Condensation Of Mixture Research Articles

The effect of plate size and corrugation pattern on plate heat exchanger performance in specific conditions of steam-air mixture condensation

The results of mathematical modelling and experimental study of plate heat exchangers (PHEs) in steam-air mixture condensation are presented. The mathematical model is validated by test data for PHE in the industry and for five experimental samples with corrugation angles, 30°, 45°, and 60° and corrugation heights 5, 7.5 and 10 mm. With no limited pressure drop in PHE, its heat transfer area can be decreased up to 4 times with the plate's corrugations angle of 60°. When pressure drop on the side of condensing stream is limited, at a small mass fraction of air, PHE with corrugated plates' heat transfer area can be smaller than in PHE assembled from flat plates about 1.5 times ± 11% at channels of different corrugations geometries. For commercially produced plate-and-frame PHE, the pressure losses at channel entrance and distribution zones should be accounted. For plates with a corrugations angle of 60°, their share in total pressure drop can be from 7% up to 39.3%, while at a corrugations angle of 30°, up to 59%. The final choice of corrugation angle and height for plates designed for specific duty can be made by solving a future optimisation problem with a developed mathematical model.

Heat transfer during condensation of water vapour in the presence of non-condensable gas in vertical tube of small diameter

The paper deals with a detailed analysis of published analytical relations for heat transfer during steam condensation in a vertical tube. The historical development of the approaches and the chronological development of the used analytical relations are presented. Attention is focused on the description of the processes at the gas phase-condensate film interface as well as on the inclusion of the influence of the presence of non-condensable gases. The analytical relations in 12 modifications are compared with each other for the same geometrical configuration of the vertical tube and identical boundary conditions. The authors performed comparative experimental measurements of the heat transfer coefficient during condensation of the vapour-gas mixture in vertical tubes of three diameters, namely 16, 20 and 26 mm. Based on a comparison of the experimental results and analytical relations, recommendations are made on the validity interval of the tested relations.

Heterogeneous condensation mechanism of methane-hexane binary mixture

The condensation mechanism of alkanes is an essential foundation for improving the liquefaction efficiency of natural gas. However, a microscopic understanding of this mechanism is still lacking. This study analyzes the homogeneous and heterogeneous condensation characteristics of methane and explores the influence mechanisms of n-hexane molecules. The results reveal that higher initial pressures cause more intense nucleation stages with more latent heat released. Moreover, changes in the monomer temperature lag behind changes in cluster temperature, which is particularly pronounced in low supersaturation systems. Trace amounts of n-hexane can greatly improve the nucleation rate and liquefaction ratio of methane. The pre-condensed n-hexane clusters serve as a surface for heterogeneous methane nucleation, lowering the nucleation barrier significantly. As the number of n-hexane molecules increases, the nucleation promotion effect is further enhanced. With increased subcooling, the promotion effect lg (J/J0) drops from 17 to approximately 2. Furthermore, the heterogeneous condensation of n-hexane and methane mixture comprises three processes: n-hexane condensation with methane molecular adhesion, methane aggregation on n-hexane nuclei, and surface growth of methane clusters accompanied by n-hexane dissolution. Moreover, methane with lower surface tension always dominates in the cluster surface region.

The Miwah high sulphidation epithermal Au–Ag deposit, Aceh, Indonesia: Dynamics of hydrothermal alteration and mineralisation interpreted from principal component analysis of lithogeochemical data

The principal component analysis (PCA) of whole-rock major and trace element data has unravelled some of the dominant geochemical processes and identified the most relevant component as an exploration vector for many types of magmatic-hydrothermal ore deposits. An important exception is the high-sulphidation (HS) epithermal class of deposits. Here, the results of a PCA of different segments of the Miwah HS epithermal Au–Ag deposit in Indonesia show that the geochemical signature of the deposit varies from a tight group of Au, Ag, Cu and As in PC1 for the predominantly hypogene main zone to a moderately correlated assemblage of Au, As, Cu and Sb in PC1 for the variably oxidised rocks along the southern periphery to an association of Au, Ni, Cr, Co and Mo in PC1 for the overlying rocks in the north. PC2 in all zones represents the largest variability of Pb and Zn and has moderate contributions from Au and As in the periphery and the highest Au contribution in the north. By contrast, PC3 in the main and peripheral zones, shows a high variability of Cu. Representatives of auriferous vuggy-massive silica rocks from the periphery are in equilibrium with hydrothermal fluids with δ18O values of +6.18, +7.48 and +9.28‰, whereas oxidised, silicified rocks from the analogous northern zone are in equilibrium with hydrothermal fluids with δ18O values of +8.0 and +8.6‰. The results of the above PCA, complemented by centred-log-ratio bivariate diagrams of grade-scaled variables, mineralogical relationships and oxygen isotopes, are interpreted to indicate that PC1 in the main zone is consistent with the deposition of Au and related metals from the condensation of magmatic gas mixtures during the early-stage silicification of protoliths. By contrast, PC2 is related to late-stage Pb- and Zn-rich fluids that migrated away from the main conduits. A hybrid process, intermediary between PC1 and PC2, leached Cr, Ni and Co from the adjacent ultramafic rocks and superimposed the metals on the Au + Cu mineralised rocks. Processes related to PC3 and other smaller PC occurred at later and lower temperature stages in which steam-heated oxidation led to the local destruction of sulphide and arsenide phases and the resulting acid fluids decoupled Au-Ag alloys and enargite to produce separate Au- and Ag-based minerals and covellite. The PCA of individual alteration types shows metal associations that mimic those of the main-stage mineralisation, thereby providing a useful exploration tool. The ability of PCA to separate Au and the associated metals from the Cr + Ni + Co assemblage can be used to identify areas that have been affected by hyperacid fluids originating from epithermal systems; hence, such areas become exploration targets not only in the vicinity of Miwah but also throughout Sumatra or elsewhere.

Machine-learning-based heat transfer and pressure drop model for internal flow condensation of binary mixtures

Machine learning regression models were developed to predict the heat transfer coefficient and frictional pressure gradient during condensation of three zeotropic mixtures (ethane/propane, R245fa/pentane, and R410A) in micro- and macro-channels (0.76 mm < D < 14.45 mm). 1032 data points were used to train, test, and validate four machine learning models: support vector regression (SVR), random forest regression (RFR), gradient boost (GB), and artificial neural networks (ANN). For data not used for training, SVR predicted the apparent Nusselt number the best, with a mean absolute percent error (MAPE) of 5.0%, while GB predicted the two-phase friction factor the best with a MAPE of 5.5%. To determine the impact of the additional heat and mass transfer resistances in zeotropic condensation, Shapley analysis was performed on the models to weigh the importance of all dimensionless parameters used to predict the heat transfer and pressure drop. Overall, the three most important parameters to predict heat transfer were the Reynolds number of both phases and a dimensionless temperature glide; while the most important parameters to predict pressure drop were the Bond number, Weber number, and vapor-phase Reynolds number. The importance of mass transfer is discussed along with the applicability of other simple mixture models.

Restoration of the heat exchange surface under conditions of its contamination during condensation of a vapor-gas mixture

THE PURPOSE. Determine the operating mode of a heat exchanger designed to transfer heat from a vapor-gas mixture containing solid particles. Get a dependency for calculating the time after which it is necessary to restore the surface by washing it with water. To carry out estimated calculations of the operating mode of the heat exchanger installed at the PULP Invest enterprise. To increase the stability of the heat exchanger and reduce environmental pollution by cellulose particles.METHODS. In solving this problem, the laws of heat and mass conservation, balance ratios in the calculation of economic costs were used.RESULTS. The article describes the relevance of the topic, discusses the features of the operation of a heat exchanger in which heat is transferred from a condensing vapor-gas mixture containing solid particles. An assumption is made about the mechanism of deposition of these particles on the heat exchange surface. A dependence is obtained that allows us to determine the time after which the surface needs to be restored, taking into account the cost of water and electricity.CONCLUSION. Studies have suggested the mechanism of sediment formation on the heat exchange surface. Choosing a rational mode of operation of the heat exchanger will significantly save water consumption for surface restoration, as well as extract the greatest amount of heat from the steam-gas mixture. The release of particles into the air can be reduced.

Current Research Trends in the Process of Condensation of Cooling Zeotropic Mixtures in Compact Condensers

This paper is an introduction to the cycle proposed by the authors related to research directions concerning the problems of condensation of zeotropic refrigerant mixtures. For over a hundred years, research has been conducted on the search for new working fluids in the cycles for cooling devices and heat pumps. Initially, the natural refrigerants used were replaced with homogeneous synthetic refrigerants, followed by mixtures of two or more refrigerants. Among the mixtures, there are azeotropic and zeotropic mixtures. In the case of an azeotrope mixture, a liquid solution of two or more chemical compounds is in thermodynamic equilibrium with the saturated vapor resulting from this mixture. The chemical composition of the liquid and vapor is identical. A zeotropic mixture is a liquid-vapor system in which the composition of a liquid mixture (solution) of two or more chemical compounds is always different from that of the saturated vapor generated from this liquid. This is due to the different boiling and condensation temperatures of the individual components of the mixture at the same pressure. There is a so-called temperature glide. The phase transformations of individual components do not run simultaneously, which means that the boiling or condensation phase transition temperature changes during the process being carried out. This raises a number of computational, design, and operational problems for power equipment. Today, however, zeotropic mixtures find an alternative to refrigerants with a high GWP potential. Despite the disadvantage of temperature glide, they also have advantages. These include ecological, energy, and economic indicators. As a result, they are increasingly used in the energy economy. This prompts researchers to conduct further research in the field of a detailed description of the phenomenon of boiling and condensation phase transformations of zeotropic mixtures under temperature glide, searching for new computational relationships, new design solutions, and applications. It is still an insufficiently recognized research problem. Bearing the above in mind, the authors made an attempt to review the state of knowledge in this area. Particular attention was paid to the progress in modeling the condensation phenomenon of zeotropic mixtures for application in compact heat exchangers. Miniaturization of cooling devices creates great application possibilities in this area.

Experimental analysis of condensation of zeotropic mixtures from 70 °C to 90 °C in a plate heat exchanger

High temperature condensation is relevant for the heat pump system used for the district heating and the organic Rankine cycle system used for combined heat and power generation. By using a zeotropic mixture as working fluid in such systems, it is possible to achieve a higher system efficiency compared with those of pure fluids. Only two previous studies addressing zeotropic mixture high temperature condensation in plate heat exchangers are available in the open literature, and these studies considered ethanol/water mixtures. The current works present an experimental analysis of high temperature condensation of zeotropic mixtures in a plate heat exchanger. We analyzed the condensation of the hydrofluoroolefin mixture R1234ze(E)/R1233zd(E) and the hydrofluorocarbon mixture R134a/R245fa with different mass compositions at various condensation temperatures and mass fluxes. Based on the experimental results, we analyzed the temperature effects on the condensation heat transfer and identified a convective-dominated condensation heat transfer process. Furthermore, the results suggest that the mixture R1234ze(E)/R1233zd(E) has the up to 8.5% and 4.4% higher heat transfer coefficient and frictional pressure drop, respectively, than the R134a/R245fa mixture. A modified Silver-Bell-Ghaly model predicted the heat transfer data with a 7.1% mean absolute percentage deviation between the predicted and experimental results, and a new pressure drop correlation developed using the mixture test data predicted the pressure drop results with a 6.2% mean absolute percentage deviation.

Detailed modeling of laminar film condensation from zeotropic binary mixtures in a vertical tube

Zeotropic binary mixtures have the potential to be suitable replacements for phased-out refrigerants. In this work, a detailed numerical model of film condensation from a binary mixture is developed as a potential tool to assist evaluating the performance of such replacements. Downward co-current laminar film condensation of a zeotropic binary mixture inside a vertical tube is modelled numerically using the full two-dimensional parabolic governing equations in both phases. The model predicts the condensation behavior of a binary mixture at any composition with properties as functions of the local pressure, temperature, and composition. Detailed results of the heat and mass transfer and the local velocity, temperature, and mass fraction in the entire domain are produced as well as the axial variation of the pressure and the film thickness. Detailed results for zeotropic mixtures of R290/R600A and mixtures of R23/R116 with an azeotrope are presented. A non-monotonic variation of the vapor mixture axial velocity is observed during the axial development of the film and the depletion of the vapor mass flow. It was found that the local heat transfer coefficient depended mainly on the liquid thermal conductivity and the film thickness. For the two refrigerant pairs studied in this work, the local heat transfer coefficient increased with the mass fraction of the less condensable component. The difference in the condensation rates of the constituting components are quantified with and without an azeotrope.

Kinetics of Resorcinol-Formaldehyde Condensation-Comparison of Common Experimental Techniques.

Porous carbons, originated from resorcinol-formaldehyde (RF) gels, show high application potential. However, the kinetics and mechanism of RF condensation are still not well described. In this work, different methods (dynamic light scattering–DLS, Fourier transform infrared spectroscopy–FTIR, low field 1H nuclear magnetic resonance relaxometry–1H-NMR, and differential scanning calorimetry–DSC) were used to follow the isothermal RF condensation of mixtures varying in catalyst content (Na2CO3) and reactant concentration. The applicability and results obtained by the methods used differ significantly. The changes in functional groups can be followed by FTIR only at very early stages of the reaction. DLS enables the estimate of the growth of particles in reaction solution, but only before the solution becomes more viscous. Following the relaxation of 1H nuclei in water during RF condensation brings a different view on the system—this technique follows the properties of the present water that is gradually captured in polymeric gel. From this side, the process behaves similarly to the nucleation reaction, which is in contradiction to the n-order mechanism confirmed by other techniques. The widest range of applicability was found for DSC measurement of the freezing/melting behavior of the reaction mixture, which is possible to use without any limitations until full solidification. Furthermore, this approach enables us to follow the gradual formation and development of the gel through the intermediate undergoing glass transition.

Experimental and theoretical study of vapor/air mixture condensation inside an inclined blind-end pipe in natural convection with considering fog formation

This study investigated the vapor condensation characteristics in an inclined pipe under natural convection conditions experimentally and numerically. The inclined blind-end concentric pipe had an inner diameter of 134 mm and a length of 680 mm, which is cooled by cooling water. The experimental pressure range was 0.2–0.6 MPa, and the dimensionless mass number range was 0.44 to 202. The fog formation phenomenon was observed in the experiment. An empirical correlation with a broad range of dimensionless mass numbers was developed based on the experimental results to predict the heat transfer coefficient (HTC). When the air mass fraction was large and the HTC was low, the effect of fog formation on the HTC had to be considered. In the numerical simulation, this study aimed to develop an HTC prediction model with broader applicability. Based on the diffusion boundary layer theory, this study improved Peterson's model by adding fog effect and wave effect. The model showed high adaptability to this experiment and other experiments in the natural convection condensation database. The improved model performed significantly better, with 96% of the data falling within an error zone of 30%. The wide range of dimensionless mass number test data might complement the natural convection condensation experimental database.

A numerical model for the flow condensation of the binary zeotropic mixture

Inspired by the quasi-static equilibrium state theory and the method of computational fluid dynamics, a mass and heat transfer model is proposed to simulate the condensation of the binary zeotropic mixtures. Combining the VOF method and species transport model, the mass transfer and heat transfer of the components in the liquid phase and vapor phase are analyzed, separately. The experiments of R32/R1234ze(E) and R134a/R1234ze(E) mixtures with different mass fluxes and mass compositions were chosen to validate this model. The results show the numerical data of heat transfer coefficients agree well with the experimental results. The condensation of R32/R1234ze(E) mixtures in mini-channels were simulated. The effects of mass flux, tube diameter and mass composition on the heat transfer coefficient, film thickness, velocity distribution, temperature distribution, and concentration distribution were investigated. The results show the mixture with more R32 has a larger HTC. The concentration of R32 vapor near the vapor-liquid interface increases with the decrease of vapor quality. And the mass flux has little effect on the concentration of R32 vapor.

Rate of convergence toward Hartree type equations for mixture condensates with factorized initial data

We consider a system of p species of bosons, each of which consists of N1, N2, …, Np particles. The bosons are in three dimensions with interactions via an interaction potential V such that V ≤ D(1 − Δ), which includes the Coulomb interaction. We set the initial condition to describe a mixture condensate, i.e., a tensor product of factorized states. We show that the difference between the many-body Schrödinger evolution in the mean-field regime and the corresponding p particle dynamics due to a system of coupled Hartree equations is O(N−1), where N=∑q=1pNq.

Sensitivity of the Non-Equilibrium Approach for Mixture Condensation to Heat and Mass Transfer Correlations and Thermophysical Properties

Abstract The prediction of mixture condensation is still complex due to the coupled heat and mass transfer and insufficient data of thermophysical mixture properties. This article analyzes the impact of various heat and mass transfer correlations on the non-equilibrium approach for mixture condensation in a vertical plain tube. Furthermore, the influence of thermophysical properties from different databases is investigated. The results are shown for ethanol-water, but allow conclusions to other fluid mixtures. They indicate that the liquid heat transfer coefficient in the non-equilibrium approach dominates the qualitative behavior of the condensation process, but the vapor mass transfer coefficient can only decrease or increase the quantitative level of the effective heat transfer with minor impact. More importantly, the logarithm in the vapor mass transfer term is central for the prediction of the condensation heat transfer. As this logarithm contains vapor-liquid equilibrium (VLE) data, it proves that there is a strong connection between VLE and overall prediction of mixture condensation. A demonstration of available data for thermophysical mixture properties of ethanol-water shows significant deviations, which affect the calculations as well. Besides, data from our own experiments are presented for mixture viscosity of ethanol-water. It is recommended to focus not only on improved heat and mass transfer correlations but also on thermophysical properties and VLE data for a precise prediction of mixture condensation.

To the issues of retrograde condensate extraction

The features of the formation of retrograde condensate in the reservoir and the method of its extraction are given. In order to improve the development of gas condensate fields and to reduce condensate losses under the reservoir pressure drawdown below the pressure of the beginning of condensate precipitation, the issue of the possibility of its extraction after precipitation in the reservoir by water or gas-water mixture displacement has been considered. The results of laboratory, analytical and field studies indicate that the retrograde condensation of the hydrocarbon mixture has a negative effect on almost all technological processes of condensate production. Reservoir condensate losses during the development of gas condensate fields in depletion mode are on average 60-78%. As an alternative to the cycling process, the use of a unified waterflooding system for the recovery of condensate from the reservoir has been considered. The results of laboratory studies are presented and the directions of the implementation of gas-water repression at gas condensate fields have been substantiated. The possibility of using reservoir gas available in the reservoir has been considered. In this case, the condensate was first flooded with water, and then, before the water broke out of the model, the system was degassed, reducing the pressure by 25% below the pressure of the onset of condensation, and again continued to displace the condensate with water. This procedure makes it possible to extract about 50% of the condensate dropped out in the reservoir.

RESEARCH OF THE COMPOSITION OF PRODUCTS OF MICROWAVE PYROLYSIS OF WOOD

A method of microwave action on wood of various species was developed, as a result of which the pyrolysis process was carried out. Allocated solid, gaseous fractions, as well as as a result of condensation of a vapor-gas mixture, pyrolysate, which is a raw material for the production of low molecular weight organic compounds of various classes. Gas chromatography-mass spectroscopic analysis of the liquid fraction was carried out, the components included in its composition were identified. The proposed method allows liquefaction of wood for 20-30 minutes in the temperature range from 230 to 423 °С.

МОДЕРНИЗАЦИЯ РАБОТЫ КОНДЕНСАЦИОННОГО ОБОРУДОВАНИЯ УЗЛОВ ПЕРЕРАБОТКИ ФРАКЦИЙ АРОМАТИЧЕСКИХ УГЛЕВОДОРОДОВ

The variants of condensation of vapor-gas mixtures formed during the dealkylation &#x0D; of aromatic hydrocarbons are considered. A comparison of the operating options of the equipment &#x0D; showed that the most profitable in the conditions of industrial use will be the use of a bypass water &#x0D; condenser.

Vapor condensation with low air mass fraction inside water seal branch tube under free convection

The pressure vessel has used a newly designed water seal structure, and the sealed water is from condensation at low hydrogen concentration. To get the condensation capacity of the water seal branch tube under the pressure vessel normal operation, the experimental loop named WASETEL was constructed, which is aimed at studying the heat transfer during the process of air-steam mixture condensation inside the inclined branch tube at the condition of low air mass fraction. The inner tube is diameter 0.134 m with length 0.68 m which is connected with diameter 1.4 m, high 2.5 m pressure vessel. A canon camera was set to record the images and videos of the condensate height through glass tube in communicating vessel liquidometer. The experiment was conducted under the pressure ranged from 0.2 to 0.6 MPa, air mass concentration ranged from 0.49 to 6.42% and wall subcooling ranged from 11 to 40 K. The test showed HTC (heat transfer coefficient) would sharply deteriorate with the small air fraction, compared with pure steam condensation, about 0.49% mass fraction of the air will reduce heat transfer coefficient by 70–80%. When air concentration is relatively small, those widely used relations can not predict the condensation well, therefore, a new heat transfer empirical correlation with air mass fraction, pressure and subcooling is proposed, covered all the experimental data within the error band ±13%.

Synthesis and Studies of Stable Nonaromatic Dithia Pyribenzihexaphyrins.

We report here one of the rare examples of expanded hexaphyrins named as dithia pyribenzihexaphyrin macrocycles containing six-membered rings such as pyridine and p-phenylene along with five-membered heterocycles such as pyrrole and thiophene as a part of a macrocyclic frame. Trifluoroacetic acid catalyzed [3 + 3] condensation of equimolar mixture of [10,10'-bis(p-tert-butyl phenyl)hydroxymethyl]-1,3-bis(2-thienyl)pyridine diol (2,6-pyri diol) and 1,4-bis(phenyl(1H-pyrrol-2-yl)methyl)benzene (p-benzidipyrrane) in CH2Cl2 followed by oxidation with DDQ afforded stable nonaromatic dithia 2,6-pyri-para-benzihexapyrins 1 and 2 in 6-8% yields. The macrocycles were characterized by high-resolution mass spectroscopy and 1D and 2D NMR spectroscopy. NMR studies revealed the nonaromatic nature of dithia 2,6-pyri-p-benzihexaphyrins and indicated that the para-phenylene ring prefers to be in quininoid form rather than in benzenoid form. The macrocycles displayed sharp absorption bands in the region of ∼380-500 nm and a broad band at ∼700 nm, reflecting their nonaromatic nature. Upon protonation, these macrocycles showed NIR absorption properties. The redox studies of macrocycles indicated their electron-deficient nature. The DFT/TD-DFT studies are in line with the experimental observations.

Experimental Study of Air-Steam–Mixture Condensation Underneath Containment Vessel Surface

Aiming at studying the condensate flow phenomenon and air-steam–mixture condensation heat transfer underneath a containment vessel surface, a test bench was constructed. The plate dimension was 1.5 × 0.6 m, with Carbozinc 11 coating on the surface, suspended in a pressure vessel with 2.5-m diameter and 4.5-m height. The air-steam mixture was condensed on an inclined plate through natural convection mode and jet mode. By observing flow behavior on the plate through a viewport, four basic regimes were obtained as the inclination angle gradually increased: droplet, droplet to rivulet transition, developed rivulet, and uniform film. During the experiment, we observed a steam atomization phenomenon; therefore, the model predicted better with the atomization effect considered. A simple formula from the condensation data is proposed when the air mole fraction is small. The error between the experimental results and the predicted data is within 25%.