• 설비공학논문집
• /
• 제13권12호
• /
• pp.1223-1229
• /
• 2001

Though conventional calorimetry methods such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA) are used generally in measuring heat of fusion, T-history method has the advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermal properties of inhomogeneous phase change materials (PCMs) in sealed tubes. However, random criteria (a degree of supercooling) used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제11권1호
• /
• pp.32-39
• /
• 2003

Though conventional calorimetry methods such as differential scanning calorimetry and differential thermal analysis are used generally in measuring heat of fusion, T-history method has advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermophyical properties of in-homogeneous phase change materials in sealed tubes. However, the degree of supercooling used in selecting a range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• 한국기계연구소 소보
• /
• 통권19호
• /
• pp.23-30
• /
• 1989

Heat transfer phenomena of solidification process of the phase change material within cylindrical can is studied experimentally. N-Eicosane paraffin wax is used for phase change material and its melting temperature is 309.8 K. In order to achieve higher heat transfer rate of latent heat storage apparatus, fins in made of copper are used in the cylindrical can. If there are fins in cylindrical can, we can know that the inward latent heat energy in paraffin can be effectively transfered to cooling water than if finless.

• 한국군사과학기술학회지
• /
• 제23권3호
• /
• pp.237-245
• /
• 2020

In this paper, I introduce Phase-Change Cooling for thermal management of high power devices that can be applied to High Power Laser and Electric Propulsion Systems which are composed of multiple distributed superheat sources. Phase-Change Cooling can be good used to efficient cooling of their heat sources. Phase-Change Cooling has extremely high efficiency of two-phase heat transport by utilizing heat of vaporization, relatively low flow rates and reduced pumps power. And I suggest TPI(Thermal Performance Index) which is a quantitative performance index of Phase-Change Cooling for thermal management. I quantify the performance of Phase-Change Cooling by introducing TPI. I present the test results of TPI's changing refrigerant, heat sink and flow rate of the Phase-Change Cooling system through the experiments and analyze these results.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집B
• /
• pp.297-303
• /
• 2000

Natural convection heat transfer have been paid attention because it can be applied to various areas such as cooling of nuclear reactor, heat storing system and so on. Among such applications, the melting process of phase change material(PCM) has been actively studied. However most researches have focused on phase change heat transfer in natural melting. Therefore, In this paper, ultrasonic vibration was adopted to increase the melting rate. In addition, general relationship and corelationship between melting with ultrasonic vibration and melting without ultrasonic vibration have been established during the melting of PCM.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집B
• /
• pp.235-240
• /
• 2001

This study presents experimental work on phase change heat transfer, in order to increase heat transfer rate, ultrasonic vibrations were introduced. Solid-liquid phase change occurs in a number of situations of practical interest. This study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. Some common examples include the melting of edible oil, metallurgical process such as casting and welding, and materials science applications such as crystal growth. Therefore, this study presented the effective way to enhance phase change heat transfer.

• 방재기술
• /
• 통권19호
• /
• pp.9-16
• /
• 1995

The spot-type heat detector is a main component of the automatic fire alarm system intended to signal when heat energy is produced in protected area. The most of protected area in our country is installed spot-type heat detector. On this study, the responsiveness to the change of environmental temp. of spot-type heat detec-tor were obtained and analyzed under specified temp., velocity in accordance with the KOFEIS stan-dard. The experiment was carried under the condition with the change of environmental temp. Concluion of this study is as follows : 1. It was confirmed that the responsiveness of rate-of rise heat detector is sensitive to temp. below 10 degrees above zero. The malfunction appeared at 40 degrees above zero and intended performance is disqualified at 50 degrees above zero. 2. The intended performance of fixed-temp. detector which is maintained for the change of envi-ronmental temp. But the responsiveneness is confirmed instability for the change of environmental temp.

• 복식문화연구
• /
• 제25권6호
• /
• pp.880-892
• /
• 2017

In this study, the appearance change and the heat moisture transfer properties of knitted fabric by yarn shrinkage were examined to obtain useful data on the development of thermo-sensitive functional materials. Eleven types of knitted fabric were knitted using highly bulky acrylic-blended yarn. After shrinking the specimens using dry heat treatment, the appearance change and thickness were measured. An HEC simulator was adopted for measuring the heat moisture transfer properties of specimens by yarn shrinkage. When holes were arranged vertically in the mesh structure, the specimens with 2,500 and 5,000 holes showed high percent change of hole area, appearance, and thickness. When holes were diagonally arranged in the mesh structure, the percent change of hole area in the specimen with 1,250 holes was larger than the one with 2,500 holes. However, the dimensional stability of the specimen with 2,500 holes was better because of its smaller appearance and thickness change. In the tuck structure, the percent change of hole area in the specimen with 625 and 416 holes was relatively large compared with the appearance and thickness change. Furthermore, the hole size in the tuck structure was smaller than that in the mesh structure but the percent change of hole area was larger. Therefore, it was proved that the tuck structure is more suitable than the mesh structure for developing thermo-sensitive functional materials. Heat moisture transfer property test verified that the change of hole area by yarn shrinkage enabled obtaining the thermal effect due to the distinct temperature difference in the inner layer.

• 설비공학논문집
• /
• 제15권8호
• /
• pp.652-660
• /
• 2003

T-history method, measuring heat-of-fusion of phase change material (PCM) in sealed tubes, has the advantages of a simple experimental device and no requirements in sampling process. However, a degree of supercooling used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion in the original method, which has been improved in order to predict better results by us. In the present study, the modified method was applied to a variety of PCM such as paraffin and lauric acid having very small or no supercooling with a satisfactory precision. Also the selection of inflection point and temperature measurement position was fumed out not to affect the accuracy of heat-of-fusion significantly. As a result, the method can provide an appropriate means to assess a new developed PCM by cycle test even if a very accurate value cannot be obtained.

• 한국측량학회지
• /
• 제28권2호
• /
• pp.197-206
• /
• 2010

최근 선진국들은 도시의 열섬현상에 대한 많은 문제점들을 인식하고, 이에 대한 대책을 마련하기 위해 끊임없이 노력하고 있다. 본 연구에서는 위성영상을 이용하여 도심의 개발사업이 진행됨에 따른 토지의 피복변화량을 추출하고 이 변화량이 도심의 열변화에 미치는 영향을 분석하고자 하였다. 1985년 4월, 1994년 8월, 2001년 5월, 2009년 5월에 해당하는 4개의 Landsat 위성영상을 이용하여 대전광역시의 토지피복변화에 따른 열변화를 분석하였다. 도심의 지표면 온도를 추출하기 위해 Landsat TM 열적외선 영역센서인 Band 6의 분광밝기정도를 이용하여 표면온도분포를 산출하였으며, 이를 통해 도시화로 인한 열분포의 변화를 탐지하고자 하였다. 그 결과, 도심지의 면적이 최대 23.59% 상승한 반면 산림지역은 최대 27.91% 감소하였고, 도시화로 인해 도심의 지표온도가 주변지보다 높게 나타났으며, 이 경우 산림지역에 비해 약 $2.4^{\circ}C{\sim}5.7^{\circ}C$ 높게 형성되어 있음을 알 수 있었다.