• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.165-168
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• 2008

A numerical analysis was conducted to predict the heat transfer characteristics of a solar receiver which is subject to very high heat fluxes and temperatures for solar thermal applications. The concentration ratio of the solar receiver ranges 1000 and the concentrated heat is required to be transported to a certain distance for specific applications. This study deals with a solar receiver according to internal geometry variation incorporating high-temperature heat pipe. The isothermal characteristics in the receiver section is of major concern. The diameter of the solar thermal receiver was 120 mm and the length was 400 mm and the angle of receiver end wall set $90^{\circ},\;60^{\circ},\;45^{\circ},\;30^{\circ}$. And the diameter of the heat pipe was 12.7 mm, 48 axial channels of the same dimensions were attached to the outer wall of the receiver with even spacing in the circumferential direction. The channels are changed to high-temperature sodium heat pipes. Commercial softwares were employed to deal with the radiative heat transfer inside the receiver cavity and the convection heat transfer along the channels. The numerical results are compared and analyzed from the view point of high-temperature solar receiver.

• 대한기계학회논문집B
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• 제32권9호
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• pp.676-682
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• 2008

Numerical analysis was carried out to examine the heat transfer and pressure drop characteristics of plate heat exchangers for absorption application using Computational Fluid Dynamics(CFD) technique. A commercial CFD software package, FLUENT was used to predict the characteristics of heat transfer, pressure drop and flow distribution within plate heat exchangers. In this paper, a welded plate heat exchanger with the plate of chevron embossing type was numerically analyzed by controlling mass flow rate, solution concentration, and inlet temperatures. The working fluid is $H_2O$/LiBr solution with the LiBr concentration of 50-60% in mass. The numerical simulation shows reasonably good agreement with the experimental results. Also, the numerical results show that plate of the chevron shape gives better results than plate of the elliptical shape from the view points of heat transfer and pressure drop. These results provide a guideline to apply the welded PHE for the solution heat exchanger of absorption systems.

• 한국전산유체공학회지
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• 제12권3호
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• pp.13-19
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• 2007

A numerical simulation on the heat transfer and flow field was carried out to improve the performance of the shell and tube heat exchanger. The steady incompressible 3-D Navier-Stokes solution is obtained with the actual operational condition and geometry of the heat exchanger. Based on this study, it is noted that the present geometry of the heat exchanger causes poor heat transfer since the air inside shell does not flow through the tube bundle, but around it. The enhancement of the heat transfer can be achieved by the variation of the design factor like the sealing strip located on the top/bottom and middle of the baffle, but it causes the increasement of the pressure drop. In this paper, the effects of the location and size of the sealing strips and flow rate through the heat exchanger on the heat transfer and pressure drop are studied.

• 한국유체기계학회 논문집
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• 제3권2호
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• pp.24-30
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• 2000

The structural analysis of a reactor coolant pump(RCP) of a nuclear power plant is very important for the safety assessment of the plant. Accurate boundary conditions for the heat transfer coefficient are required for reliable thermal stress analysis of the pump casing, especially in transient operations of the pump since the coolant properties are largely dependent on operational conditions. In the present study, a 3D mixed flow type coolant pump was modeled from the RCP drawings and analyzed in the steady state and number of transient flow conditions by using a commercial code STAR-CD. From the result of the computation, it is seen that the average heat transfer coefficients for the cases considered are found to be the suggested values of the manufacturer, Westinghouse Energy System. The unevenness in local heat transfer coefficients, however, is found to be considerable so that the use of average heat transfer coefficients in all boundaries might not give reliable thermal stress predictions.

• 대한기계학회논문집A
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• 제27권3호
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• pp.393-400
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• 2003

Excessive generation of BOG during the LNG transportation not only causes the severe financial loss but also leads to the unexpected disaster. Therefore, the carrier cargo insulating interior LNG should be carefully designed based upon an accurate heat transfer analysis. However. it is not simple to analyze heat transfer of LNG cargo, because it is in a complex insulation structure and LNG carrier experiences a complicated heat transfer according to various kinds of voyage conditions. In this paper, we carried out the transient finite element heat transfer analysis for a cargo of Mark-111 membrane-type LNG carrier during laden voyage, and we compared heat transfer rates between considering natural convection and considering conduction. For this goal, we developed a PCL program incorporating with a commercial MSC/NASTRAN FEM code.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.194-198
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• 2006

In this study, numerical modeling was performed to analyze air flow including radiation heat transfer inside a small chamber. Characteristics of heat transfer between source plate and target through glass are investigated for various surface temperature of heat source plate with buoyancy effect due to gravity force. Conduction heat transfer through the glass is considered and heat source plate is assumed to be a black body. Target surface temperature is largely affected by the radiation heat transfer. It can also be seen that as the source temperature increases target surface is dominated by radiation rather than convective heat transfer by air.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.97-98
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• 2012

The rotary kiln is one of the most widely used industrial reactors for contacting gases and solids. Kilns are mainly used for drying, calcining and reducing solid materials. In an indirected fired rotary kiln, heat is supplied to the outside of the kiln wall. Heat transfer in indirected fired rotary kilns encompasses all the modes of transport mechanisms, that is, conduction, convection and radiation. This paper deal with the heat transfer characteristics of indirect fired rotary kiln for scale up.

• 대한조선학회논문집
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• 제39권2호
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• pp.52-60
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• 2002

선상가열은 고온의 열원을 강판에 가하여 잔류변형을 얻음으로써 곡면을 성형하는 과정이다. 잔류 변형 제어를 위해서 열원과 강판 사이의 열전달 현상 및 강판의 온도 분포에 대한 이해가 필요하다. 본 연구는 가스 토오치로부터 분출된 연소 불꽃에 의한 가스가 강판을 가열하는 선상 가열 과정을 고온, 고속의 충돌 분출류와 그에 의한 열 대류 전달 현상으로 간략화 하여 강판의 온도 분포에 대한 해석을 시도하였다. 해석을 위하여 토오치에서의 연소 현상을 고온, 고속의 충돌 분출 현상으로 간략화 시키고 난류열 유동 해석을 수행하였다. 난류 열 유동 해석을 통하여 토오치와 강판 사이의 온도장 분포를 계산하였고 충돌 분출류에 관한 근사 누설트 실험식을 이용하여 분출류와 강판 사이의 열 대류 계수를 계산하였다. 온도 분포와 열 대류 계수를 통해서 강판에 유입되는 열 유속을 계산할 수 있었고 열 유속을 표면력으로 하는 열 전도 전달 해석을 통해 강판 내의 온도장 분포를 구할 수 있었다. 난류 열 유동 해석 및 전도 열 전달 해석을 위하여 유한 요소법을 이용하였으며, 유한 요소 해석결과를 실험 결과와 비교함으로써 본 연구에서 수행한 해석 과정의 타당성에 대한 검증을 수행하였다.

• 설비공학논문집
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• 제29권11호
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• pp.570-579
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• 2017

In this study, we examined the multi-stage piston-type air compressors typically used in a railroad vehicle, and the heat transfer efficiency was analyzed according to the design conditions of the heat exchanger (a compressor component module for cooling the compressed high temperature air). For the fin-tube heat exchanger used in the most air compressors, numerical analysis was performed to analyze heat transfer by defining the various rectangle tube sizes and the number of fin-per-unit area as design variables under the same flow rate of compressed air. Also, this analysis compared the temperature of the compressed air. Regarding environmental conditions for analysis, the flow rate of the external cooling air was measured and the mean value of the values was applied. And a "turbulence model" was considered in both the external flow of the cooling air and the internal flow inside the tube. From the results of analysis, it was found that the change of the aspect ratio value of the tube greatly influences the heat transfer efficiency of the compressed air, and influences if the fin density is relatively small. As a result, the optimum design specifications of the heat exchanger for air compressors were confirmed based on the analysis of the heat transfer efficiency, according to the design conditions of fin and tube by the operating temperature range of the compressed air.

• 한국태양에너지학회 논문집
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• 제22권1호
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• pp.9-21
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• 2002

To develope chemical heat pump using available energy sources, solar heat and other kinds of waste thermal energy, we have studied the heat transfer rate in cylindrical bed reactor packed with calcined Dolomite. Two dimensional (radial and circumferential) Partial differential equations, concerning heat and mass transfer in packed bed of calcined Dolomite, are solved numerically to describe the characteristics of the reaction of calcined Dolomite and heat transfer. The results obtained by numerical analysis about two dimensional profiles of temperature and conversion of reactant in the packed bed reactor and the amount of exothermic heat released from the reactor are follows. It was found that all of calcined Dolomite packed bed kept the reaction temperature of about 750K throughout the entire part of the bed, immediately after the steam was introduced exothermic reaction of hydration was proceeded from the packed bed inpu to output and from wall side to center. The rate of thermochemical reaction depends on the temperature and concentration and it is also governed by the boundary conditions and heat transfer rate in the particle packed bed.