• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.379-392
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• 2021

In this study, an improved acetone-water fractional precipitation process for paclitaxel using ultrasonic cavitation bubbles and gas bubbles was developed. Compared to the conventional method, the time required for precipitation has been reduced by 20~25 times. In addition, the particle size of paclitaxel decreased by 3.5~5.5 times and the diffusion coefficient of paclitaxel increased by 3.5~6.7 times. In the case of precipitation using ultrasonic cavitation bubbles, as the ultrasonic power increased and the temperature decreased, the precipitation rate constant increased. In the case of precipitation using gas bubbles, as the gas flow rate increased and the temperature decreased, the precipitation rate constant increased. Thermodynamic parameters revealed the exothermic, irreversible, and nonspontaneous nature of the improved fractional precipitation.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.335-346
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• 2021

Since epoxy resin coating shows excellent properties in formability, adhesion, and corrosion resistance, they have been extensively used in many industries. However, various types of damages in the epoxy coated tube within a relative short time have been reported due to cavitation erosion, liquid impingement, variation of temperature and pressure. Nevertheless, there has been little research on the effect of temperature on the cavitation degradation of epoxy coatings. Therefore, this work used an ultrasonic cavitation tester to focus on the effect of solution temperature on the cavitation properties of 3 kinds of epoxy coatings in 3.5% NaCl. The cavitation properties were discussed basis on the material properties and environmental aspects. As the solution temperature increased, even though with large fluctuation, the cavitation degradation rates of A and B coatings were reduced rapidly, but the rate of C coating was decreased gradually. In addition to the cushioning effect, the reason that the cavitation degradation rate reduced with solution temperature was partly related to the brittle fracture and water absorptivity of the epoxy coatings, and the water density, but was little related to the shape and composition of the compound in the coatings or the phase transition of the epoxy coating.

• Journal of Soil and Groundwater Environment
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• v.18 no.5
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• pp.39-45
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• 2013

Many researchers have studied the effectiveness of ultrasound in chemical and environmental engineering fields including material synthesis, pollutant removal, cleaning, extraction, and disinfection. Acoustic cavitation induced by ultrasound irradiation in aqueous phase can cause various sonophysical and sonochemical reactions without any chemicals. However most of the previous studies focused only on the relationships between ultrasonic conditions and the results of sonochemical reactions in lab-scale sonoreactors. As a results of this, only a few studies have been devoted to design and optimization of industrial scale sonoreactors. In this study, the effect of the distance between two opposite transducer modules on sonochemical reactions was investigated in single and dual irradiation systems (334 kHz) for four distances including 50, 100, 150, and 200 mm using KI dosimetry. It was found that the dual irradiation systems provided higher performance in terms of the zeroth reaction coefficient and the cavitation yield compared to the single irradiation systems. The sonochemiluminescence (SCL) images for the visualization of the cavitation field showed that cavitation active zone was larger and sonochemical reaction intensity was much higher in the dual irradiation system than in the single irradiation system.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.98-105
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• 2007

The objectives of this study were to demonstrate that enhanced anaerobic digestion could be achieved by adopting ultrasonic cavitation pretreatment on the basis of the biogas production and to compare the simulation results of ADM1 (Anaerobic Digestion Model No. 1) with results of the experimentally operated digester the ultrasonic pretreatment of sewage sludge showed the hindered effect on the dewaterbility and the increase of SCOD production. In this study, four sets of lab-scale anaerobic digester were operated with untreated(control), 30 min, 60 min and 90 min ultrasonic pretreated sludge. TCOD removal efficiencies in digesters of control, 30, 60, 90 min sonicated sludge were 31.9%, 37.9, 38.5% and42.2%, and 75 removal were 15.9%, 20.8%, 21.5%, 24.1% respectively. Also more biogas was produced gradually with the increased sludge loading and the pretreatment time. Overall the simulation results had a correspondence tendency with the experimental efficiencies.

• The Journal of the Acoustical Society of Korea
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• v.18 no.5
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• pp.68-77
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• 1999

The paper looked into the effects of the spectral properties (waveform) of the high intensity focused ultrasound on suppression of the ultrasonic cavitation. Three different types of ultrasound were considered in the study, which were sinusoidal (1 MHz, 5 MPa), frequency modulated (from 1 MHz to 6 MHz for 10 ㎲, 5 MPa), asymmetrically shocked (fundamental frequency 1 MHz, peak positive pressure 12 MPa, peak negative pressure -4 MPa). The temporal response of an air bubble in water initially 1 ㎛ in radius to each type of the ultrasound was predicted using Gilmore bubble dynamic model and Church's rectified gas diffusion equation. It was shown that the radially pulsating amplitude of the bubble was greatly reduced for the frequency modulated wave and was little decreased for the shock wave, compared to the case that the bubble was exposed to the sinusoidal wave. It is interesting that the bubble response to the frequency modulated wave remains similar when the frequency component of the modulated ultrasound is beyond the bubble resonant frequency 3 MHz. This implies that, although the ultrasound is modulated up to 3MHz rather than up to the present 6 MHz, it is likely to produce similar cavitation suppression effects. In practice, it means that a typical narrow band ultrasonic transducer can be taken to generate an appropriate frequency modulated ultrasound to reduce cavitation activity. The present study indicates that ultrasonic cavitation may be suppressed to some extent by a proper spectral modification of high intensity ultrasound.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.2
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• pp.92-98
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• 2015

The physical effect induced by acoustic cavitation was investigated to accumulate basic data for the design of ultrasonic soil washing processes using aluminum foil erosion tests. A square aluminum foil was placed on the glass beads in the pyrex vessel submerged in the sonoreactor equipped with a 36 kHz ultrasound transducer module at the bottom. Cavitational erosion of foils was quantitatively analyzed for various glass bead diameter conditions (1, 2, and 4 mm), glass bead height conditions (5, 10, 15, and 20 mm), and water height conditions (5, 10, 15, and 20 mm). It was found that aluminum foil erosion significantly increased as the glass bead diameter increased and water height over the glass bead increased due to less attenuation of ultrasound and the optimization of sound field for cavitation. Moreover mechanical mixing was suggested to move constantly particles to the bottom area where the acoustic cavitation occurs most violently. It was because aluminium foil erosion by ultrasound transmitted through glass beads was relatively too weak.

• Journal of Energy Engineering
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• v.11 no.3
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• pp.262-268
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• 2002

The present paper investigated the effect of ultrasonic vibrations on the melting process of phase-change materials (PCM). Furthermore, the present study considered constant heat-flux boundary condition, whereas many of the previous researches had adopted constant wall-temperature condition. The results of the present study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming, cavitation, and thermally-oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They speed up the melting process as much as 2.5 times, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, temperature and Nusselt numbers over time provided a conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.235-240
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• 2001

This study presents experimental work on phase change heat transfer, in order to increase heat transfer rate, ultrasonic vibrations were introduced. Solid-liquid phase change occurs in a number of situations of practical interest. This study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. Some common examples include the melting of edible oil, metallurgical process such as casting and welding, and materials science applications such as crystal growth. Therefore, this study presented the effective way to enhance phase change heat transfer.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.211-219
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• 2023

This study analyzes the changes in the physical properties of grout by irradiating it with ultrasonic energy and assesses the injectability of the grout into deep rock fractures. The materials used in the research are OPC (Ordinary Portland Cement) and MC (Micro Cement), and are irradiated depending on the water/cement ratio. After irradiating the grout with ultrasonic energy, viscosity, compressive strength, and particle size are analyzed, and the results of the particle size analysis were applied to Nick Barton's theory to evaluate the injectability of the grout into deep rock fractures under those conditions. It was found that the viscosity of the grout decreased after ultrasonic wave irradiation, and the rate of viscosity reduction tended to decrease as the water/cement ratio increased. Additionally, an increase in compressive strength and a decrease in particle size were observed, indicating that the grout irradiated with ultrasonic energy was more effective for injection into rock fractures.

• Textile Coloration and Finishing
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• v.14 no.4
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• pp.214-222
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• 2002

In order to give a silk-like touch to PET fabrics, the PET fabrics were treated with NaOH alkaline solution in various conditions. In alkaline treatment, the liquor flow type pilot weight reduction apparatus with magnetostrictive ultrasonic transducer was used for the study. The weight loss of PET fabrics hydrolyzed in 4% and 6% NaOH solution, at $95^\circ{C}$ and $99^\circ{C}$ for 60min. with ultrasonic application showed 3.7~4.6% higher than that of treated fabric without ultrasonic application. From the difference of specific weight loss, the treatment condition of the maximum of hydrolyzation effect appeared at $95^\circ{C}$ in $4^\circ{C}$ and at $90^\circ{C}$ in 6% NaOH solution, respectively. During the alkali hydrolysis of PET fabrics, the decomposition rate constant(k) increased exponentially with the treatment temperature and were not related with ultrasonic cavitation. The activation energy$(E_a)$ in decomposition of PET fabrics were 21.06kcal/mol with ultrasonic application and 21.10kcal/mol without ultrasonic application. The ultrasonic application gave a little higher value of the activation entropy$(\Delta{S}^\neq)$ and a little lower value of Gibbs free energy$(\Delta{S}^\neq)$ compared with not used ultrasonic apparatus.