• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.2
• /
• pp.153-161
• /
• 2009

Three-dimensional finite-element methods(FEM) have been used to analyze the thermal stress of an exhaust gas recirculation(EGR) cooler due to thermal and pressure load. Since efficiency and capability of the heat exchanger are mainly dependent on net heat transferring area of the EGR cooler system, the tube inside the system has a numerous dimples on the surface. Thus for finite element analysis, firstly the dimple-typed tube is modeled as a plain element without the dimple, and then the equivalent thermal conductivities and elastic modulus are calculated. This work describes the numerical homogenization procedure of the dimple-typed tube and verifies the equivalent material properties by comparison of a single unit and the actual full model. Finally, the homogenization scheme presented in this study can be efficiently applied to finite element analyses for the thermal stress and deformation behavior of the EGR cooler system with the dimple-typed tube.

• International Journal of Precision Engineering and Manufacturing
• /
• v.8 no.4
• /
• pp.56-62
• /
• 2007

An analytical method to predict the post-weld deformation at the heat-affected zone (HAZ) is presented in this paper. The method was based on the assumption that the post-weld deformation is caused by external forces resulting from the inherent strain, which is defined as the irrecoverable strain after removing structural restraints and loadings. In general, the equivalent loading method can be used to analyze distortions in welding areas because it is efficient and effective. However, if additional loads are applied after welding, it is difficult to determine the final strain on a welded structure. To determine the final strain of a welded structure at the HAZ more accurately, we developed a modified equivalent loading method based on the inherent strain that incorporated hardening effects. The proposed method was applied to calculate the residual stress at the HAZ. Experiments were also conducted on welded plates to evaluate the validity of the proposed method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.2
• /
• pp.117-124
• /
• 2005

Aluminum plate heat exchanger, rotary wheel heat exchanger, and heat pipe heat exchanger have been used (or ventilation heat recovery in the air-conditioning system. The purpose of this research is to develop high efficiency plastic plate heat exchanger which can substitute aluminum plate heat exchanger. Because thermal conductivity of plastic is quite small compared to that of aluminum, various heat transfer enhancement techniques are applied in the design of plastic plates. Five types of heat exchanger model are designed and manufactured, which are plate type, plate-fin type, turbulent promoter type, corrugate type, and dimple type. Thermal performance and pressure loss of each heat exchangers are measured in various operating conditions, and compared each other. Test results show that heat transfer performance of corrugate type, turbulent promoter type, and dimple type are increases about $43\%$, $14\%$, and $33\%$ at the equivalent fan power compared to those of plate type, respectively. On the other hand, the heat transfer performance of plate-fin type decreases $9\%$ because fins can not play their own role.

• The Korean Journal of Food And Nutrition
• /
• v.13 no.1
• /
• pp.1-5
• /
• 2000

Detection for heat-labile enterotoxin(LT) of enterotoxigenic Escherichia coli(ETEC, EC81, O148:H28) and enterotoxin of enterotoxigentic Clostridium perfringents type A(CP, NCTC8238, Hobbs serotype 2) by use of a polymerase chain reaction (PCR) assay were positive reaction, which using LT gene-specific primers of ETEC with a detection limit equivalent from 100ng/${\mu}\ell$ to 1 pg of a DNA fragment of 417-bp in EC81 and enterotoxin gene-specific primers of CP with a detection limit equivalent from 100ng/${\mu}\ell$ to 10pg of a DNA fragment of 364-bp in NCTC8238. Detection for a LT gene of ETEC highly appeared 10-fold sensitivity than an enterotoxin gene of CP.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.35S no.1
• /
• pp.122-129
• /
• 1998

For generation and analysis of the multi-sensory image, we propose a new three dimensional (3D) modeling method considering an iternal heat source. We represent the heat conduction process within th object as an equivalent thermal circuit. Therefore, without a complex computation, our modeling approach can obtain thermal features of the object. By using the faceted model, the proposed method can express the accurate visual signatures of the object. Comparing the estimates datum with the obtained surface temperatures, we have demonstrated that the proposed method can provide a precise thermal features. The thermal images by out model is applicable to simulate a tracking loop of an IR missile.

• Special Issue of the Society of Naval Architects of Korea
• /
• 2011.09a
• /
• pp.106-111
• /
• 2011

The use of thin plate increases due to the need for light weight in large ship. Thin plate is easily distorted and has residual stress by welding heat. Therefore, the thin plates should be carefully joined to minimize the welding deformation. In this study, the welding deformation of PCTC which use a thin plate is investigated by using equivalent load method. The analysis model of 10, 11, 12, upper and garage deck is composed of thin plate of 6mm which is susceptible to welding heat. For two different welding sequences, the welding deformation is calculated and its trend is investigated. The influence of gravity on welding deformation is studied.

• Journal of the Korean Society for Railway
• /
• v.16 no.2
• /
• pp.99-103
• /
• 2013

In this paper, research on the thermal analysis method is reported for the characterization of heat generation while operating an Interior Permanent Magnet Synchronous Motor (IPMSM) for railway vehicles. Efficient cooling of the heat generated in the IPMSM is important because the excessive heat generated from the winding, core and permanent magnets increases the difficulty of continuously operating an IPMSM over long time periods. Therefore, in this study, in order to analyze the heat generation characteristics of the IPMSM for advanced research in the application of IPMSMs to cooling devices, the heat transfer coefficients for each component of the IPMSM were derived and the thermal equivalent circuit was configured to perform thermal analyses. Finally, the validation of the suggested thermal analysis method was performed through comparison with the heat experimental data of an IPMSM prototype.

• Geomechanics and Engineering
• /
• v.6 no.1
• /
• pp.79-98
• /
• 2014

This paper presents an experimental and numerical study on the evaluation of a thermal response test using a precast high-strength concrete (PHC) energy pile and a closed vertical system with W-type ground heat exchangers (GHEs). Field thermal response tests (TRTs) were conducted on a PHC energy pile and on a general vertical GHE installed in a multiple layered soil ground. The equivalent ground thermal conductivity was determined by using the results from TRTs. A simple analytical solution is suggested in this research to derive an equivalent ground thermal conductivity of the multilayered soils for vertically buried GHEs. The PHC energy pile and general vertical system were numerically modeled using a three dimensional finite element method to compare the results with TRTs'. Borehole thermal resistance values were also obtained from the numerical results, and they were compared with various analytical solutions. Additionally, the effect of ground thermal conductivity on the borehole thermal resistance was analyzed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.4
• /
• pp.570-578
• /
• 1997

At design stage of new motor or when taking remedial action of old motor, a lot of information can be obtained from thermal parameters analysis. This study focused on the temperature rise of TEFC induction motor with respect to various thermal parameters. Frame heat transfer had the most important effect on coil temperature rise. But those of air gap and rotor fan had no effect. This fact shows fan action is more important than fin action in the case of rotor fan. Coil temperature can be more decreased by cooling near the heat sources than any other parts from the results of thermal conductivity and loss tests. Variation of cooling air flow rate and motor volume effects on coil temperature were also tested. These tests suggest that improvement of cooling fan performance is important in reducing the coil temperature rise. Thermal equivalent program was verified by comparison of some experimental results.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.9 no.5
• /
• pp.568-576
• /
• 2017

With an increase in the usage of LNG, there is a heightened interest about its safety aspects regarding the explosion of LNG carrier tank. The need for a cryogenic explosion-proof camera has increased. The camera has to work in cryogenic environment (below $-160^{\circ}C$) in LNG carrier. This study conducted design and heat transfer analysis of cryogenic camera to secure working time in limitation of heat source. The design with gap width of double pane windows was conducted based on simple vertical cavity model to insulate from cryogenic environment. The optimal gap width was 12.5 mm. For effective analysis considering convection within the camera, equivalent thermal conductivity method was adopted with ABAQUS. The working time of the camera predicted was over 10 h at warm-start condition. In cold-start condition, it required about 5 h of pre-warming time to work. The results of analysis were compared with the ones of the actual cryogenic test.