• Proceedings of the KSME Conference
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• 2001.11b
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• pp.837-841
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• 2001

Almost all power plant boiler has temperature distribution nonuniformity problem in heat transfer tube flow path. It can cause hot spot damage of superheated or reheated heat transfer section and reduce maintenance schedule when nonuniformity is severe. There are two solutions for improvement temperature nonuniformity. one is change of gas flow distribution of gas path and the other is contorl steam flow in tube bank. Of course, first method is very difficulty to apply but second method is'nt. In this paper, control steam flow is used to solve temperature nonuniformity of power plant boiler.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.721-727
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• 2010

The spontaneous ignition of coal stockpile causes serious safety and economic problems. Such spontaneous ignition occurs in coal stockpile when the rate of heat released by the oxidation of coal is greater than the rate of heat lost to the surroundings. In this study, a two-dimensional unsteady model is adopted for studying spontaneous ignition and the numerical results are compared with experimental results. The numerical results are in a good agreement with the experimental ones. Depending on the porosity, the internal maximum temperature, pressure, and oxygen mass fraction during spontaneous ignition are investigated. On the basis of the numerical results, the transient temperature variations for several shapes of coal stockpiles are analyzed. Further, the physical mechanisms of hot-spot formation and spontaneous ignition are analyzed.

• Food Science and Preservation
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• v.23 no.3
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• pp.422-431
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• 2016

To investigate the causes of the thermal deformations of packaging materials when microwave-heating ready-to-eat sauce products packaged in stand-up pouches, patterns of temperature changes were determined using an infra-red thermal imaging camera, a thermo-sensitive tape, and a fiver-optic thermometer. The temperature distributions of spicy chicken sauce and Indian curry samples in a stand-up pouch were found to be uneven during micrewave heating. A sharp increase in the temperature was detected, especially above the filling layers and in the corners of sealing layers of the package. The temperature measurements using an infra-red thermal imaging camera are restricted to the surface, and therefore might underestimate the actual temperature. Using a thermo-sensitive tape, temperature up to $200^{\circ}C$ were measured in the spicy chicken sauce sample showing package deformation. When the temperature is measured using a fiber-optic thermometer, it is crucial to have precise sensor performance to accurately measure the temperature in a narrow hot-spot area of the package. In this experiment, the fiber-optic thermometer was attached to a GaAs crystal sensor, which obtained more sensitive and accurate temperature measurements than those by a convectional sensor.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.926-927
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• 2011

In this paper, temperature distribution of 24 MVA distribution cast-resin transformers is analyzed by using CFD. Usually heat generated in transformer causes many problems. To radiate the heat, conduction and convection are done through the duct between winding. Considering natural convection, fluid analysis is applied to the fluid region surrounding the transformer. As a result of the analysis, hot spot temperature point is predicted at the low-voltage winding. Through this paper, heat distribution and cooling characteristics property can be predicted by analyzing transformer heating characteristic required when designing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1154-1159
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• 2006

The mold transformers have been widely used in underground substations of large building and have some advantages when compared with oil-transformer. Those advantages are low fire risk, environmental compatibility, compact size and high reliability. The mold transformer is generally known to have cooling duct between low voltage and high voltage coil. To achieve better compact structure and low loss, mold transformers made by one body molding method has been developed. Nevertheless, such kinds of transformer need better cooling method because heat radiation between each winding is still of problem. The life of transformer is significantly dependent on the thermal behavior in windings. Many designers have calculated temperature distribution in transformers and hot spot point by finite element method(FEM) to analyze winding temperature rise. In this paper, the temperature distribution analysis of 100 kVA pole mold transformer for power distribution were investigated by FEM program and the thermal analysis results were compared with temperature rise test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.132-137
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• 2002

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. The life of transformer is significantly dependent on the thermal behavior in windings. To analyse winding temperature rise, many transformer designer have calculated temperature distribution and hot spot point by finite element method(FEM). Recently, numerical analyses of transformer are studied for optimum design, that is electric field analysis, magnetic field, potential vibration, thermal distribution and thermal stress. In this paper, the temperature distribution of 50 kVA pole mold transformer for power distribution are investigated by FEM program and the temperature rise test of designed mold transformer carried out and test result is analyzed compare to simulation data. In this result, the designed mold transformer is satisfied to limit value of temperature and the other property is good such as voltage ratio, winding resistance, no-load loss, load loss, impedance voltage and percent regulation.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1996.11a
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• pp.72-75
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• 1996

The objectives of this paper investigate the effect of installed spacing on the activation of spot type heat detection devices. The flow of hot gases under a ceiling resulting from the impingement of a fire plume activates heat detectors and sprinklers. Local temperature and velocity in this ceiling jet are usually expressed with the function of a ceiling height, the distance from a fire location and the heat release rate of fire. And detectors having different. RTI respond in different ways to the same temperature and velocity of ceiling jet. Thus great care should be taken to decide installed spacing of heat detection devices by considering above effects.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.292-295
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• 1991

The life of the transformers is significantly dependent upon the rate of thermal deterioration in the employed insulating materials. Therefore, the study should be based on hot-spot temperature considerations for the life expectancy and possible overload of transformer. We have measured directly temperature of the winding using thermocouples and these test results are compared with those obtained from computer simulation. In this work, our fundamental investigations are well described for the analysis in the thermal distribution of the oil-immersed transformer with the rating of 30kVA.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.784_785
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• 2009

본 논문에서는 2[MVA]급 배전용 몰드변압기의 온도분포를 유한요소해석을 통하여 수행하였다. 몰드변압기의 온도상승한도와 허용최고온도를 전자기적 열원에 대한 분석을 통하여 계산하고 그 계산된 열원을 바탕으로 열적 해석의 열원으로 사용하여 계산하였다. 일반적으로 변압기의 수명은 내부의 전반적인 열적 특성보다는 특정 부위의 온도 분포에 의해 결정되며, 특히 변압기 내부 최고점의 온도(hot spot temperature)값이 허용치 이상으로 상승할 경우 절연내력의 저하로 인해 변압기의 수명은 급격히 감소한다. 이러한 수명개선을 위해 몰드 변압기의 철심과 고압.저압권선의 Joule's loss을 계산하여 열원을 계산하였고, 그 결과를 토대로 배전용 몰드변압기의 철심과 고압 저압권선의 온도상승 분포와 최고점의 온도분포를 예측하였다.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.461-463
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• 2000

As increasing the accident of distribution transformers, we need to manage them efficiently. This paper proposes the method for transformer's management using multi-channel wireless data communication. The Data Acquisition System(DAS) was developed to manage transformers and the HDLC protocol applied to the system. Additionally, it will be feasible to diagnose distribution transformers by checking load conditions such as hot spot temperature, ambient temperature, load current, etc. and using adequate algorithm.