• Journal of Energy Engineering
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• v.23 no.1
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• pp.75-80
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• 2014

The past several years have seen a substantial growth in mathematical modeling activities whose interests are to describe the performance, efficiency and emissions characteristics of various types of internal combustion engines. The key element in these simulations of various aspects of engine operation is the model of the engine combustion process. Combustion models are then classified into three categories: zero-dimensional, quasi-dimensional and multidimensional models. zero-dimensional models are built around the first law of thermodynamics, and time is the only independent variable. This paper presents a introduction to the combustion characteristics of a spark ignition combustion modeling by zero-dimensional model.

• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.380-387
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• 2012

The present investigation is to examine the thermal behaviors of air flows inside Korean traditional house made of the construction materials transmitted. The methodology is numerical predictions of air flows depend on the temperature distribution inside the indoor spaces. The transient computational simulations are performed along with the different house types, weather condition, and operating time. Thermal properties of building units have been obtained by the parallel measurements and utilized in the numerical works. Consequently, the details of flows and temperature of air in the houses illustrate the thermal design of the traditional Korean house satisfy the requirements of human living.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.743-748
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• 2017

For diseases that are difficult to detect by conventional imaging techniques, the development of a diagnostic method that allows sensors to be inserted into the human body to aid the diagnosis of local spots of the target tissue, is highly desirable. In particular, it is extremely difficult to determine whether vulnerable plaque can later develop into atherosclerosis using only imaging techniques. However, vulnerable plaques are expected to have slightly different mechanical properties than healthy tissue. In this study, we aim to develop a piezoelectric cantilever-type sensor that can be inserted into the human body and can detect the local mechanical properties of the target tissue. A piezoelectric polymer composite based on $BaTiO_3$ nanoparticles was optimized for fabrication of a piezoelectric cantilever. Next, a micro-cone tip was fabricated at the end of the piezoelectric cantilever by thermal drawing. Finally, stiffness of biological tissue samples was measured with the piezoelectric cantilever sensor for verifying its functionality.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.1-9
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• 2008

Fiber Reinforced Polymer (FRP) composites are used extensively in aerospace, marine, automotive, infrastructure, chemical processing and sporting good applications. A concern with using FRP composites in some engineering structures is their high flammability and poor fire resistance In this research, material properties of FRP composites at increasingly high temperatures was measured and verified. The obtained mechanical properties of FRP composites were performed according to ASTM D3039/D3039M and tested to a wide range of heat conditions with temperatures from Room-temp. to 300 for times up to 30 min. It is found that the mechanical properties of FRP composites dropped with increasing heat or temperature. The reduction to the properties was due mainly to thermal degradation and combustion of the polymer matrix.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.285-291
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• 2017

In this study, a case analysis for thermal design of electronic equipment using a phase change material(PCM) was performed numerically using ANSYS Fluent. Experiments were conducted to find the temperature increase(${\Delta}T_m$), melting temperature($T_m$), and volume expansion of the PCM under the melting process. To verify the accuracy of the Fluent solver model, $T_m$, ${\Delta}T_m$, and the melting time were compared with experimental results. To simulate the temperature stagnation phenomenon under the melting process, the equivalent specific heat method was applied to calculate the thermal properties of the PCM in the solver model. To determine the thermal stability of electronic equipment, we paid special attention to finding a thermal design for the PCM using fins. Further, an additional numerical analysis is currently underway to find an optimum design.

• 기계와재료
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• v.24 no.2
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• pp.48-61
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• 2012

NOx 저감방법으로 여러 가지 방법들이 존재하며 연구되고 있다. 그중 Urea-SCR은 적용가능한 온도범위가 넓고 우수한 저감효율을 보여 자동차엔진의 NOx 저감장치로 많은 연구가 진행되어 왔다. Urea-SCR은 고체 Urea의 열 해리반응으로 생성되는 암모니아가스와 NOx 와의 화학반응으로 제거하는 것이 목적이다. NOx저감효율에 직접적인 영향을 주는 변수에는 분사노즐의 분무특성, 배기관내 분사위치, 요소수의 유량제어 등 여러 가지가 존재한다. 따라서 본문에서는 여러 가지 분사노즐, 유량제어방법, 배기가스 물성치 및 관내 유동특성 등에 대해 소개하고 Urea-SCR시스템 적용가능성을 언급하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.641-648
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• 1996

Thermophoretic particle deposition on a circular cylinder in a uniform laminar air flow was numerically investigated using a control volume method based on the generalized non-orthogonal coordinate system. Variation of air properties due to the change of temperature was taken into account. Effects of variable property on the distribution of heat transfer and deposition rates of particle were discussed. A new correlation of thermophoretic particle deposition on a circular cylinder was proposed in the present study.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.99-102
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• 2011

본 연구는 일본 교토대학의 유전사회(有田史繪)의(2000년(年)) "화재시 고강도 콘크리트의 폭렬에 관한 이론적 연구(火災時における高强度コンクリ-トの爆裂に關する理論的硏究)"를 고찰 한 결과 콘크리트 압축강도 Fc[kgf/$cm^2$]와 밀도[kg/$cm^3$]가 분리되면, 열과 수분의 이동에 관련된 물성치가 예측되며, 해석 모델을 통해 해석된다. 이에 대하여 내부응력과 더불어 열특성, 콘크리트의 역학특성, 강재의 역학특성을 파악하여 내화설계를 구축을 위한 기초자료로 제시하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1095-1105
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• 2005

Numerical analysis has been carried out to investigate transient turbulent convective heat transfer in a vertical tube for supercritical water near the thermodynamic critical point. Heat transfer and fluid flow in the tube we strongly coupled due to the large variations of thermodynamic and transport properties such as density, specific heat, and turbulent viscosity. As pressure in the tube approaches to the critical pressure, the properties variation with time becomes larger. Heat transfer coefficient rapidly decreases along the tube near the pseudocritical temperature at the tube wall for $P_R<1.2$. Stanton number variation with time is largely reduced in the region of gas-like phase in comparison with Nusselt number. Turbulent viscosity ratio close to the wall increases near the pseudocritical temperature and it gradually decreases with time.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.53-61
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• 2006

Axisymmetric numerical thermal analysis for a 3-dimensional regenerative cooling system in a rocket engine is carried out. To predict the accurate heat transfer with the stiff temperature distribution, several tests have been conducted for the grid size, the properties variation of the coolant and the combustion gas depending on temperature. The axisymmetric heat flux model is defined using fin efficiencies and is designed to be equivalent to the heat flux of the 3-dimensional coolant channel. For comparison purpose, the 1-dimensional analysis using Bartz equation is also conducted. The performance of the present model in predicting the cooling characteristics of a 3-dimensional regenerative cooling system is compared with the 3-dimensional results of RTE(Rocket Thermal Evaluation). It is found that the present method predicts much closer results to those of RTE code than 1-dimensional analysis.