Vapor Condensation Research Articles

Three condensation paths of exhaust and its five effects on exhaust gas recirculation (EGR) cooler fouling and thermal performance: A review

Fouling has limited the evolution of compact heat exchangers (represented by EGR cooler) to smaller and more efficient sizes, an important reason is the unclear mechanism of the effect of exhaust gas condensation on fouling and thermal performance. This paper reviews the effects of hydrocarbon vapor, water vapor and acid vapor condensation on EGR cooler fouling and thermal performance from 1998 to 2023. Three paths of vapors condensation can occurr: interaction with particles, homogeneous nucleation and interaction with fouling. Beneficial effect (3) and harmful effects (2) to EGR cooler thermal performance have identified: filling, removal and chemical are beneficial effects whereas adhesion and nucleation are harmful effects. Three pathways and five effects play a key role on the composition, the mass, the thickness, density, the morphology and thermal resistance of fouling layer. The involvement level of sub-paths and contribution degree of sub-effects of vapor condensation under different boundary conditions, standard database, holistic model and the effect of renewable synthetic fuels on fouling and thermal performance can be further explored. The results will help researchers to understand the logical relationship between exhaust vapor condensation and fouling and thermal performance from the new perspective of condensation.

Condensation heat transfer characteristics of flue gas moisture recovery using ceramic membranes

The use of a ceramic membrane condenser (TMC) can help recover moisture from flue gas, resulting in a reduction in white smoke, smog, and resource conservation. Although several studies have investigated TMC heat and mass transfer and water vapor condensation mechanisms, few have analyzed the effect of membrane area on thermal mass performance. This paper presents a comparative study of ceramic membranes with different pore sizes to address this gap. In this study, the influence of the condensation mechanism along the flow direction on the heat transfer is innovatively analyzed by combining the mass transfer characteristics. The results show that capillary condensation is more pronounced in high-temperature flue gas, which improves heat transfer efficiency and results in a higher wall temperature rise at the flue gas outlet. The capillary condensation mechanism can also increase the condensation depth, facilitating the removal of water vapor. In particular, in the treatment of 10000 m3/h flue gas, the maximum water recovery rate of the 0.4 nm pore size ceramic membrane is 26.6 kg/(m2·h), which is 27.9% higher than that of the 1 μm pore size ceramic membrane. However, it is important to note that nanomembranes cost 4.62 times more than micro membranes under the same flue gas conditions.

Thermodynamic performance of heat pump with R1234ze(E)/R1336mzz(E) binary refrigerant

In order to solve the temperature mismatch issue of cold and hot fluids in evaporation and condensation processes for heat pump system, binary refrigerant R1234ze(E)/R1336mzz is recommended in the present research due to its large temperature glide. Through theoretical analysis, multiple configurations under conditions of three different temperature heat sources (70/50 °C, 60/40 °C and 50/30 °C) and two different heat targets (steam above 100 °C and hot water with 70 °C) are constructed adopted Ebsilon code. The optimum mass proportion is obtained as 0.3/0.7 for R1234ze(E)/R1336mzz(E), because of its maximum temperature glide (can reach 21.52 °C) and excellent thermal performance (large COP, ECOP and exergy efficiency). COP of steam high temperature heat pump with R1234ze(E)(0.3)/R1336mzz(E)(0.7) binary refrigerant and the ratio of transferred heat of 110 °C condenser to all output heat (containing 110 °C and 100 °C steam intercooler and condensers) respectively increase up to 67.25% and 335.16% under some certain conditions, compared with that with pure R1336mzz(E). COP of hot water heat pump with R1234ze(E)(0.3)/R1336mzz(E)(0.7) binary refrigerant are respectively 10.31 and 6.89 under 60/40 °C and 50/30 °C heat source conditions, which greatly increases compared with that of heat pump with pure R1234ze(E) (6.67 and 5.03) and R1336mzz(E) (6.74 and 4.54). The present research may lay a foundation for binary refrigerant adoption to replace the scheme of multi-stage evaporator or multi-stage condenser, which could reduce the irreversible loss of phase change equipment and improve thermodynamic performance of heat pumps.

Fabrication and Experimental Study of Micro/Sub-Micro Porous Copper Coating for Anti-Icing Application.

Micro and sub-micro-spherical copper powder slurries were elaborately prepared to fabricate different types of porous coating surfaces. These surfaces were further treated with low surface energy modification to obtain the superhydrophobic and slippery capacity. The surface wettability and chemical component were measured. The results showed that both the micro and sub-micro porous coating layer greatly increased the water-repellence capability of the substrate compared with the bare copper plate. Notably, the PFDTES-fluorinated coating surfaces yielded superhydrophobic ability against water under 0 °C with a contact angle of ~150° and a contact angle of hysteresis of ~7°. The contact angle results showed that the water repellency of the coating surface deteriorated with decreasing temperature from 10 °C to -20 °C, and the reason was probably recognized as the vapor condensation in the sub-cooled porous layer. The anti-icing test showed that the ice adhesion strengths of the micro and sub-micro-coated surfaces were 38.5 kPa and 30.2 kPa, producing a 62.8% and 72.7% decrease compared to the bare plate. The PFDTES-fluorinated and slippery liquid-infused porous coating surfaces both produced ultra-low ice adhesion strengths of 11.5-15.7 kPa compared with the other non-treated surfaces, which showed prominent properties for anti-icing and deicing requirement of the metallic surface.

Formation Mechanisms of the “5·31” Record-Breaking Extreme Heavy Rainfall Process in South China in 2021

Based on the fifth-generation European Center for Medium-Range Weather Forecasts reanalysis data (ERA5), the real-time observation data from weather stations, and the radar products in Guangdong Province, we analyze the precipitation properties and formation mechanisms of the “5·31” extreme heavy rainfall process with record-breaking 3-h accumulated rainfall in South China during 2021. The results show that the extreme heavy rainfall process is caused by the joint actions of weather systems such as a weak upper-level short-wave trough, a surface stationary front, and a low-level southwesterly jet. Before the heavy precipitation process, there is large precipitable water content and deep warm clouds, which provides a potential for the occurrence and development of the heavy rainfall process in Longhua Town of Longmen County and its surrounding areas. Simultaneously, the low-level southwesterly jet provides abundant warm-wet water vapor for the heavy rainfall area. The vertical atmospheric environmental conditions, such as strong horizontal temperature gradient, high convective available potential energy, high-temperature difference between 850 hPa and 500 hPa, and low convective inhibition, maintain for a long duration in the heavy rainfall area, which are favorable for the occurrence and development of high-efficiency convective precipitation caused by water vapor condensation due to the uplift of low-level warm-wet airflows. The combined effects of the enhanced low-level southwesterly airflow, the stationary front, the mesoscale surface convergence line generated by cold pool outflows, the terrain influence, and the train effect of the precipitation echoes make heavy precipitation near Longhua last longer and stronger than other areas, leading to the extreme heavy rainfall with the record-breaking 3-h accumulated rainfall in Longhua.

Experimental study on wet gas condensation heat transfer and flow resistance in horizontal intensified tube

The heat transfer and flow resistance characteristics of in-tube vapor condensation with high content non-condensable gas is significant for designing waste heat recovery devices of gas-fired boilers. In this paper, the forced convection condensation of wet gas in the horizontal tube is experimentally investigated with a non-condensable gas mass fraction of 83–95%. The condensation heat transfer coefficient, thermal resistance and pressure drop are compared between bare tube and two intensified tubes, i.e., the corrugated and spiral tube, under various Reynolds number, wall subcooling degree and inlet humidity. The results show that the in-tube condensation heat transfer coefficient increases with increasing Reynolds number and inlet humidity, but decreases with increasing wall subcooling degree. Compared with the bare tube, the heat transfer coefficient and pressure drop increase up to 47.13% and 16.00% respectively for the spiral tube, and 116.04% and 88.48% respectively for the corrugated tube. When combing the heat transfer and flow resistance factors, the maximum comprehensive performance coefficients are 1.71 and 1.44 for corrugated tube and spiral tube respectively. The superiority of corrugated tube in the wet gas condensation is benefit from effective breaking the non-condensable gas film and promoting the vapor diffusion on the interface.

CFD modeling of double-partition divided-wall column for mass transfer characteristics

In this study, a coupled two-fluid computational fluid dynamics (CFD)–component transfer (CT) model was constructed to investigate the mass transfer behavior and distribution of component concentration fields on trays within the two-staggered wall regions of a double-partition divided-wall column (DPDWC). By comparing the simulation results of the coupled CFD-CT model with the height-dependent calculation of the clear-liquid layer, this study validated the model, and then proceeded to analyse its effect on mass transfer in multiple zones of the tower under varying gas velocity conditions. The results showed that the mass-transfer efficiency increased initially, but then decreased with an increase in gas velocity within the studied gas velocity range. In addition, the evaporative condensation effect of the component mass transfer cause temperature variations across different regions of the tower.

Converting N2 molecules into NH3 with TiO2/Fe3O4 composite covered with a thin water layer under ambient condition

As ammonia manufacture today require huge energy and very pure hydrogen gas and moreover emit large quantities of CO2, researches for new ammonia synthesis methods are actively performed. Here, author reports the novel method through which N2 molecules in air is reduced into ammonia with TiO2/Fe3O4 composite having thin water layer on composite’s surface under ambient condition (less than 100 °C and atmospheric pressure). The composites were composed of both nm-sized TiO2 particles and μm-sized Fe3O4 ones. First, composites were held in refrigerator, mainly at that time, N2 molecules in air adsorbed onto surface of composite. Next, the composite was irradiated with various lights including solar light, 365 nm LED light and tungsten light through thin water layer formed by condensation of water vapour in air. Reliable amount of ammonia was obtained under 5 min’s irradiation of solar light or of both 365 m LED light and 500 W tungsten light. This reaction was catalytic reaction promoted by photocatalytic one. In addition, holding in freezer instead of refrigerator provided larger amount of ammonia. Maximum ammonia yield was approximately 18.7 μmol/g 5 min under irradiation of 300 W tungsten light only.

Metal-anchoring, metal oxidation-resistance, and electron transfer behavior of oxygen vacancy-rich TiO2 in supported noble metal catalyst for room temperature HCHO conversion

Thermal catalytic oxidation at room temperature using a noble metal catalyst is a rapid, stable, and efficient removal strategy for HCHO, a ubiquitous indoor air pollutant. However, the catalytic oxidation optimization through the support defect control has been barely explored. We prepared an oxygen vacancy-rich anatase TiO2 (VO-TiO2) as electron transfer catalyst support for the efficient catalytic conversion of HCHO to CO2 and H2O. VO-TiO2, prepared by chemical vapor condensation with post heat treatment, exhibits void-embedded nanostructures and electron paramagnetic activity, which governs the deposition pattern of Pt nanoparticles upon the impregnation. Pt/VO-TiO2 (0.086 wt% Pt) converted 100% of 10 ppm HCHO at room temperature and 200,000 cm3 h−1 gcat−1 GHSV in >250 min. The X-ray absorption (XAS) studies of used catalysts confirmed the conservation of metallic state of Pt only in oxygen vacancy-rich anatase TiO2 (VO-TiO2). The First-principles density-functional theory calculations revealed that the excess electrons at the oxygen vacancies in VO-TiO2 stabilize the otherwise-vulnerable Pt nanoparticles. This study demonstrates an effective defect control strategy for transforming a TiO2 support into a dynamic electron transfer catalyst platform.

Metal Nanoparticles: Synthesis Approach, Types and Applications – A Mini Review

The study of nanoparticles has grown in significance during the last several years. Nanoparticles are a kind of material that is composed of very tiny particles. Nanoparticle characteristics vary greatly depending on their size and form. The surface of a nanoparticle significantly affects its optical, mechanical, magnetic, and other characteristics. Nanoparticles are categorised according to their size, origin and chemical composition. We created nanoparticles using both top-down and bottom-up techniques. In this article, we discuss various different methods for creating nanomaterials, such as sol-gel processes, gas condensation, vacuum deposition and vaporisation, chemical vapour deposition and condensate, mechanical attrition, chemical precipitation, electrodeposition, and chemical vapour condensation. When it comes to creating nanoparticles, green synthesis is one of the most effective approaches. In this article, we explore eco-friendly techniques for manufacturing alloy nanoparticles, silver, gold, silver oxide and silver sulphide. We also explore the process by which microorganisms in this setting produce nanoparticles. Size and form must be maintained under certain conditions. We consider ways in which to enhance the production of nanoparticles in the future. The risks posed by nanoparticles and the ways in which to mitigate them were also taken into account.

Enhanced performance of diurnal radiative cooling for solar cells based on a grating-textured PDMS photonic structure

The extra heat generated by solar cells during the daytime will inevitably erode its efficiency and shorten working lifetime. In this work, a grating-textured polydimethylsiloxane (PDMS) photonic structure is proposed to lower the working temperature and enhance the efficiency through radiative cooling. A comprehensive study is carried out to enhance the infrared thermal radiation in the atmospheric window. It can effectively reflect the waste solar irradiance of 128.95 W/m2 at 300 K. In addition, the photonic cooler features angle and polarization-independent properties, which is desirable in the application of solar panels. As a case study of encapsulated solar cells, it can ideally realize a temperature drop of 11.47 K through thermal analysis, achieving an efficiency enhancement of 1.39%. The improvement in other types of solar cells is also carried out. Therefore, this cooler paves a new avenue to explore thermal management of solar energy harvesting and radiative vapor condenser systems.

Hydrophobic Membrane for Water Recovery from Humid Gas by Membrane Condenser: Effects of Membrane Properties on Recovered Water Quality

Two hydrophobic porous ethylene-chlorotrifluoroethylene (ECTFE) membranes quenched in water and air were fabricated by thermally induced phase separation and used for water recovery from ammonia-containing humid gas via vapor condensation. The ECTFE membranes were further hydrophobically modified to enhance their condensation performance. The condensate water quality of the modified membrane significantly improved. The mechanisms of the NH3 contamination in the condensate water were discussed. Surface hydrophobic modification slightly increased the flux and recovery stabilities of the membranes. However, the modification also increased the membrane surface roughness, which adversely affects the vapor condensation and droplet evolution on the membrane surface and reduced the recovered water quality. From the material perspective, desirable porous membranes for vapor condensation should have high surface hydrophobicity and smoothness and reasonably large pore sizes. The reasonably large pore sizes would promote noncondensable gaseous contaminants (e.g., ammonia) to go through the membrane, thereby improving the recovered water quality.

Analysis of Variance of the Heat and Mass Transfer Coefficients in an Evaporative Condenser

Modelling of evaporative condensers relies heavily on the correct choice of the correlations for transport coefficients to give an accurate estimate of the dissipated thermal load and evaporated water mass flowrate, yet the literature does not cover all flow arrangements, nor operating conditions. In order to avoid expensive, and often impractical, experimental campaigns devoted to the determination of these quantities for a specific piece of equipment, a statistical approach based on the analysis of variance can be adopted: by analysing the sensitivity of the dependent variables on the choice of the transport coefficients, the best set of correlations can be determined, depending on whether a more accurate estimate is desired for the heat flux or evaporated mass flowrate, or if both are equally important.

Wood Vinegars: Production Processes, Properties, and Valorization

Abstract Pyrolysis of lignocellulosic biomass is widely used for the production of charcoal, pyroligneous liquid, and noncondensable gases. All three are value-added products that are exploited in several fields. However, this review focuses on three main areas: wood vinegar production methods, its physicochemical properties, and the use of wood vinegar or pyroligneous acid in agriculture and the environment. Wood vinegar is a liquid derived from wood by the condensation of gases and vapors released during the carbonization process, which is the transformation of wood into charcoal. It is mainly composed of aliphatic, aromatic, and naphthenic hydrocarbons and other oxygenated compounds such as alcohols, aldehydes, ketones, furans, acids, phenols, and ethers. Wood vinegar has antioxidant and free-radical-scavenging properties and is used in agriculture as an antimicrobial, antifungal, insecticide, and plant germination and growth agent. It is also used in food preservation, in medicine, and in the ecological preservation of wood. This review also examines the state of the art in pyroligneous liquid production techniques and factors that could potentially affect its quality.

The Transient Performance-Evaluation Model for Desalination of Seawater Based on Matrix Algorithm – a Requirement for a Ported Arabic Smart City

Abstract Based on the transient performance model for desalination of seawater based on the matrix algorithm, the desalination device is designed according to the evaporation condensation mechanism of falling film in horizontal tube, and its structure operation and operation principle are analyzed. Then, the differential equation of the transient heat-conduction problem of the seawater desalination device is constructed. On the basis of experimental data or numerical calculation results, the temperature field of structure at some time is selected to form the snapshots matrix, and a set of optimal eigenorthogonal decomposition bases is obtained by eigenorthogonal decomposition of the snapshots matrix. Finally, the finite-element discrete scheme of the nonlinear transient heat-conduction problem is reduced by using eigenorthogonal decomposition bases of the linear problem, and the lower-order ordinary differential equations of the reduced-order model for the nonlinear transient heat-conduction problem of the seawater desalination device are obtained. The ordinary differential equations of the reduced-order model are solved by solving the ordinary differential equations of the reduced-order model. The distribution of the temperature field at each time of the structure is obtained. The performance of the model is verified by numerical examples under the conditions of two-stage temperature-difference heating and only the top-level heating. The results show that the model has good accuracy and efficiency.

Numerical Study of Air Flow and Distribution of Temperature in A Room with Dislocation Ventilation and A Chilled Ceiling

In the present study, numerical analysis has been employed to investigate the distribution of velocity and temperature of the air in space conditioned with corrugated ceiling radiant cooling panels (RCP). The model of the study is a three-dimensional room with dimensions of (5.0*4.0*3.2) m. The initial and boundary conditions of the models are set to start the simulation in which the mean cooling panel temperature (Tmp) is (15 °C), where Tmp must not be lesser than that variety to avoid the danger of water vapor condensation on the surface of panels and tubes. The air inlet temperatures Tin is taken as (15, 20, and 25) °C and inlet velocities Vin are (1 and 0.5) m/s with an outdoor air temperature of (40 °C). Ansys Fluent software is considered in this study to simulate the flow field under the influence of several factors including outdoor air temperature, mean panel temperature, air inlet velocity, and temperature. The outcomes show an improvement in the overall cooling capacity and the mixed convection heat transfer. Many of the calculated outcomes were displayed as velocity vectors and temperature contour diagrams. Numerical studies assist in using the chilled ceiling technique for cooling aims in Iraqi weather for its simplicity, easiness, and better comfort presentation.

Heterogeneous Ion-Induced Nucleation of Water and Butanol Vapors Studied via Computational Quantum Chemistry beyond Prenucleation and Critical Cluster Sizes.

Water and butanol are used as working fluids in condensation particle counters, and condensation of a single vapor onto an ion can be used as a simple model system for the study of ion-induced nucleation in the atmosphere. Motivated by this, we examine heterogeneous nucleation of water (H2O) and n-butanol (BuOH) vapors onto three positively (Li+, Na+, K+) and three negatively charged (F-, Cl-, Br-) ions using classical nucleation theory and computational quantum chemistry methods. We study phenomena that cannot be captured by Kelvin-Thomson equation for small nucleation ion cores. Our quantum chemistry calculations reveal the molecular mechanism behind ion-induced nucleation for each studied system. Typically, ions become solvated from all sides after several vapor molecules condense onto the ion. However, we show that the clusters of water and large negatively charged ions (Cl- and Br-) thermodynamically prefer the ion being migrated to the cluster surface. Although our methods generally do not show clear sign-preference for ion-water nucleation, we identified positive sign-preference for ion-butanol nucleation caused by the possibility to form stabilizing hydrogen bonds between butanol molecules condensed onto a positively charged ion. These bonds cannot form when butanol condenses onto a negatively charged ion. Therefore, we show that ion charge, its sign, as well as vapor properties have effects on the prenucleation and critical cluster/droplet sizes and also on the molecular mechanism of ion-induced nucleation.

Numerical model of an industrial refrigeration system for condensation temperature optimisation

Refrigeration plants in the food industry have a key role, yet are very energy-intensive, which poses a serious problem given the current steep rise of energy prices. In this framework, energy consumption minimisation represents a paramount goal for plant managers, yet most are loathe to test new control strategies in real-life plants, lest normal operation be disrupted and food be spoiled as a consequence. In this view, numerical models able to demonstrate the reduction in energy consumption which can be achieved with suitable conduction strategies, especially in the case when evaporative condensers are employed, appear the ideal tool to provide the manager with an estimation of the potential savings and spur them into adopting such strategies. In this work one such model is developed for the primary loop of the refrigeration plant of a warehouse for food storage located in northern Italy. The choice of the model type is discussed at length, as are modelling issues related to all main components of the loop. The model has been validated with operational data from the real-life plant and employed to determine the optimal condensation pressure corresponding to the minimum total energy consumption according to ambient conditions. The method and model can be applied to other, similar plants in order to minimise their energy consumption.

Condensation characteristics of air–water vapor mixture on the surface of vertical flat plate

The condensation heat transfer of air–water mixed vapor is an important heat transfer phenomenon in production life. An experimental system for condensation heat transfer of the air–water vapor mixed vapor is built in this paper. The condensation characteristics of the mixed vapor and the double boundary layer structure characteristics were investigated. The study mainly discussed the influence of flow velocity on the condensation performance of mixed vapor and summarized the experimental correlation equations considering flow velocity. Results indicate that the condensation performance decreases significantly as the air concentration increases. The mixed vapor flow velocity was increased from 1 to 3 m/s, and the condensation heat transfer coefficient was increased by 34.9–121.0%. The enhanced effect of flow velocity was also observed at high air concentration and low subcooling. The ratio of convective and condensation heat transfer coefficients increases with the rise in air concentration, reaching a maximum of 0.12. The proportion of convective heat transfer can be reduced by increasing the mixed vapor flow velocity. The gas film thickness is substantially higher than the liquid film thickness in mixed vapor condensation, and the gas/liquid film thermal resistance ratio can be more than 30 times. And increasing the flow velocity can significantly reduce the gas film/liquid film thermal resistance ratio. A new experimental correlation equation is fitted based on the experimental results, and this equation can be used as a reference for the design of related heat exchangers.

Boosting potassium-based dual ion battery with high energy density and long lifespan by red phosphorous

The potassium dual-ion batteries (DIBs) have been attracting a great attention in recent years due to their promising environmental benignancy, high energy density, and long lifespan. The active materials based on conversion reaction mechanism are favorable and widely expected to alleviate the dendrite formation, red phosphorous was thus employed and fabricated into a three-dimensional porous carbon matrix anchored by P–O–C chemical bonding using vaporization–condensation–conversion process. Meanwhile, the elements modified carbon can not only guarantee the electronic conductivity and ions diffusion, but also alleviate the red phosphorous volumetric expansion and detachment. When coupled with graphite, the K-DIBs demonstrate excellent electrochemical performance with a high 213 Wh kg−1 energy density and a promising stability up to 650 cycles. This explored material will provide highly relevant insights for next-generation advanced energy storage systems.