• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.2
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• pp.76-82
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• 2005

In this paper, a method for analyzing the thermal recovery characteristics of the nozzle of gas circuit breaker was described. In order to obtain thermal recovery characteristics, the transient simulation of SF6 arc plasma within the nozzle was carried out. In particular, the nozzle ablation was taken into account by simultaneously solving the PTFE concentration equation with the governing equations such as continuity, momentum and energy equation. After that, post arc current calculation was performed with the rate of rise of recovery voltage changed. From the calculated post arc current, it was possible to suggest the thermal recovery characteristics of the nozzle of gas circuit breaker.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.449-453
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• 2000

In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. This paper models of the thermal errors for error analysis and develops on-the-machine measurement system by which the volumetric error are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses, a designed spherical ball artifact, and five gap sensors. In order to analyze the thermal characteristics under several operating conditions, experiments performed with the touch probe unit and five gap sensors on the vertical and horizontal machining centers.

• Journal of the Korean Solar Energy Society
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• v.28 no.1
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• pp.65-74
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• 2008

In this study, dynamic characteristics analysis of AC system is investigated using a cool thermal storage system. A analysing program for cool thermal storage AC system is developed. The performances are studied by several variables and dynamic characteristics. Comparing the result at conventional operation condition with that at the condition using ice storage system, this study showed the effects of the sub cooled degree, superheated degree, efficiency of compressor and evaporating temperature. At the condition using thermal storage system, the thermal storage process was operated during midnight being not needed the cooling of the AC unit through the continuous running of the condenser. The refrigerant was sub-cooled using stored energy after being discharged from the air source condenser during the daytime. The COP was increased owing to the sub-cooling of refrigerant during daytime, thus the power consumption was effectively decreased.

• Journal of the Korean Applied Science and Technology
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• v.28 no.1
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• pp.10-14
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• 2011

Emulsion polymerization was carried out using RMA like MMA, EMA, BMA and Styrene(St.) as monomer for core-shell latex preparation. It was synthesized at $80^{\circ}C$ in the presence of anionic surfactant SLS. FT-IR, TGA and DSC analysis are used to confirm synthesized core-shell emulsion latexes and to investigate the thermal characteristics of them. From analysis of TGA and DSC, the differences of the decomposition rate and the activation energy are not so large. It considers that the pendent group is not affect of the thermal characteristics and stability on core-shell latexes, which is synthesized with RMA and Styrene.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.145-148
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• 2003

Thermal characteristics according to the bearing preload arc studied for the four type spindles with high frequency motor. For the analysis. three dimensional models are built considering heat transfer characteristics such as natural and forced convection coefficients, Bearing and motor are main heat generation, and heat generation by ball bearings as a function of load. viscosity and gyroscopic moment effect are considered. Unsteady-state temperature distributions and thermal displacements according to the bearing preload are analyzed by using the finite clement method.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2094-2099
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• 2008

A numerical and experimental studies are carried out to investigate the transient heat transfer characteristics of 5kWth dish-type solar air receiver. Measured solar radiation and temperatures at several different locations are used as boundary conditions for numerical simulation. Many parameters' effects (reflectivity of the reflector, the thermal conductivity of the receiver body, transmissivity of the quartz window, etc.) on the thermal performance are investigated. Discrete Transfer Method is used to calculate the radiation heat exchange in the receiver. A transient heat transfer model is developed and the rate of radiation, convection and conduction heat transfer are calculated. Comparing the experimental and numerical results, good agreement is obtained. Using the numerical model, the transient heat transfer characteristics of volumetric air receiver for dish-type solar thermal systems are known and the transient thermal performance of the receiver can be estimated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.208-212
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• 2003

Silicon transient voltage suppressors (TVSs) are clamping devices that limit voltage spikes by low impedance avalanche breakdown of a rugged silicon PN junction. They are used to protect sensitive components from electrical overstress such as that caused by induces lightning, inductive load switching and electrostatic discharge. In this paper, we present static and dynamic characteristics of TVS diode using thermal analysis simulation software. And also, it is presented that the thermal dissipation characteristics of TVS diode in the transient state.

• Fashion & Textile Research Journal
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• v.20 no.6
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• pp.744-751
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• 2018

This study aimed to provide the information on the thermal sensation and the amount of clothing worn of junior high school students in winter classroom the relation with their climate adaptability. Total usable questionnaires were obtained from 467 male and female students. The questionnaire included general characteristics, physical characteristics, self awareness of body shape, climate adaptability and subjective thermal sensation in winter classroom. The data were analyzed using SPSS Statistics 18.0 for frequency analysis, factor analysis, chi-square analysis, t-test and correlation analysis. The results were as follows. The average body type based on BMI was normal($20.1kg/m^2$ ). Females perceived their body type as thinner than males. They wore more (8.67 garment items compared to 8.14 for males). Only about 25% of students voted the thermal sensation to neutral(47% cool~very cold, 28% warm~very hot). Females were more sensitive to the cold, perceived less healthy, and wore more garments in the cold. Students felt colder in winter classroom when their cold adaptability was lower and they actively adjusted thermal insulation against the cold. It is recommended to suggest the guidelines for the proper indoor temperature and for the wear behavior in classroom in the perspectives of increasing the learning efficiency and improving the students' climate adaptability.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.20-26
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• 2016

For power electronic devices, the thermal energy density per unit volume has seen a rapid increase in recent years, owing to the miniaturization and dense integration of electronic components, as well as the continuous development in performance and function. This research examined the validity and reliability of a thermal safety model for managing the heating conditions of TRIAC electronic components. Among the electronic components of a PCB, these can be considered as a heat source. Using the model, the heating conditions of TRIAC components were maintained at their design target levels in the process of developing an LMT motor drive board. In addition, the heating characteristics of the entire PCB were analyzed to verify its thermal safety. Finally, the reliability and validity of the thermal safety model for maintaining the heating conditions of the TRIAC electronic elements at adequate levels was verified using a numerical analysis method.

• Safety and Health at Work
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• v.11 no.4
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• pp.405-417
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• 2020

Background: Electrical socket outlets are used continuously until a failure occurs because they have no indication of manufacturing date or exchange specifications. For this reason, 659 electrical fires related to electrical socket outlets broke out in the Republic of Korea at 2018 only, an increase year on year. To reduce electrical fires from electrical socket outlets, it is necessary to perform an accelerated test and analyze the thermal, insulation resistance, and material properties of electrical socket outlets by installation years. Methods: Thermal characteristics were investigated by measured the temperature increase of electrical socket outlets classified according to year with variation of the current level. Insulation resistance characteristics was measured according to temperature for an electrical socket outlets by their years of use. Finally, to investigate the thermal and insulation resistance characteristics in relation to outlet aging, this study analyzed electrical socket outlets' conductor surface and content, insulator weight, and thermal deformation temperature. Results: Analysis showed, regarding the thermal characteristics, that electrical socket outlet temperature rose when the current value increased. Moreover, the longer the time that had elapsed since an accelerated test and installation, the higher the electrical socket outlet temperature was. With respect to the insulation resistance properties, the accelerated test (30 years) showed that insulation resistance decreased from 110 ℃. In relation to the installation year (30 years), insulation resistance decreased from 70 ℃, which is as much as 40 ℃ lower than the result found by the accelerated test. Regarding the material properties, the longer the elapsed time since installation, the rougher the surface of conductor contact point was, and cracks increased. Conclusion: The 30-year-old electrical socket outlet exceeded the allowable temperature which is 65 ℃ of the electrical contacts at 10 A, and the insulation resistance began to decrease at 70 ℃. It is necessary to manage electrical socket outlets that have been installed for a long time.