• Composites Research
• /
• 제28권3호
• /
• pp.99-103
• /
• 2015

본 논문에서는 복합재료 제조공정 중 온도에 따른 경화 반응을 이해하고 열분석을 수행하였으며, 이 결과를 바탕으로 온도에 따른 수지의 경화도 및 비열의 변화를 수식화하였다. 온도에 따른 경화도와 비열은 DSC와 MDSC (Modulated DSC)를 활용하여 측정하였다. DSC와 MDSC 분석은 Isothermal과 Dynamic 조건으로 수행하여 Cure Kinetics, 유리전이온도 및 비열을 측정하고, 회기 분석 방법을 이용하여 물성거동을 수학적으로 모델링하였다.

• 센서학회지
• /
• 제32권1호
• /
• pp.39-43
• /
• 2023

Microscale thermophysical property measurements of liquids have been developed considering the increasing interest in the thermal management of cooling systems and energy storage/transportation systems. To accurately predict the heat transfer performance, information on the thermal conductivity, heat capacity, and density is required. However, a simultaneous analysis of the thermophysical properties of small-volume liquids has rarely been considered. Recently, we proposed a new methodology to simultaneously analyze the aforementioned three intrinsic properties using heater-integrated fluidic resonators (HFRs) in an atmospheric pressure environment comprising a microchannel, resistive heater/thermometer, and mechanical resonator. Typically, the thermal conductivity and volumetric heat capacity are measured based on a temperature response resulting from heating using a resistive thermometer, and the specific heat capacity can be obtained from the volumetric heat capacity by using a resonance densitometer. In this study, we analyze methods to improve the thermophysical property measurement performance using HFRs, focusing on the effect of the ambience around the sensor. The analytical method is validated using a numerical analysis, whose results agree well with preliminary experimental results. In a vacuum environment, the thermal conductivity measurement performance is enhanced, except for the thermal conductivity range of most gases, and the sensitivity of the specific heat capacity measurement is enhanced owing to an increase in the time constant.

• 한국전기전자재료학회논문지
• /
• 제30권5호
• /
• pp.318-324
• /
• 2017

Powder compaction technology is widely used to prepare thermal battery components. This method, however, is limited by the size, thickness, and geometry of the battery components. This limitation leads to excessive cell capacity, overweight, and higher cost of the pellets, which decreases the specific capacities and delays the activation time of thermal batteries. $FeS_2$ thin-film cathodes were fabricated by tape-casting technology and analyzed by SEM and EDS in this paper. The residual organic binder of the $FeS_2$ thin-film cathodes decreased with the temperature of the heat treatment, which improved the specific capacity because of the lower resistance. Specific capacities of the $FeS_2$ thin-film cathodes decreased because of the higher residual binder and the restrictive reaction of active materials with molten salts as the thickness increased. $FeS_2$ thin-film cathodes showed much higher specific capacity (1,212.2 As/g) than pellet cathodes (860.7 As/g) at the optimal heat-treatment temperature ($230^{\circ}C$).

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집C
• /
• pp.305-310
• /
• 2001

Within some degree of journal misalignment, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined under the condition of variable density and specific heat. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the effects of variable density and specific heat on shaft misalignment are significant in determining the load capacity of a journal bearing operating at high speed.

• 방사성폐기물학회지
• /
• 제15권3호
• /
• pp.199-206
• /
• 2017

고준위폐기물을 처분하기 위한 심층 처분시설은 지하 500~1,000 m 깊이의 암반층에 설치된다. 심층 처분시스템의 구성 요소로는 처분용기, 완충재, 뒷채움 및 근계 암반이 있다. 이 중 완충재는 심층 처분시스템에 있어 필수적인 요소인데, 완충재는 지하수 유입으로부터 처분용기를 보호하고, 방사성 핵종 유출을 저지한다. 처분용기에서 발생하는 고온의 열량은 완충재로 전파되기에 완충재의 열물성은 처분시스템의 안정성 평가에 상당히 중요하다고 할 수 있다. 완충재의 열전도도 규명에 대한 연구는 많이 진행되고 있는 반면, 비열에 대한 연구는 미진한 상태이다. 따라서 본 연구에서는 국내 경주산 압축 벤토나이트 완충재(KJ-II)에 대한 비열 추정 모델을 개발하고자 하였다. 압축 벤토나이트 완충재의 비열은 이중 탐침법을 이용하여 다양한 포화도와 건조밀도에 따라 측정하였으며, 총 33개의 실험 데이터를 토대로 회귀분석을 이용하여 경주 압축 벤토나이트의 비열을 추정할 수 있는 모델을 제시하였다.

• 임산에너지
• /
• 제21권2호
• /
• pp.62-68
• /
• 2002

본 실험에서는 합판벽체내의 단열재 종류에 따른 단열성능을 비교 평가하였다. 열의 통과량을 비교해 보기 위하여 열관류 실험을 하였다. 열관류 실험결과 스티로폼과 유리섬유의 열관류율이 적게 나타났다. 용적비열은 황토보드와 집성목이 높은 결과를 나타내었다. 합판 벽체로 제작된 모형 주택을 이용한 실내외 온도변화를 비교해 본 결과 단열재료로스티로폼과 유리섬유를 사용한 벽체의 경우 외부 온도에 쉽게 영향을 받는 것을 알 수 있었으며 용적비열이 높은 황토보드, 황토ㆍ톱밥 혼합재, 집성목을 사용한 벽체의 경우는 외부온도의 변화에 비해 적은 온도변화를 보였다. 실험결과 열관류율은 스티로폼과 유리섬유가 작았지만 용적비열이 높은 황토보드와 황토ㆍ톱밥 혼합재, 집성목이 단열성능면에서 우수함을나타내었다.

• 열처리공학회지
• /
• 제13권4호
• /
• pp.231-238
• /
• 2000

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of pouring temperature on the damping capacities and mechanical properties were investigated in 3.6%C cast iron. At $1400^{\circ}C$, specific damping capacity showed the maximum value, and decreased with increase pouring temperature. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ni on the damping capacities and mechanical properties have been investigated in 3.6%C gray cast iron. At 0.2%Ni content, specific damping capacity showed the maximum value, and decreased with further increase in Ni content. Graphite length also showed same behavior. This indicates that the specific damping capacity has a close relation with graphite length. In case of Mo addition in 3.6%C-0.2%Ni cast iron, specific damping capacity and tensile strength was 27% and $20kgf/mm^2$ at 3.6%C-0.2%Ni-0.3%Mo cast iron respectively.

• 한국초전도ㆍ저온공학회논문지
• /
• 제21권1호
• /
• pp.40-44
• /
• 2019

This study investigates mixtures of water and cryoprotectant agents (CPAs) to store high-grade cold energy. Although water is an ideal material for a cold thermal storage (CTS) due to its high specific heat, undesirable volume expansion may cause structural stresses during freezing. The volume expansion can be alleviated by adding the CPAs to water. However, the CPA aqueous solutions not only have different thermal properties but also transit to amorphous state different from pure water. Therefore, these characteristics should be considered when using them as material of the CTS. In experiments, glycerol and dimethyl sulfoxide (DMSO) are selected as the candidate CPA. The volume expansion of the solution is measured by an in-situ strain gauge in low temperature region. The specific heat capacity of the solution is also measured by differential scanning calorimetry (DSC). Both the amount of volume expansion and the specific heat capacity of the CPA aqueous solution decrease in the case of higher concentration of CPA. These characteristics should be contemplated to select optimal aqueous solution for CTS for liquid air energy storage system (LAES). The CPA solutions have advantages of having wide temperature range to utilize the latent heat of water and higher sensible heat of the CPA. The CPA solutions which can satisfy the allowable stress of the structure are determined. Consequently, among the CPA solutions investigated, DMSO 20% w/w solution is the most suitable for the CTS.

• 열처리공학회지
• /
• 제14권6호
• /
• pp.330-335
• /
• 2001

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which Is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of Sb on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni gray cast iron. At 0.02%Sb, specific damping capacity showed the maximum value, and decreased with further increase in Sb content. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ti on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni-0.02%Sb gray cast iron. Specific damping capacity increased with increase in Ti content. Graphite length also showed same behavior. Tensile strength increased with Ti content due to refinement of pearlite. In the case of 0.14%Ti addition in 3.6%C-0.2%Ni-0.02%Sb cast iron, specific damping capacity and tensile strength was 36% and 25 $kgf/mm^2$ which are higher than 32% and 15 $kgf/mm^2$ at 3.6%C-0.2%Ni cast iron respectively.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
• /
• pp.489-494
• /
• 2004

In this paper, we investigated impurities content and thermal properties showing by changing the content of carbon black which is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICP-AES(Inductively Coupled Plasma Atomic Emission Spectrometer), and density of specimens were measured by density meter. And then heat capacity(${\Delta}H$) and melting temperature(Tm), specific heat(Cp) were measured by DSC(Differential Scanning Calorimetry). The dimension of measurement temperature was $0[^{\circ}C]\;to\;200[^{\circ}C]$, and rising temperature was $4[^{\circ}C/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result also density was increased according to these properties. Specially, impurities content values of the A1 and A2 of existing resins were measured more than 4000[ppm]. Heat capacity, melting temperature, and specific heat from the DSC results were simultaneously decreased according to increasing the content of carbon black. Because metallic impurities of carbon black having Fe, Co, Mn, A1 and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.