Condensation Efficiency Research Articles

Dynamic omniphobic surfaces enable the stable dropwise condensation of completely wetting refrigerants

Condensation is a vital process integral to numerous industrial applications. Enhancing condensation efficiency through dropwise condensation on hydrophobic surfaces is well-documented. However, no surfaces have been able to repel liquids with extremely low surface tension, such as fluorinated solvents, during condensation, as they nucleate and completely wet even the most hydrophobic interfaces. Here, we introduce a surface functionalization methodology that enables dropwise condensation of fluorinated refrigerants. This approach, compatible with various substrates, combines low contact angle hysteresis Parylene-C with low surface energy silane (P-HFDS) using a highly scalable atmospheric vapor phase deposition technique. Our experimental results demonstrate that the omniphobic P-HFDS coating facilitates dropwise condensation of both natural refrigerants (water, ethanol, hexane, pentane) and synthetic low-global-warming-potential refrigerants (HCFO R1233zd(E) and HFO R1336mzz(Z)) with surface tension as low as 14.6 mN m−1 at 25°C. The P-HFDS coating improves condensation heat transfer coefficients by 274%, 347%, 636%, and 688% for ethanol, hexane, pentane, and R1233zd(E), respectively, compared to filmwise condensation on uncoated metal surfaces. Additionally, the coating demonstrates long-term durability, sustaining steady dropwise condensation for 170 days without apparent degradation. This work pioneers stable dropwise condensation of multiple refrigerants on a structure-less surface, offering a durable, substrate-independent, and scalable solution for low surface energy coatings.

Coevolution and Adaptation of Transition Nuclear Proteins and Protamines in Naturally Ascrotal Mammals Support the Black Queen Hypothesis.

Protamines (PRMs) and transition nuclear proteins (TNPs) are two key classes of sperm nuclear basic proteins that regulate chromatin reorganization and condensation in the spermatozoon head, playing crucial roles in mammalian spermatogenesis. In scrotal mammals, such as humans, cryptorchidism, the failure of the testes to descend into the scrotal sac is generally associated with higher rates of defective spermatozoon quality and function. However, ascrotal mammals, such as cetaceans, with naturally undescended testes, produce normal spermatozoa similar to their scrotal counterparts. This study investigates the evolutionary pattern and functional changes in PRMs and TNPs to explore the potential molecular mechanisms underlying spermatogenesis in naturally ascrotal mammals. Although we found a conserved genomic arrangement for PRM and TNP genes across mammals, the coevolutionary loss of intact PRM2 and TNP2 was observed in several species, correlating significantly with diverse testicular positions. Notably, in cetaceans, which lack intact PRM2 and TNP2, we detected enhanced thermostability and DNA binding in PRM1, along with superior DNA repair capability in TNP1. These findings suggest that gene loss of PRM2 and TNP2, combined with functional enhancements in PRM1 and TNP1 proteins, evolved in response to physiological challenges posed by natural cryptorchidism in most ascrotal lineages. This evolutionary strategy enhances chromatin condensation efficiency and promotes DNA repair during spermatogenesis in natural cryptorchid mammals, supporting the Black Queen Hypothesis.

Numerical investigation and optimization of heterogeneous-homogeneous coupled condensation in steam turbines of tower solar power system

The significant potential for stage efficiency improvement is in steam turbines of solar thermal power plants, which operate in difficult atmospheric conditions contributing to the high pressure in the condenser and steam impurities. Presented study aims to examine the influence of three steam impurities on the condensing flow through turbine stage rotor. Firstly, the modified condensation model is validated using experimental data. Next, the flow characteristics and losses of pure steam and steam containing heterogeneous particles in three-dimensional turbine are investigated separately, and the effects of particles on the flow process and system performance are analyzed. Finally, the effect of backpressure on the condensation flow and the turbine performance is investigated. The results reveal that homogeneous condensation predominantly occurs at higher blade height, NaCl particles have the most significant impact on condensation. At a particle concentration of 10151/kg, the thermal efficiency of heterogeneous condensation on solid particles and tiny droplets increases by 1.6 % and 2.3 %, respectively, compared to homogeneous condensation. Conversely, NaCl particles exhibit a reduction of 0.2 %. Lastly, by strategically raising the backpressure, it is feasible to decrease the humidity on the final stage blades, enhancing thermal efficiency and ultimately optimizing tower solar power generation system operation.

A hybrid approach portraying the dynamics of free convection condensation around a circular cylinder

We introduce a hybrid framework to model the fluid dynamics of free convection condensation of saturated steam outside a circular cylinder. The liquid film is modeled analytically, and the adjacent vapor flow field is resolved numerically. The model incorporates temperature-dependent thermophysical properties of the condensate. We explore the subtle role of Jakob number (Ja) and Weber number (We) in the two-phase flow and establish the criteria for dynamic similarity of the flow field with two new dimensionless numbers, viz., free-fall Reynolds number and similarity number. For fixed base Prandtl number of the condensate, the increases in the subcooling rate with Ja and the cylinder's surface area to volume ratio with We cause film thickening. We develop a theoretical correlation to predict the average film thickness (δm). We identify entrainment and bypass zones in the vapor flow field demarcated by a separating streamline. The entrainment zone's streamlines converge to the interface, yielding a net condensate drainage. The bypass streamlines never reach the interface and reduce the condensation efficiency. The results show that the tangential velocity is dominant within the liquid film, the radial velocity is dominant within the vapor flow field, and they are of the same order at the interface. We locate the point of flow separation influenced by a surface tension-induced adverse pressure gradient. The location of the flow separation point shifts upstream, and the separating streamlines become steeper with the increase in We. Our investigation reveals the zone of tangential flow reversal near the interface, promoted with increasing We.

Optimizing steam condenser efficiency: integrating logarithmic spiral search and greedy selection mechanisms in gazelle optimizer for PI controller tuning

Steam condensers are critical for maintaining efficiency and stability in thermal power plants by converting exhaust steam back into water. Controlling the pressure within the condenser is essential for optimal performance and operational safety. This paper presents a dynamic model of a steam condenser, with pressure control achieved through a proportional-integral (PI) controller. The PI controller parameters are optimized using the gazelle optimization algorithm (GOA), which is applied for the first time to this system in the literature. Additionally, novel enhancements, the logarithmic spiral (Ls) search with greedy selection, are integrated into GOA to further enhance control effectiveness. The performance of the optimized PI controller is evaluated using nonlinear simulations, which include statistical analysis and fitness function assessments. To validate the effectiveness of the proposed approach, comparisons are made with other widely used optimization techniques. The results reveal that the GOA notably enhances control accuracy and stability, with the enhanced GOA (Ls-GOA) achieving the most significant improvements. This underscores its potential for enhancing steam condenser efficiency in thermal power plants.

Sustained Condensation Efficiency on 3D Hybrid Surfaces

Condensation plays a crucial role in various applications. While superhydrophobic surfaces have been employed to enhance condensation, their performance significantly deteriorates with increasing subcooling, limiting their practicality. Hybrid surfaces offer a potential solution for improved condensation at high subcooling, but current designs fail to sustain effective condensation as subcooling rises. This study presents a three‐dimensional (3D) hybrid surface integrating short hydrophobic silicon nanowire arrays with hydrophilic microchannels. The formation of bridging droplets across multiple channels is observed, but they are efficiently removed from the 3D hybrid surface. The 3D hybrid surface exhibits sustained, simultaneous dropwise and filmwise condensation under medium to high subcooling conditions. Notably, it maintains a stable heat transfer coefficient across these subcooling conditions without experiencing the typical decline due to flooding observed on conventional surfaces at elevated subcooling temperatures. When compared to a plain hydrophilic surface at high subcooling, the 3D hybrid surface achieved remarkable improvements of 198% in condensation heat flux and 216% in heat transfer coefficient. This 3D hybrid surface represents a significant breakthrough for enhancing condensation in practical systems operating under high subcooling conditions.

Numerical investigation of thermal-flow processes in the ejector-condenser for selected geometrical parameters

The paper presents the results of analysis of thermal-flow processes in the ejector-condenser for selected geometrical param-eters using CFD (Computational Fluid Dynamics) methods. The ejector-condenser is the water-driven, two-phase ejector responsible for creating a sub-pressure allowing exhaust gases (steam and CO2 mixture) to be entrained, condensing steam, and then increasing the pressure above the atmospheric conditions. The axisymmetric numerical model was developed to take into account multiphase, turbulent flow with steam condensation in the presence of inert gas. The influence of the selected geometrical parameters, such as the motive nozzle's and mixing chamber's diameters on the ejector performance was investi-gated. CFD analysis results are presented in the form of developed scalar distributions as well as pressure, temperature and steam mass flow changes along the flow path. Performances for different geometry modes were calculated and compared using parameters such as compression ratio, expansion ratio, mass entertainment ratio and condensation efficiency. The max-imum achieved compression ratio for the analyzed geometrical variants is 1.113 for the assumed mass entertainment ratio of 0.0295. The condensation efficiency varies in a range of 49.6%–91.4% depending on motive fluid inlet conditions and geom-etry mode.

Performa Termal Kondensor Udara pada Wind Tunnel: Evaluasi Perpindahan Panas

Heat transfer in air condenser systems is a critical aspect in various industrial applications, especially refrigeration and air conditioning systems. The thermal efficiency of condensers is greatly influenced by airflow characteristics, but airflow velocity optimization remains a challenge due to the trade-off between improved heat transfer and energy consumption. Although previous research has examined various aspects of condenser design, there is still a need to explore the optimal limit of airflow velocity that can maximize thermal efficiency without excessively increasing system workload. This study aims to evaluate the thermal performance of an air condenser in a wind tunnel, focusing on the effects of airflow velocity variations on heat transfer rate and thermal efficiency. The experimental method uses a wind tunnel with dimensions of 280x28x28 cm, equipped with a precise temperature and flow velocity measurement system. The flow velocity was varied from 0.8 to 1.8 m/s. The results showed a significant increase in the heat transfer coefficient (h) and heat transfer rate (Q) as the flow velocity increased. Analysis of Reynolds and Nusselt numbers revealed the transition of the flow from laminar to turbulent, which contributed to the increase in heat transfer efficiency. Comparison of experimental results with simulations showed good agreement in the middle velocity range, but there were deviations at extreme velocities. In conclusion, increasing the airflow velocity proved effective in improving the thermal performance of the condenser, but further optimization is required to balance the thermal efficiency with the energy consumption of the system.

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.