• Title/Summary/Keyword: Total heat

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Structural transition of Ti-Cr-V alloys with hydrogenation and dehydrogenation and the improvement of their hydrogen storage properties by heat treatment (Ti-Cr-V 합금의 수소화-탈수소화에 따른 상천이 및 열처리에 의한 수소저장특성의 향상)

  • You, Jeong-Hyun;Cho, Sung-Wook;Shim, Gun-Choo;Choi, Good-Sun;Park, Choong-Nyeon;Choi, Jeon
    • Journal of Hydrogen and New Energy
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    • v.17 no.2
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    • pp.125-132
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    • 2006
  • The alloys which compositions were represented by the formula, $Ti_{(0.22+X)}Cr_{(0.28+1.5X)}V_{(0.5-2.5X)}$ ($0{\leq}X{\leq}0.12$), had the total hydrogen storage capacity higher than 3 wt% and the effective hydrogen storage capacity higher than 1.4 wt%. Particularly, among all the tested alloys, the $Ti_{0.32}Cr_{0.43}V_{0.25}$ alloy exhibited the best effective hydrogen storage capacity of 1.65 wt%. Furthermore, the reversible bcc${\leftrightarrow}$fcc structural transition was observed with hydrogenation and dehydrogenation, which predicted the possibility of pressure cycling. EDS analysis revealed micro-segregation, which suggested the necessity of microstructure homogenization by heat treatment. The $Ti_{0.32}Cr_{0.43}V_{0.25}$ alloy was selected for heat treatment and for other related studies. The results showed that the total and the effective hydrogen storage capacity increased to 3.7 wt% and 2.3 wt%, respectively. The flatness of the plateau region was also greatly improved and heat of hydride formation was determined to be approximately -36 kJ/mol $H_2$.

Effects of Grouts and Temperature Change on Microorganisms in Geothermal Heat Pump (지열시스템의 그라우트 및 수온변화가 미생물에 미치는 영향 실험)

  • Jo, Yun-Ju;Lee, Jin-Yong;Kim, Chang-Gyun;Han, Ji-Sun
    • Journal of Soil and Groundwater Environment
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    • v.14 no.4
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    • pp.10-14
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    • 2009
  • Objective of this study was to examine the effects of grouts and temperature change on microorganisms in geothermal heat pump. Groundwater samples were obtained from wells in the heat pump system during installation (Oriental medicine hospital) and in the heat pump system under operation (Business incubation center). Grouts are the volclay sodium bentonite. Real-time PCR was used to evaluate total bacterial number and 16S rDNA. The results showed that total bacterial number of groundwater in the heat pump operation was greater than that of non-operation case, which indicates a temperature effect on the bacterial culture. In addition, high concentration of grout showed an elevated bacteria number. In the mean time, a long-term field monitoring is essentially required to confirm the effects of the grouts and the temperature changes.

Case Report of Menopausal Vasomotor Symptoms (Heat Flashes and Sleep Disorders) in a Middle-Aged Female Patient Treated with Korean Medicine (중년 여성의 갱년기 혈관운동신경증상(안면홍조, 불면)에 대한 한방 치료 1례)

  • Park, Jin-hun;Kim, So-won;Kim, Sang-yoon;Wang, Yen-min;Baek, Gil-geun;Yun, Sang-hun;Kang, Man-ho;Park, Sung-hwan;Lee, Hyung-chul;Lim, Yong-ha
    • The Journal of Internal Korean Medicine
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    • v.43 no.5
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    • pp.940-950
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    • 2022
  • Objectives: The purpose of this study is to report on the efficacy of Korean medical treatment for treating menopausal vasomotor symptoms (heat flashes and sleep disorders). Methods: We treated a menopausal female patient with heat flashes and sleep disorders using Korean medical treatments (herbal medicines, acupuncture, pharmacopuncture, moxibustion, and chuna). To evaluate the results of this treatment, we used Kupperman's Index and the Numerical Rating Scale to measure heat flashes and total sleeping time, respectively. The patient's general health status was evaluated using the European Quality of Life 5 Dimensions Scale. Results: We observed improvements in Kupperman's Index, the Numerical Rating Scale, the patient's total sleeping time, and the European Quality of Life 5 Dimensions Scale following the treatments. Conclusions: This study suggests that Korean medicine may be an effective treatment for menopausal vasomotor symptoms (heat flashes and sleep disorders).

An Experimental study on heat transfer of a falling liquid film in air channel flow (채널내 공기유동이 있는 유하액막의 열전달특성에 관한 실험적 연구)

  • Oh, Dong-Eun;Kang, Byung-Ha;Kim, Suk-Hyun
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2291-2296
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    • 2007
  • Thermal transport from vertical heated surface to falling liquid film in a channel has been investigated experimentally. Air-flow is introduced into channel to make a counter flow against falling liquid film. This problem is of particular interest in the design of direct contact heat exchange system, such as cooling tower, evaporative cooling system, absorption cooling system, and distillation system. The effects of channel width and air flow rate on the heat transfer to falling liquid film are studied in detail. The results obtained indicate that heat transfer rate is gradually decreased with an increase in the channel width without air flow as well as with air flow in a channel. It is also found that heat transfer rate of air-flow is increased while heat transfer rate of falling liquid film is decreased with an increase in the air flow rate at a given channel width. However, total heat transfer rate form the heated surface is increased as the air flow rate is increased.

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Maximum Power Output Condition of the Binary Power Cycle Composed of Two Carnot Cycles (이중 동력 사이클의 최대 출력 조건)

  • 김창욱;김수연;정평석
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.1
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    • pp.349-354
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    • 1991
  • The power output behavior of the binary cycle composed of two Carnot cycles is analyzed with considering heat transfer processes, in which the finitely constant temperature differences between heat sources and working fluids exists. The power output has the maximum value as an extremum for cycle temperatures and capacities of heat exchangers. In the internally reversible cycle, the power output is independent of the cycle temperature in the intermediate heat exchanger. In this case when the total capacities of heat exchangers are given, three heat exchangers have the same capacities at the maximum power output condition. In addition, when the cycle is not extremum for cycle temperatures and capacities of heat exchangers. At the maximum power output condition, the capacity of heat exchanger at the cold side is slightly more than the hot side as the cycle effectiveness decreases.

The Change of Crystal Structure and Physical Properties of Partially Oriented Polyester Yarn(POY) on the Draw Ratio and Heat Setting Temperature (연신비와 열고정 온도에 따른 Partially Oriented Polyester Yarn(POY)의 구조변화와 물성)

  • 박명수;윤종호
    • Textile Coloration and Finishing
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    • v.12 no.2
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    • pp.103-110
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    • 2000
  • To examine the physical properties of POY through the microstructure control, the crystal structure such as the crystallinity, the crystallite size, the orientation, the shrinkage, the tensile properties, and the thermal stress of POY(80/48, SD) were examined at different draw ratios and annealing temperatures. From the examination following conclusions were obtained : 1. The crystallinity was more effected by the heat setting temperature than by the draw ratio. The increasing rate was greatest at the heat setting temperature range of $170~190^\circ{C}$. 2. The crystallite size perpendicular to the fiber axis was more effected by the annealing temperature at lower draw ratios. On the other hand, the crystal and amorphous orientations were more effected by the heat setting at higher draw ratios. 3. The boiling shrinkage did not change significantly, but the total shrinkage showed 13% at the draw ratio 1.9 and the heat setting temperature $170^\circ{C}$. 4. The maximum thermal stress increased with increasing the draw ratio and decreasing the heat setting temperature in the temperature range of $170~210^\circ{C}$. At the draw ratio 1.9 and the heat setting temperature $170^\circ{C}$, the maximum thermal stress found was 1.1gf/d. 5. In the heat setting temperature above $170^\circ{C}$ after the drawing, the crystallinity, the crystallite size, the orientation, and the strength increased with increasing temperature, but the shrinkage and the maximum thermal stress decreased with increasing temperature.

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Effects of radiation on wall-friction and heat-transfer in a convergent- divergent nozzle (복사가 수축 확대 노즐의 벽면에서 열전달과 벽마찰에 미치는 효과)

  • 강신형;이준식;김성훈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.6
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    • pp.1639-1644
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    • 1990
  • Effects of radiation on the wall-friction and heat transfer in the convergent and divergent nozzle of a rocket motor are investigated in the present paper. Radiative heat transfer cools down the core gas, and the decrease in the gas temperature reduces the convective heat transfer on the wall. Radiation heat transfer is estimated by using mean-beam-length approach and core flow is assumed to be one-dimensional isentropic. The compressible thermal boundary layer is solved by a finite difference method. The Cebeci-Smith eddy viscosity model is adopted for the present study. Convective heat transfer is reduced at the throat of the nozzle and is almost compensated with an increase in radiative transfer. In the sequel total heat transfer rate is slightly reduced. However, radiation heat transfer is dominant in the converging part of the nozzle.

Parametric Study on the Heat Loss of the Reactor Vessel in the Nuclear Power Plant (원자력 발전 원자로 용기의 열손실 설계인자에 관한 연구)

  • Jong-Ho Park;Seoug-Beom Kim
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.5
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    • pp.827-836
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    • 2004
  • The design parameter of the heat loss for the pressurized water reactor has been studied. The heat loss from the reactor vessel through the air gap. insulation are analysed by using the computational fluid dynamics code, FLUENT. Parametric study has been performed on the air gap width between the reactor vessel wall and the inner surface of the insulation, and on the insulation thickness. Also evaluated is the performance degradation due to the chimney effect due to gaps left between the panels during the installation of the insulation system. From the analysis results, the optimal with of air gap and insulation thickness and the value of heat loss are obtained The results show how the heat loss varies with the air gap width and insulation thickness. The temperature and the velocity distributions are also presented. From the results of the evaluation. the optimal air gap width and the optimal insulation thickness are obtained. As the difference between the predicted heat loss and measured heat loss from the reactor vessel is construed Primarily as losses due to chimney effect. the contribution of the chimney effect to the total heat loss is quantitatively indicated.

Analysis of the thermal management of a high power LED package with a heat pipe

  • Kim, Jong-Soo;Kim, Eun-Pil
    • Journal of Advanced Marine Engineering and Technology
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    • v.40 no.2
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    • pp.96-101
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    • 2016
  • The thermal management of high-power LED components in an assembly structure is crucial for the stable operation and proper luminous function. This study employs numerical tools to determine the optimum thermal design in LEDs with a heat sink consisting of a crevice-type vapor-chamber heat pipe. The effects of the MCPCB are investigated in terms of the substrate thicknesses on which the LEDs are mounted. Further, different placement configurations in a system module are considered. This study found that for a confined area, a power of 40 W/LED is applicable to a high-power package. Furthermore, the thermal conductivity of dielectric layer materials should ideally be greater than 0.9 W/m.K. The temperature conditions of the vapor chamber in a heat pipe greatly affect the thermal performance of the system. At an offset distance of 9.0 mm and a $2^{\circ}C$ increase in the temperature of the heat pipe, the resulting maximum temperature increase is approximately $1.9^{\circ}C$ for each heat dissipation temperature. Finally, at a thermal conductivity of 0.3 W/m.K, it was found that the total thermal resistance changes dramatically. Above 1.2 W/m.K, the resistance change reduces exponentially.

Thermal Response Property of Grout Materials from In-situ Test and Temperature Variation of Ground Heat Exchanger (그라우트 재료별 열응답 특성 및 열교환기 운전온도 변화)

  • Kim, Kap-Duk;Lee, Soung-Ju;Yun, Yeo-Sang
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.769-775
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    • 2008
  • The objective of this report is to determine the difference of thermal response that grouted two different materials, and compare the simulation result of the length of total ground heat exchanger length that using the ground thermal conductivity. And also to know heat exchange variation of ground heat exchanger temperature that measured with various test depth. The result shows that the test hole grouted with water permeable material got better thermal response than grouted with water impermeable material. However, with consideration of ingnore for the initial 12 hour data, the test hole grouted with impermeable material has larger thermal conductivity than the other. By former thermal conductivity, simulated data by engineering program shows only 3.4% difference or less. This result shows that ground thermal conductivity is not the main variables for the design program of ground heat exchanger. At the cooling or heating mode, base on the depth of -150m, the ground heat exchanger has best temperature at $-90{\sim}-60m$ and than getting worse because of entering water heat exchanged with leaving water in the same hole.

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