• 한국수소및신에너지학회논문집
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• 제15권3호
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• pp.235-243
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• 2004

A number of potential applications of aluminum foams are being identified and renewed interest in these engineering materials is also reflected by several current research projects. One of the key issues for industrial exploitation of aluminum foams is the development of cost-effective manufacturing strategies facilitating, preferably, net shape production of foams with controlled porosity and cell size, and minimized structural imperfection. Especially, melt route to aluminum foam production based on the foaming agents offer attraction of low cost and the potential for good microstructure. The present paper is focused mainly on foaming agents of melt-foam aluminum such as $TiH_2$ or $TiH_2-Al$ mixture. For the purpose of economical manufacturing, we are proposed to hydrogen induced mechanical alloying (HIMA) process. Thermo-physical properties of particles synthesized are compared with conventional methods. Specimens synthesized are characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), thermo- gravimetry-differential scanning calorymetry (TG-DSC), pressure-composition-isotherm. (PCI).

• 한국추진공학회지
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• 제17권3호
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• pp.67-75
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• 2013

케로신-액체산소 로켓 엔진에 적용되는 산화제 과잉 예연소기의 냉각 성능 확인을 위한 수치 해석을 수행하였다. 예연소기 1차 연소구역을 상사하기 위하여 분사기 배열에 따른 혼합비를 바탕으로 연소가스 물성치를 계산하였고, 냉각제로서 채널을 흐르는 산소의 물성치는 실제기체 조건에 대하여 적용하였으며, 1차 연소구역과 냉각제로 쓰인 액체산소의 혼합과정은 다상혼합모델을 적용하였다. 수치 해석으로 계산된 결과를 연소시험과 비교하였으며, 이를 통하여 재생냉각 채널과 연소실에서의 물성 등을 정량적으로 파악할 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.209-218
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• 2002

The temperature field of a counterflow non-premixed flame is investigated using thermocouples of two sizes. A thermal balance is performed on the thermocouple in order to calculate the magnitude of the radiation corrections involved. Both the thermocouple wire and bead are separately considered to be the relevant thermal surface to which convective heat transfer takes place, and from which radiation lasses occur. The flame is also simulated by using a detailed chemical kinetic mechanism in a previously developed computer code. The local thermo-physical properties of the gas mixture, required to calculate the corrections, are determined both from the simulation, and by approximating the properties of the mixture as those of molecular nitrogen at the measured temperatures. It is concluded that the thermocouple wire is the appropriate thermal surface to which radiation corrections apply, in the absence of information about the gas mixture, its properties can be reasonably approximated by those of nitrogen rm ($N_2$), and the radiation corrections are very sensitive to misalignments in the temperature and velocity fields.

• 한국산학기술학회논문지
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• 제21권6호
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• pp.490-497
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• 2020

국내 아스팔트 포장 도로는 전체 포장의 약 90%이상을 차지하고 있으며, 건설구조물 중에서는 가장 광범위하게 시공되어지고 있다. 아스팔트 포장의 열전달 특성은 도심지 열섬효과(Heat island effect)에 원인이 되고 있으며, 높은 아스팔트 표면 온도 증가로 인해 파손에 원인이 되고 있다. 이처럼 본 연구에서는 열 변화에 민감한 포장 재료인 아스팔트 혼합물에 태양열 에너지 누적에 따른 열전달 특성 인자를 평가하였다. 평가한 아스팔트 혼합물은 3종류로 밀입도인 WC-2와 배수성 입도인 PA-13, 순환골재를 적용한 WC-2 입도에 대해서 열전달 특성인자(열전도도, 비열용량, 열확산율)와 열에너지 누적에 따른 열전도도변화를 평가하였다. 해당 연구에서 진행한 열누적에 따른 열전도도 실험과 HFM실험 비교 결과, 1.2~2.0배의 차이를 나타냈다. 이는 아스팔트혼합물이 열에너지 누적에 따라 열전도도가 변화한다는 것을 의미한다. 실험결과를 이용하여 아스팔트 혼합물의 표면온도와 입도에 따른 열전도도의 상관관계를 분석하였으며, WC-2 입도의 경우 로그형태의 상관관계를 PA-13의 입도의 경우 선형상관관계를 나타내고 있다. 향후 이러한 열전달 특성 인자는 열에너지에 의한 아스팔트 혼합물의 파손평가 및 모형 개발 연구에 활용 가능한 선행연구가 될 것이라 판단된다.

• 한국세라믹학회지
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• 제49권4호
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• pp.385-396
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• 2012

Thermal shock test methods and thermal shock parameters for ceramics were reviewed from the following viewpoints: (1) The test methods should be based on the precise estimation of both temperature and thermal stress distributions in a specimen taking into account the temperature-dependent thermo-mechanical properties; (2) The thermal shock parameters must be defined as a physical property of the materials and described as a function of temperature at the fracture point of the specimen; (3) The relation between the strength and fracture toughness of brittle ceramics under a thermal shock load must be the same as the relation under a mechanical load. In addition, appropriate thermal shock parameters should be defined by the thermal shock strength and thermal shock fracture toughness based on stress and energy criteria, respectively. A constant heat flux method is introduced as a testing technique suitable for estimating these thermal shock parameters directly from the electric power charged.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.116-124
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• 2002

In order to investigate the soot formation and oxidation processes, we employed the two variable approach and its source terms representing soot nucleation, coagulation, surface growth and oxidation. For the simulation of the taxi-symmetric turbulent reacting flows, the pressure-velocity coupling is handled by the pressure based finite volume method. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical models used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reacting flow field.

• 설비공학논문집
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• 제21권10호
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• pp.575-582
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• 2009

The optimum rotation speed of a desiccant rotor is studied theoretically based on a theoretical solution to the heat and mass transfer processes in the desiccant rotor. A simple correlation equation for the optimum rotation speed is derived to show the effects of various parameters including the thermo-physical properties, the geometric dimension, and the operating condition of the desiccant rotor. The theoretical result is compared with existing experimental data to validate the linearization and simplification included in the solution procedure. Based on the theoretical solution, the effects of major parameters on the optimum rotation speed are studied and the fundamental mechanism of the influences is investigated.

• KSTLE International Journal
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• 제7권1호
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• pp.22-26
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• 2006

A simple finite element analysis is performed to simulate the thermal characteristics of a micro sensor package with thin film heater embedded in the glass wall of a micro-channel. In this paper, Electric characteristics of ITO sputtered heater were presented in this study, which can be used as a map of heater design in the range of available system temperature. The effects of thermo-physical properties of materials, geometrical structure and boundary condition on the thermal performance are also investigated. Finally, the design of micro-flow induced thermal sensor that is capable of measuring fluid flow with a lower flow detection limit of approximately 24pL/s is presented.

• 한국자동차공학회논문집
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• 제10권6호
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• pp.80-89
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• 2002

The flame structure and soot formation in Acetylene-Air nonpremixed jet flame are numerically analyzed. We employed two variable approach to investigate the soot formation and oxidation processes. The present soot reaction mechanism involves nucleation, surface growth, particle coagulation, and oxidation steps. The gas phase chemistry and the soot nucleation, surface growth reactions are coupled by assuming that the nucleation and soot mass growth has the certain relationship with the concentration of pyrene and acetylene. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical model used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reaction flow field.

• 반도체디스플레이기술학회지
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• 제11권4호
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• pp.7-12
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• 2012

Extrusion is one of the most important operations in the polymer-processing industry. Development of models for extrusion and computer tools offer a route to developing reliable and optimized process designs. The models are based on the analysis of physical phenomena encountered during the process. Balance equations for mass, momentum and energy are fundamental to the problem. A predictive computer model has been developed for the single screw extruders with conventional screws of different geometry. The model takes into account melting zones of the extruder and describes an operation of the extruder system, making it possible to predict mass flow rate of the polymer, pressure and velocity profiles along the extruder screw channel. The simulation parameters are the material and rheological properties of the polymer; the screw pitch, and screw speed.