Equilibrium segregation patterns and alloying in Cu/Ni nanoparticles: Experiments versus modeling

We analyze the segregation behavior of bimetallic nanoparticles (NPs) with moderate miscibility gap by applying a combined experimental/simulation approach to Cu/Ni as a model system. Using a hybrid molecular dynamics/Metropolis Monte Carlo algorithm (MD/MMC) based on the embedded atom method (EAM), we derive the equilibrium distribution of atomic species in the clusters for varying concentrations and particle structures. To cross-check the predictive power of our approach, we compare these results with modified EAM (MEAM) and density functional theory based ab initio calculations. This permits to identify possible shortcomings of the EAM when used to describe bimetallic NPs. Additionally, we isolate vibrational entropy contributions to the free energy of the NPs and special focus is put on the possibility of entropic stabilization of segregated versus solid solution NPs. Finally, we complement our simulations by experimental results, which are obtained by studying the behavior of plasma gas condensation synthesized Ni@Cu core-shell (CS) particles upon annealing.

$\frac{{\rm SO}(2N)}{U(N)}$ Riccati–Hartree–Bogoliubov equation based on the SO(2N) Lie algebra of the fermion operators

In this paper we present the induced representation of SO (2N) canonical transformation group and introduce [Formula: see text] coset variables. We give a derivation of the time-dependent Hartree–Bogoliubov (TDHB) equation on the Kähler coset space [Formula: see text] from the Euler–Lagrange equation of motion for the coset variables. The TDHB wave function represents the TD behavior of Bose condensate of fermion pairs. It is a good approximation for the ground state of the fermion system with a pairing interaction, producing the spontaneous Bose condensation. To describe the classical motion on the coset manifold, we start from the local equation of motion. This equation becomes a Riccati-type equation. After giving a simple two-level model and a solution for a coset variable, we can get successfully a general solution of time-dependent Riccati–Hartree–Bogoliubov equation for the coset variables. We obtain the Harish-Chandra decomposition for the SO (2N) matrix based on the nonlinear Möbius transformation together with the geodesic flow on the manifold.

Morphology and Structure Evolutions of Self-Assembled Silver Atomic Islands on Liquid Substrates

We report on the morphology and structure evolutions of silver (Ag) atomic islands deposited on liquid substrates by vapor deposition. It is found that, as the nominal film thickness h is less than or equal to the critical value hc, the morphology of the islands evolves gradually from compact to branched islands, and the apparent Ag surface coverage ρ of the total area increases linearly with h. For h > hc, however, network-structural islands form and the corresponding ρ decreases sharply and then shows a fluctuation behavior. Meanwhile, the average number density n of the islands decreases rapidly. These interesting phenomena mirror the fact that the percolation behavior is observed at hc = 0.8 nm and the condensation behavior appears for h > 0.8 nm. Atomic force microscopy measurements reveal that the Ag islands tend to show three-dimensional growth. Finally, the detailed growth mechanism of the Ag islands is presented.

Ultrafast dynamics of fluctuations in high-temperature superconductors far from equilibrium.

Despite extensive work on high-temperature superconductors, the critical behavior of an incipient condensate has so far been studied exclusively under equilibrium conditions. Here, we excite Bi(2)Sr(2)CaCu(2)O(8+δ) with a femtosecond laser pulse and monitor the subsequent nonequilibrium dynamics of the midinfrared conductivity. Our data allow us to discriminate temperature regimes where superconductivity is either coherent, fluctuating or vanishingly small. Above the transition temperature T(c), we make the striking observation that the relaxation to equilibrium exhibits power-law dynamics and scaling behavior, both for optimally and underdoped superconductors. Our findings can in part be modeled using time-dependent Ginzburg-Landau theory, and they provide strong indication of universality in systems far from equilibrium.

Proton Dissociation of Sulfonated Polysulfones: Influence of Molecular Structure and Conformation

The counterion condensation behavior of proton conducting sulfonated polysulfones has been investigated by combining electrophoretic NMR, pulsed magnetic field gradient NMR, and conductivity measurements on monomeric and polymeric samples with concentrations of ionic groups in the range where dissociation is not complete (IEC = 4.55–7.04 mequiv g–1). In this regime, counterion condensation is shown to critically depend on details of the molecular structure, and all atom molecular dynamics (MD) simulations reveal the formation of well-defined ionic aggregates (e.g., triple ions). The corresponding global minima of the free energy are suggested to be the result of a delicate balance of the energetics involved in conformational changes, formation of ionic aggregates, and solvation. This goes beyond Manning’s counterion condensation theory and has important implications for the development of membranes with high ionic conductivity as needed for many electrochemical applications such as fuel cells and batteries.

ICONE23-1114 BEHAVIOR OF CONDENSED DROPLETS FOR REDUCED HEAT TRANSFER ON HYDROPHOBIC MICRO/NANO STRUCTURES DURING DROPWISE CONDENSATION AT HIGH HEAT FLUX

The heat transfer efficiencies of hydrophobic micro/nano structured (HMN) surfaces that have 〜160° contact angle under atmospheric conditions were investigated experimentally. The departing diameter and the contact angle hysteresis of droplets were .measured by capturing top and tilted side views of condensation phenomena with a high speed camera and an endoscope, respectively. Condensation behaviors on the surface were observed at the micro-scale using an environmental scanning electron microscope (ESEM). Apparently-spherical droplets formed at very low heat flux q" 〜20 kW/m^2 but hemispherical droplets formed at high q" 〜440 kW/m^2. At high q", heat transfer coefficients were lower on the HMN surface than on a hydrophobic smooth (HS) surface although the HMN surface is water repellent so droplets roll off. The results of contact angle hysteresis and ESEM image revealed that the reduced heat transfer of the surface can be attributed to the large size of departing droplets caused by pinning of condensed droplets at nucleation sites. The results suggest that the effect of q" or degree of sub-cooling of a condensed wall depends on the droplet shape, which is closely related to removal rates of condensates and finally to heat transfer.

Condensation Behavior of Heavy Metal Vapors upon Flue Gas Cooling in Oxy-fuel versus Air Combustion

Vaporization of Pb and Zn-loaded model compounds has been carried out in a lab-scale rotary kiln reactor to clarify their condensation behavior upon flue gas cooling in both air-firing and oxy-fuel combustion modes. The influence of flue gas impurities including HCl, SO2 and H2O has been examined systematically. For the two metals existing separately in the reactor, namely in single mode, both preferentially condensed as chlorides in the presence of HCl, under air-firing and oxy-fuel conditions. SO2 and steam in flue gas promote chloride into sulfide at high temperature. It was noticed that the deposition propensities of Pb and Zn vapors under the oxy-fuel condition of the single mode were slightly enhanced over the air-firing condition. This is due to the lower Lewis number of oxy-fuel combustion that is in favor of the formation of highly polydispersed fine particles. However, this discrepancy was diminished in the case where both metals co-existed as in the mixture mode in the reaction system. In the mixture mode from 700 to 400 K, the condensation fraction of either Pb or Zn was confirmed higher than that in the single mode, due to an enhanced heterogeneous nucleation of Zn vapors on PbSO4 nuclei.

Characterization of zinc vapor condensation in fly ash particles using synchrotron X-ray absorption spectroscopy

Heavy metals released from municipal solid waste incinerators have become a major environmental concern. A comprehensive knowledge of metal vapor condensation in fly ash particles during incineration is essential for alleviating heavy metal toxicity, and for optimizing incineration process parameters and flue-gas cleaning systems. In this paper, the condensation of zinc vapor during flue-gas cooling in a 200 t/d fluidized bed incinerator and a 150 t/d moving grate incinerator was characterized and comparatively studied using high resolution synchrotron X-ray absorption spectroscopy (XAS). Principal component analysis, target transformation, and linear combination fitting were employed to identify zinc species directly from size fractionated fly ash particles. The chemical reaction behaviors of different zinc species were described by thermodynamic equilibrium simulations. Consistent with previous theoretical analysis and laboratory scale tests, the condensation behavior of zinc in an industrial incineration system is mainly affected by the sulfur/chlorine ratio and the inorganic particulates. It is found that zinc chloride is the major zinc species in a moving grate incinerator but willemite dominates in the fluidized bed incinerator. The high sulfur and silica/alumina particle concentration in the fluidized bed system changes the condensation propensity of vapors of Zn compounds. Adjusting the concentrations of SO2 in flue-gas can inhibit the formation of zinc chlorides. Silica, alumina, aluminosilicates, and calcium-based compounds are potential sorbents for transforming zinc to less harmful species. To prevent toxic zinc species contained in fine particles from escaping into the atmosphere, wet scrubbers are more suitable for cleaning flue-gases in moving grate incineration systems, while improving the efficiency of dust removal is more important for fluidized bed incineration systems.