• Title/Summary/Keyword: Thermal capacitance

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A Study on the Flat-Plate Solar Collector Performance taking into account of the Collector Thermal Capacitance (집열기(集熱器) 열용량(熱容量)을 고려(考慮)한 평판형집열기(平板型集熱器) 성능(性能)에 관(關)한 연구(硏究))

  • Lee, Young-Soo;Yong, Ho-Taek;Seoh, Jeong-Ill
    • Solar Energy
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    • v.2 no.1
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    • pp.17-23
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    • 1982
  • This paper presents the performance of a Flat-Plate Solar Collector in case of taking into account of the thermal capacitance. The relationships among energy absorption, overall heat loss coefficient and temperature distribution are studied theoretically. And the thermal capacitance of the collector is considered. Also, the results obtained are compared with those of model in which the thermal capacitance is neglected. As the results of this study, the efficiency of the collector having double glazing is higher than the other cases. It is shown that the fluid temperature in the tubes are rising close to linearly. The variations of the outlet temperature of tubes in the model neglecting the effect of thermal capacitance are tend to represent lower slope than that of considering the effect of thermal capacitance.

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The thermal effect on electrical capacitance sensor for two-phase flow monitoring

  • Altabey, Wael A.
    • Structural Monitoring and Maintenance
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    • v.3 no.4
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    • pp.335-347
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    • 2016
  • One of major errors in flow rate measurement for two-phase flow using an Electrical Capacitance Sensor (ECS) concerns sensor sensitivity under temperature raise. The thermal effect on electrical capacitance sensor (ECS) system for air-water two-phase flow monitoring include sensor sensitivity, capacitance measurements, capacitance change and node potential distribution is reported in this paper. The rules of 12-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance and sensitivity map the basis of Air-water two-phase flow permittivity distribution and temperature raise are discussed by ANSYS and MATLAB, which are combined to simulate sensor characteristic. The cross-sectional void fraction as a function of temperature is determined from the scripting capabilities in ANSYS simulation. The results show that the temperature raise had a detrimental effect on the electrodes sensitivity and sensitive domain of electrodes. The FE results are in excellent agreement with an experimental result available in the literature, thus validating the accuracy and reliability of the proposed flow rate measurement system.

Dynamic Simulation of Annual Energy Consumption in an Office Building by Thermal Resistance-Capacitance Method

  • Lee, Chang-Sun;Choi, Young-Don
    • International Journal of Air-Conditioning and Refrigeration
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    • v.6
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    • pp.1-13
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    • 1998
  • The basic heat transfer process that occurs in a building can best be illustrated by an electrical circuit network. Present paper reports the dynamic simulation of annual energy consumption in an office building by the thermal resistance capacitance network method. Unsteady thermal behaviors and annual energy consumption in an office building were examined in detail by solving the simultaneous circuit equations of thermal network. The results are used to evaluate the accuracy of the modified BIN method for the energy consumption analysis of a large building. Present thermal resistance-capacitance method predicts annual energy consumption of an office building with the same accuracy as that of response factor method. However, the modified BIN method gives 15% lower annual heating load and 25% lower cooling load than those from the present method. Equipment annual energy consumptions for fan, boiler and chiller in the HVAC system are also calculated for various control systems as CAV, VAV, FCU+VAV and FCU+CAV. FCU+CAV system appears to consume minimum annual energy among them.

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Analysis of energy consumption of office building by thermal resistance-capacitance method (열저항-열용량법에 의한 사무실용 건물의 소비에너지 해석)

  • Lee, C.S.;Choi, Y.D.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.9 no.1
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    • pp.1-13
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    • 1997
  • This paper reports the dynamic analysis of energy consumption for an office building by heat resistance-capacitance method. If a building is divided into several wall components and the wall components is replaced by one thermal capacitance and several thermal resistances, the building becomes an electric circuit. By solving the simultaneous equations of the circuit, the dynamic heat transfer characteristics and the energy consumption rate of the building were predicted. Accuracy of modified BIN method was evaluated by the present resistance-capacitance method. The result shows that modified BIN method overpredicts the heating load of the office building 15%. Annual energy consumptions of equipments(fan, boiler, chiller) for various ventilating control system(CAV, VAV, FCU+VAV, FCU+CAV) were compared. FCU+CAV shows the minimum annual energy consumption.

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A Study on Electricity Properties of Polyethylene Terephthalate Film due to Thermally Degradation (열 열화에 의한 폴리에틸렌 테레프탈레이트 필름의 전기 특성에 관한 연구)

  • Lee, Sung Ill
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.11
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    • pp.693-698
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    • 2017
  • In this study, the thermal degradation properties of polyethylene terephthalate film has been examined by the capacitance, Tan ${\delta}$, thermography, FTIR, and SEM results at temperatures of $90{\sim}170^{\circ}C$ and frequencies of 0.3~3,000 kHz. It was found that the capacitance decreased with increasing thermal imaging temperature, probably caused by weakening of chemical bond with increasing temperature. Tan ${\delta}$ decreased upon increasing temperature from $90^{\circ}C$ to $170^{\circ}C$, probably due to the molecular motion of COOH radical or OH radical. The FT-IR measurement reveals that no structural change of the material occurs upon thermal radiation. The SEM measurement shows that the material is stabilized by thermal decomposition with increasing temperature; however, excessive thermal degradation obstructs the stabilization of the material.

Electrochemical Capacitance of Activated Carbons Regenerated using Thermal and Chemical Activation

  • Park, Jung Eun;Lee, Gi Bbum;Hwang, Sang Youp
    • Journal of Electrochemical Science and Technology
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    • v.12 no.3
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    • pp.339-345
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    • 2021
  • Spent activated carbons (SACs) collected from a water treatment plant were regenerated and then adopted as electrochemical material in capacitors. The SACs used in this study were regenerated via two steps, namely thermal and chemical activation. However, during the activation process, the adsorbates were converted into ashes, which caused pore blockage and decreased specific surface area. The regenerated SACs were washed with acid solutions with different levels of acidity (strong: HCl, mild: H3PO4, and weak: H2O2) to remove the ashes. The regenerated SACs washed with HCl exhibited the highest specific surface area, although their capacitance was not the highest. Conversely, the specific surface area of regenerated SACs washed using H3PO4 was slightly lower than that of HCl, but exhibited higher capacitance and electrochemical stability. Although the strong acid removed the generated ashes in the pores efficiently, it could adversely affect their structural stability, which would lead to lower capacitance.

Medium Voltage HTS Cable Thermal Simulation using PSCAD/EMTDC

  • Jung, Chaekyun;Kang, Yeonwoog;Kang, Jiwon
    • KEPCO Journal on Electric Power and Energy
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    • v.1 no.1
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    • pp.145-150
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    • 2015
  • This paper described the medium voltage high temperature superconducting cable thermal simulation and its application. New simulation method for HTS cable modeling using PSCAD/EMTDC is introduced in this paper. The developed simulation method consists of electrical model part and thermal model part. In electrical model part, power loss and thermal capacitance can be calculated in each layer, then the temperature of each layer can be calculated by power loss and thermal capacitance in thermal model part. This paper also analyzes the electrical and thermal characteristic in the case of normal operating condition and transient including single line to ground fault and line to line ground fault using new simulation method.

Thermal Analysis of Lithium-ion Cell Using Equivalent Properties and Lumped Capacitance Method (등가물성 및 집중용량법을 이용한 리튬-이온 전지의 열해석)

  • Lee, Hee Won;Park, Il Seouk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.8
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    • pp.775-780
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    • 2013
  • In general, the battery module of an electric vehicle (EV) consists of lithium-ion cells. A lithium-ion battery is a secondary rechargeable battery, and it consists of numerous stacked plates that serve as electrodes and separators. Owing to these microstructural features, its numerical analysis is very expensive. Therefore, this study aims to present a simplified thermal analysis model using equivalent thermal properties, and we compare the experimental results with numerical results for 185.3Ah and 20Ah cells. Furthermore, we show the thermal behavior of cells without the finite element method (FEM) or finite volume method (FVM) by adopting the lumped capacitance method (LCM).

The study on dielectric properties of $Ta_2O_5$ thin films obtained by thermal oxidation (Thermal Oxidation 법으로 제조된 $Ta_2O_5$ 박막의 유전체 물성에 관한 연구)

  • Kim, I.S.;Kim, H.J.;Min, B.K.;Song, J.S.
    • Proceedings of the KIEE Conference
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    • 2002.07c
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    • pp.1473-1475
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    • 2002
  • This study presents the dielectric properties of $Ta_2O_5$ MIM capacitor structure processed by thermal oxidation. The AES(auger electron emission) depth profile showed thermal oxidation effect gives rise to the $O_2$ deficiened into the new layer. The leakage current density respectively, at $1{\sim}3{\times}10^{-3}$(kV/cm) were $3{\times}10^{-4}-10^{-8}(A/cm^2)$. Leakage current density behavior is stable irrespective of applied electric field, the frequency va capacitance characteristic enhanced stability. The capacitance vs voltage measurement that, $V_{fb}$(flat-band voltage) was increase dependance on the thin films thickness, it is changed negative to positive.

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Effect of Thermal Treatment Temperature on Electrochemical Behaviors of Ni/trimesic Acid-based Metal Organic Frameworks Electrodes for Supercapacitors (수퍼커패시터용 니켈/트리메식 산 기반 금속-유기구조체 전극의 전기화학적 거동에 열처리 온도가 미치는 효과)

  • Kim, Jeonghyun;Jung, Yongju;Kim, Seok
    • Applied Chemistry for Engineering
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    • v.30 no.1
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    • pp.11-16
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    • 2019
  • Ni-benzene-1,3,5-tricarboxylic acid based metal organic frameworks were successfully synthesized by hydrothermal method and thermally treated at various temperature. The electrochemical performance of composites was investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Among all prepared composites, the samples annealed at $250^{\circ}C$ showed the highest capacitance with a low resistance, and high cycle stability. It was possible to obtain the low electrical resistance and high electric conductivity of the electrode by improved microstructure and morphology after the thermal annealing at $250^{\circ}C$. The samples annealed at $250^{\circ}C$ also displayed the maximum specific capacitance with a value of $953Fg^{-1}$ at a current density of $0.66A/g^{-1}$ in 6 M KOH electrolyte. Moreover, a 86.4% of the initial specific capacitance of the composite was maintained after 3,000 times charge-discharge cycle tests. Based on these properties, it can be concluded that the composite could be applied as potential supercapacitor electrode materials.