Water Condensation Research Articles

Modal Analysis and Optimization of Fluid-Structure Coupling for Rotor and Inner Cylinder of Vertical Condensate Pump

Background: Low-frequency resonance is one of the common issues encountered during the variable-frequency operation of condensate water pumps. There have been numerous patents and papers proposing solutions to address the low-frequency resonance problem in condensate water pumps. However, the solutions for resonance problems often need to be tailored to specific circumstances. Methods: Based on the acoustic method, the dynamic model of the rotor and inner cylinder of Jiangsu Guohua Chenjiagang Power Plant 2B condensate pump is established to compare the difference between dry modal and fluid-structure coupling modal, the influence of perpendicularity, concentricity and bearing wear on the natural frequency of rotor is studied. Results: The rotor is rigid under normal conditions. When the bearing is worn, the frequency of the rotor will be greatly reduced and may fall into the frequency conversion operation range to excite resonance. The deviation of perpendicularity and concentricity will not directly lead to the decrease of rotor modal but will lead to the increase of bearing stress, aggravate bearing wear, and then affect the rotor modal. As the inner cylinder only relies on the fixed support at the top, the structure stiffness is low, which may lead to low-frequency resonance. By adding two support structures at the guide vane, the first-order modal frequency of the inner cylinder can be increased from 3.29 Hz to 28.88 Hz, effectively avoiding the operating frequency range of the system. Conclusion: This study can guide the optimization of similar pump structures.

Numerical simulation of an externally heated fixed bed reactor for coal pyrolysis based on porous media

A cutting-edge three-dimensional transient model utilizing porous media has been developed to accurately simulate the pyrolysis process of externally heated coal. This innovative model comprehensively considers the evaporation and condensation of water, as well as the release of volatiles. In addition, it meticulously examines the change in coal seam porosity and the interphase heat transfer between pyrolysis gas and solid coal seam. The model's precision has been appropriately confirmed through validation against the central temperature evolution inside the experimental reactor. Notably, this model systematically illustrates various aspects, including the evolution of coal layer temperature, evaporation and moisture density, changes in coal layer density, porosity distribution, volatile release, and interphase heat transfer. The obtained results reveal that the heat absorption by moisture phase change causes the coal seam temperature to relatively stabilize at around the water boiling point for a period, thus delaying the initiation of the coal pyrolysis reaction. The pyrolysis gas released by center coal seam pyrolysis tends to flow radially toward the heating wall before flowing out of the reactor. Additionally, the change in coal seam porosity increases the heat transfer rate by an average of 1.5 °C/min during the rapid heating stage. The analysis also highlights the significant occurrence of interphase heat transfer throughout the pyrolysis process and elucidates its mechanism in various stages. Ultimately, this work offers essential theoretical guidance for the design, optimization, and scaling of subsequent externally heated fixed-bed coal pyrolysis reactors.

Experiments’ feasibility study of solar stills in Indonesia, using evaporator covers and cornerless solar collectors

Desalination is a pivotal method for purifying water, offering a reliable means to obtain clean, potable water. Its operational simplicity and utilization of solar energy render desalination a promising technology. In desalination, condensation is the final stage for collecting purified water. However, the persistent challenge of high evaporator glass temperatures significantly impacts the nucleation rate and subsequent condensate release. This research aims to enhance the efficiency of the desalination system by focusing on increasing the rate of condensate water collection. The methodology involves a seven-day direct testing period using a single slope model desalination device featuring dimensions of 1 m2 and an evaporator glass tilt angle of 35°. Solar energy is the primary energy source, absorbed by a collector comprising 3/4-inch diameter copper pipes (14 pipes, 1 m in length) designed without slope. The glass cover is insulated with Styrofoam covered by aluminum foil to mitigate heat ingress from the sun, thereby reducing the temperature of the inner glass surface and accelerating nucleation rates. The maximum water temperature in the evaporator reached 68.7 °C, with the system absorbing energy at a rate ranging from 1048.40 W/m2 to 289.19 W/m2. The energy efficiency of the desalination system was measured at 39.82 %. The highest freshwater production during testing reached 2.33 L/day, with a daily average of 1.52 L/day. Overall, the solar test results still have the potential to be utilized and continue to be developed due to low-cost materials that can overcome the clean water crisis, especially in remote areas.

Sustainability Assessment of Harvesting Rainwater and Air-Conditioning Condensate Water in Multi-Family Residential Buildings under Various Conditions in Israel—A Simulation Study

The environmental impacts and water savings of different configurations of non-potable domestic water use (toilet flushing and laundry), sourced from rainwater harvesting (RWH) and air-conditioning condensate water (ACWH), in multi-family buildings in Israel are examined. Two building types differing in specific roof areas, and three climatic sub-regions were modeled. RWH satisfied 23 and 46% of the water demand for toilet flushing and laundry in high-rise and low-rise buildings, respectively. Air conditioning is used almost daily during Israel’s hot and dry summers. Hence, the combined RWH-ACWH system saved 42 and 64% in high- and low-rise buildings, respectively. Displacing desalinated seawater, a significant water source in Israel, with alternative water sources lowered the environmental impacts with an increase in storage, up to a certain volume, beyond which impacts started rising. The same infrastructure is used during winter for RWH and for ACWH during summer; thus, combining the two exhibits significant water savings, with marginal extra costs while lowering the environmental impacts.

Effect of Discharge Cooling using Condensate Water on the Performance of an Air Conditioner: A Field Testing

The effect of discharge cooling using condensate water from the evaporator on the performance of an air conditioner has been experimentally investigated. Instead of laboratory testing, the air conditioner was tested under real conditions, as is generally an AC unit installed in a room. The indoor unit was installed inside the room at a height of 2.6 m from the floor, while the outdoor unit was installed outside at floor level. In this research, the air conditioner was tested under two conditions, i.e., normal condition without discharge cooling and modified condition in which the condensate from the evaporator was flown and dripped to the discharge pipe. The use of discharge cooling could decrease suction and discharge pressure, as well as suction and discharge temperature. It also slightly decreases supply air temperature. Better performance of the air conditioner with the use of discharge cooling was shown by the decrease of power consumption by 3.5% and increase of cooling capacity by 2.45%. As a result, the coefficient of performance (COP) increases by 6.31%.

Performance Evaluation of a Condenser at a Combined Cycle Power Plant Using the LMTD Method

This study evaluates the performance of the condenser at the Cilegon Combined Cycle Power Plant (CCPP) using the Logarithmic Mean Temperature Difference (LMTD) method to measure the heat transfer rate. Routine maintenance carried out on the condenser in the form of cleaning the condenser water box and condenser tube from garbage and crust on the condenser tube wall. Currently, condenser maintenance follows a routine schedule that is tied to steam turbine maintenance, without taking actual condenser performance into account. This can lead to inefficiencies and unnecessary downtime. The goal of this research is to assess the heat transfer rate of the condenser before and after maintenance to judge its effectiveness. Data on temperature changes were gathered in June 2023, before maintenance, and again in July 2023, after an overhaul. The analysis shows that the heat transfer rate increased from 51,362,294.48 kcal/h to 127,246,219.7 kcal/h, while the LMTD value rose from 0.76°C to 1.86°C. Based on these results, the study suggests a new approach to maintenance that focuses on performance. Specifically, maintenance should be done when the heat transfer rate drops below 110,000,000 kcal/h. This approach will help ensure the condenser works at its best, improve the plant's overall efficiency, and prevent the need for unnecessary maintenance. By aligning maintenance with performance data, the plant can boost output while lowering costs and downtime.

Off-design performance optimization for steam-water dual heat source ORC systems

High-pressure steam and hot water often coexist as industrial waste heat. In this study, dual loop and single loop ORC systems are designed for 700 kPa, 4.1 kg/s steam, and 90 ℃, 122.36 kg/s hot water conditions to study the off-design performance when steam or hot water conditions change. To maximize net output power, we employ a particle swarm optimization algorithm to optimize the evaporation and condensation temperatures. The results show that within the specified hot water conditions, the evaporation and condensation temperatures of D-ORC's low-pressure loop and S-ORC increase with rising hot water inlet temperature and flow rate. The S-ORC demonstrates a higher net output power growth rate as hot water flow rate and temperature rise. Under specific steam conditions, when the steam outlet is in a gas-liquid two-phase state, D-ORC's maximum net output power is 1.7 % higher than that of the S-ORC, with little variation in optimal evaporation and condensation temperatures with respect to steam inlet pressure. At a 3.5 kg/s steam flow rate, the D-ORC's high-pressure loop becomes ineffective, whereas S-ORC efficiently adjusts heat exchange capacity under diverse steam-water conditions, Consequently, the D-ORC's average net output power is 34.2 % lower than that of the S-ORC.

Clean and sustainable recovery of valuable materials from InP scrap via controlled-pressure pyrolysis–spray condensation

Indium phosphide (InP) semiconductors play an irreplaceable role in optical communication, and with the expansion of the market scale, the amount of InP scrap, which has become an important secondary resource for recovering phosphorus and indium, has considerably increased. However, as a typical phosphorus containing material, InP scrap recycling is difficult and dangerous because phosphorus is flammable and releasing toxic and irritating smoke during combustion. In this study, a safe, clean, and sustainable “controlled-pressure pyrolysis–spray condensation” process is proposed. Firstly, InP is decomposed into phosphorus and indium under high-temperature conditions; phosphorus then evaporates into the vapor phase and is sprayed with warm water for condensation in water, whereas indium is enriched in the liquid phase. The feasibility of this process is proven by performing thermodynamic calculations and scaled-up experiments (hundred grams to kilograms) by using a self-designed equipment. At a decomposition temperature of 1323 K, micro-negative pressure, and holding time of 5 h, an indium ingot with a purity of 99.59 wt.% was obtained and the direct yield reached 98.2%. Industrial α-yellow phosphorus with a purity of >98 wt.% was obtained and safely stored in water, and the comprehensive recovery rate is >90%. The overall process produces zero waste gas, liquid, or residue. The new process is easy to implement in industrial applications when the equipment is fitted with a continuous feeding and discharging system. A convenient and safe method for the X-ray diffraction detection of yellow phosphorus is also developed in this study.

NaCl aerosol filtration over filter media with intrafiber porosity: can filtrate capacity be increased by wicking into this pore volume?

This paper investigates a novel fiber-based filter media wherein a NaCl filtrate is collected and reservoired not only onto the surfaces of the fibers and within their inter-fiber voidage but also within the internal porosity of high pore volume nanoporous fibers or vapor grown carbon nanofibers (VGCF) floc used to fabricate the media. This transport process is shown to occur through a NaCl dissolution into the water-filled nanopores of the fiber and a subsequent intra-fiber wicking phenomenon. The study further elucidates two distinct NaCl accommodation mechanisms which are uniquely available to filter media containing nanoporous intrafiber porosity: (1) wicking and capillary condensation of liquid NaCl aerosols directly into the intrafiber pores at high RH, and (2) dissolution of otherwise solid NaCl aerosols deposited onto fiber surfaces (at low RH) into the interior nanopores of the fiber because these pores (when hydrophilic) are saturated with water (even at low RH). To investigate these two mechanistic regimes, various media were fabricated possessing multiscale porosity in the form of: (i) embedded flocs of VGCFs (4.108 cm3gm-1pore volume), (ii) hydrophilic and high pore volume activated carbon fibers (ACFs, 0.950 cm3gm-1) and (iii) solid graphite fibers. These media were then comparatively evaluated toward NaCl aerosol filtration at different relative humidities. Pressure drop measurements versus filtrate accumulation and SEM-EDAX VGCF demonstrated the location and transport of NaCl into the intrafiber voidage. Media containing both VGCF floc and ACF accumulated 1200% more NaCl at low RH (and a specified pressure drop) than similar media prepared from non-porous graphite fibers, with an additional 315% increase from low to high RH. A Gibbs free energy driving force model is provided to illustrate the driving forces favoring water condensation into the nanopores and solid NaCl aerosol dissolution into the water phase. Filtration efficiency and quality factor assessments for the various media are also systematically evaluated to demonstrate the observed mechanistics.

A comparative study of the potentials of Oman and UAE in condensate water recovery

<p class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph; line-height: 120%; mso-pagination: none; layout-grid-mode: char; mso-layout-grid-align: none; text-autospace: none; margin: 12.0pt 0cm 6.0pt 147.4pt;"><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;">Freshwater is essential for everyday activities including drinking, irrigation, farming and many industrial processes. However, freshwater is less than 1% of the total water resources in the planet and, therefore, it is considered a very valuable commodity. Limited resources and growing needs for freshwater triggered global exploration for alternatives to produce enough freshwater for human needs. Today’s most widely used methods to produce freshwater is desalination. However, critical appraisal of the desalination procedures raised the alarm about </span><span lang="EN-GB" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-font-width: 105%; mso-font-kerning: 0pt; mso-ligatures: none; mso-ansi-language: EN-GB;">sustainability</span><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;"> of desalination and indicated that significant research is needed to develop alternative green resources of freshwater. Countries in the Gulf area such as Oman and UAE experience hot and humid climates and use air-conditioning units to achieve acceptable comfort levels and create a </span><span lang="EN-GB" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-font-width: 105%; mso-font-kerning: 0pt; mso-ligatures: none; mso-ansi-language: EN-GB;">healthier</span><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;"> indoor environment. The cooling process release a large amount of condensate water through cooling coils. This amount of water is usually considered as a problem rather than opportunity and, thus, is wasted into municipal sewerage systems via a system of drainage pipes. This alternative source can be utilized in various drainage, irrigation, and cooling applications to reduce the use of considerable amount of municipal potable water. This source not only takes part in controlling the water scarcity, but also in saving energy and to reducing the carbon footprint. This paper focus on highlighting the opportunities for Oman and UAE to utilize the condensate water from air-conditioning process, as a viable alternative source of green </span><span lang="EN-GB" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-font-width: 105%; mso-font-kerning: 0pt; mso-ligatures: none; mso-ansi-language: EN-GB;">fresh</span><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;"> water. It provides a comparison of the potentials of both countries to collect condensate water, based on meteorological data, location and climate. It was concluded that both countries have great potentials and opportunities to utilize this wasted resource. </span></p>

Enhancing Photoswitchable Wetting Properties of Hydrophobic Porous Spiropyran Copolymer Surfaces Through Surface Roughness Engineering

AbstractSurfaces with photoswitchable wettability are of great interest for various applications such as smart coatings or liquid condensation. The photochromic ring opening reaction of spiropyran (SP) to merocyanine (MC) implies a high dipole moment change, making it interesting for photo‐controlled wetting properties. In addition to the material chemistry, surface wettability is influenced by the surface topography. Porous SP copolymers with various micro‐/nanostructures, that is, different submicron roughness, are fabricated via polymerization‐induced phase separation. The influence of the surface topography on the photoswitchable wetting properties is studied. Surfaces with arithmetic mean roughness (Sa) below 150 nm exhibited a maximum static contact angle (SCA) photoswitch up to 16° from 124 ± 6° to 108 ± 4° upon UV exposure. While superhydrophobic surfaces with higher Sa (157 – 608 nm) showed an insignificant SCA switch. The latter surfaces have a SCA above 150° and low CA hysteresis indicating small and insufficient contact with SP/MC surface asperities for the switch. With the optimized surfaces, photo‐controlled water condensation is studied on microscale and showed that the condensate droplets merged faster, and formed larger droplets pinned to the original contact lines on surfaces switched to the less hydrophobic state.

EXPERIMENTAL STUDY OF HYDRATE FORMATION PECULIARITIES FOR CONDITIONS OF THE TURNO AND CENOMANIAN DEPOSITS: Part II

This paper is the second part of the research devoted to the study of hydrate formation features for the conditions of Turonian and Cenomanian deposits. The launch of new gas projects at the Turon and Senoman production facilities in Western Siberia provided a good opportunity to critically analyze the known methods of protecting production, gathering and transportation facilities of the gas field from the formation of solid gas hydrates. The paper presents the experience of implementing a program of laboratory studies of conditions of gas hydrate formation with their subsequent processing and in-depth analysis. The research program covered the area of thermobaric parameters typical for the conditions of Turon-Senoman deposits exploitation with localization of hydrate-hazardous areas in the conditions of Technological Regimes for full development. The description of laboratory studies is given, in which two gas compositions of Senoman and Turon objects, different variants of mineralization and ionic composition corresponding to formation and condensation water, as well as hydrate formation conditions under changing dosages of basic inhibitor on the basis of methanol were considered. The details of the experiment based on the method of swinging cells and the subsequent analysis of the results of the completed experiments to determine the thermobaric conditions of formation and decomposition of hydrates are given. The main features of the experiment are specified, estimates of the rate of change of the influencing parameters of the experiment on its quality are given. In the process of implementation of the experimental program, the optimal values of these parameters were selected, which allowed us to significantly reduce the variation of experimental results to determine the thermobaric conditions of hydrate formation. It is experimentally established that the temperature of hydrate decomposition is higher than the temperature of its formation at all investigated gas compositions and water mineralization.

Short-Term Influence of Water Ingress on Wear in Pitch Bearings of Wind Turbines

The pitch bearings of wind turbines are slowly oscillating, grease-lubricated slewing bearings. They facilitate the pitching movements of blades which control aerodynamic loads. These bearings have diameters of several meters, their blade-side sealings can face the environment, bending moment loads can cause radial deformation of the bearing rings, and their highly variable operating temperatures can facilitate condensation of water inside them. All of this makes water ingress into the lubricant possible. There is limited public knowledge with regards to the maximum water content for safe operation in this application. This work presents the results of a series of scaled wind turbine time series tests with both ‘dry’ (no water contamination) and ‘wet’ (10 mass % demineralized water added) greases. A set of four commercially available greases were tested. The time series were scaled from wind turbine operation and represented a 13.7 h worst-case scenario of operation with small oscillation amplitudes and no longer lubrication runs in between. Three of the greases showed reduced friction and no or limited raceway damage in the wet condition, whereas one showed increased friction and raceway damages.

Numerical Investigation of Enhanced Heat Transfer with Micro Pin Fins in Heat Exchangers.

Pin-fin and flat-tube heat exchangers (PFFTHXs) offer a promising alternative to traditional louvered-fin and flat-tube heat exchangers (LFFTHXs), especially when used as evaporators. The streamlined structure of pin fins helps to effectively remove condensate and defrost water. In this study, we conducted a numerical analysis of 60 different pin-fin configurations across three pin diameters to enhance heat transfer in PFFTHXs. Our investigation focused on how pin pitch affects both airflow and heat transfer efficiency. The results show that a closer pin pitch increases both the heat transfer rate per unit area and the pressure drop for a given airflow velocity. We evaluated the overall performance of these configurations using the heat transfer rate per unit frontal area obtained at equivalent fan power levels. The analysis identified optimal configurations for each pin diameter, with the 0.2 mm diameter configuration demonstrating the highest heat transfer efficiency-this was on par with louvered fins but used fewer resources. This makes it an ideal choice for evaporative applications in PFFTHXs.

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.

Oxyfuel combustion based carbon capture onboard ships

Reducing greenhouse gas emissions in the shipping sector is a challenging task. While renewable fuels stand out as the most promising long-term solution, their near- and mid-term viability is hampered by limited availability and high costs. An alternative approach is onboard carbon capture, which can reduce emissions from new ships as well as retrofitted vessels. This paper examines the techno-economic potential of oxyfuel combustion based carbon capture on ships. The oxyfuel concept uses an oxygen-rich atmosphere in the combustion process, resulting in a mixture of carbon dioxide and water. After the condensation of water, the carbon dioxide rich gas can be directly stored on board. Various onboard oxygen supply concepts are investigated, including different technologies for onboard air separation and liquid oxygen bunkering. Influences on the ship energy system are studied by system simulation of a deep-sea container vessel. Benchmarked against a technologically mature post-combustion carbon capture system, the results show that the oxyfuel concepts have limited competitiveness because of reduced engine efficiencies and high energy demands for onboard oxygen supply. Avoiding onboard oxygen supply by using liquefied oxygen as a byproduct from onshore electrolysis increases energy efficiency and the competitiveness of oxyfuel combustion but requires additional storage space. Sensitivity analyses highlight that the engine combustion concept and engine efficiency are the most critical influences on the techno-economic performance.

Corrosion at Top-of-the-Line in High Pressure and Dense CO2 Environments

This study presents unique data on top-of-the-line corrosion (TLC) occurring in high-pressure environments where CO2 was in the gaseous, liquid, or supercritical state. While CO2 is traditionally in a gaseous phase, this form of degradation is referred to as TLC. In this study, similar phenomena with different mechanisms were observed in liquid CO2 and supercritical states all of which are referred to as TLC due to the location of specimens and ease of comprehension. Experiments were conducted to investigate the effect of CO2 partial pressure (ranging from 20 bar to 100 bar) with temperatures (30°C to 50°C) relating to different water condensation rates (0.001 mL/m2/s to 0.1 mL/m2/s). Uniform and localized TLC rates increased with a higher water condensation rate and surface temperature. As long as CO2 remained gaseous, its partial pressure (pCO2) showed a negligible influence on both uniform and localized TLC rates. At the highest gaseous CO2 content tested, the formation of a protective iron carbonate (FeCO3) layer decreased the TLC rate, with this effect being more pronounced at lower water condensation rates. The risk of localized corrosion for specimens exposed to this environment at high and medium water condensation rates remained an issue. In the dense phase CO2 environment, the difference in temperature between the bulk environment and the specimen’s surface caused a similar phenomenon to water condensation, termed water drop-out, which resulted in corrosion. The rate of water drop-out could not be measured experimentally or estimated theoretically but is a complex function of temperature, pCO2, and CO2 physical state. The interplay between high pCO2 and low pH of the dropped-out water led to elevated uniform and localized corrosion rates. The depth of localized corrosion, at the high and medium water drop-out conditions, reached its maximum at the surface temperature of ca. 45°C. At a lower surface temperature of ca. 25°C and a higher surface temperature of ca. 65°C, the maximum penetration rate was decreased due to slower kinetics of reactions and the formation of a more protective FeCO3 layer, respectively. The results presented in this study highlight the significant difference between corrosion rates, especially in the form of localized damage, in gaseous and dense-phase CO2 environments.

Imaging Dissolution Dynamics of Individual NaCl Nanoparticles during Deliquescence with In Situ Transmission Electron Microscopy.

Water vapor condensation on hygroscopic aerosol particles plays an important role in cloud formation, climate change, secondary aerosol formation, and aerosol aging. Conventional understanding considers deliquescence of nanosized hygroscopic aerosol particles a nearly instantaneous solid to liquid phase transition. However, the nanoscale dynamics of water condensation and aerosol particle dissolution prior to and during deliquescence remain obscure due to a lack of high spatial and temporal resolution single particle measurements. Here we use real time in situ transmission electron microscopy (TEM) imaging of individual sodium chloride (NaCl) nanoparticles to demonstrate that water adsorption and aerosol particle dissolution prior to and during deliquescence is a multistep dynamic process. Water condensation and aerosol particle dissolution was investigated for lab generated NaCl aerosols and found to occur in three distinct stages as a function of increasing relative humidity (RH). First, a < 100 nm water layer adsorbed on the NaCl cubes and caused sharp corners to dissolve and truncate. The water layer grew to several hundred nanometers with increasing RH and was rapidly saturated with solute, as evidenced by halting of particle dissolution. Adjacent cube corners displayed second-scale curvature fluctuations with no net particle dissolution or water layer thickness change. We propose that droplet solute concentration fluctuations drove NaCl transport from regions of high local curvature to regions of low curvature. Finally, we observed coexistence of a liquid water droplet and aerosol particle immediately prior to deliquescence. Particles dissolved discretely along single crystallographic directions, separated by few second lag times with no dissolution. This work demonstrates that deliquescence of simple pure salt particles with sizes in the range of 100 nm to several microns is not an instantaneous phase transition and instead involves a range of complex dissolution and water condensation dynamics.

Modeling of microwave thawing and reheating of multiphase foods: A case study for packed rice

Microwave (MW) thawing and reheating of porous foods such as rice is a common practice, but uniform heating can be difficult to achieve. Computer simulation models were developed using the finite-element method to study MW thawing and reheating of packed rice. A method to obtain an apparent thermal conductivity was proposed, which accounts for heat distribution by water evaporation and condensation through the air pores in the sample. Reheating experiments of mashed compact rice and regular porous rice were carried out on a flatbed MW oven for 90 s. Similarly, thawing experiments were conducted on porous rice for 180 s. Good agreement between simulated and experimental results was obtained when correcting for thermal conductivity of the pores and for the volumetric power absorption between the frozen and thawed fractions This can help in the design of specifically designed porous foods and containers that allow for fast and homogeneous reheating.

Water vapor condensation behavior on different wetting surfaces via molecular dynamics simulation

Understanding water vapor condensation behavior at molecular level provides critical insights and useful guidance towards applications such as atmospheric water harvesting. In this work, condensation behavior of water vapor with a range of concentrations is investigated by molecular dynamics simulation on surfaces with different wetting states, viz. hydrophilic, hydrophobic, superhydrophilic, and superhydrophobic under five levels of water vapor content. The effect of water vapor content on condensation morphology, condensation beginning time, number of water molecules condensed over time, and accumulation rate are quantitatively examined. The results demonstrate that water condensation mass increases linearly with time on hydrophilic and superhydrophilic surfaces, while displaying a two-stage behavior on hydrophobic and superhydrophobic surfaces. The increase at the first stage is slower than the second stage. Higher water vapor content enables earlier nucleation and shortens the duration of the slow increase stage for hydrophobic and superhydrophobic surfaces. Quantitatively, water condensation mass increases linearly with the relative humidity of the vapor, and the coefficient with relative humidity on the hydrophilic, hydrophobic, superhydrophilic and superhydrophobic surfaces is 25.74 × 10–19, 8.31 × 10–19, 27.63 × 10–19, and 1.34 × 10–19, respectively. Our results show that increasing water vapor content has more significant impact on hydrophilic and superhydrophilic surfaces than hydrophobic and superhydrophobic surfaces. In addition, increasing water vapor content has minor effect on condensation rate in the slow increase stage on hydrophobic and superhydrophobic surfaces, but significantly increase the condensation rate on the rapid increase stage.