• Journal of Advanced Marine Engineering and Technology
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• v.28 no.4
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• pp.648-656
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• 2004

In this study, a highly efficient shell-and-tube heat exchanger with plate fins is considered to improve thermal performance of the conventional shell-and-tube heat exchanger. This type of shell-and-tube heat exchanger with plate fins of various shape is simulated three-dimensionally using a commercial thermal-fluid analysis code. CFX4.4. The effect of the shape of the plate fin on heat transfer characteristics is also investigated by the simulation. Plate fins of four different shapes. plane, plane-slit. wave. and wave-slit fins, are considered. The flow fields, pressure drop and heat transfer characteristics in the heat exchanger are calculated. It is proved that the shell-and-tube heat exchanger with plate fins is superior to the conventional shell-and-tube heat exchanger without plate fins in terms of heat transfer. The shape of the plate fin is important in the performance of a heat exchanger such as heat transfer and pressure drop.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.7
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• pp.531-542
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• 2002

Transcritical$CO_2$ systems are under consideration for use as residential/mobile air conditioners. In these systems, an internal heat exchanger is usually adopted to improve both capacity and/or COP of the $CO_2$ system in lower operating pressure range of gas cooler. A program has been developed to analyse the performance of internal heat exchangers using the section-by-section method. The internal heat exchanger of coaxial configuration is first analyzed and fairly good agreements with the data are obtained, And then the internal heat exchanger of multiple circular coil configuration has been investigated. The results obtained from the parametric study provide the guidelines for the initial design and manufacturing concepts of the internal heat exchanger in transcritical $CO_2$ system. Further studies are necessary to develop the heat transfer correlations of carbon dioxide in the tubes to obtain more accurate results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.281-284
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• 2008

Film insert melding is one of the surface processes that enhances functional or aesthetic qualities of an existing product's surface. In general, film insert molding consists of three processes including thermoforming, trimming and injection molding. Thermoforming, which is the first process of film insert molding, is the most important process because the variation of film thickness has an effect on the mold design and process conditions for the subsequent processes, that are, trimming and injection molding. This study is focused on predicting the film thickness distribution through film insert thermoforming process using commercial FEM code. In order to describe rheological behavior of thermoplastic film (ABS), G'Sell's viscoelastic constitutive law was adopted. The numerical model of film insert thermoforming was established, and the simulation to predict film thickness distribution was performed. Comparison between the results of simulation and experiment was made to validate the proposed finite element analysis.

• Design & Manufacturing
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• v.17 no.4
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• pp.52-56
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• 2023

In this study, numerical simulation of the thermoforming process of PVC film material was performed using PAMForm. For this purpose, tensile tests were performed at various temperatures and the coefficients of the G'Sell model were obtained and used. As a result of the analysis, it was confirmed that the thickness decreased by up to 55% in the section where the film was in contact with the vertical direction and was greatly stretched. If the thickness is excessively thin, the part may become structurally weak, so in the thermoforming process, numerical simulation of the thickness in advance is expected to be helpful in successfully performing the process.

• Journal of the Korean Solar Energy Society
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• v.24 no.4
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• pp.19-25
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• 2004

A numerical study is performed to investigate the effect of sun tracking on the thermal performance of the evacuated compound parabolic concentrator (CPC) collectors. The evacuated CPC collectors consist of a two-layered glass tube, a copper tube and a reflector. The collector has a copper tube as an absorber and a reflector inside a glass tube. The water is used as a working fluid. The length and the diameter of the glass tube are 1,700mm and 70mm, respectively. The length and the diameter of the copper tube are 1,700mm and 25.4mm, respectively. Ray tracing analysis is carried out in order to compare absorbed heat fluxes on the absorber surface of the stationary and tracking collectors. The collected energy is calculated and compared with that on a fixed surface tilted at $35^{\circ}$ on the ground and facing south. The results indicate that the collected solar energy of the sun tracking system is significantly larger than that of a stationary collector. The sun tracking evacuated CPC collectors show a better performance with an increase in the thermal efficiency of up to 14% compared with an identical stationary collector.

• KOREAN POULTRY JOURNAL
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• v.43 no.10
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• pp.98-100
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• 2011

국내 동물약품회사 대표주자로 성장해온 (주)고려비엔피가 뉴캣슬병(이하 ND) 생독백신 시장에 도전장을 던졌다. 제1종 법정 전염병인 ND는 급성 열성 호흡기 질병으로 국내를 비롯한 아시아 전역에 확산되면서 발병을 막기 위해 생독백신을 사용해왔다. 지금까지 대부분 수입 생독백신이 사용되어 왔지만, 국내기업에서 '달구방 N+ 생백신' 제품이 출시되면서 동물약품 업계가 주목하고 있다. 특히 '달구방 N+생백신'은 최근 유행하고 있는 7형 유전형에 방어력이 뛰어난 제품으로 항원 상동성이 매우 높고 안전성이 뛰어난 차세대 ND 생백신이라는 점에서 인정받고 있다. 지난달 '달구방 N+ 생백신' 출시와 관련 기자간담회를 통해 송기연 대표이사를 만나 인터뷰한 내용을 정리하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2393-2400
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• 2013

This research presents an experimental study of heat exchange rate of U, W, 2U and coil type ground heat exchangers (GHEs) measured by thermal performance tests (TPTs). The four types of GHEs were installed in a partially saturated dredged soil deposit of Incheon International Airport area. Thermal response tests (TRTs) were conducted for U, W and 2U type GHEs to deduce the ground thermal conductivity. Besides, TPTs were also conducted for U, W, 2U and coil type GHEs to evaluate heat exchanger rates under 100-hr continuous and 8-hr intermittent operation conditions for five days. Coil shaped GHE showed about twice higher thermal performance than the others GHEs. Furthermore, intermittent operation condition showed 30~40% higher heat exchange rates than continuous operation condition.

• Composites Research
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• v.16 no.2
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• pp.33-40
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• 2003

In order to overcome one of the most pronounced shortcomings of conventional laminated composites, such as the low damage tolerance due to delamination, the thermoplastic materials and 3D (three-dimensional) preforms have been utilized in the manufacture of composite materials. From the newly developed process termed as the co-braiding, hybrid yarns of the thermoplastic fibers (PEEK) and reinforcing fibers (carbon) have been fabricated. In order to further enhance the delamination suppression, through thickness fibers have been introduced by way of 3D weaving technique in the fabrication of textile preforms. The preforms have been thermoformed to make composite materials. Complete impregnation of the PEEK into the carbon fiber bundles has been confirmed. For the comparison of mechanical performance of 3D woven composites, quasi-isotropic laminates using APC-2/AS4 tapes have been fabricated. Tensile and compressive properties of both the composites have been determined. Furthermore. the open hole, impact and CAI(Compression After Impact) tests were also carried out to assess the applicability of 3D woven textile reinforced thermoplastic composites in aerospace structures.

• The Korean Journal of Rheology
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• v.11 no.1
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• pp.18-27
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• 1999

Predicting the deformation behaviors of sheets in thermoforming processes has been a daunting challenge due to the strong nonlinearities arising from very large deformations, mold-polymer contact condition and hyperelasticity constitutive equations. Nonlinear numerical analysis is always required to face this challenge especially for realistic processing conditions. In this study a 3-D algorithm and the membrane approximation are developed for thermoforming processes. The constitutive equation is expressed in terms of the 2nd Piola-Kirchhoff stress tensor and the Cauchy-Green deformation tensor. The 2-term Mooney-Rivlin model is used for the material model equation. The algorithm is established by the finite element formulation employing the total Lagrangian coordinate. The deformation behavior and the stress distribution results of 3-D algorithm with various point boundary conditions are compared to those of the membrane approximation algorithm. Also, the slip boundary condition and the no-slip boundary condition are applied for the systems that have molds. Finally, the effect of sheet temperatures on the final thickness distribution is investigated for the ABS material.

• Composites Research
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• v.31 no.4
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• pp.139-144
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• 2018

Long Fiber-reinforced composites have advantages of excellent production efficiency and formability of complex shapes compared to conventional continuous fiber reinforced composite materials. However, if we need to make complicated composite shapes or to assemble parts made of different materials, a variety of joining methods are needed. In general, long fiber prepreg sheet (LFPS) contains mold release agent to facilitate demolding after thermoforming. Therefore, mechanical fastening is required in addition to the adhesive bonding to get proper joining strength. In this study, we proposed a stainless steel insert for co-cure bonding which cures LFPS and bonds the stainless steel insert through thermoforming process. The wing of the insert which is spread during the thermoforming process induces adhesion and mechanical wedging effect and serves as a hook to resist the pulling force. The burn-out method was used to confirm the unfolded state of the stainless steel insert wings inserted into the composite material. The static pull-out test was performed to quantitatively evaluate the joining strength. From these experimental results, the condition which guarantees the most appropriate joining strength was derived.