• Journal of Mechanical Science and Technology
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• 제17권7호
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• pp.1063-1072
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• 2003

Direct immersion cooling has been considered as one of the promising methods to cool high power density chips. A fluorocarbon liquid such as FC-72, which is chemically and electrically compatible with microelectronic components, is known to be a proper coolant for direct immersion cooling. However, boiling in this dielectric fluid is characterized by its small value of the critical heat flux. In this experimental study, we tried to enhance the critical heat flux by increasing the nucleate boiling area in the heat spreader (Conductive Immersion Cooling Module). Heat nux of 2 MW/㎡ was successfully removed at the heat source temperature below 78$^{\circ}C$ in FC-72. Some modified boiling curves at high heat flux were obtained from these modules. Also, the concept of conduction path length is very important in enhancing the critical heat flux by increasing the heat spreader surface area where nucleate boiling occurs.

• 설비공학논문집
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• 제2권3호
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• pp.234-242
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• 1990

In this study, heat transfer characteristics of vertical fixed bed with air flowing through were experimentally investigated. The experiments were conducted for cases where heat was transfer steady state conditions from an immersed cylindrical heated to the surrounding fixed ved of steel balls. Based on the experimental data, the optimum conditions for heat transfer augmentation have been determined and shows in empirical forms. For the same power loss, comparison of heat transfer effect between the fixed bed and single phase forced convection device indicates that both miniaturization of heat exchange device and heat transfer augmentation at low flow velocity are possible by application of the fixed bed to heat exchangers. The present results could provide a useful design information for the heat exchangers where fixed beds are used.

• Journal of Photoscience
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• 제8권1호
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• pp.19-22
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• 2001

It was reported that Red ginseng contains specific ginsenoside-Rg$_2$,-Rg$_3$,-Rh$_1$and -Rh$_2$, which show various pharmacological effects. However, production of these specific ginsenosides from Red ginseng is not commercially applicable because of high cost of the raw material, roots. This work was carried out to examine the production of Red ginseng specific ginsenosides from Agrobacterium-transformed hairy roots. Hairy roots were induced from 3 year-old root segment of Korean ginseng (Panax ginseng C.A. Meyer) after infection with Agrobacterium rhizogenes A4. Among many lines of hairybroots, KGHR-8A was selected. Steam heat treatment of hairy roots was resulted in the changes of ginsenoside composition. Eleven ginsenosides were detected in heat-treated hairy roots but eight in freeze dried hairy roots. In heat treated hairy root, content of ginsenoside-Rb$_1$,Rb$_2$,Rc, Rd, Re, Rf, and Rg$_1$were decreased compared to those of freeze dried hairy roots. However, heat treatment strongly enhanced the amount of Red ginseng specific ginsenogides (ginsenoside-Rg$_2$,-Rg$_3$,-Rh$_1$and -Rh$_2$). Amounts of ginsenoside-Rg$_3$,-Rh$_1$and -Rh$_2$ in heat-treated hairy roots were 2.58, 3.62 and 1.08 mg/g dry wt, respectively, but these were detected as trace amount in hairy roots without heat treatment. Optimum condition of heat treatment for the production of Red ginseng specific ginsenoside was 2 h at 105$^{\circ}C$. This result represents that Red ginseng specific ginsenoside can be producted from hairy roots by steam heat treatment.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1219-1224
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• 2004

The objective of this study is to propose an experimental calibration facility in which a heat flux sensor can be calibrated under conductive condition by using helium gas. The heat flux calibration facility was designed, simulated and manufactured for use in a high heat transfer condition. It delivers heat fluxes up to a maximum of 35 KW $m^{-2}$. A copper block heated electrically with 3.5 KW power is designed to produce uniform temperature up to 600 K across its face. High heat fluxes are provided between hot plate and cold plate by 1 mm height helium filled gap. A cold plate is maintained around 300 K through pool boiling using a refrigerant and water-cooled heat exchanger. A simulation was conducted to verify the design of the main test section. To verify the performance of calibration facility, a heat flux sensor was examined. The measured heat fluxes were compared to the calculated one.

• 설비공학논문집
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• 제9권1호
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• pp.73-81
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• 1997

In this experimental study, the air cooling radial shape heat exchanger which influences on the COP and the cooling capacity by heat and mass transfer rate in the adsorbent bed was designed and applied to test its performance for adsorption heat pump(AHP). Zeolite-water was used for the adsorbent-adsorbat pair. As a result, the cooling COP and a cycle period of this adsorption heat pump are 0.28 and 2 hours, respectively, on the condition of none heat recovery from the adsorption reactor(absorber). The other results and recommendations are mainly related to improving the heat and mass transfer inside the absorber to reduce a cycle period.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.709-712
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• 2006

It is necessary to develop a new technology for controling thermal cracking by hydration heat according to the increase construction of massive concrete structures, high strength concrete and early strength concrete. Therefore, it was investigated the characteristics of hydration heat generation of low heat concrete using hydration heat reducing admixtures in this study. To investigate the performance of hydration heat reducing admixtures, it was evaluated hydration heat according to the kind and replacement ratio of phase change material series I, II and the way of using hydration heat reducing admixtures in series III.

• 대한한의학원전학회지
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• 제19권4호
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• pp.241-256
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• 2006

Aversion to wind is a feeling of cold when exposed to wind; aversion to cold is a feeling of cold. The distinction between aversion to wind and aversion to cold is ambiguous because in greater yang disease the two terms seem to be used indiscriminately. It is, however, worth noting that "aversion to wind" does not occur in the lines presenting disease of the three yin. In this text, we render as "heat effusion" rather than "fever," since the Chinese term is somewhat wider in meaning than familiar English term, Heat effusion is associated with many conditions and occurs both in externally contracted disease and miscellaneous disease (雜病), disease due to causes other than external evils). In externally contracted disease of the three yang channels, heat effusion is a manifestation of the struggle between right qi and evil qi; it does not necessarily indicate the presence of evil heat. In diseases of the three yin, right qi is not strong enough to counter evil qi; hence heat effusion is absent, and instead only aversion to cold is present. Sweating occurs in a variety of patterns. A distinction is made between spontaneous and night sweating(自汗). Spontaneous sweating is so called because it occurs spontaneously without exertion. it has numerous causes. Night sweating(盜汗) is sweating during sleep that ceases on awakening.

• 한국주조공학회지
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• 제25권6호
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• pp.226-232
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• 2005

Contact material is widely used in the field of electrical parts. Ag-CdO material has a good wear resistance and stable contact resistance. In order to establish optimizing heat treatment condition, rolling temperature and oxidation process, we studied the microstructure of Ag-CdO material with various conditions. The experimental procedure were melting using high frequency induction, heat treatment, rolling and internal oxidation. And we experimented on difference process, Post-oxidaion. In this study, we obtained the optimizing heat treatment condition was $700^{\circ}C$ for 15 min. and the optimizing rolling temperature was $730^{\circ}C$. In investigation of the microstructure of oxidized material, coarse oxide and depleted oxidation layer existed. The hardness was average Hv 70. When we used Post-oxidation, oxides were finer than prior process and depleted oxidation layer did not exist. The hardness of Post-oxidation material was average Hv 80. And the optimizing rolling temperature was $800^{\circ}C$.

• 한국가구학회지
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• 제20권6호
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• pp.560-565
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• 2009

It is known that heat treatment decreases the hygroscopicity of wood. Thus heat-treated wood is good for outdoor construction due to its improved dimensional stability. This study is to investigate the hygroscopicity and discoloration of spruce and birch boards heat-treated above $190^{\circ}C$. The equilibrium moisture contents (EMCs) at all relative humidities decreased with the increase of heat treatment temperature and/or time for both spruce and birch. It was revealed that heat-treatment temperature affected more on the hygroscopicity thaan heat-treatment time. The average basic densities decreased for the spruce specimens, but increased for the birch specimens with an increase of the treatment time and/or temperature. The same heat treatment condition (190-8) made the birch specimens darker than the spruce specimens.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.417-420
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• 2006

Recently, the attention is paid to the problem of thermal crack by hydration heat according to the increase of high strength and mass concrete structures. At this point, various research has been carried out for the control of hydration heat in high strength and mass concrete. As a part of the research, it was investigated application of hydration heat reduction agent (HR) for the control of thermal crack by hydration heat in this study. To investigate the application, it was selected HR which can reduce hydration heat of concrete with effect in series I and II. Also, it was investigated the characteristics of hydration heat generation of low heat concrete using HR with binder types in seriesIII.