Condensation Efficiency Research Articles

Enhancement of copper nanoparticle yield in magnetron sputter inert gas condensation by applying substrate bias voltage and its influence on thin film morphology

Large-scale synthesis of high-purity nanoparticles is an intense topic of scientific research, with magnetron sputter inert gas condensation recognized as a promising, environmentally friendly technique avoiding wet chemical processes. This study explores the deposition of size-selected nanoparticles under varied substrate bias voltages and reports on a consequent increase in deposition rates up to 32 %. These alterations in substrate bias voltage induce a progressive change in the morphology of the resulting nanoparticle thin films, attributable to the increased kinetic energy of the nanoparticles. Comprehensive characterization via quadrupole mass spectroscopy of the nanoparticle flux, scanning electron microscopy, X-ray photoelectron spectroscopy, and low-energy ion scattering spectroscopy of the deposited nanoparticles corroborates the enhanced nanoparticle yield associated with increased substrate bias voltage. These findings signify a methodological advancement, enhancing the efficiency of magnetron sputter inert gas condensation and moving the technology a step further towards feasible industrial production.

Micrometer Groove Array Structures Inspired by Desert Grasses on Curved Substrates for Enhanced Surface Condensation Efficiency.

Drawing inspiration from the microstructures on biological surfaces to create highly efficient water-collecting surfaces is an effective way to address water scarcity. Inspired by the role of the convex and concave grooves on the surface of Namib desert grass in promoting condensation, we show that optimizing the curvature radius improves the condensation rate of droplets. This convex-concave geometry, combined with nanoneedle structures on the groove ridges, facilitates droplet merging and self-removal through jumping, refreshing the condensation site and further enhancing condensation efficiency. Meanwhile, reducing the adhesive resistance in the groove valleys accelerates droplet migration and removal. We believe this design strategy can be applied to a wide range of water collection and phase change heat transfer applications.

Self-draining microchannel surface structure for droplet condensation with controlled droplet radius distribution

Surface dewetting is technically important in industrial applications, particularly where phase change processes are involved. We present an intrinsically driven water-permeable microchannel surface system. It has two important advantages: its self-draining capability to remove surface droplets and its ability to limit both the maximum size of droplets condensing on the surface and the thickness of the water film in the microchannel system. This results in a reduction in the overall thermal resistance of the condensate on the cooled surface. We have successfully applied this surface drainage concept to water condensation. An improved condensation efficiency of 5%–9% has been achieved operating the device in an environmental chamber (60% relative humidity, 30 °C chamber temperature, 6 °C cooling temperature) without any optimization of the stable surface structure involved.

Innovative dual-mode device integrating capacitive desalination and solar vapor generation for high-efficiency seawater desalination

Solar-driven interface evaporation with high solar-to-steam conversion efficiency has shown great potential in seawater desalination. However, due to the influence of latent heat and condensation efficiency, the water yield from solar-driven interface evaporation remains insufficient, posing a significant challenge that requires resolution. In this work, we designed a dual-mode high-flux seawater desalination device that combines solar-driven interface evaporation and capacitive desalination. By utilizing coupled desalination materials exhibiting both photothermal conversion and capacitance activity, the device demonstrated photothermal evaporation rates of 1.41 and 0.97 kg m−2 h−1 for condensate water yield under one-sun irradiation. Additionally, the device exhibited a salt adsorption capacity of up to 48 mg g−1 and a salt adsorption rate of 2.1 mg g−1 min−1. In addition, the salt adsorption capacity increased by approximately 32% under one-sun irradiation. Furthermore, photo-enhanced capacitive desalination performance was explored through numerical simulations and theoretical calculations. Theoretical calculations and characterizations confirmed that the defect energy levels formed by the introduction of sulfur vacancies can effectively widen the light absorption range, improve photothermal conversion performance, and stimulate more photoelectrons to participate in capacitive desalination. Concurrently, the electron distribution state of molybdenum disulfide with sulfur vacancies and surface defect sites contributes to ion/electron transport at the solid-liquid interface. This work provides a novel pathway for integrating solar vapor generation with other low-energy desalination technologies.

Experimental investigation of humidified air condensation in different rows of serpantine heat exchanger – Cooling water flow rate effect

Condensing economizers are used in the industry as they enable the acquisition of additional heat during vapor condensation. In condensing heat exchangers, water is the usual cooling agent due to its high specific heat capacity and thus efficient heat removal. Therefore, experiments of hot humid air condensation in a serpentine economizer being cooled by water were performed to reveal the effect the cooling water flow rate has on humidified air condensation in separate rows of the serpentine type economizer (with vertical tubes). The results have shown that the cooling ratio (mass flow ratio between the coolant and the humid air) had a minor effect on the distribution of the humidified air temperature along test section for inlet Reynolds number of 3000–10000. The effects on the condensation flux distribution in different rows were much stronger. The most optimal cooling ratio was determined to be 3. The results have shown that the biggest condensation efficiency is up to 35%. It was revealed that in some cases the convection was prevailing in the first rows of the economizer and this resulted in a decreased efficiency/performance of the exchanger.The obtained results from the practical point of view will provide an extended basis for the optimisation of the design of economizers for waste heat recovery in the cases of different cooling water flow rates. It could also be applied to validate computational models developed for condensation heat transfer and condensate flux numerical modelling along economizer.

Intensifying CO2 condensation in the flue gas through the supersonic separators by hydrogen enriching: A computational study

The presence of carbon dioxide in combustion products is one of the main reasons for global warming. Supersonic separation is a modern, eco-friendly, and cost-efficient technology for capturing carbon dioxide. In this study, the physics of CO2 condensation through a supersonic separator nozzle for purifying the flue gas mixture is modeled using a numerical programming method based on the finite volume AUSM scheme. A limiting maximum for condensation efficiency relative to the CO2 content in the flue gas was demonstrated for fixed inlet conditions. The idea of enhancing the carrier gas heat capacity by hydrogen enriching for promoting droplet formation and condensation of CO2 in the mixture is being studied for further increasing condensation efficiency. The analysis uses the Peng-Robinson equation of state formulation, the multi-diameter growth model appropriate for the Eulerian-Eulerian problem, and the nucleation model suitable for high-speed mixture flows. The results show that adding about 48 % molar fraction of hydrogen increases the growth of droplet and condensation efficiency about 1.3 and 1.5 times, respectively. This technique can significantly increase the separation efficiency in supersonic separators.

Selection of ideal emissivity spectrum for radiative cooling and its application in water harvesting

Radiative cooling, a novel cooling technology for condensation water harvesting without energy input, offers a promising solution to the water scarcity. According to the actual locations and atmospheric conditions, selecting the ideal radiative cooling spectrum is crucial to achieve improved condensation efficiency. In this work, we analyze the condensation rate and condensation power in the southern, middle and northern China with three ideal radiative cooling emitters, namely, 4-infinite, single-window, and double-window emitter. Depending on variations in temperature, relative humidity, or the heat transfer coefficient, an optimal emitter can be selected based on the calculated boundary conditions and differences in condensation rate. Meanwhile, three multilayer design of 4-infinite emitter, double-window emitter and single-window emitter are developed using the memetic algorithm. Their emissivity aligns well with the impedance theory. They are then applied to a case study that assesses condensed water collection in Hangzhou, utilizing real-time atmospheric and environmental data in the whole year. Regarding the all-day dew collection, the average daily water generation per week in Hangzhou can be up to 256.94 mLm−2. For the solar water purification, the average condensation rate throughout the year is 1.956 Lm−2hour−1 withh=10Wm−2K−1. Our findings demonstrate that the multilayer design significantly enhances the water harvesting. Hence, our research provides valuable insights for selecting suitable ideal radiative coolers for water harvesting in specific atmospheric conditions and geographical locations.

Optimization of Membrane Condenser Process with PTFE Hollow Fiber Membrane.

A membrane condenser (MC) is a novel membrane separation technology that utilizes the hydrophobic nature of porous membranes to capture water vapor from humid gas. Factors such as temperature, pressure, flow rate, and gas composition entering the membrane condenser play a crucial role in water recovery efficiency. This study utilized hydrophobic polytetrafluoroethylene (PTFE) hollow fiber membranes to create multiple identical membrane modules. This research investigated the impact of temperature, flow rate, pressure on the intake side, gas flow on the cooling side, membrane area, and other variables on the performance of the membrane condenser process. This study compared water extraction efficiency under different conditions, focusing on feed flow temperature and sweeping flow. Results showed that at a temperature of 60 °C, the water recovery rate was 24.7%, while a sweep gas flow rate of 4 L/min resulted in a recovery rate of 22.7%. The efficiency of the membrane condenser decreased with higher feed flow rates but increased with larger membrane areas. A proportional relationship between inlet flow and membrane area was observed, suggesting an optimal range of 0.51-0.67 cm/s for both parameters. These findings offer valuable insights for the practical implementation of hydrophobic membrane-based membrane condenser technology.

Variation of stable isotope signals in precipitation during Typhoon In-Fa (2021), Eastern China

ABSTRACT High-resolution stable isotope precipitation records are crucial for understanding the mechanism of isotope variations during typhoon precipitation events. We present hourly stable isotope time series of precipitation during Typhoon InFa (2021) in Kunshan and Yangzhou, in the lower reaches of the Yangtze River, Eastern China. Precipitation δ18O in Kunshan and Yangzhou ranged from −1.3‰ to −12.3‰ and −2.8‰ to −17.1‰, respectively. Both δ18O time series shifted to more negative values as the typhoon approached. The evolution of precipitation δ18O during the typhoon is likely caused by a combination of Rayleigh distillation and microphysical processes. Precipitation δ18O values in Yangzhou are more negative than those in Kunshan with a lag of ~14 h. This was mainly controlled by further continuous rainout processes during the movement of Typhoon InFa from Kunshan to Yangzhou and higher condensation efficiency. This study improves our understanding of the mechanisms underlying stable isotope changes during typhoon precipitation.

A novel dual condensers heat pipe photovoltaic/thermal (PV/T) system: Numerical dynamic modelling and effect factors analysis in dual-function operation mode

This paper presents a dual condensers heat pipe PV/T system with multiple operating modes, including hot water, space heating, and dual-function. To exploiting the system's potential of energy supply, this paper proposes a dynamic model of the system in dual-function mode on the basis of the verified dynamic heat transfer model and condenser distributed parameter model. Several effect factors on the system performance have been analyzed, including water tank capacity, air-cooled condenser area and the dual condensers installation height difference. The simulated results show that the above parameters have little effect on the system's total thermal efficiency but a significant effect on single condenser heat gain distribution. When the water tank capacity increases from 100 L to 200 L, the thermal efficiency of the water-cooled condenser increases from 10.68 % to 17.82 %, while the air-cooled condenser's decreases from 48.12 % to 40.72 %. As the air-cooled condenser area is changed from model 1 to 4, the total efficiency increase from 58.13 % to 71.41 %. The system's thermal efficiency falls from 58.66 % to 47.50 % and its overall efficiency falls from 71.41 % to 60.40 % when the height difference rises from 0 m to 0.7 m.

Introducing terminal alkyne groups at the reducing end of cellulose nanocrystals by aldimine condensation for further click reaction

In recent years, click reactions with cellulose nanocrystals (CNC) participation have gradually become a research hotspot. Carboxylamine condensation is the most used method to introduce terminal alkyne groups at the reducing end of CNC as reaction sites for click reactions. However, hydroxyl groups on CNC surface would be slightly oxidized during the carboxyamine condensation process, inducing the potential positions of introduced alkynes would be not only at the reducing end but also on CNC surface. Here, aldimine condensation was proposed to introduce terminal alkyne groups just at the reducing end of CNC, and a systematic comparison analysis was conducted with carboxylamine condensation. Firstly, the selectivity and extent of alkynylation were characterized by XPS and EA. Secondly, the end aldehyde content in these CNC samples was measured by the BCA method, which quantitatively explained the grafting efficiency of aldimine condensation and further verified its feasibility. Thirdly, the clickability of the modified CNC samples was confirmed through XPS analysis of the products after a pre-designed click reaction. In sum, aldimine condensation was proven to be a simple and effective strategy for introducing terminal alkyne groups at the reducing end of CNC, which could be used as reaction sites for further click reactions.

Structured and disordered regions of Ataxin-2 contribute differently to the specificity and efficiency of mRNP granule formation.

Ataxin-2 (ATXN2) is a gene implicated in spinocerebellar ataxia type II (SCA2), amyotrophic lateral sclerosis (ALS) and Parkinsonism. The encoded protein is a therapeutic target for ALS and related conditions. ATXN2 (or Atx2 in insects) can function in translational activation, translational repression, mRNA stability and in the assembly of mRNP-granules, a process mediated by intrinsically disordered regions (IDRs). Previous work has shown that the LSm (Like-Sm) domain of Atx2, which can help stimulate mRNA translation, antagonizes mRNP-granule assembly. Here we advance these findings through a series of experiments on Drosophila and human Ataxin-2 proteins. Results of Targets of RNA Binding Proteins Identified by Editing (TRIBE), co-localization and immunoprecipitation experiments indicate that a polyA-binding protein (PABP) interacting, PAM2 motif of Ataxin-2 may be a major determinant of the mRNA and protein content of Ataxin-2 mRNP granules. Experiments with transgenic Drosophila indicate that while the Atx2-LSm domain may protect against neurodegeneration, structured PAM2- and unstructured IDR- interactions both support Atx2-induced cytotoxicity. Taken together, the data lead to a proposal for how Ataxin-2 interactions are remodelled during translational control and how structured and non-structured interactions contribute differently to the specificity and efficiency of RNP granule condensation as well as to neurodegeneration.

Condensation of water on PDMS-coated copper surfaces for fresh water harvesting

With an increased need to solve fresh water scarcity for humanity in many places around the world, dew water harvesting is one promising approach to improve the situation. While condensation from humid air has been a research topic for many years, it is still unclear how surface wettability influences the condensation efficiency and the fresh water harvest. In this work, we contribute to bridging this knowledge gap by comparing the condensation efficiency of PDMS-coated hydrophobic and uncoated hydrophilic surfaces. We characterize the humid air velocity field to enable comparability of the present results on condensation efficiency with the results gained at other conditions. In addition, the surface wetting behavior prior to and after the condensation experiment is investigated to analyze the PDMS-coating longevity and allow to draw conclusions on their suitability for long term use in condensation applications.

Effects of primary flow temperature on phase change characteristics in hydrogen recirculation ejector for PEM fuel cell system

The hydrogen recirculation ejector, known for its low cost and simple structure, has garnered widespread attention in PEM fuel cell applications. As a fluid-driven passive component, the fluid dynamics inside the ejector play a pivotal role in determining its entrainment performance. This study explores the impact of the primary flow temperature on phase change characteristics based on the Euler-Lagrange model. Results indicate that at a primary flow temperature of −40 °C, the mass flow rate of droplets at the outlet reaches 285.2 mg/s, representing a condensation efficiency of 24.1%. Concurrently, condensation elevates the outlet temperature by 31.2 °C, resulting in an 8.8% reduction in the entrainment ratio. The mass flow rate of droplets decreases significantly as the primary flow temperature increases. As the temperature rises to 60 °C, homogeneous droplets vanish entirely. Simultaneously, foreign heterogeneous droplets evaporate by 42.0%, attributed to the negative subcooling degree at the diffuser and outlet pipe. This study emphasizes the significance of controlling the primary flow temperature for the hydrogen recirculation ejector.

Steam Condensation Heat Transfer in the Presence of Noncondensable Gases (NCGs) in Nuclear Power Plants (NPPs): A Comprehensive Review of Fundamentals, Current Status, and Prospects for Future Research

Efficient steam condensation is crucial for safe nuclear power plant (NPP) operations, preventing pressure buildup, overheating, and the release of radioactive materials. However, the presence of noncondensable gases (NCGs), such as air, nitrogen, hydrogen, or helium, can hinder the condensation process by creating a thermal resistance layer that impedes steam diffusion and condensation on the system’s surface. Maximizing the efficiency of steam condensation requires a thorough grasp of the fundamental processes, theories, advancements, and technical hurdles. Therefore, this work thoroughly addresses these needs, with a particular emphasis on addressing the challenges posed by NCGs by dividing the work into four thematic areas. The first theme relates to a comprehensive examination of pure steam condensation phenomena, which includes an exploration of familiar condensation scenarios and various film condensation types. The second theme examines condensation in the presence of NCGs, their mixture properties, and related theories and modelling of heat and mass transfer. The third theme investigates condensation in NPP by exploring passive cooling systems and condensation phenomena under both natural and forced convection conditions during nuclear accidents, the origin of NCGs in NPP and their transportation aspects. This is followed by experimental work related to condensation scenarios and scale. Finally, the last theme looks upon the recent advancements in computational fluid dynamics (CFD) modelling of wall condensation, system analysis codes coupling with CFD, and the implementation of machine learning (ML) for predicting the condensation HTC. By bridging the gap between fundamental knowledge and practical applications, the four thematic areas presented in this work are aimed at providing a comprehensive foundation for researchers and experts in the field of steam condensation when NCGs are involved. The ultimate objective is to bolster the safety and efficacy of NPP operations by understanding the heat and mass transfer mechanisms while mitigating the risk of catastrophic events.

Exploring water desalination in an arid climate: An experimental and numerical analysis of a compact solar chimney

Water scarcity has been proclaimed one of the biggest challenges in the 21st century. This study developed a novel compact solar desalination system based on a chamber (basin) and a chimney where water is evaporated and condensed, respectively. A transient numerical model based on fundamental principles was developed, which uses actual weather conditions to predict the performance of the solar tower desalination system. It was validated with the obtained experimental hourly water production and temperatures in the chimney in a city with a desert climate. A detailed thermal analysis with contours of temperature and mass fraction and streamlines is presented. Also, profiles of water evaporated/condensed are exhibited. Finally, the overall and condensation efficiencies were computed. The transient computational model could replicate experimental hourly water production and temperatures in the chimney with good agreement. The system in the actual state could produce up to 6052 mL of clean water under summer weather conditions. The increase in air velocity to 3.5 m/s improved clean water production by 19.82 % and condensation efficiency by 18.38 %.

Advanced Exergy Assessment of an Air Source Heat Pump Unit

Conventional exergy-based analysis methods are used for evaluating the performance of the energy conversation systems. Conventional exergy-based analyses identify the sources, amounts, and reasons of irreversibilities (exergy destructions), costs and environmental effects, and provide a general direction for improvement. However, interactions between system components (endogenous/exogenous) and technical limitations (avoidable/unavoidable) cannot be identified with any conventional analysis. Hence, the real potential for improvement and optimization strategies can be misguided. Advanced exergy based analysis seeks to overcome this limitation. An air source heat pump unit was assessed applying conventional and advanced exergy analysis approaches respectively. Avoidable/unavoidable and endogenous/exogenous exergy destructions, modified exergy efficiencies and modified exergy losses ratios were calculated for every single component of the system. The results showed that while the evaporator and condenser efficiencies could be upgraded via constructional enhancements to the overall system and other system components, internal operating conditions were mainly responsible of the inefficiencies regarding with the compressor. The analysis demonstrated that while it was possible to improve evaporator and condenser efficiency by making constructive enhancements to whole system design, the efficiency of the compressor was mainly determined by the internal conditions in which the compressor operated.

M3D: Dataset Condensation by Minimizing Maximum Mean Discrepancy

Training state-of-the-art (SOTA) deep models often requires extensive data, resulting in substantial training and storage costs. To address these challenges, dataset condensation has been developed to learn a small synthetic set that preserves essential information from the original large-scale dataset. Nowadays, optimization-oriented methods have been the primary method in the field of dataset condensation for achieving SOTA results. However, the bi-level optimization process hinders the practical application of such methods to realistic and larger datasets. To enhance condensation efficiency, previous works proposed Distribution-Matching (DM) as an alternative, which significantly reduces the condensation cost. Nonetheless, current DM-based methods still yield less comparable results to SOTA optimization-oriented methods. In this paper, we argue that existing DM-based methods overlook the higher-order alignment of the distributions, which may lead to sub-optimal matching results. Inspired by this, we present a novel DM-based method named M3D for dataset condensation by Minimizing the Maximum Mean Discrepancy between feature representations of the synthetic and real images. By embedding their distributions in a reproducing kernel Hilbert space, we align all orders of moments of the distributions of real and synthetic images, resulting in a more generalized condensed set. Notably, our method even surpasses the SOTA optimization-oriented method IDC on the high-resolution ImageNet dataset. Extensive analysis is conducted to verify the effectiveness of the proposed method. Source codes are available at https://github.com/Hansong-Zhang/M3D.

Numerical Study on the Condensation Performance of Triethylene Glycol Regenerated Exhaust Gas in Elliptical Tube

Condensation technology has been widely applied in industries such as energy, metallurgy, refrigeration, petrochemicals, and chemical engineering. Steam condensation is a complex phase change process, and its heat transfer characteristics are significantly different from convective heat transfer without phase change. This article is based on the condensation treatment process of triethylene glycol dehydration regeneration tail gas, proposing the use of elliptical tubes instead of circular tubes for condensation of regeneration tail gas. The finite volume method was used to numerically study the condensation process of regenerated exhaust gas inside an elliptical tube, and compared with a circular tube. The effect of different structural parameters on condensation was also studied. The results show that the use of elliptical tubes can effectively improve condensation efficiency, with a maximum condensation effect of 2.04 times. The research results can provide guidance for enhancing condensation of triethylene glycol regeneration exhaust gas.

Droplet migration induced by non-uniform wetting microgroove structure promotes condensation water collection

Microgroove structure, as an efficient condensation structure, has good application prospects in many fields. However, the interconnection of surface droplets caused by the inability to remove droplets from the ridge of the microgroove in a timely manner affects the efficiency of droplet condensation on the surface of the microgroove. In this paper, we report the promotion of droplet migration by designing non-uniform wetting surfaces with hydrophilic microgrooves and hydrophobic waxy layer ridges. The results indicate that the generation of a liquid film at the bottom of the microgroove is critical to facilitate the adsorption of ridge liquid to the bottom of the microgroove. In addition, the difference in high wettability between the ridges and the bottom contributes to bottom liquid film generation, and ridge adhesion affects the state of the surface after the ridge droplets are detached. This work is of great significance as it provides a reference for the structural design of high-efficiency fog collection systems.