• 한국음향학회지
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• 제34권6호
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• pp.493-498
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• 2015

물로 채워진 음향 펄스 튜브 내에는 가진 조건들에 따라 복잡한 형태의 음향 신호들이 형성될 수 있다. 이는 펄스 튜브를 이용해 저주파수 대역에서 평면파 반사계수를 측정하는 것을 어렵게 한다. 본 연구에서는 COMSOL Multiphysics를 이용하여 튜브 벽이 가진되는 경우 펄스 튜브 내에 평면파 뿐 아니라 비평면파 모우드의 복잡한 음장이 발생됨을 보였다. 모우드 분리 방법인 이차원 푸리에 필터링으로 입사 또는 반사하는 평면파 모우드만을 각각 분리할 수 있었다. 이에 시간 게이팅을 적용하므로 음향 시편의 평면파 반사계수를 보다 정확하게 결정할 수 있게 하였다.

• 한국결정성장학회지
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• 제26권6호
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• pp.252-257
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• 2016

Tonpilz 트랜스듀서를 이용한 미세먼지의 포집 거동을 살펴보기 위하여 유한요소법(FEM) 시뮬레이션을 이용하여 미세먼지의 응집 거동을 모사하였다. 원판형 head mass의 두께와 tail mass의 직경, 그리고 고정 볼트의 깊이를 트랜스듀서의 형상 변수로 고려하였다. 도넛형 압전체의 소재로는 기존의 PZT-4 소재와 서로 다른 특성의 두 가지 압전 단결정에 대하여 그 출력에 미치는 형상 변수의 최적화를 구현하였고 이를 통하여 얻은 트랜스듀서를 이용하였을 때 나타나는 미세먼지의 응집 거동을 다중 물리해석 S/W인 COMSOL을 이용하여 모사하였다.

• 한국응용과학기술학회지
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• 제27권4호
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• pp.415-420
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• 2010

This study is focused on the channel design of bipolar plate in the electrode of hydrogen gas generator. The characteristics of hydrogen gas generation was studied in view of efficiency of hydrogen gas generation rate and a tendency of gas flow through the riv design of electrode. Since the flow rate and flow pattern of generated gas in the two phase flow system are the most crucial in determining the efficiency of hydrogen gas generator, we adopted the commercial analytical program of COMSOL MultiphysicsTM to calculate the theoretical flow rate of hydrogen gas from the outlet of gas generator and flow pattern of two phase fluid in the electrode. In this study, liquid electrolyte flows into the bipolar plate and decomposed into gas phase, two phase flow simulation is applied to measure the efficiency of hydrogen gas generation.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.150-160
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• 2011

This study focuses on the Achard turbine, a vertical axis, cross-flow, marine current turbine module. Similar modules can be superposed to form towers. A marine or river hydropower farm consists of a cluster of barges, each gathering several parallel rows of towers, running in stabilized current. Two-dimensional numerical modelling is performed in a horizontal cross-section of all towers, using FLUENT and COMSOL Multiphysics. Numerical models validation with experimental results is performed through the velocity distribution, depicted by Acoustic Doppler Velocimetry, in the wake of the middle turbine within a farm model. As long as the numerical flow in the wake fits the experiments, the numerical results for the power coefficient (turbine efficiency) are trustworthy. The overall farm efficiency, with respect to the spatial arrangement of the towers, was depicted by 2D modelling of the unsteady flow inside the farm, using COMSOL Multiphysics. Rows of overlapping parallel towers ensure the increase of global efficiency of the farm.

• 한국농공학회논문집
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• 제55권4호
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• pp.107-119
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• 2013

바이오매스 가스화는 세계적인 증가 추세에 있는 에너지 수요를 충족할 수 있는 기술 중의 하나이다. 바이오매스 가스화를 통해서 농업 폐기물 등 다양한 바이오매스 자원을 에너지로 전환할 수 있고 $CO_2$ 배출량 또한 줄일 수 있다. 본 연구에서는 COMSOL$^{(R)}$ 3.4 소프트웨어를 이용하여 바이오매스 원료와 운전 조건에 따른 가스화 효율 및 합성가스 조성의 변화를 분석하였다. 원료와 구동조건을 최적화하기 위해 가스화 모델을 세우고 원료와 구동조건을 달리하여 합성가스의 성분을 분석 및 예측하였다. 이 모델은 물리적인 실험을 통해 알고 있는 조건을 통해서 합성가스 성분을 시간에 따라 예측할 수 있다. 모델을 이용하여 함수비 5~30 %, 공기중 산소함량 5~50 %, 공기공급 유량 5~45 L/min, 온도 973~1273 K의 조건에서 합성가스의 성분을 예측한 결과 실제 실험 결과와 일치하는 것을 알 수 있다. 모델링 결과 양질의 합성가스를 생산하려면 원료의 회분함량이 적어야 하고 수소 함량이 높은 합성가스를 생산하려면 반응 온도가 높게 유지되고 원료의 함수비가 높아야 한다. 가스화장치의 온도를 높이면 합성가스의 성분 중 CO의 함량이 많아지고, CO의 함량이 많아지면 가스의 발열량이 높아지는 것을 알 수 있다. 또한 CO의 농도가 높고 발열량이 높은 합성가스를 생산하기 위해서는 ER값은 작아야 한다.

• 한국전기전자재료학회논문지
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• 제33권4호
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• pp.321-325
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• 2020

Atmospheric environmental problems have a major impact on human health and lifestyle. In humans, inhalation of nitrogen oxides causes respiratory diseases, such as bronchitis. In this paper, thermal analysis of a gas sensor was carried out to design and fabricate a wearable nylon-yarn gas sensor for the detection of NO_x gas. In the thermal analysis method, the thermal diffusion process was analyzed while operating the sensors at 40 and 60℃ to secure a temperature range that does not cause thermal runaway due to temperature in the operating environment. Thermal diffusion analysis was performed using the COMSOL software. The thermal analysis results could be useful for analyzing gas adsorption and desorption, as well as the design of gas sensors. The thermal energy diffusion rate increased slightly from 10.05 to 10.1 K/mm as the sensor temperature increased from 40 to 60℃. It was concluded that the sensor could be operated in this temperature range without thermal breakdown.

• Geomechanics and Engineering
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• 제16권5호
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• pp.503-512
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• 2018

Globally there is an increasing need to reduce the greenhouse gas emissions and increase the use of renewable sources of energy. The storage of solar thermal energy is a crucial aspect for implementing the solar energy for space heating in high latitudes, where solar insolation is high in summer and almost negligible in winter when the domestic heating demand is high. To use the solar heating during winter thermal energy storage is required. In this paper, equations representing the single U-tube heat exchanger are implemented in weak form edge elements in COMSOL Multiphysics(R) to speed up the calculation process for modelling of a borehole storage layout. Multiple borehole seasonal solar thermal energy storage scenarios are successfully simulated. After 5 years of operation, the most efficient simulated borehole pattern containing 168 borehole heat exchangers recovers 69% of the stored seasonal thermal energy and provides 971 MWh of thermal energy for heating in winter.

• Current Applied Physics
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• 제18권11호
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• pp.1381-1387
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• 2018

One dimensional (1D) grating has been fabricated (using focused ion beam) on 50 nm gold (Au) film deposited on higher refractive index Gallium phosphate (GaP) substrate. The sub-wavelength periodic metal nano structuring enable to couple photon to couple with the surface plasmons (SPs) excited by them. These grating devices provide the efficient control on the SPs which propagate on the interface of noble metal and dielectric whose frequency is dependent on the bulk electron plasma frequency of the metal. For a fixed periodicity (${\Lambda}=700 nm$) and slit width (w = 100 nm) in the grating device, the efficiency of SPP excitation is about 40% compared to the transmission in the near-field. Efficient coupling of SPs with photon in dielectric provide field localisation on sub-wavelength scale which is needed in Heat Assisted Magnetic recording (HAMR) systems. The GaP is also used to emulate Vertical Cavity Surface emitting laser (VCSEL) in order to provide cheaper alternative of light source being used in HAMR technology. In order to understand the underlying physics, far-and near-field results has been compared with the modelling results which are obtained using COMSOL RF module. Apart from this, grating devices of smaller periodicity (${\Lambda}=280nm$) and slit width (w = 22 nm) has been fabricated on GaP substrate which is photoluminescence material to observe amplified spontaneous emission of the SPs at wavelength of 805 nm when the grating device was excited with 532 nm laser light. This observation is unique and can have direct application in light emitting diodes (LEDs).

• 한국재료학회지
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• 제32권7호
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• pp.313-319
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• 2022

Double-layer capacitors (DLCs) are developed with high surface electrodes to achieve a high capacitance value. In the present work, the initial bulk concentration of 1 mol/m³ and 3 mol /m³ are selected to show the consequential effects on the performance of a double-layer capacitor. A 1D model of COMSOL Multiphysics has been developed to analyze the electric field and potential in cell voltage, the electric displacement field and polarization induced by the field, and energy density in a double-layer structure. The electrostatics and the electric circuit modes in COMSOL are used to simulate the electrochemical processes in the double-layer structure. The analytical analysis of a double-layer capacitor with different initial bulk concentrations is investigated by using Poisson-Nernst-Plank equations. From the simulation results, the differential capacitance changes as a function of compact layer thickness and initial bulk concentration. The energy density varies with the differential capacitance and voltage window. The values of energy density are dominated by the interaction of ions in the solution and electrode surface.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2828-2839
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• 2022

This study developed a safety assessment tool for geological disposal systems called APro, a systemically integrated modeling system based on modularizing and coupling the processes which need to be considered in a geological disposal system. Thermal, hydraulic, chemical, canister failure, radionuclide release and transport processes were considered in the current version of APro. Each of the unit processes in APro consists of a single Default Module, and several Alternative Modules which can increase the flexibility of the model. As an initial stage of developing the modularization concept and modeling interface, the Default Modules of each unit process were described, with one Alternative Module of chemical process. The computation part of APro is mainly a MATLAB workspace controlling COMSOL and PHREEQC, which are coupled by an operator splitting scheme. The APro model domain is a stylized geological disposal system employing the Swedish disposal concept (KBS-3 type), but the repository layout can be freely adjusted. In order to show the applicability of APro to the total system performance assessment of geological disposal system, some sample simulations were conducted. From the results, it was confirmed that coupling of the thermal and hydraulic processes and coupling of the canister failure and the radionuclide release processes were well reflected in APro. In addition, the technical connectivity between COMSOL and PHREEQC was also confirmed.