• Title/Summary/Keyword: thermal NO

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A Study on the Effects of Water Absorption on the Thermal Conductivity of Insulation Materials (수분 흡수가 단열재의 열전도계수에 미치는 영향에 관한 연구)

  • Yoo, Seong-Yeon;Kim, Tae-Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.3
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    • pp.119-125
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    • 2013
  • IInsulation material is generally used for preventing heat loss from heat transport fluids, and water absorption severely reduces the insulation property. The purpose of this study is to evaluate the amount of water absorption supplied by the pouring method and spraying method, to investigate the effects of water absorption on the thermal conductivity of an insulation material, and modeling the relation between water absorption and thermal conductivity. E-glass, a kind of glass fiber, and HYPERLITE, mainly composed of pearlite, are selected, to compare hygroscopic and insulation properties. E-glass is found to have much higher water absorptivity, compared to HYPERLITE. The thermal conductivity of the water-absorbed E-glass is increased by more than 150%, compared to that of no absorption, while variation of the thermal conductivity of HYPERLITE with water absorption is insignificant. A three-stage model of water absorption for thermal conductivity is developed, and the modeling results are found to be in good agreement with the experimental data.

The effects of various thermal parameters on coil temperature rise in TEFC induction motor (여러가지 열적 변수가 전폐형 유도전동기의 코일온도상승에 미치는 영향에 관한 연구)

  • Yun, Myeong-Geun;Ha, Gyeong-Pyo;Go, Sang-Geun;Lee, Yang-Su;Han, Song-Yeop
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.4
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    • pp.570-578
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    • 1997
  • At design stage of new motor or when taking remedial action of old motor, a lot of information can be obtained from thermal parameters analysis. This study focused on the temperature rise of TEFC induction motor with respect to various thermal parameters. Frame heat transfer had the most important effect on coil temperature rise. But those of air gap and rotor fan had no effect. This fact shows fan action is more important than fin action in the case of rotor fan. Coil temperature can be more decreased by cooling near the heat sources than any other parts from the results of thermal conductivity and loss tests. Variation of cooling air flow rate and motor volume effects on coil temperature were also tested. These tests suggest that improvement of cooling fan performance is important in reducing the coil temperature rise. Thermal equivalent program was verified by comparison of some experimental results.

An Experimental Study on the Thermal Insulation of the Linin Fabrics (의복 안감의 보온성에 관한 실험적 연구)

  • Jeong Young Ok;Choi Jeong Wha
    • Journal of the Korean Society of Clothing and Textiles
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    • v.8 no.1
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    • pp.1-11
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    • 1984
  • An attempt was made to determine individual thermal resistances of 2-lining fabrics ad 4-outer fabrics for Korean-styled clothes, and 4-lining fabrics ad 5-outer fabrics for Western-styled clothes at $19^{\circ}C$ and $24^{\circ}C$. The thermal insulation effects for different lining fabrics in Korean and Western-styled clothes were deduced in determining heart rate, rectal temperature, mean skin temperature and microclimates of subjects. The subjects were dressed experimental clothing which were made of lining and outer fabrics in question, and seated in an environmental chamber during the experiment. 1. Thermal resistances of lining fabrics : For Korean-styled clothes. nylon sheer is larger than unzosa. For Western-styled clothes, rayon, acetate, nylon(taffeta) and kalkali in that order. 2. Thermal resistances of lining fabrics combined : with outer fabrics: For Korean-styled clothes. the measured value is larger than the one of simple aggregate value. But in the case of Western-styled clothes, the measured value is smaller than simple aggregate value. 3. The effects of lining on the thermal insulation of the whole clothing: In case when subjects wore unlimited number of underwear, no matter what lining fabrics were used in Korean and Western-styled clothes less thermal insulation effects were indicated. For the case, however, if subjects wore only limited underwear, there are significant differences of thermal insulation between experimental clothings.

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Thermal analysis on composite girder with hybrid GFRP-concrete deck

  • Xin, Haohui;Liu, Yuqing;Du, Ao
    • Steel and Composite Structures
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    • v.19 no.5
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    • pp.1221-1236
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    • 2015
  • Since the coefficients of thermal expansion (CTE) between concrete and GFRP, steel and GFRP are quite different, GFRP laminates with different laminas stacking-sequence present different thermal behavior and currently there is no specification on mechanical properties of GFRP laminates, it is necessary to investigate the thermal influence on composite girder with stay-in-place (SIP) bridge deck at different levels and on different scales. This paper experimentally and theoretically investigated the CTE of GFRP at lamina's and laminate's level on micro-mechanics scales. The theoretical CTE values of laminas and laminates agreed well with test results, indicating that designers could obtain thermal properties of GFRP laminates with different lamina stacking-sequence through micro-mechanics methods. On the basis of the CTE tests and theoretical analysis, the thermal behaviors of composite girder with hybrid GFRP-concrete deck were studied numerically and theoretically on macro-mechanics scales. The theoretical results of concrete and steel components of composite girder agreed well with FE results, but the theoretical results of GFRP profiles were slightly larger than FE and tended to be conservative at a safety level.

Residual DC characteristic on Twisted Nematic Liquid Display on the Polyimide Surface by the Thermal Stress (열적 stress에 의한 폴리이미드 표면에서의 TN-LCD의 잔류DC 특성)

  • Bae, Yu-Han;Hwang, Jeoung-Yeon;Kim, Jong-Hwan;Mun, Hyun-Chan;Han, Jung-Min;Kim, Young-Hwan;Seo, Dae-Shik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.11a
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    • pp.498-501
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    • 2004
  • In this study, the threshold voltage and the response time of thermal stressed TN-LCDs showed the same performances on no thermal stressed TN-LCDs. There was little change of value in TN cells. Also, the transmittances of TN-LCDs on the rubbed PI surface were almost same while increasing thermal stress time. However, the thermal stability of TN cell was decreased by the high thermal stress for the long duration. Residual DC was decreased as the thermal stress increases. Especially, when TN cell was stressed more and more by heating, residual DC was changed a lot. As a result, the residual DC property of LCD in projection TV is affected very much by heating.

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NOx Formation Characteristics with Oxygen Enrichment in Nonpremixed Counterflow and Coflow Jet Flames (비예혼합 대향류 및 동축 제트화염에서 산소부화에 따른 NOx 생성특성)

  • Yoo, Byung-Hun;Hwang, Chul-Hong;Han, Ji-Woong;Lee, Chang-Eon
    • 한국연소학회:학술대회논문집
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    • 2004.11a
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    • pp.169-174
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    • 2004
  • The NOx emission characteristics with oxygen enrichment in nonpremixed counterflow and coflow jet flame of $CH_4$ fuel have been investigated numerically. A small amount of nitrogen is included in oxygen-enriched combustion, in order to consider the inevitable $N_2$ contamination by air infiltration. The results show that the initial increase of NO with increasing oxygen enrichment is due to increasing temperature and residence time, while its subsequent decrease above 75% oxygen is due to decreasing the consumption rate of nitrogen. When oxygen addition exceeds 30%, Thermal NO gradually becomes the dominant production pathway and Prompt NO becomes negative pathway for net NO production rate. It is also seen that Thermal NO plays an important role in NO reduction when strain rate increase in oxygen-enriched combustion. Finally, the results of EINOx with oxygen enrichment in coflow jet flame show the similar profile with those of conterflow flame. It is confirmed that, with leakage of 1% nitrogen in the oxidizer stream, the corresponding EINOx is eight times of that emitted from regular $CH_4$/Air flame.

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Fuel Concentration and Flame Temperature Distribution in Model Gas Turbine Combustor with Various Spray Angles (모형가스터빈 연소기에서 분무각 변화에 따른 연료농도 및 화염온도 분포)

  • Hwang, Jin-Seok;Byun, Yong-Woo;Seong, Hong-Gye;Koo, Ja-Ye;Kang, Jeong-Sik
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.10
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    • pp.1011-1016
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    • 2008
  • Jet-A spray and combustion were numerically analyzed in annular type combustor model using KIVA3V. The combustor geometry have 6 dilute holes. Swirl effect and thermal NO were considered in this investigation to analyze mixing and combustion characteristics. Fuel vapor, flame temperature, NO generation were investigated for various spray angle. As increase of spray angle, Jet-A vapor appeared uniformly in primary zone and evaporation rate was increased. Mixing between fuel vapor and ambient gas was enhanced as increase of spray angle. As a result, high temperature region appeared widely and thermal NO generation rate was increased.

Effects of Risering Design and Alloying Element on Formation of Shrinkage Cavity in Ductile Cast Iron (구상흑연주철의 수축결함생성에 미치는 주조방안 및 합금원소의 영향)

  • Yu, Sung-Kon
    • Korean Journal of Materials Research
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    • v.13 no.2
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    • pp.74-80
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    • 2003
  • The effects of risering design and alloying element on the formation of defects such as external depression, primary and secondary shrinkage cavities in ductile cast iron were investigated. Two types of risering design for the cylindrically step-wise specimen, No. 1(progressive solidification) and No. 2(directional solidification) risering designs, were prepared and six different alloy compositions were casted. In the No. 1 risering design, external depression or primary shrinkage cavities due to liquid contraction were observed in all the specimens from SG 10 to SG 60. The defects caused by liquid contraction seemed to be more affected by risering design than alloying elements. The secondary shrinkage cavities were also observed in all the specimens but a swollen surface was not observed in all the castings. The primary shrinkage cavities were located right under the top surface or connected to the top surface, and were characterized by smooth surfaces. On the other hand, the secondary shrinkage cavities were positioned in the thermal center of the specimen steps 3 and 4, and characterized by rough surfaces. In the No. 2 risering design, no external depression or primary shrinkage cavities due to liquid contraction were observed in all the specimens from SG 10 to SG 60. However, the secondary shrinkage cavities were formed in the thermal center of specimens SG 40, 50 and 60. Like the No. 1 risering design, a swollen surface was not observed in all the castings.

Effects of Addition of Hydrogen and Water Vapor on Flame Structure and NOx Emission In $CH_4$-Air Diffusion Flame (메탄-공기 확산화염에서 수소와 수증기 첨가가 화염구조와 NOx 배출에 미치는 효과)

  • Park, Jeong;Keel, Sang-In;Yun, Jin-Han
    • Transactions of the Korean hydrogen and new energy society
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    • v.18 no.2
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    • pp.171-181
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    • 2007
  • Blending effects of hydrogen and water vapor on flame structure and NOx emission behavior are numerically studied with detailed chemistry in methane-air counterflow diffusion flames. The composition of fuel is systematically changed from pure methane and pure hydrogen to the blending fuels of methane-hydrogen-water vapor through the molar addition of $H_2O$. Flame structure is changed considerably for hydrogen-blending methane flames and hydrogen-blending methane flames diluted with water vapor in comparison to pure methane flame. These complicated changes of flame structures also affect NOx emission behavior considerably. The changes of thermal NO and Fenimore NO are analyzed for various combinations of the fuel composition. Importantly contributing reaction steps to thermal NO and Fenimore NO are addressed in pure methane, hydrogen-blending methane flames, and hydrogen-blending methane flames diluted with water vapor.

TENSILE BOND STRENGTH BETWEEN NON-PRECIOUS DENTAL ALLOY AND VENEERING REINFORCED COMPOSITE RESINS (치과용 비귀금속 합금과 전장용 강화형 복합레진의 인장결합강도)

  • Yang, Byung-Duk;Park, Ju-Mi;Ko, Sok-Min;Kang, Geon-Gu
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.4
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    • pp.427-437
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    • 2000
  • Recently the 2nd generation laboratory composite resins were introduced. Although the mechanical properties of these composite resins have been improved, there were some disadvantages such as discoloration, low abrasion resistance and debonding between metal and resin. The purpose of this study was to evaluate the tensile bond strength between non-pecious dental alloy(verabond) and four veneering reinforced composite resins ; Targis(Ivoclar Co., U.S.A.), Artglass(Kulzer CO., Germany), Sculpture(Jeneric Pentron Co., U.S.A.), and Estonia(Kurary Co., Japan). All test metal specimens were polished with #1,000 SiC paper, and sandblasted with $250{\mu}m$ aluminum oxide. After then. according to manufacturer's instructions metal adhesive primer and veneering resins were applied. All test specimens were divided into two groups. One group was dried in a desiccator at $25^{\circ}C$ for 3 days, the other group was subjected to thermal cycling($2,000{\times}$) in water($5/55^{\circ}C$). Tensile bond strength was measured using Instron Universal Testing machine and the fractured surface was examined under the naked eyes and scanning electron microscope. Within the limitations imposed in this study, the following conclusions can be drawn: 1. In no-thermal cycling groups, there were no significant differences between Estenia and VMK68 but there were significant differences between Targis, Artglass, Sculpture and VMK68(p<0.05). 2. In no-thermal cycling resin groups, the highest tensile bond strength was observed in Estenia and there were significant differences between Estenia and the other resins(p<0.05). 3. Before and after thermal cycling, there were significant differences in tensile bond strength of Targis and Artglass(p<0.05). The tensile bond strength of Artglass was decreased and that of Targis was increased. 4. In no-thermal cycling groups, Artglass showed mixed fracture modes(95%), but after thermal cycling, Artglass showed adhesive fracture modes(75%).

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