• 한국세라믹학회지
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• 제37권4호
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• pp.332-337
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• 2000

Forming mechanism of fibrous TiC during self-propagating high temperature synthetic reaction was analyzed and suggested. It was revealed that critical temperature for the stable fiber formation was not the melting point of TiC, but the eutectic reaction temperature of TiC and C. Minimum amount of TiC diluent addition required to form fibers was calculated to be 25.6%, which was consistent with the experimental result. Synthesized fibers were found hollow tube-like. The morphology was explained by the diffusion rates of C and Ti in TiC, and by the molar volume chnage of C during the reaction. Expanding shell model was suggested for the hollow fiber formation mechanism.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.19-24
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• 2003

Potential applications of foam-filled section are the automotive structures. A foam-filled section can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision. In the case of side collision where bending is involved in the crushing mechanics, the foam filler will be significant in maintaining progressive crushing of the thin-walled structures so that more impact energy can be absorbed. In this study, the manufacturing process of closed cell aluminum alloy foam filled stainless steel tube was studied, and the various foam filled specimens including piecewise fillers were prepared, tested and discussed about the bending behaviors.

• Journal of Advanced Marine Engineering and Technology
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• 제24권5호
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• pp.119-124
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• 2000

A finite element method is applied to investigate the characteristics of the fluid flow and heat transfer performance in a channel in terms of the various effects of baffle cuts, baffle angles, and leakages. The results show that the decrease of a baffle cut gives a good heat transfer enhancement. However, it also increases pressure drop. In the case of an inclined baffle, the result shows that the pressure drop decreases with a reasonable heat transfer performance. But a steeply inclined baffle gives adverse effects on the performance of the channel. The clearances between baffle-to-shell and tube-to-baffle affect the overall performance. The effects of these parameters are discussed in details.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.65-72
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• 2006

Heat transfer augmentation in heat exchangers has received much attention in recent years, mainly due to energy efficiency and environmental considerations. Many active and Passive techniques are currently being employed in heat exchangers, with some inserts providing a cost-effective and efficient means of augmenting heat transfer. The Purpose of this paper is to determine the pressure loss and heat transfer characteristics of a heat exchanger using static mixing technology. Experimental measurements were taken on two set-ups: a single tube heat exchanger and a shell-tube heat exchanger with two static mixing inserts. It was concluded that the static mixing inserts resulted in an increase in the pressure loss and heat transfer characteristics as can be expected.

• 한국가스학회:학술대회논문집
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• 한국가스학회 2007년도 춘계학술발표회 논문집
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• pp.27-32
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• 2007

Dimethyl Ether (DME, $CH_3OCH_3$) is the simplest ether and is considered as one of the leading candidates in the quest for a substitute fur petroleum-based fuels. In this work, we analyzed the one-step synthesis of DME in a shell and tube type fixed bed reactor and carried out a simulation with a one-dimensional, steady state model of a heterogeneous catalyst bed, while taking into consideration the heat and mass transfer between the catalyst pellets and reactants gas and the effectiveness factor of the catalysts, together with the reactor cooling through the reactor tube wall. The reactor simulation was carried out under steady state condition and we compared the simulation results with the experimental data obtained from operations of a pilot-scale reactor and found good agreement between them.

• 한국소음진동공학회논문집
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• 제13권5호
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• pp.400-408
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• 2003

This paper investigates the vibration characteristics of steam generator (SG) U-tubes with defect. The operating SG shell-side flow field conditions for determining the fluidelastic instability parameters such as added mass are obtained from three-dimensional SG flow calculation. Modal analyses are performed for the U-tubes either with axial or circumferential flaw with different sizes. Special emphases are on the effects of flaw orientation and size on the modal and instability characteristics of tubes, which are expressed in terms of the natural frequency, corresponding mode shape and stability ratio. Also, addressed is the effect of the internal pressure on the vibration characteristics of the tube.

• 대한기계학회논문집
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• 제17권10호
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• pp.2574-2581
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• 1993

A Shadow mask in C. R. T. (Cathod Ray Tube) undergoes a temperature increase due to impinging electron beams emitted from guns, and thermal deformation from such temperature rise may cause the electron beams to island on the panel, and thus give rise to depolarization. Hence the analysis of temperature distribution for a shadow mask is an important procedure for designing the shadow mask. In this paper, we are concerned with nonlinear finite element analysis of the temperature distribution on a shadow mask. First of all, we replace shadow mask, containing numerous apertures of a slit type, by an orthotropic shell without apertures, and calculate the apparent thermal conductivities. Because of thermal radiation, which is one of the major heat transfer mechanism for shadow masks, the resulting finite element equation is nonlinear and solved by the Newton method. Finally numerical examples are illustrated for a 21" FST(Full Square Tube) shadow mask, and followed by discussion.sion.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.418-421
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• 2006

Appropriate analysis models for concrete-filled steel tube (CFT) subjected to bending moment were determined to assess flexural behavior of CFT member. Applying this model, finite element analyses was performed and compared against experimental data considering the compressive strength of in-filling material and the composite action between tube shell and in-filling core. Analysis results showed that the FE model proposed in this study is feasible for the analytical investigation of the flexural behavior of CFT member according to loading conditions, effect of compressive strength of various core materials and other design parameters.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.681-691
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• 2006

Nucleate boiling heat transfer for refrigerants, R113, and R113+wt4% ethanol mixture, an azeotropic mixture under electric field was investigated experimentally in a single-tube shell/ tube heat exchanger. A special electrode configuration which provides a more uniform electric field that produces more higher voltage limit against the dielectric breakdown was used in this study. Experimental study has revealed that the electrical charge relaxation time is an important parameter for the boiling heat transfer enhancement under electric field. Up to 1210% enhancement of boiling heat transfer was obtained for R113+wt4% ethanol mixture which has the electrical charge relaxation time of 0.0053 sec whereas only 280% enhancement obtained for R113 which has relaxation time of 0.97 sec. With artificially machined boiling surface, more enhancement in the heat transfer coefficient in the azeotropic mixture was obtained.

• 대한설비공학회지:설비저널
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• 제28권5호
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• pp.389-395
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• 1999

냉동공조설비, 발전설비, 화학플랜트설비 등에 사용되는 응축기는 주로 증기가 관의 외부에서 응축을 하고 냉각수가 관 내부로 흐르는 쉘-튜브(shell and tube)형 태를 취하고 있다. 초기투자비용 및 운전비용을 줄이기 위해서는 응축기의 열교환 성능을 향상시키는 일이 필수적이며 이를 위해 코팅 표면(coated surfaces), 거친 표면(rough surfaces), 코일 튜브(coiled tubes), 선회 흐름장치(swirl flow), 전열면적을 넓힌 낮은 핀관과 3차원 형상을 갖는 열전달 촉진관의 사용이 제시되고 있다.