• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.817-822
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• 2017

The braking system is one of the most important components in vehicles and machines. It must exert a reliable braking force when they are brought to a halt. Generally, frictional heat is generated by converting kinetic energy into heat energy through friction. As the kinetic energy is converted into heat energy, high temperature heat is generated which affects the mechanical behavior of the braking system. Frictional heat affects the thermal expansion and friction coefficient of the brake system. If the temperature is not controlled, the brake performance will be decreased. Therefore, it is important to predict and control the heat generation of the brake. Various numerical analysis studies have been carried out to predict the frictional heat, but they assumed the existence of boundary conditions in the numerical analysis to simulate the frictional heat, because the simulation of frictional heat is difficult and time consuming. The results were based on the assumption that the frictional heat is different from the actual temperature distribution in a rotating brake system. Therefore, the reliability of the cooling effect or thermal stress using the results of these studies is insufficient. In order to overcome these limitations and establish a simulation procedure to predict the frictional heat, this study directly simulates the frictional heat generation by using a thermal-structure coupling element. In this study, we analyzed the thermo-mechanical behavior of a brake model, in order to investigate the thermal characteristics of brake systems by using the Finite Element method (FEM). This study suggests the necessity to directly simulate the frictional heating and it is hoped that it can provide the necessary information for simulations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.624-628
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• 1996

Unsteady-state temperature distributions in the high precision spindle system with built-in motor are studied. For the analysis, three dimensional model is built for the high precision spindle. The three dimensional model includes the estimation on the amount of heat generation of bearing and built-in motor and the thermal characteristic values such as heat transfer coefficient. Temperature distributions are computed using the finite element method. Analysis results are compared with the measured data. Analysis shows that temperature distributions of high precision spindle system can be estimated resonably using the three dimensional model through the finite element method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.44-51
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• 1997

Unsteady-state temperature distributions and thermal deformations of the spindle of a high precision lathe are studied in this paper. Three dimensional model is built for analysis, and the amount of heat generation of bearing and the thermal characteristic values including heat transfer coefficient are estimated. Temperature distributions and thermal deformations of a model are analyzed using the finite element method and the thermal boundary values. Numerical results are compared with the measured data. The results show that the thermal deformations and the temperature distributions of the dpindle of a high precision lathe can be reasonably estimated using the three dimensional model and the finite element method.

• Journal of Energy Engineering
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• v.17 no.2
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• pp.47-53
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• 2008

The objective of this paper is to clarify the flow characteristic, velocity distribution, pressure loss, and other such fundamental data for the canister during loading and purging. The amount of gas that is loaded increases as the loading rate is decreased and the time increased, and the purging improves as the purge rate is increased. The hydrocarbons that are purged initially have a high concentration, and a large amount is purged. During loading and purging, the temperature initially increases and decreases drastically due to heat generation and heat loss.

• Journal of the Korean Applied Science and Technology
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• v.23 no.2
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• pp.147-152
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• 2006

The accidents occurred by unstable material which is easily exploded or burnt up were caused by heat and collision under the condition of relatively low temperature without oxygen, have been reported frequently. However, the amount of the unstable material is getting higher by development of fine ceramic research area even though its dangerous characteristic is disregarded. This research studied a heat stability and measured boiling point of various carpet material. Carpet has been used in home as well as general indoor usage. Now a day, carpet material which is hardly burnt has been on commercial, but its detailed unstable conditions is not mentioned. This research reports the measurement of the initial temperature of generation heat and heat-radiation change on differential scanning calorimeter (DSC). The DSC data of nylon bulked continuous filament (N-BCF) yam 100%, nylon (NY), poly propylene (PP), and a new material named polytrimethylene terephthalate (PTT) are studied and researched about the effect of them using TGA, furnace, and direct-burning experiment.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.31.2-31.2
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• 2009

In this research, single walled carbon nano-tube film was manufactured with spray coating method on glass for application as transparent heat element. SWNTs solution to be used for spraying is obtained by dispersion of 0.01 wt% purified SWNTs in dimethylformamide (DMF) solution through ultrasonification and centrifugation. The transmittance and sheet resistance of SWNTs film were determined by the number of spray injection. Manufactured SWNTs film will have sheet resistance range of $200\;\Omega/\square-900\;\Omega/\square$ at transmittance range of 70-90 %. Heat generation characteristic of SWNTs film was measured by applying constant DC voltage of 15V. The result confirmed that SWNTs film with sheet resistance of $200\;\Omega/\square$ reaches surface temperature of $80^{\circ}C$ within several seconds. In addition, PET coating film was coated on top of the SWNTs film by using laminator in order to solve weak adhesive property of the spray coated SWNTs film on the substrate as well as to maintain its electrical and optical properties.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.5
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• pp.12-23
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• 1994

The two-phase flow is observed in power plants, chemical process plants, and refrigeration systems etc., and it is very important to solve the heat transfer mechanism of a boiler, an automic reactor, a condenser and various types of evaporators. Recently, the problem of two phase heat transfer is braught up in many regions with development of energy saving technique. In flow boiling system it is necessary to store data in each condition because the heat transfer characteristics of flow boiling region vary by the change of flow pattern and the magnetude of heat flux to tube length, and be subtly affected by the flow and heating condition. So basic study for knowing flow pattern in heat transfer region and the relation between heat transfer characteristic and flow condition is desired to accumulate data in wide variety of liquid and flow system in the study of heat transfer of two phase flow. In this study R-113 was selected as working fluid whose properties were programmed by least square method, and experiment was conducted in the region of mass flow $1.628{\times}10^6$~$4.884{\times}10^6$/kg/$m^2$hr with inlet subcooling 10~3$0^{\circ}C$, sustaining test section inlet pressure to 1.5kg$_f$/$cm^2$abs.

• Journal of Ocean Engineering and Technology
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• v.36 no.4
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• pp.211-216
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• 2022

Since liquefied natural gas (LNG) is imported in a liquid state of about -162℃ to increase transportation efficiency in Korea, it must be vaporized in a gaseous state to supply it to consumers. Among them, ambient air vaporizer (AAV) has caught attention due to eco-friendly and low costs characteristics. However, there is a disadvantage that the performance of the heat exchanger is deteriorated due to frost due to mist and icing when used for a long time. In this paper, frost generation model in AAV vaporizer was investigated with numerically to examine utilizing the vaporizer performance with the frost generation behavior. The frost generation behavior of AAV vaporizers was examined with humidity, fin characteristic, and temperature effects. As for the LNG discharge temperature, the 12 fin vaporizer showed the highest discharge temperature when the atmospheric temperature was 25℃, and the 8 fin vaporizer had the lowest LNG discharge temperature when the atmospheric temperature was 0℃. In the case of frost formation, in the case of the 12 fin vaporizer, it was formed the most at the atmospheric temperature of 25℃, and the least was formed in the vaporizer at the 0℃ condition of the atmospheric temperature of 8 fins.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.195-197
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• 2005

An intermediate heat exchanger(IHX) is a key component in a next-generation VHTR with process heat applications such as hydrogen production and also for an indirect gas turbine system. Therefore, high temperature brazing with nickel-based filler metal(MBF-15) was carried out to study the joining characteristic(microstucture, joining strength) of nickel-based superalloy(Haynes 230) by vacuum brazing. The experimental brazing was carried out at the brazing process, an applied pressure of about 0.74Mpa and the three kinds of brazing temperatures were 1100, 1150, and $1190^{\circ}C$ with holding time 5 minute. It's joining phenomena were analyzed by optical microscopy and scanning electron microscopy with EPMA. The results of microstructure in the centre-line region of a joint brazed with MBF-15 show a typical ternary eutectic of v-nickel, nickel boride and chromium boride.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.4
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• pp.68-76
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• 2004

Inherent strain method for analyzing deformation of line-heating is substituting experiments of high cost, because of its high accuracy and quickness. Nowadays, the progressing forms of line-heating are not straight moving motions used to traditional studies, but weaving motions which can diversely input heat source. In shipyard, reasons of weaving motions are induction of a special characteristic by water cooling, maximum temperature limitation for keeping plates from melting, and rhythm for workman's maintaining velocity. On this study, a method which can obtain optimal weaving heating condition was presented, some examples were introduced, and the results corresponded to works of shipyard. Lastly, what the specifications of plates on efficiency are is presented, through the quality standard of shipyard and FEM heat transfer simulation. The ultimate purpose of line heating is the automation, so in case of plates which need weaving heating, the optimal heating condition suggested by this study can be used well in designing coil specifications of induction heaters which are heat input sources of new generation.