• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2000년도 춘계 학술발표회 논문집
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• pp.201-207
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• 2000

This study was carried out to optimize burner and heat exchanger of the condensing gas boiler which can save energy by utilizing latent heat of combustion gas and reduce pollutant in exhaust gas. The heat exchanger of the gas boiler was composed of three parts, which were an upper. lower , and coil heat exchanger . The upper heat exchanger was placed outside of the premixed burner and a lower heat exchanger was located under the upper heat exchanger. And, coil heat exchanger rounded the outer surface of an upper and lower heat exchanger. The boiler designed by this research reaches turn-down ratio 4 : 1 in the domain of equivalence ratio 0.75-0.8 and thermal efficiency of 97% . Emission of NOx and CO concentration was under 20ppm and 140ppm at equivalence ratio 0.8 . When diameter of the burner replace 60mm by 50mm. emission of CO was reduced about 50ppm remarkably.

• 대한기계학회논문집B
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• 제21권3호
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• pp.457-472
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• 1997

We studied the temperature distribution and heat transfer characteristics of TEFC induction motor with thermal network program for more efficient design and better cooling performance of it. We knew the characteristics and the windage loss of outer cooling fan from fan test experiments. Frame axial and peripheral heat transfer coefficients and endwinding heat transfer coefficient were measured by various model experiments and then, compared with other experimental results. Frame was the main heat transfer surface, load-side and fan-side surface were not thermally symmetric from the heat flux distribution analysis. Steady and unsteady temperature distributions were measured by real motor experiments. From the results, we knew that rotor surface temperature was higher than coil temperature and the hottest spot in the coil was loadside endwinding outside surface. We compared the simulation results with those of real motor test and the two results showed a good agreement.

• Journal of Biosystems Engineering
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• 제31권5호
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• pp.430-435
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• 2006

Greenhouse horticulture in South Korea covered about 52,000 ha in 2005. Greenhouse area of about 12,000 ha has been heated during winter season with heating cost of $20{\sim}40%$ of total Production cost. Farmers engaged in greenhouse horticulture were changed into aged people. Therefore the laborsaving of working process and the saving of greenhouse heating cost should be accomplished simultaneously to increase income of greenhouse horticulture. The best method for saving of greenhouse heating cost is to install thermal tunnels into greenhouse. Then hot air heaters using fossil fuel should be changed into hot water heaters. In other words air heating using forced convection should be changed into natural convection system. In this research coil tube made of flexible PE pipe was designed as hot water heat exchanger and its heat exchanging characteristics were analyzed. This new heat exchanger has been adopted as a natural convection system for hot water heating of greenhouse horticulture.

• 설비공학논문집
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• 제21권12호
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• pp.656-662
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• 2009

In this paper, the heat resistance reliability of an axial smoke exhaust fan was investigated. An axial smoke exhaust fan should be capable of operating at $250^{\circ}C$ for 2 hours. The heat resistance reliability was evaluated by the heat resistance reliability test. A B10 life with a 90% confidence level was estimated to be about 48 minute. The failure occurred in the motor due to high temperature. The main failure mechanisms of the motor were melting of bond and insulating paper and burning of insulating materials in the coil. The heat resistance reliability was improved by changing the way to unite the core and the coil and by replacing the insulating paper and the insulating materials of the coil. A B10 life with a 90% confidence level of a modified axial smoke exhaust fan was estimated to be over 120 minute.

• 한국지열·수열에너지학회논문집
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• 제15권1호
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• pp.1-8
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• 2019

In this study, the effect of operating conditions of fan-coil unit with an oval tube type heat exchanger on its non-dimensional performance coefficient has been investigated. Pressure drops and heat transfer rates were measured under heating condition for various water flow rates, inlet temperatures and wind speeds. As a non-dimensional performance coefficient, Colburn j-factor was evaluated. The results show that the most sensitive parameter on heat flux is the inlet temperature, which affects the heat flux 4.7 and 7.2 times more than the wind speed and water flow rate, respectively. On the other hand, the Colburn j-factor as a non-dimensionalized index decreases with the wind speed, and has an maximum when the wind speed is about 1 m/s. the Colburn j-factor increases slowly with the water flow rate and inlet temperature but at a certain range of inlet temperature, the opposite phenomenon is found.

• 에너지공학
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• 제15권4호
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• pp.235-242
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• 2006

본 연구는 공기 열원 열펌프의 성능 향상을 위한 연구로써 제상 방법으로 고온냉매 우회방법을 사용하고 내부열교환기를 장착한 열펌프 시스템의 성능을 ISO5151의 표준제상 조건에서 실험하였다. 실험은 고온냉매 우회방법과 가장 일반적인 제상 방법인 시간주기 제상방법을 비교하였으며 착상 발생 후 압축기 출구의 고온냉매를 실외기 입구로 우회시킬 때 실외기 홴 속도를 정상속도에 대하여 0%, 30%, 60%, 90%로 변화 시키면서 열펌프의 성능변화를 관찰하였다. 연구결과 210분의 열펌프 가동시간 동안 고온냉매 우회방법은 시간주기 제상방법 보다 $2.2{\sim}6%$ 높은 평균 성능계수를 나타냈으며 고온냉매 우회방법에서는 실외기의 홴 속도가 60%일 때 가장 좋은 성능계수와 난방용량을 나타냈다.

• 설비공학논문집
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• 제14권7호
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• pp.531-542
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• 2002

Transcritical$CO_2$ systems are under consideration for use as residential/mobile air conditioners. In these systems, an internal heat exchanger is usually adopted to improve both capacity and/or COP of the $CO_2$ system in lower operating pressure range of gas cooler. A program has been developed to analyse the performance of internal heat exchangers using the section-by-section method. The internal heat exchanger of coaxial configuration is first analyzed and fairly good agreements with the data are obtained, And then the internal heat exchanger of multiple circular coil configuration has been investigated. The results obtained from the parametric study provide the guidelines for the initial design and manufacturing concepts of the internal heat exchanger in transcritical $CO_2$ system. Further studies are necessary to develop the heat transfer correlations of carbon dioxide in the tubes to obtain more accurate results.

• 해양환경안전학회지
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• 제24권3호
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• pp.360-366
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• 2018

In shipyards hull forming is performed by the line heating method using a gas torch and by cold treatment using a roll-press. However, this forming process has some issues, such as difficulties in controlling and accurately estimating the amount of the heat input, as well as a harsh working environment due to exposure to loud noises and air pollution. The induction heating method, which is introduced in this paper, exhibits good control and allows for the estimation of precise heat input. Also, workers can carry out the induction heating in a comfortable working environment. In this research, the induction heating simulation, which consists of electro-magnetic, heat transfer and thermal elasto-plastic analysis, was developed and modified through induction heating experiments. Finally, the effective heating coil was designed for the automatic hull forming system based on the results of induction heating simulation. For the purposes of a future study, if an algorithm to obtain optimal working conditions is developed, automatic systems for hull forming can then be constructed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.280-285
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• 2001

This paper presents a modelling of thermal discharge performance for a static ice-on-coil ice-storage tank. Through the present study, discharging characteristics were examined with the existing results of theoretical and numerical heat transfer analyses. Also, an experiment was conducted to obtain a real set of discharge performance. The thermal effectiveness, the ratio of the actual heat transfer rate to the maximum possible heat transfer rate, decreased when the stored energy decreased during discharging period. And the effectiveness increased as the coolant flow rate through the storage increased, of which increasing rate decreased abruptly near the maximum and the minimum stored energy. An empirical correlation was obtained from the experimental and the numerical analysis data.

• Journal of Advanced Marine Engineering and Technology
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• 제32권2호
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• pp.292-298
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• 2008

This study was experimentally investigated to understand the ice making characteristics of ice on a coil type ice maker. The experiment was carried out under the following conditions which are the brine temperatures of $-10[^{\circ}C],\;-8[^{\circ}C],\;-6[^{\circ}C]$, brine flow velocities of 1.0[m/s], 1.4[m/s], 1.8[m/s] and initial water temperatures of $6[^{\circ}C],\;9[^{\circ}C],\;12[^{\circ}C]$, ect. The acquired conclusions shows: 1) Ice making amount is increased with decreasing in the temperature of brine. 2) Total ice making amount shows higher value in larger size coil. However, the ice making amount per heat transfer area is increased in smaller one. 3) The ice making amount is increased with decreasing in the initial water temperature. 4) It is cleared that the overturn of natural convection existed in this experimental result.