Condensation Behavior Research Articles

Experimental method for observing the fate of SO3/H2SO4 in a temperature-decreasing flue gas flow: Creation of state diagram

The condensation behavior of sulfur trioxide/sulfuric acid (SO3/H2SO4) in flue gas is closely related to corrosion, aerosol formation, and blue plume discharge. Thus, it has become a hot issue in energy and environmental fields. However, no accurate method is currently available to observe this condensation behavior. In this work, an experimental method was developed to explore the fate of SO3/H2SO4 in a temperature-decreasing flue gas flow among the range of 260 °C–40 °C. A novel sampling unit with quartz wool and sodium chloride (NaCl) layer in series was adopted to accomplish the task of collecting aerosol and gaseous H2SO4, respectively, from flue gas. Bench scale experiments were performed to verify the reliability of the method. A state diagram was created according to the experimental results to reveal the fate evolution of H2SO4 as the flue gas temperature dropped. On the basis of the state diagram, the existing empirical models for predicting acid dew point (ADP) were evaluated. The predicted ADP values were found to deviate from the definition, falling within the temperature range in which H2SO4 condensed rapidly instead of the point in which H2SO4 was beginning to condense. The state diagram derived in this work can reveal slight acid condensation behavior better than other methods could.

Experimental investigation on thermal stratification induced by steam direct contact condensation with non-condensable gas

Thermal stratification induced by steam direct contact condensation is a significant technical concern to consider in the energy industry. Thirty experiments have been performed to investigate the effect of steam mass flux, bulk water temperature and air mass fraction on temperature distribution in the water pool. The condensation behavior and time evolution of temperature distribution are recorded and analyzed. Two condensation regimes of chugging and bubbling are observed. Three flow patterns, namely chugging-induced synthetic jets, steam-driven negative buoyancy jets and plume, are discussed. Three thermal patterns of mixing, stratification and re-mixing are identified. A small amount of air (1–2%) could make stratification pattern occur earlier and severer. The maximum vertical temperature difference is about 30 °C in pure steam experiments and 60 °C in mixture gas experiments. Re-mixing pattern occurs when the bulk water temperature is close to 80 °C. In addition, thermal penetration depth, the velocity of thermocline moving down and the thickness of thermocline are estimated through temperature data.

Dependence of nano-confined surface condensation on tangentially external force field

Molecular dynamics (MD) simulations were conducted to investigate the dependence of nano-confined surface condensation on tangentially external force filed. The dynamic behaviors of surface condensation were simulated on a smooth solid surface with fixed wettability (denoted by β) and different external force fields (denoted by fe), and on surfaces with different β and fixed fe. The heat transfer analysis shows that fe, as a bulk factor, indirectly influences the interfacial thermal resistance (R) by direct influence on surface condensation resulting from the viscous and frictional dissipated heats. This is because the dissipated heats result in superheat of the vapor, leading to the delay or elimination of onset of surface condensation. This finding extends the general understanding that R is only dependent on the interfacial factors, such as β and surface topology. The energy balance analysis shows that, for condensation cases, the largest proportion of the heat transferred through the fluid-solid interface is attributed to the change in the internal energy, while for non-condensation cases, it is attributed to the dissipated heats due to fe. As fe increases or β decreases, the dissipated heats increase and gradually take over the total heat transferred from fluid to solid, which finally reduces or suppresses the occurrence of surface condensation.

Constructing hierarchically hydrophilic/superhydrophobic ZIF-8 pattern on soy protein towards a biomimetic efficient water harvesting material

Inspired by the Stenocara beetle that can collect water from moist air in the Namib desert, here, we propose a simple dynamic control of crystal growth of ZIF on a natural polymer, soy protein. By adjusting the precursor concentration as well as the crystal growth time, hierarchical micro-/nano-crystals are constructed on the protein film surface. Taking advantage of the size difference of such crystals, selectively hydrophobic modification with a low surface-energy agent, stearic acid, can be performed on the surface, creating controllably hydrophilic/superhydrophobic patterns in favor of efficient water harvesting from fog. The effects of the as-prepared patterns on the water condensation behavior and collection efficiency are investigated; the maximum water collection efficiency, notably, can reach as high as 917.6 mg·cm−2·h−1. The results suggest that the biomimetic films hold a potential application in atmospheric water collection and the simple pattern-constructing approach is helpful to develop functional surface-patterned materials.

Experimental study of the steam condensate dripping behavior on the containment dome

Under accident conditions of CAP1400, recycling of condensate film from the inner containment wall is a significant aspect for the water level maintenance of the in-containment refueling water storage tank, whilst dripping from the containment dome is the dominant factor that causing the condensate loss. Therefore, experimental investigations on the dripping phenomena were carried out in this study. A pressure vessel was set to simulate the condensing atmosphere in the containment, in which a 1.5 × 0.6 m2 rotatable test section was suspended with similar surface condition as CAP1400. Experimental results show that the condensate flow patterns could be divided into four types. It was found that dripping was triggered by the condensate mass flow flux exceeding the critical value on an unobstructed condensing surface. Meanwhile, the dripping fraction increases with the difference between condensate mass flow flux and the critical value. Besides, the effects of inclination, bulk pressure, air concentration etc. on dripping were experimental analyzed. In general, this study hopes to provide data support and theoretical guidance for the further studies of the condensate loss under accident conditions.

Steam condensate behavior and heat transfer performance on chromium-ion-implanted metal surfaces

Aluminum, copper, nickel, and stainless steel 304 (SUS304) are widely used to construct heat exchangers. In this work, test specimens made of these metallic materials were irradiated with chromium ions. The static and dynamic contact angles of water droplets on the test specimens were measured to examine changes in the surface characteristics. Condensate behavior was visually observed and condensation heat transfer performance was experimentally measured. Filmwise condensation occurred on the surfaces of all the specimens that had no ion implantation. After these specimens were irradiated with chromium ions, filmwise condensation or dropwise condensation was induced depending on the ion irradiation conditions. When the substrates were irradiated with chromium ions at an ion energy level of 100 keV and an ion dose of 3 × 1016 ions/cm2, dropwise condensation occurred regardless of material. When the specimens were irradiated at an ion energy level of 70 keV, dropwise condensation, filmwise condensation, or both occurred depending on the substrate material. The condensation heat transfer coefficient of the surface where dropwise condensation occurred appeared to be more than 3.2 times larger than the theoretical value according to Nusselt’s film theory in the subcooling region below 9.5 K.

Gas condensate treatment: A critical review of materials, methods, field applications, and new solutions

Recently, exploration operations for gas wells target deep reservoirs, where the temperature and pressure are very high. High temperature (more than 200 °C) and pressure (more than 5500 psi) result in degrading the complex organic molecules into dry gas or gas condensate. During gas production the reservoir pressure will decrease below the gas dew point and form a condensate bank near to the borehole. Condensate banking has been branded to cause serious drop in the gas effective permeability, gas productivity and results in formation damage. Numerous techniques have been adapted to mitigate gas condensate banking effects in gas wells. These approaches include the injection of solvents and chemicals to alter formation wettability to minimize condensate blockage. Other methods include acids injection, fracturing treatments, and drilling horizontal wells. These methods will lower the rate of pressure drop and permit the production of a single phase gas. This paper critically reviews the causes and instants of condensate banking in gas reservoirs. The developed models that capture and enumerate this phenomenon, and the most adapted mitigation techniques in accordance to the leading conditions are thoroughly discussed. The most successful agents for enhancing condensate production are reported and their effects on the condensate behavior is identified. Furthermore, novel and new technique for permanent condensate removal is presented in this paper. This review will fill the gap in the area of condensate removal treatments by critically analyzing and summarizing the techniques proposed in the literature.

Properties and phase behavior of Shtokman gas condensate at high pressure

Thermal conductivity, heat capacity per unit volume and phase behavior of Shtokman gas condensate were investigated at high pressure up to 1800 MPa in the temperature interval of 245-373 K using the transient hot-wire method. No crystallization was observed in the sample. The glass transition process in the Shtokman gas condensate takes place in the thermobaric interval which lies outside the range of temperatures and pressures corresponding to the production and transport of the gas condensate.

The condensation behaviours of carbon dioxide on MgO surface

Various separation methods for carbon dioxide gas have been proposed to control its release to the atmosphere, including the separation using an inorganic membranes such as ceramic MgO. In this work, molecular dynamics simulations are performed to clarify the condensation behaviour of carbon dioxide, in its pure and mixture state, onto the surface of MgO at a high operational temperature. The results show that no condensation of pure carbon dioxide is observed on MgO surface. However, the presence of methane impurity can promote the condensation of carbon dioxide on MgO surface as a single layer with an ordered configuration.

Numerical Investigation of a Steam Nozzle with Focus on Non-Equilibrium Condensation and Unsteady Flow Behavior

Present work analyses the condensation of superheated water vapor in supersonic Barschdorff nozzle. The influence of pneumatic mounts in 3D laval nozzle is analyzed using steady and unsteady two phase non-equilibrium condensation steam flow model in Ansys CFX16. Mesh independency studies in 2D model showed that at a lower inlet total temperature and very fine mesh (e.g. 100.2°C and 77k mesh elements) there is problem with the convergence using steady simulation. This is possibly due to the ability of very fine mesh to capture the small flow unsteadiness. The variation in location of Wilson’s point, Wilson’s pressure and maximum sub-cooling rate at the centerline of the nozzle is below 1.5%. The 2D CFD nucleation rate is 50% stronger and droplet diameter is 18% higher compared to the 3D CFD results. The deviation in nucleation rate and droplet diameter at nozzle outlet is the result of dissipation due to wing structure in the 3D model. Nucleation zone predicted by Ansys CFX16 is far upstream the experimental one. Different correction factors in modified nucleation model were used to fit the computed pressure distribution with the experimental one. The correction factor is dependent on boundary conditions and nozzle profile. It is thus concluded that the significance of such correction factor is not unique.

Predicting the growth of many droplets during vapor-diffusion-driven dropwise condensation experiments using the point sink superposition method

Water vapor present in humid air will condense in the form of many small droplets on a cooled substrate. After nucleation, the diffusion of vapor from the environment to the droplets dominates their growth by condensation, and therefore, all droplets must compete for the vapor available in the surroundings. Models that assume droplets grow in isolation or as an equivalent film poorly capture their interaction during vapor-diffusion-driven condensation and do not correspond with experimental condensation rates. By treating the droplets as point sinks, the interaction between all droplets in a system can be captured by superposing the vapor distributions of each droplet. This paper presents direct comparisons of condensation rates measured in experiments and predicted with a point sink superposition method. The results indicate that it is critical to consider a large number of interacting droplets to accurately predict the condensation behavior. Even though the intensity of the interaction between droplets decreases sharply with their separation distance, droplets located relatively far away from a given droplet must be considered to accurately predict its condensation rate, due to the large aggregate effect of all such far away droplets. By considering an appropriate number of interacting droplets in a system, the point sink superposition method is able to predict experimental condensation rates to within 5%.

Three-dimensional lattice Boltzmann modeling of droplet condensation on superhydrophobic nanostructured surfaces

Superhydrophobic surfaces resulting from nanoarrays have good performance in anti-condensation. However, the study of droplet nucleation during water vapor condensation is a challenge because of the limitation of observation on a nanoscale, and therefore the fundamental understanding of the influence of geometrical parameters of nanoarrays on the condensation behavior is still less clear. In this work a three-dimensional (3D) multiphase lattice Boltzmann (LB) model is employed to simulate the phenomenon of droplet condensation on the superhydrophobic nanostructured surface. The model validation is carried out through the comparison of the simulations with the results from the Laplace's law and the intrinsic contact angle theory. The LB simulations accord well with the results from Laplace's law. The relative deviation between the simulated intrinsic contact angle and the theoretical value is less than 0.14%, demonstrating the validity of the LB model. Then, the 3D LB model is used to simulate the different preferential nucleation positions and final wetting states of condensate droplets by changing the geometrical parameters, including interpost space, post height and post width, and local wettability of the nanoarrays on superhydrophobic surfaces. It is found that for the nanostructured surfaces patterned with tall posts, the droplets nucleate in the upside interpost space and at the bottom of nanostructures simultaneously. By designing wider and thinner interpost spaces at the downside and upside of the tall nanostructures, respectively, the phenomenon of droplet nucleation at the bottom can be avoided. The simulation results show that the condensate droplets nucleated in the upside interpost space of tall nanostructures migrate upwards during growth, producing a Wenzel-to-Cassie wetting state transition. On the other hand, the condensate droplets nucleated at the bottom of nanostructured surface patterned with short posts produce the Wenzel state. However, by setting non-uniform hydrophilic and hydrophobic regions on the top of the short nanostructures, the condensate droplets are found to nucleate on the hydrophilic top and generate a Cassie state. The simulated final wetting states of condensate droplets on the nanostructures, having various geometrical parameters, compare reasonably well with the experimental observations reported in the literature. It is demonstrated that the migration of condensate droplets is correlated with the evolution of the statistical average force. If the direction of the statistical average force acting on the droplet is upward, the condensate droplets nucleated in the upside interpost space move upward during growth. The 3D LB simulations provide an insight into the physical mechanism of droplet nucleation, growth and wetting state transitions on superhydrophobic nanostructured surfaces.

Critical exponents of finite temperature chiral phase transition in soft-wall AdS/QCD models

Criticality of chiral phase transition at finite temperature is investigated in a soft-wall AdS/QCD model, with two, three degenerate flavors (Nf = 2, 3) and two light plus one heavier flavor (Nf = 2 + 1). It is shown that in quark mass plane (mu/d − ms) chiral phase transition is second order at a certain critical line, by which the whole plane is divided into first order and crossover regions. The critical exponents β and δ, describing critical behavior of chiral condensate along temperature axis and light quark mass axis, are extracted both numerically and analytically. The model gives the critical exponents of the values beta =frac{1}{2},delta =3 and beta =frac{1}{3},delta =3 for Nf = 2 and Nf = 3 respectively. For Nf = 2 + 1, in small strange quark mass (ms) region, the phase transitions for strange quark and u/d quarks are strongly coupled, and the critical exponents are beta =frac{1}{3},delta =3 ; when ms is larger than ms,t = 0.290 GeV, the dynamics of light flavors (u, d) and strange quarks decoupled and the critical exponents for ūu and overline{d}d becomes beta =frac{1}{2},delta =3 , exactly the same as Nf = 2 result and the mean field result of 3D Ising model; between the two segments, there is a tri-critical point at ms,t = 0.290 GeV, at which beta =frac{1}{4},delta =5 . In some sense, the current results is still at mean field level, and we also showed the possibility to go beyond mean field approximation by including the higher power of scalar potential and the temperature dependence of dilaton field, which might be reasonable in a full back-reaction model. The current study might also provide reasonable constraints on constructing a realistic holographic QCD model, which could describe both chiral dynamics and glue-dynamics correctly.

The interaction effects between droplets condensing from moist air using a distributed point sink method

In modelling dropwise condensation, growth of the droplet is frequently assumed in an isolated form. However, for dropwise condensation of moist air the vapor diffusion from the surrounding to the droplet surface will be tremendously influenced by the blocking effect of the neighboring droplets. The influenced spatial distribution of water vapor totally determines a different condensation rate comparing with that by the isolated droplet model. In this work, a distributed point method (DPSM) as the methodof Green function is developed to capture the interaction effects of droplets without requiring solution of the diffusion equation and the numerical discretization. Due to its nature, the automaticallysatisfied boundary conditions make sure the solution accuracy based on the uniqueness theorem. The significant characteristics for the interaction effects between droplets are investigated by handling a series of droplet arrays. During dropwise condensation, a typical droplet array containing up to 1000 droplets is considered. The results indicate that the interaction effect between droplets is critical in accurately predicting the condensation behavior for dropwise condensation in the presence of non-condensable gas.

Contact Angle and Condensation of a CO2 Droplet on a Solid Surface

Anthropogenic release of carbon dioxide (CO2) is a major contribution to manmade increase in global warming. Carbon capture and storage (CCS) is a necessary technology for lowering CO2 emissions to an acceptable level that limits global warming to below 2 °C. Liquefaction of CO2 is a key process both in capture technologies and in conditioning before ship transport. The efficiency of this process can be remarkably enhanced by promoting dropwise CO2 condensation on cooling surfaces, yet this remains largely unexplored. Here, using molecular dynamics (MD) simulations, we report for the first time the contact angle and condensation behavior of CO2 droplets on a smooth solid surface. The contact angle of the condensed CO2 droplet is greatly dependent on the CO2–solid characteristic interaction energy, but this does not hold true for the sum of condensed molecules. In contrast, the sum of condensed molecules for the filmwise condensation regime increases monotonically at first, but then remains constant as the...

Numerical study on indirect evaporative coolers considering condensation: A thorough comparison between cross flow and counter flow

Indirect evaporative cooling is recognized as an alternative air-cooling solution with low carbon potential and considerable energy efficiency. An indirect evaporative cooler (IEC) can handle both of the sensible and latent cooling loads because of possible condensation when it is used as a precooling unit in an air-conditioning system in hot and humid regions. Cross flow and counter flow, as two basic flow configurations of an IEC, differ in condensation behavior that affects their cooling performance. In this paper, a novel 2-D model of cross flow IEC considering condensation is established and validated. The performance of the cross flow and counter flow IEC is thoroughly compared under the same configuration. The channel gap and height to length ratio (H/L) are optimized to provide references for the design and operation of the IEC under condensation conditions. Results show that under the same operating conditions, the condensation ratio of counter flow IEC is 2–15% higher than that of the cross flow IEC, leading to 2–7% decrease of wet-bulb effectiveness. The difference in the total heat transfer rate between the two configurations is less than 5% when the number of transfer units (NTUp) is lower than 3.1. For cross flow IEC, there is an optimal value in H/L among 0.4–0.8 considering the cooling capacity and energy consumption.

Correlation between nanodispersion of organo-modified nanodiamond in solvent and condensed behavior of their organized particle films

Organo-nanodiamond (ND) by surface modification using several surfactants has achieved nanodispersion in organic solvent as if these nanoparticles were dissolved. High surface coverage has reduced the aggregated particle size of organo-ND particles in the solvent, and their modification by fluorocarbon chain has achieved nanodispersion in a nonpolar solvent. By using a spreading solvent for single particle layers on the water surface of various organo-NDs of resulting dispersion medium, a close relation was found between the dispersion characteristics of organo-nanoparticles in the solvent and the condensation behavior in their two-dimensional single particle layer. Organo-ND with high dispersion ability in solvent has inferior two-dimensional condensability as a single particle layer. Sufficient retention time is necessary to form a homogeneous single particle layer on the water surface. The reason behind this property was found to be the secondary aggregation of organo-modified nanoparticles at the air/water interface. Since lipophilicized ND is not necessarily stable on the water surface, increasing aggregated particle size and three-dimensionality were confirmed in the case where the particle compression rate during two-dimensional integration was relatively fast.

Chiral symmetry breaking and restoration in 2+1 dimensions from holography: Magnetic and inverse magnetic catalysis

We study the chiral symmetry breaking and restoration in $ (2+1) $-dimensional gauge theories from the holographic hard and softwall models. We describe the behavior of the chiral condensate in the presence of an external magnetic field for both models at finite temperature. For the hardwall model we find Magnetic Catalysis (MC) in different set ups. For the softwall model we find Inverse Magnetic Catalysis (IMC) and MC in different situations. We also find for the softwall model a crossover transition from IMC to MC at a pseudocritical magnetic field. This study also shows spontaneous symmetry breaking for both models. Interestingly, for $B=0$ in the softwall model we found a nontrivial expectation value for the chiral condensate.

Transient Oscillatory Behaviors of Polariton Condensates

We experimentally studied the transient properties of polariton relaxation dynamics through the oscillatory behavior of an exciton-polariton condensate. The oscillations show characteristic pump po...

For high-precision bosonic Josephson junctions, many-body effects matter

Typical treatments of superconducting or superfluid Josephson junctions rely on mean-field or two-mode models; we explore many-body dynamics of an isolated, ultracold, Bose-gas long Josephson junction using time-evolving block decimation simulations. We demonstrate that with increasing repulsive interaction strength, localized dynamics emerge that influence macroscopic condensate behavior and can lead to the formation of solitons that directly oppose the symmetry of the junction. Initial state population and phase yield insight into dynamic tunneling regimes of a quasi one-dimensional double well potential, from Josephson oscillations to macroscopic-self-trapping. Population imbalance simulations reveal substantial deviation of many-body dynamics from mean-field Gross–Pitaevskii predictions, particularly as the barrier height and interaction strength increase. In addition, the sudden approximation supports localized particle–hole formation after a diabatic quench, and correlation measures unveil a new dynamic regime: the Fock flashlight.