•Ultrasound was used to extract phenolics from grape marc.•Effects of acoustic energy density and temperature were studied.•Extraction kinetic curves were modeled.•Effective diffusion coefficients ...were determined.•Diffusion coefficients were correlated with acoustic energy density and temperature.
The effects of acoustic energy density (6.8–47.4W/L) and temperature (20–50°C) on the extraction yields of total phenolics and tartaric esters during ultrasound-assisted extraction from grape marc were investigated in this study. The ultrasound treatment was performed in a 25-kHz ultrasound bath system and the 50% aqueous ethanol was used as the solvent. The initial extraction rate and final extraction yield increased with the increase of acoustic energy density and temperature. The two site kinetic model was used to simulate the kinetics of extraction process and the diffusion model based on the Fick’s second law was employed to determine the effective diffusion coefficient of phenolics in grape marc. Both models gave satisfactory quality of data fit. The diffusion process was divided into one fast stage and one slow stage and the diffusion coefficients in both stages were calculated. Within the current experimental range, the diffusion coefficients of total phenolics and tartaric esters for both diffusion stages increased with acoustic energy density. Meanwhile, the rise of temperature also resulted in the increase of diffusion coefficients of phenolics except the diffusion coefficient of total phenolics in the fast stage, the value of which being the highest at 40°C. Moreover, an empirical equation was suggested to correlate the effective diffusion coefficient of phenolics in grape marc with acoustic energy density and temperature. In addition, the performance comparison of ultrasound-assisted extraction and convention methods demonstrates that ultrasound is an effective and promising technology to extract bioactive substances from grape marc.
Power ultrasound has been proven to be useful in promoting the nucleation of ice in water-based solutions, and different mechanisms have been proposed to describe this phenomenon. In the present ...work, the use of ultrasound waves to induce dynamic nucleation in deionised water, sucrose solution, and agar gel samples was studied, and the mechanism of ultrasound assisted nucleation was discussed. The samples were frozen in an ethylene glycol–water mixture (−
20
°C) in an ultrasonic bath system after putting them into tubing vials. Ultrasound irradiation (25
kHz, 0.25
W
cm
−1) was applied continuously for 1, 3, 5, 10 or 15
s at different sample's temperatures in the range of 0
°C to −
5
°C. The nucleation temperatures of the water, sucrose solution and agar gel samples without ultrasound irradiation, occurred stochastically at −
7.4
±
2.4
°C, −10.6
±
1.7
°C and −
7.5
±
0.92
°C, respectively and followed normal distributions. Unlike agar gel samples, the nucleation temperatures of water and sucrose were induced by applying ultrasound for 5
s at different temperatures after a short delay, and linear relationships between the ultrasound irradiation temperatures and the nucleation temperatures were observed. Evaluation of the effect of different durations of ultrasound application on agar gels indicated that 1
s was not long enough to induce nucleation, 3
s was optimal, 5
s and 10
s produced heat and inhibited nucleation, and 15
s did not exhibit significant differences from 3
s and 10
s. It was concluded that longer irradiation durations (especially 5
s and 10
s) caused the sample to heat up, which interrupted or delayed the nucleation. Ultrasound irradiation for 3
s induced nucleation in agar gel samples at different temperatures resulting in a linear relationship between irradiation and nucleation temperatures. The observations indicated that the Hickling's theory, according to which vigorous collapses of bubbles are the only driving mechanism of nucleation, is not adequate to describe the ultrasound assisted nucleation. The results, however, were in agreement with results of some other researchers suggesting that secondary phenomena such as flow streams are also important for the initiation of nucleation. In conclusion, the use of ultrasound as a means to control the crystallisation process offers promising application in food freezing, though further investigations are needed for understanding the mechanisms, especially in solid foods.
► Ultrasound can be used to control the onset of nucleation in both fluid and solid model foods. ► Ultrasound was able to induce nucleation in fluid samples more efficiently. ► An optimum condition was needed for repeatable results in the solid samples. ► The strong bubble collapses are not necessarily the main cause of nucleation. ► Irradiation time was an important parameter for nucleation in agar gel.
The transport of virus-laden aerosols from a host to a susceptible person is governed by complex turbulent airflow and physics related to breathing, coughing and sneezing, mechanical and passive ...ventilation, thermal buoyancy effects, surface deposition, masks, and air filtration. In this paper, we study the infection risk via airborne transmission on an urban bus using unsteady Reynolds-averaged Navier–Stokes equations and a passive-scalar model of the virus-laden aerosol concentration. Results from these simulations are directly compared to the widely used well-mixed model and show significant differences in the concentration field and number of inhaled particles. Specifically, in the limit of low mechanical ventilation rates, the well-mixed model will overpredict the concentration far from the infected passenger and substantially underpredict the concentration near the infected passenger. The results reported herein also apply to other enclosed spaces.
•Ultrasound was used to assist the release of phenolics from oak chips into model wine.•The effect of acoustic energy density on release kinetics was not prominent.•The increase of temperature can ...increase the total phenolic yield.•The release kinetics were modeled by a second-order model and a diffusion model.
The enhancement of release of oak-related compounds from oak chips during wine aging with oak chips may interest the winemaking industry. In this study, the 25-kHz ultrasound waves were used to intensify the mass transfer of phenolics from oak chips into a model wine. The influences of acoustic energy density (6.3–25.8W/L) and temperature (15–25°C) on the release kinetics of total phenolics were investigated systematically. The results exhibited that the total phenolic yield released was not affected by acoustic energy density significantly whereas it increased with the increase of temperature during sonication. Furthermore, to describe the mechanism of mass transfer of phenolics in model wine under ultrasonic field, the release kinetics of total phenolics was simulated by both a second-order kinetic model and a diffusion model. The modeling results revealed that the equilibrium concentration of total phenolics in model wine, the initial release rate and effective diffusivity of total phenolics generally increased with acoustic energy density and temperature. In addition, temperature had a negative effect on the second-order release rate constant whereas acoustic energy density had an opposite effect.
•Effects of high pressure freezing (HPF) includes cold and pressure denaturation.•Actomyosin denaturation was related to ice formation paths during HPF.•Freezing-Factors weakened the effects of high ...pressure on protein denaturation.•HPF caused higher conformation of actomyosin during crystallization period.
Effects of protein denaturation caused by high pressure freezing, involving Pressure-Factors (pressure, time) and Freezing-Factors (temperature, phase transition, recrystallization, ice crystal types), are complicated. In the current study, the conformation and functional changes of natural actomyosin (NAM) under pressure assisted freezing (PAF, 100,150,300,400,500MPaP−20°C/25min), pressure shift freezing (PSF, 200MPaP−20°C/25min), and immersion freezing (0.1MPaP−20°C/5min) after pressure was released to 0.1MPa, as compared to normal immersion freezing process (IF, 0.1MPaP−20°C/30min). Results indicated that PSF (200MPaP−20°C/30min) could reduce the denaturation of frozen NAM and a pressure of 300MPa was the critical point to induce such a denaturation. During the periods of B→D in PSF or B→C→D in PAF, the generation and growth of ice crystals played an important role on changing the secondary and tertiary structure of the treated NAM.
► Ultrasound (US) irradiation increased the cooling rate of a copper sphere notably. ► Higher cooling rates were achieved by increasing the US intensity. ► Acoustic streaming and cavitation were the ...main mechanisms of increased cooling rate. ► The position of the sphere affected the heat transfer phenomenon significantly. ► Different positions exhibited different cavitation bubble population.
It has been proven that ultrasound irradiation can enhance the rate of heat transfer processes. The objective of this work was to study the heat transfer phenomenon, mainly the heat exchange at the surface, as affected by ultrasound irradiation around a stationary copper sphere (k=386Wm−1K−1, Cp=384Jkg−1K−1, ρ=8660kgm−3) during cooling. The sphere (0.01m in diameter) was immersed in an ethylene glycol–water mixture (−10°C) in an ultrasonic cooling system that included a refrigerated circulator, a flow meter, an ultrasound generator and an ultrasonic bath. The temperature of the sphere was recorded using a data logger equipped with a T-type thermocouple in the center of the sphere. The temperature of the cooling medium was also monitored by four thermocouples situated at different places in the bath. The sphere was located at different positions (0.02, 0.04 and 0.06m) above the transducer surface of the bath calculated considering the center of the sphere as the center of the reference system and was exposed to different intensities of ultrasound (0, 120, 190, 450, 890, 1800, 2800, 3400 and 4100Wm−2) during cooling. The frequency of the ultrasound was 25kHz. It was demonstrated that ultrasound irradiation can increase the rate of heat transfer significantly, resulting in considerably shorter cooling times. Higher intensities caused higher cooling rates, and Nu values were increased from about 23–27 to 25–108 depending on the intensity of ultrasound and the position of the sphere. However, high intensities of ultrasound led to the generation of heat at the surface of the sphere, thus limiting the lowest final temperature achieved. An analytical solution was developed considering the heat generation and was fitted to the experimental data with R2 values in the range of 0.910–0.998. Visual observations revealed that both cavitation and acoustic streaming were important for heat transfer phenomenon. Cavitation clouds at the surface of the sphere were the main cause of heating effect. The results showed that closer distances to the transducer surface showed higher cooling rates. On the other hand, despite having a bigger distance from the transducer, when the sphere was located close to the gas–liquid interface the enhancement factor of heat transfer was higher. Ultrasound irradiation showed promising effect for the enhancement of convective heat transfer rate during immersion cooling. More investigations are required to demonstrate the behavior of ultrasound assisted heat transfer and resolve the proper way of the application of ultrasound to assist the cooling and/or freezing processes.
•Novel fluidized bed drying methods saved seaweed drying time significantly.•Airborne ultrasound assisted drying method retained highest total phenolic content.•Page model was the best fitting ...ultrasound assisted fluidized bed drying kinetics.•Seaweed drying after pretreatments saved more energy.
In this study, ultrasound either as a pretreatment technique or as an integrated technique was employed to enhance fluidized bed drying of Ascophyllum nodosum, and drying kinetics and dried product quality were assessed. In order to compare technology efficiency and dried product qualities, oven drying and fluidized bed drying (FBD) were employed. The novel drying methods included airborne ultrasound-assisted fluidized bed drying (AUA), ultrasound pre-treatment followed by FBD (USP), and hot water blanching pre-treatment followed byFBD (HWB). Six drying kinetics models were used to describe the drying curves, among which the Page model was the best in fitting USP and AUA. Model by Millidi et al. was employed to describe HWB. Airborne ultrasound in AUA did not reduce energy consumption or drying time, but retained total phenolic content (TPC) as well as colour, and exhibited the highest yield among the novel drying methods. USP and HWB showed lower energy consumption and drying time considerably, but the TPC was the lowest among the studied methods. At the same time, USP dried product exhibited the lowest aw, followed by HWB and then AUA. This studyalso demonstrated that FBD could be a very practical drying method on Irish brown seaweed, and ultrasound-assisted drying methods may have potential developments in Irish brown seaweed drying process.
Renewable energy power generation systems such as photovoltaic and wind power have characteristics of intermittency and volatility, which can cause disturbances to the grid frequency. The battery ...system of electric vehicles (EVs) is a mobile energy storage system that can participate in bidirectional interaction with the power grid and support the frequency stability of the grid. Lithium iron phosphate (LiFePO4) battery systems, with their advantages of high safety and long cycle life, are widely used in EVs and participate in frequency regulation (FR) services. Accurate assessment of the state of charge (SOC) and remaining available energy (RAE) status in LiFePO4 batteries is crucial in formulating control strategies for battery systems. However, establishing an accurate voltage model for LiFePO4 batteries is challenging due to the hysteresis of open circuit voltage and internal temperature changes, making it difficult to accurately assess their SOC and RAE. To accurately evaluate the SOC and RAE of LiFePO4 batteries in dynamic FR working conditions, a thermal-electric-hysteresis coupled voltage model is built. Based on this model, closed-loop optimal SOC estimation is achieved using the extended Kalman filter algorithm to correct the initial value of SOC calculated by ampere-hour integration. Further, RAE is accurately estimated using a method based on future voltage prediction. The research results demonstrate that the thermal-electric-hysteresis coupling model exhibits high accuracy in simulating terminal voltage under a 48 h dynamic FR working condition, with a root mean square error (RMSE) of only 18.7 mV. The proposed state estimation strategy can accurately assess the state of LiFePO4 batteries in dynamic FR working conditions, with an RMSE of 1.73% for SOC estimation and 2.13% for RAE estimation. This research has the potential to be applied in battery management systems to achieve an accurate assessment of battery state and provide support for the efficient and reliable operation of battery systems.
•Ultrasound assisted freezing of potatoes was evaluated experimentally and mathematically.•Freezing time was decreased, with an optimum irradiation in the range of 30–70% duty cycle.•A finite volume ...numerical model was developed by using OpenFOAM® CFD software.•The numerical model predicted freezing times in accordance with the experimental results.•The model can improve the understanding of the ultrasound assisted freezing process.
In recent years, innovative methods such as ultrasound assisted freezing have been developed in order to improve the freezing process. During freezing of foods, accurate prediction of the temperature distribution, phase ratios, and process time is very important. In the present study, ultrasound assisted immersion freezing process (in 1:1 ethylene glycol–water solution at 253.15K) of potato spheres (0.02m diameter) was evaluated using experimental, numerical and analytical approaches. Ultrasound (25kHz, 890Wm−2) was irradiated for different duty cycles (DCs=0–100%). A finite volume based enthalpy method was used in the numerical model, based on which temperature and liquid fraction profiles were simulated by a program developed using OpenFOAM® CFD software. An analytical technique was also employed to calculate freezing times. The results showed that ultrasound irradiation could decrease the characteristic freezing time of potatoes. Since ultrasound irradiation increased the heat transfer coefficient but simultaneously generated heat at the surface of the samples, an optimum DC was needed for the shortest freezing time which occurred in the range of 30–70% DC. DCs higher than 70% increased the freezing time. DCs lower than 30% did not provide significant effects on the freezing time compared to the control sample. The numerical model predicted the characteristic freezing time in accordance with the experimental results. In addition, analytical calculation of characteristic freezing time exhibited qualitative agreement with the experimental results. As the numerical simulations provided profiles of temperature and water fraction within potatoes frozen with or without ultrasound, the models can be used to study and control different operation situations, and to improve the understanding of the freezing process.
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