• Journal of the Korean Society of Visualization
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• v.22 no.1
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• pp.79-84
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• 2024

As microchips' degree of integration is getting higher, its cooling problem becomes important more than ever. One of the promising methods is using fractal microchannel heat sink by mimicking nature's Murray networks. However, most of the related works have been progressed only by numerical analysis. Perhaps such lack of direct experimental studies is due to the technical difficulty of the temperature and heat flux measurement in complex geometric channels. Here, we demonstrate the direct visualization of in situ temperature profile in a fractal microchannel heat sink. By using the temperature-sensitive fluorescent dye and a transparent Polydimethylsiloxane window, we can map temperature profiles in silicon-based fractal heat sinks with various fractal scale factors (a=1.5-3.5). Then, heat transfer rates and pressure drops under a fixed flow rate were estimated to optimize hydrodynamic and thermal characteristics. Through this experiment, we found out that the optimal factor is a=1.75, given that the differences in heat transfer among the devices are marginal when compared to the variances in pumping power. This work is expected to contribute to the development of high-performance, high-efficiency thermal management systems required in various industrial fields.

• Transactions on Electrical and Electronic Materials
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• v.15 no.5
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• pp.270-274
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• 2014

Currently, LED headlamps are only attached to newly manufactured vehicles, and it remains difficult to mount LED headlamps on used cars. Therefore LED headlamps need to be developed for used cars as a replacement of their halogen lamps. Due to a number of spatial limitations, it is critical to ensure a certain level of thermal performance. In order to obtain a design for efficient heat radiation, this paper aimed to optimize thermal management through a combination of heat sinks, heat pipes and fans. Based on such a design, this paper succeeded in developing LED headlamps of the desired performance to replace the halogen bulbs of used cars.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.3
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• pp.50-54
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• 2008

This study is analyzed by the simulation of heat exchanger. As heat conduction happens as contact begins, the temperature increases until $70^{\circ}C$ at the contact part. The displacement increases until 33mm at its maximum and maximum equivalent stress at final stage increases 20 times as much as that of first contact. The expenses about maintenance, repair and management of parts can be reduced largely by applying the simulation about various parts of heat exchanger.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2310-2312
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• 2004

In Korea Electric Power Corporation (or KEPCO), several Demand-Side Management (or DSM) program have been carried out to effectively meet electric power demand at least costs by modifying customers electricity use patterns. As one of them, KEPCO applies low-priced night thermal-storage power service for heat appliances to facilitate efficient use of power facilities by shifting relatively high daytime demands to night hours to build loads during the off-peak periods. In the market of heat-storage type water-heater, electric water-heater has been mostly used, but it has low energy efficiency and needs high capacity electric equipments. So in order to replace these electric water heaters, 15 HP air-source heat pump water heater is developed in Korea Electric Research Institute (or KEPRI). This paper shows that measurement system for performance testing of heat pump water heater is established and heating capacity and performance is analyzed and measured for out-door environmental change.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.04a
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• pp.132-135
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• 1996

This study is to develop an ammonia based chemical heat pump(STELF) for a freezing and refrigeration system coupled to gas, fuel and/or waste from industrial processes as heat sources. Recently it has been continually taking a growing interest in chemical heat pumps without electric power and having higher COP's than those of existing compression type refrigeration systems using freon. By introducing STELF technology, efficient heat recovery utilizing enormous amount of waste heat in energy consuming large scale industries or building for their own refrigeration purposes is possible. Moreover, air-conditioning systems coupled to city gas for small scale industries or building can be realized. Therefore, STELF technology can contribute much for overall energy savings and efficient energy management.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.2
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• pp.27-31
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• 2015

Thermal management becomes a key technology as the power density of high performance and high density devices increases. Conventional heat sink or TIM methods will be limited to resolve thermal problems of next-generation IC devices. Recently, to increase heat flux through high powered IC devices liquid cooling system has been actively studied. In this study a chip-level liquid cooling system with TSV and microchannel was fabricated on Si wafer using DRIE process and analyzed the cooling characteristics. Three different TSV shapes were fabricated and the effect of TSV shapes was analyzed. The shape of liquid flowing through microchannel was observed by fluorescence microscope. The temperature differential of liquid cooling system was measured by IR microscope from RT to $300^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.822-828
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• 2013

Since the operating temperature of Solid Oxide Fuel Cell (SOFC) is high, the heat management of the gases supplied to fuel cell system is important. In this paper, the temperature characteristic of the gases supplied to the anode and the cathode of the fuel cell is studied in case of utilizing the waste heat contained in the ship exhaust gas as a heat source to heat up the fuel, gas and water supplied to a 500kW SOFC system for a ship power. For the fuel cell system proposed in this paper, the temperature of gases supplied to the anode and the cathode was the highest temperature at 963K when the exhaust gas of the fuel cell was utilized as the heat source for gases supplied to fuel cell system instead of utilizing the ship exhaust gas. In addition, the engine power did not effect on the temperature of gases supplied to the fuel cell stack.

• Nuclear Engineering and Technology
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• v.45 no.7
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• pp.969-978
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• 2013

A full-sized model for the horizontally oriented metal cask containing 21 spent fuel assemblies has been considered to evaluate the internal natural convection behavior within a dry shield canister (DSC) filled with helium as a working fluid. A variety of two-dimensional CFD numerical investigations using a turbulent model have been performed to evaluate the heat transfer characteristics and the velocity distribution of natural convection inside the canister. The present numerical solutions for a range of Rayleigh number values ($3{\times}10^6{\sim}3{\times}10^7$) and a working fluid of air are further validated by comparing with the experimental data from previous work, and they agreed well with the experimental results. The predicted temperature field has indicated that the peak temperature is located in the second basket from the top along the vertical center line by effects of the natural convection. As the Rayleigh number increases, the convective heat transfer is dominant and the heat transfer due to the local circulation becomes stronger. The heat transfer characteristics show that the Nusselt numbers corresponding to $1.5{\times}10^6$ < Ra < $1.0{\times}10^7$ are proportional to 0.5 power of the Rayleigh number, while the Nusselt numbers for $1.0{\times}10^7$ < Ra < $8.0{\times}10^7$ are proportional to 0.27 power of the Rayleigh number. These results agreed well with the trends of the experimental data for Ra > $1.0{\times}10^7$.

• Nuclear Engineering and Technology
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• v.21 no.1
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• pp.48-55
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• 1989

In this study, simple functional forms which could predict decay heat are referred to and modified in order to analyse more easily long-term behavior of decay heat generated from domestic PWR and CANDU spent fuel. To reduce the difference between the predicted data by functional forms and ORIGEN 2 results and to predict the decay heat under the important parameter(s), sensitivity analysis is performed. By introducing the identified hey parameter, turnup, into the functional forms, the decay heat of spent fuels within a limited rangs of cooling time(3~500 years) becomes predictable for various turnup rates. The predicted decay heat of spent fuels with representative turnup rates such as 33, 37 and 40 GWD/MTU by the functional forms is in so good agreement with ORIGEN 2 results within $\pm$10% difference over the cooling time from 1 to 10$^{5}$ years that the functional forms presented here may be used for engineering purposes such as the thermal design and assessment of the facilities associated with spent fuel management.

• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.174-186
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• 1996

This study was carried out in order to understand the plan, design, constructing and actual condition of management of modernized horticultural facilities in Kyungpook Province which had been constructed from 1992 to 1995 funded by Government support. The aim of this study is to provide reference data for success of the forth project. It was performed by making up a question about driving of project and management condition of equipment after constructing. The results obtained from this study are as follows: 1. 73.5% of facilities horticulture farmhouse recognized that the prospect of greenhouse is bright, but 92.5% of the farmhouse also recognised that they need technical consultation on protected horticulture farming. Therefore, technical educations would must be enhanced about foundation of greenhouse and cultivation technique. 2. The holding times of explanatory meetings, cause of understanding to farmhouse, were one or two times in greenhouse construction, and 62.5% of the farmhouse expressed the insufficiency at the explanation and educational data. For this reason, it was judged that the construction contract had been delayed more than 5 months in 49.3% of the farmhouse after the decision of project budget. 3. In constructing after a contract, the rates of construction delay is 53.4% and defect occurrence is 41.1%. The biggest reasons of construction delay was insufficiency of worker and materials supply. Each percentage is 29.1%. And the reason of defect occurrence is badness of machinery equipment(62.9% ). 4. In management of greenhouse, a pipe-constructed plastic film greenhouse changes plastic film every one and three years because of sticking dust on plastic film. It was needed to about in cleaning technique of coverings. Because that used 3-5 years only half of the expected life span. 5. The order of broken rating in the subsidiary equipment is like this lollop ventilator (42.8%), a general control system(33.3%) especially, in the case of a general control system, the rate of all family can control is 52.7%. so, it is time to develop easy control equipment which every one could use as soon as possible. 6. When choose heat generator as decide capacity, the most priority is the mount of heat generator the percent is 45.5% heat generator and as decide model, the private purchase's percent is 77.3%. It is higher than a public bidding heat generator the percent is 22.7% heat generator when it compare with a public bidding. In the case of $CO_2$ generator, using rate is only 19.0%. The using rate is very low, so it needs education how to use depends on the way of the subsidiary equipment. 7. In the case of seedlings, it is asked to use factory-processed seedling effectively. because it's difficult to get security of labors(58.8%), hoped crops (55.9%) access same crops(29.4%) much more and changing of crops depends on market situation. that is the main reason the lack of knowhow.