Impact Of Condensation Research Articles

Specific protein-RNA interactions are mostly preserved in biomolecular condensates.

Many biomolecular condensates are enriched in and depend on RNAs and RNA binding proteins (RBPs). So far, only a few studies have addressed the characterization of the intermolecular interactions responsible for liquid-liquid phase separation (LLPS) and the impact of condensation on RBPs and RNAs. Here, we present an approach to study protein-RNA interactions inside biomolecular condensates by applying cross-linking of isotope labeled RNA and tandem mass spectrometry to phase-separating systems (LLPS-CLIR-MS). LLPS-CLIR-MS enables the characterization of intermolecular interactions present within biomolecular condensates at residue-specific resolution and allows a comparison with the same complexes in the dispersed phase. We observe that sequence-specific RBP-RNA interactions present in the dispersed phase are generally maintained inside condensates. In addition, LLPS-CLIR-MS identifies structural alterations at the protein-RNA interfaces, including additional unspecific contacts in the condensed phase. Our approach offers a procedure to derive structural information of protein-RNA complexes within biomolecular condensates that could be critical for integrative structural modeling of ribonucleoproteins (RNPs) in this form.

Fastchem cond: equilibrium chemistry with condensation and rainout for cool planetary and stellar environments

ABSTRACT Cool astrophysical objects, such as (exo)planets, brown dwarfs, or asymptotic giant branch stars, can be strongly affected by condensation. Condensation not only directly affects the chemical composition of the gas phase by removing elements but the condensed material also influences other chemical and physical processes in these objects. This includes, for example, the formation of clouds in planetary atmospheres and brown dwarfs or the dust-driven winds of evolved stars. In this study, we introduce fastchem cond, a new version of the fastchem equilibrium chemistry code that adds a treatment of equilibrium condensation. Determining the equilibrium composition under the impact of condensation is complicated by the fact that the number of condensates that can exist in equilibrium with the gas phase is limited by a phase rule. However, this phase rule does not directly provide information as to which condensates are stable. A major advantage of fastchem cond is its ability to automatically select the set stable condensates satisfying the phase rule. Besides the normal equilibrium condensation, fastchem cond can also be used with the rainout approximation that is commonly employed in atmospheres of brown dwarfs or (exo)planets. fastchem cond is available as open-source code, released under the GNU General Public Licence 3 (GPLv3). In addition to the c++ code, fastchem cond also offers a python interface. Together with the code update, we also add about 290 liquid and solid condensate species to fastchem.

On the Impact of Condensation and Liquid Water on the Radial Turbine of a Fuel Cell Turbocharger

The air-management system of a proton exchange membrane fuel cell (PEMFC) is responsible for supplying the fuel cell stack with ambient air at appropriate conditions. The compressor of the air-management system can be partly driven by utilizing the fuel cell exhaust gas in a turbine. The fuel cell exhaust is partially or fully saturated with water vapor. When the exhaust gas is expanded in the turbine, supersaturation occurs. This leads to the nucleation of droplets and their subsequent growth by condensation. This study provides an overview and understanding of the various phenomena caused by condensation and liquid water in the turbine of a PEMFC air-management system. The basis for this work is previously published numerical simulations that focused on individual aspects of the above phenomena. The present work revisits these results and puts them in context to provide a comprehensive understanding. Important phenomena are the effects of condensation on turbine performance through phase change losses, release of latent heat and thermal throttling. In addition, the released latent heat offers a power potential for downstream turbine stages. Through these effects, condensation can also impact the entire air-management system. However, condensation may occur unevenly, causing a circumferential asymmetry of the turbine outflow. Liquid water in the turbine can lead to droplet erosion, corrosion, and water-induced damage. In summary, it is essential to consider condensation and liquid water when developing turbines for PEMFC air-management systems.

A comprehensive analysis of the moist air transonic flow in a nozzle with a very low expansion rate

• Experimental study of the moist air transonic flow in a nozzle with a low expansion rate. • Mathematical models of homogeneous condensation. • The study of the effect of air relative humidity on the expansion process. • The study of the interaction between condensation and pressure waves. Inevitable and undesirable as it is, phase transition has a significant impact on the fluid flow efficiency in many energy processes. This paper deals with the impact of water vapour condensation and liquid water evaporation in the moist air expansion in a nozzle with a low expansion rate. The presented comprehensive analysis includes a numerical study supported by analytical and experimental research. The experimental study concerning measurements of atmospheric air transonic flows was carried out using an in-house experimental test rig. A nozzle with a low expansion rate of P ̇ ≈ 1000 s - 1 was investigated experimentally at different inlet air relative humidity values included in the range of 25 to 51 %. The nozzle was measured for supersonic outlet conditions, as well as with elevated back pressure (78 kPa). The technique of Schlieren photography and static pressure measurement on the nozzle wall were used for qualitative identification of both condensation and shock waves. The presented numerical modelling was conducted using commercial computational fluid dynamics software extended with an in-house condensation model. The code was validated against experimental data and data available in the literature. The analysis of the flow in the nozzle with a very low expansion rate revealed very interesting structures of pressure waves. The impact of relative air humidity on the condensation process and the interaction of the condensation wave with aerodynamic oblique as well as normal shock waves were investigated. It is observed that the higher the air relative humidity value, the more difficult it is to identify aerodynamically induced oblique shock waves in the flow. Finally, considering that the efficiency drop induced by the phase change can reach up to 10 %, the impact of condensation on the expansion process efficiency is presented.

Thermoeconomic analysis on a molten salt parabolic trough‐based concentrated solar organic Rankine cycle system

Solar thermal electricity generating technology is an alternative solution to energy crises and environmental problems, which has caused wide concern in recent decades. In this paper, a molten salt parabolic trough-based concentrated organic Rankine cycle system is proposed and investigated. A quadribasic nitrate salt with low melting temperature is employed as a heat transfer and storage medium. A stable heat transfer and economic model is established with Matlab. The radial and axial temperature distributions in the collector tube are obtained, and the impact of condensation and evaporation temperatures on the heat transfer area is analyzed. Results show that the temperature along the axial direction linearly increases, and the temperature at the collector tube exit decreases with the increase of molten salt mass flow rate. The maximum temperature difference along the radial direction of the collector tube happens in the annular gap. Heat transfer and thermodymanic analysis indicates that condensation temperature has a more evident effect on heat transfer area than that of evaporation temperature. An increase in condensation temperature leads to a decrease in the evaporator area, the condenser area increases, and the total area decreases. Economic analysis indicates the collector cost plays a predominant role in total capital costs, and decreasing molten salt mass flow rate can considerably reduce collector cost. Levelized energy cost sensitivity analysis indicated that operation time per year has a more evident effect than that of the four factors. Heat transfer and economic analysis on the system helps in the selection of operation parameters.

Cluster formation in copper vapor jet expanding into vacuum: the direct simulation Monte Carlo

Expansion of the condensing copper vapor into vacuum from a high-temperature source is studied for transient and near-continuum flow regimes within the direct simulation Monte Carlo method. Kinetic approach, which assumes cluster formation/decay description via monomer-cluster reactions with corresponding cross-sections, is employed. Clusters observed in calculations are of subnanoscale size. Impact of condensation on gas-dynamic jet parameters is significant for the regimes for which the terminal mole cluster fraction in the jet exceeds 1%. For such regimes both velocities and translation temperatures of clusters and monomers, are close to each other, while cluster internal temperature is higher than the translational vapor temperature. Characteristic clusterization modes are revealed depending on the intensity of the cluster formation process in the source domain and in the jet. Obtained values of the internal dimer temperature and average cluster size in the jet far field are in a good agreement with the experimental data and known scaling laws.

Impact of Condensates Containing Chloride and Sulphate on the Corrosion in Automotive Exhaust Systems

The chemical composition of condensates recovered from a test car was systematically analysed in this study. It was found that most condensates contain a higher concentration of chloride than that of sulphate. In order to understand the effect of sulphate on the pitting behaviour of 436SS and to predict whether pitting will occur in these condensates, pitting potentials were determined in a 0.2M sulphate solution with varying chloride concentration by using the potentiodynamic cyclic polarization curve method. The results demonstrate that sulphate prevents pitting initiation of 436SS when the concentration of sulphate is higher than that of chloride. However, no inhibitory effect of sulphate was observed when the sulphate concentration is lower than the chloride concentration. As the condensate recovered from the muffler contains more chloride than sulphate, the muffler is most likely suffering from pitting. This was confirmed by the microscopic observation of the corroded muffler from the test car.

CFD Prediction of Odour Dispersion and Plume Visibility for Alumina Refinery Calciner Stacks

Computational fluid dynamics (CFD) models are developed to examine the behaviour of moisture-laden buoyant plumes emitted from Alumina refinery calciner stacks. The CFD modelling is carried out to complement traditional atmospheric dispersion modelling undertaken as part of a study to develop odour reduction strategies for Alcoa's Wagerup refinery in Western Australia. The commercial package CFX-4.4 is used to develop a plume model which incorporates source terms for condensation, evaporation and associated heat transfer. The model is used to examine issues that cannot be assessed with standard atmospheric dispersion models, such as the impact of condensation on plume rise and ground-level odour and the impact of ambient air addition on plume visibility. A second model developed in the commercial package CFX-5.5 is used to examine the potential to reduce ground-level odour through the construction of a 100 m high multiflue stack. Solution-adaptive meshing is used to reduce initial model set-up time and to optimize the mesh size in regions of high concentration gradients. The relationship between the CFD models developed and traditional atmospheric dispersion models is discussed and the paper illustrates how the different techniques can be used in a complimentary fashion to develop engineering solutions to reduce the impact of emissions from an industrial plant.

Numerical investigation of condensing steam flow in boundary layers

Abstract The paper describes a numerical method for the prediction of condensing steam flow within compressible boundary layers. The method is based on a simple stream function technique, which enables straightforward integration of the nucleation and droplet growth equations in a Lagrangian frame of reference. Calculations show how viscous dissipation and reduced expansion rate within a typical boundary layer influence nucleation and growth, leading to droplet radii and size distributions that differ substantially from those predicted in inviscid flow. The impact of condensation on temperature and velocity profiles, and the implications for thermodynamic loss are also considered.

Importance of diabatic processes on ageostrophic circulations observed during the FRONTS 87 experiment

AbstractThe impact of condensation and evaporation on real cross‐frontal circulations is studied, using data from the FRONTS 87 field experiment. The Sawyer‐Eliassen equation is solved numerically in its primitive equation form, for one intensive observing period of FRONTS 87. Three different schemes of parametrization of condensation heating are used. Comparison between diagnosed and observed ageostrophic circulations shows that latent heat release plays an important role in enhancing the ascending branch of the ageostrophic circulation ahead of the frontal zone. In particular, when a parametrization scheme for the low‐level moisture convergence is applied, a cell of strong ascending motion is formed ahead of the frontal zone, in good agreement with the observations. Further, a simple parametrization of evaporative cooling below the frontal discontinuity leads to a reinforcement of downdraughts in the cold sector of the front, as observed in regions where precipitation originating from the strong line convection evaporates. In comparison with their adiabatic counterparts, the current solutions show strong similarities with the observed circulation and indicate the predominance of diabatic effects in the frontal zone.

Importance of diabatic processes on ageostrophic circulations observed during the FRONTS 87 experiment

The impact of condensation and evaporation on real cross-frontal circulations is studied, using data from the FRONTS 87 field experiment. The Sawyer-Eliassen equation is solved numerically in its primitive equation form, for one intensive observing period of FRONTS 87. Three different schemes of parametrization of condensation heating are used. Comparison between diagnosed and observed ageostrophic circulations shows that latent heat release plays an important role in enhancing the ascending branch of the ageostrophic circulation ahead of the frontal zone. In particular, when a parametrization scheme for the low-level moisture convergence is applied, a cell of strong ascending motion is formed ahead of the frontal zone, in good agreement with the observations. Further, a simple parametrization of evaporative cooling below the frontal discontinuity leads to a reinforcement of downdraughts in the cold sector of the front, as observed in regions where precipitation originating from the strong line convection evaporates. In comparison with their adiabatic counterparts, the current solutions show strong similarities with the observed circulation and indicate the predominance of diabatic effects in the frontal zone.