• 한국안전학회지
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• 제16권4호
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• pp.22-28
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• 2001

Heat transfer and pressure distribution for heat exchanger type of domestic gas boiler are different from shape, pitch, thickness of fin and array of pipe respectively. In order to measure the pressure distribution across the heat exchanger, a suction type wind tunnel was constructed and velocity distribution was measured for pilot tube(4 point) of rack type. The experiments were performed for 5 different air flow mass, rpm=3,6,9,12,15 and transverse axis of heat exchanger(x-length) is 5cm respectively. Results showed that above 9.5m/s, pressure distribution dispersion for wet type of heat exchanger is on the increase and above 5.5m/s, pressure distribution dispersion for dry type of heat exchanger is on the increase. Also, pressure distribution dispersion by comparing two different types heat exchanger, dry type of heat exchanger showed a higher augmentation than wet type of heat exchanger.

• International Journal of Korean Welding Society
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• 제4권1호
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• pp.23-29
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• 2004

In weaving welding where a V groove exists, the heat input distribution is an important factor that determines the defectiveness of the bead shape, undercut and over-lap. In this study, the amount of heat input, which is determined by the welding current, voltage, speed and weaving conditions is calculated through mathematical development and numerical methods. Furthermore, the heat input distribution as a two- dimensional heat source was observed when applied to each groove.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.316-319
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• 2001

In weaving welding where a V groove exists, the heat input distribution is an important factor that determines the defectiveness of the bead shape, undercut and over-lap. In this study, the amount of heat input, which is determined by the welding current, voltage, speed and weaving conditions is calculated through numerical methods. Furthermore, the heat input distribution as a two- dimensional heat source was observed when applied to each groove. Therefore, a heat input control algorithm is suggested to prevent the defects generated from undercut or over-lap, which was verified through an analysis of the heat input distribution.

• ETRI Journal
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• 제19권2호
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• pp.59-70
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• 1997

A study on the operation of a heat pipe with two heat sources has been performed to optimize the heat distribution of satellite equipment. A numerical modeling is used to predict the temperature profile for the heat pipe assuming cylindrical two-dimensional laminar flow for the vapor, and the conduction heat transfer for the wall and wick. An experimental study using the copper-water heat pipe with the length of 0.45 m has been performed to evaluate the numerical model and to compare the temperature distribution at the outer wall for the non-uniform heat distribution. The results on temperature profiles for the heat input range from 29 W to 47 W on each heater are presented. Also the correlation between the heat input and the temperature increase is presented for the optimum distribution on two heaters. The result shows that the outer wall temperature can be controlled by redistribution of heat sources. It is also concluded that the heat source closer to the condenser can carry more heat while maintaining lower temperatures at the outer wall.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1171-1184
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• 2003

An experimental study on critical heat flux (CHF) has been performed in an internally heated vertical annulus with non-uniform heating. The CHF data for the chopped cosine heat flux have been compared with those for uniform heat flux obtained from the previous study of the authors, in order to investigate the effect of axial heat flux distribution on CHF. The local CHF with the parameters such as mass flux and critical quality shows an irregular behavior. However, the total critical power with mass flux and the average CHF with critical quality are represented by a unique curve without the irregularity. The effect of the heat flux distribution on CHF is large at low pressure conditions but becomes rapidly smaller as the pressure increases. The relationship between the critical quality and the boiling length is represented by a single curve, independent of the axial heat flux distribution. For non-uniform axial heat flux distribution, the prediction results from Doerffer et al.'s and Bowling's CHF correlations have considerably large errors, compared to the prediction for uniform heat flux distribution.

• 대한한의학회지
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• 제27권2호
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• pp.244-252
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• 2006

Objectives : To examine any potential relationships between the types of alopecia and the facial heat distribution in patients with alopecia. Methods : 183 patients with alopecia participated in this study to provide facial heat distribution measured by the Infrared Thermography Scanner (ITS, Nec San-ei Instruments Ltd, Japan). The thermography scan was used in a light- and heat-protected room after 20 minutes' of rest. 1.5m of distance was maintained between the patients and the scanner. Results : Specificity in the type of facial heat distribution was found as follow. 1. Types of facial heat distribution can be classified as T-type and diffused patterns. 2. There was a significant difference in the pattern of facial heat distribution among different types of alopecia (p=0.002): facial heat distribution appeared T-type in androgenic alopecia, alopecia areata, and telogen effluvium (71.3%, 85.7%, 70.4%), whereas diffused pattern was dominant in seborrheic alopecia (55.6%). 3. There was a significant difference in the pattern of facial heat distribution between men and women (p<0.001) : While the T-type and diffused type appeared equally in men (50.6% : 49.4%), T-type was dominant in women (88.0% vs. 12.0%). Conclusions : We conclude that the pattern of facial heat distribution differs depending on the types of alopecia and gender. These differences may provide useful information for diagnosis and clinical therapy for this population.

• 한국기계가공학회지
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• 제16권5호
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• pp.150-156
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• 2017

This study tests the characteristics of heat radiation by applying the pin-height variables to 30-W LED floodlights. The angle of the heat sink enables us to identify the characteristics of the heat radiation based on the temperature distribution. The results of the study are as follows. When the heat sinks are set towards the ground, the heat transfer decreases in speed only to expands the temperature distribution, which adversely affects the characteristics of heat radiation and expands the temperature distribution of PCB with the LED chip. We verify that the characteristics of heat radiation are adversely affected when the height of the cooling pin decreases and the heat radiation area decreases, which impedes the heat transfer and increases the temperature distribution on the heat sink.

• 대한한방체열의학회지
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• 제5권1호
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• pp.78-86
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• 2006

Objectives: To examine any potential relationships between the types of alopecia and the facial heat distribution in patients with alopecia Methods: 183 patients with alopecia participated in this study to provide facial heat distribution measured by the Infrared Thermography Scanner (ITS, Nec San-ei Instruments Ltd, Japan). The thermography scan was used in a light-and heat-protected room after 20 minutes’of resting period. 1.5m of distance maintained between the patients and ITS. Results: Specificity in the type of facial heat distribution was found as follow. 1. Types of facial heat distribution can be classified as T-type and diffused patterns. 2. There was a significant difference in the pattern of facial heat distribution among different types of alopecia (p=0.002): facial heat distribution appeared T-type in Androgenic Alopecia, Alopecia Areata, and Telogen Effluvium (71.3%, 85.7%, 70.4%), whereas diffused pattern was dominant in Seborrheic Alopecia(55.6%). 3. There was a significant difference in the pattern of facialheat distribution between men and women (p<0.001): While the T-type and diffused type were equally appeared in men (50.6%: 49.4%), T-type was dominant in women (88.0% vs. 12.0%). Conclusions: We conclude that the pattern of facial heat distribution differs depends on the types of alopecia and gender. These differences may provide useful information for the diagnosis and clinical therapy for this population.

• Journal of Mechanical Science and Technology
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• 제15권11호
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• pp.1563-1571
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• 2001

The effect of flow distribution on thermal and flow performance of a parallel flow heat exchanger has been numerically investigated. The flow distribution has been altered by varying the geometrica l parameters that included the locations of the separators, and the inlet/outlet of the heat exchanger. Flow nonuniformities along paths of the heat exchanger, which were believed to be dominantly influential to the thermal performance, have been observed to eventually optimize the design of the heat exchanger. The optimization has been accomplished by minimizing the flow nonuniformity that served as an object function when the Newton's searching method was applied. It was found that the heat transfer of the optimized model increased approximately 7.6%, and the pressure drop decreased 4.7%, compared to those of the base model of the heat exchanger.

• 대한조선학회지
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• 제9권2호
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• pp.49-55
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• 1972

The temperature distribution and cooling rate play an important role in the investigation of heat affected zone of weldment. All the problems such as metallurgical changes, welding thermal stress, welding residual stress and welding deformation in the heat affected zone of welded joint are due to the temperature distribution and cooling rate. In this paper, one dimensional temperature distribution and cooling rate due to transient arc welding heat in the heat affected zone of the base metal are studied. Heat transfer equation for one dimensional heat flow is formed, and solution is obtained. Weld heat input formula is also formed and used. Computed numerical results show a good agreement with the experimented temper color.