• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.4
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• pp.88-96
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• 2002

The CSCM Upwind method and Material Transport Analysis(MTA) have been used to predict the thermal response and shape changes for charring/non-charring material which can be used as thermal protection material(TPM) on blunt-body nose tip. We performed intensive flight trajectory simulations to compare 1-D MTA results with those of 2-D/Axisymmetric MTA by using MTAs and Navier-Stokes code. Theheat-transfer rate and pressure distribution were predicted at selected altitudes and wall temperature along the flight trajectory and the shape changes of blunt-body nose tip were predicted subsequently by using current procedure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.3
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• pp.414-421
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• 1999

Falling film rectification involves simultaneous heat and mass transfer between vapor and liquid interface. In the present work, the adiabatic rectification process of ammonia-water vapor on the vertical plate was investigated. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer in each phases were investigated. The stripping of water in vapor mixture occurred new the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer in falling film.

• Plant Journal
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• v.15 no.1
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• pp.25-30
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• 2019

In this study, by varying flow patterns, which is one of the hydraulic factors of FAC, a strategy to reduce pipe wall thinning by mass transfer has been investigated. A similarity between heat transfer and mass transfer was verified via theoretical analysis, and local convective heat transfer coefficients were analyzed using a commercial numerical analysis program. When ribs were installed inside and outside of the internal surface in the straight section of the pipe, the maximum local heat transfer coefficient was shown to decrease substantially by up to 24.9% compared to the basic flow depending on the position and shape of ribs. If a guide vein was inserted in the pipe elbow, the maximum local heat transfer coefficient decreased by up to 26.7% compared to the basic flow depending on the internal surface area of the pipe by the guide vein.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.221-230
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• 2002

In this study, in-situ performance test of an air source heat pump which has a arted capacity of 10 RT is carried out. Since test conditions, such as indoor and outdoor air conditions cannot be controlled to satisfy the standard test conditions, experiments are done with the inlet air conditions as they exist. To estimate the performance for other conditions, he heat pump is modeled with a small number of selected parameters. The values of the parameters are determined from the few measurements measured on-site during normal operation. A simulation program is developed to calculate cooling capacity and power consumption t any other operating conditions. The simulation results are in good agreement with the experiment. This study provides a method of an on-site performance diagnosis of an air source heat pump.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.818-826
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• 2001

In this study, in-situ performance test of a wet surface finned-tube evaporator of an air source heat pump which has a rating capacity of 20RT is carried out. Since test conditions, such as indoor and outdoor air conditions cannot be controlled to satisfy the standard test conditions, experiments are done with the inlet air conditions as they exist, From the experimental data, air side heat and mass transfer coefficients were calculated by the well known heat and mass transfer analogy and tube-by-tube method. since current procedure underpredicted the experimental sensible heat factor(SHF), a proper empirical parameter was introduced to predict the experimental data with satisfactory results. This study provides the method of evaluating the heat and mass transfer coefficients of a wet surface finned-tube evaporator of which in-situ performance test in necessary.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.600-609
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• 1998

The experimental investigation of thermal response characteristics by the air flow through the porous media has been carried out. The packed spheres of steel or glass were considered as the porous media in the present study. Temperature distributions of the fluid in the porous media as well as pressure drops through the porous media were measured. The transient temperature variations in the porous media are compared favorably with the analytical results in the high Reynolds number ranges. However, in the low Reynolds number ranges, the experimental data deviate from the analytical results, due to the dominant heat conduction penetration to the upstream direction, which is not considered in the analytical model. The cool-down response of porous media is found to be dependent upon the specific dimensionless time considering the material property and air velocity. The heat discharge process is recommended to be operated until a certain time, considering the cost efficiency.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.604-609
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• 2008

This study is about the modeling and simulation of heat transfer in the box for packaging and shipping of vaccines. Comparison of the simulation results with experimental data revealed that a one-dimensional model (a spherical model of using a radius equivalent to the rectangular geometry of box) showed good agreement with experimental data during cooling process but did not successfully simulate heating process. It is considered that a rigorous boundary condition is not properly applied for outer surface of the box. However, we could successfully develop a basic algorithm for simulating heat transfer through multi-slabs combined with different materials including phase change material.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.8-9
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• 1997

산업의 발달과 환경에 대한 관심이 높아짐에 따라 고효율, 저공해인 가스터빈의 응용범위가 넓어지고 있는 추세이다. 가스터빈 기관의 효율을 높이기 위해서는 터빈 입구온도를 높이는 것이 필수적인데 이는 재질에 의해 제한 받게 되고 이 때문에 효과적인 냉각방법의 필요성이 대두되었다 충돌제트는 국소적으로 높은 열/물질 전달 효과를 얻을 수 있어서 터빈 블레이드 냉각과 연소기 벽면 냉각에 효과적으로 응용 될 수 있다. 이러한 충돌제트의 냉각효과는 제트출구의 초기조건에 매우 민감한데 Kelvin-Helmholts 불안정은 불안정한 자유전단층에서 자연적인 와류생성(roll up)과 개개의 와류고리 형성의 원인이 되고 이 고리의 성장과 병합(pairing)은 제트의 유동특성에 상당히 영향을 미친다. 제트주위에 생성되는 이러한 와류에 의해 제트중심에서 속도와 난류강도가 변하게 된다. 이러한 제트초기의 불안정성은 하류에서의 와류성장에 영향을 끼치기 때문에 와류의 조절에 의한 충돌 면에의 열 전달 효과 상승을 기대할 수 있다. 이 조절방법은 크게 두 가지로 나눌 수 있는데 하나는 제트주의 환형관에 이차유동을 가하여 와류를 직접 제어함으로써 자유전단류(free shear layer flow)의 안정성 원리를 이용하여 열 전달을 촉진하는 것이고 다른 하나는 음향여기(acoustic exitation)를 사용하여 제트주위의 와류형성을 조절하는 것인데, 자연적으로 형성되는 와류의 주파수(와류의 고유주파수)나 부조화 주파수(subharmonic)로 음향여기 시키는 경우 제트 주위 와류는 더욱 증폭되고 그렇지 않은 경우 제트주위 와류의 형성이 억제되어 더 긴 제트코어의 길이 및 제트코어 주위에서 작은 크기의 와류들이 형성된다.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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• pp.1341-1352
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• 2001

Vacuum freeze drying process by which frozen water in a drying material is removed sublimation under vacuum condition, is now applied to various industrial field such as the manufacturing and packaging of pharmaceuticals in pharmaceutical industry, the drying of bio- products in bio-technology industry, the treatment of various quality food stuff in food technology, and so on. The Knowledge about the heat and mass transfer characteristics related with the vacuum freeze drying process is crucial to improve the efficiency of the process as well as the quality of dried products. In spite of increasing needs for understanding of the process, the research efforts in this fields are still insufficient. In this paper, a numerical code that can predict primary drying in a vial is developed based on the finite volume method with a moving grid system. The calculation program can handle the axis- symmetric and multi-dimensional characteristics of heat and mass transfer of the vial freeze drying process. To demonstrated the usefulness of the present analysis, a practical freeze drying of skim Milk solution in a vial is simulated and various calculation results are presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.9
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• pp.885-894
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• 2012

A numerical study of a microchannel steam methane reforming reactor has been performed to understand the characteristics of heat and mass transfer. The integration of Rh-catalyzed steam methane reforming and Pt-catalyzed methane combustion has been simulated. The reaction rates for chemical reactions have been incorporated into the simulation. This study investigated the effect of contact time, flow pattern (parallel or counter), and channel size on the reforming performance and temperature distribution. The parallel and counter flow have opposite temperature distribution, and they show a different type of reaction rate and species mole fraction. As the contact time decreases and channel size increases, mass transfer between the catalyst layer and the flow is limited, and the reforming performance is decreased.