• Journal of Mechanical Science and Technology
• /
• 제15권11호
• /
• pp.1533-1540
• /
• 2001

A high-temperature sodium stainless steel heat pipe was fabricated and its performance has been investigated. The working fluid was sodium and it was sealed inside a straight tube container made of stainless steel. The amount of sodium occupied approximately 20% of the total volume of the heat pipe and its weight was 65.7gram. The length of a stainless steel container is 1002mm and its outside diameter is 25.4mm. Performance tests were carried out in a room air condition under a free convective environment and the measured temperatures are presented. The start-up behavior of the heat pipe from a frozen state was investigated for various heat input values between 600W and 1205W. In steady state, axial temperature distributions of a heat pipe were measured and its heat transfer rates were estimated in the range of vapor temperature from 50$0^{\circ}C$ to 63$0^{\circ}C$. It is found that there are small temperature differences in the vapor core along the axial direction of a sodium heat pipe for the high operating temperatures. But for the range of low operating temperatures there are large temperature drops along the vapor core region of a sodium heat pipe, because a small vapor pressure drop makes a large temperature drop. The transition temperature was reached more rapidly in the cases of high heat input rate for the sodium heat pipe.

• 청정기술
• /
• 제18권3호
• /
• pp.320-324
• /
• 2012

본 연구에서는 리튬이온전지의 방전특성에 따른 열발생 속도를 계산하여 전지의 특성을 평가하였다. 이를 위하여 Butler-Volmer 식을 지배방정식으로 하여, 유사 2차원 모델링을 적용하고, 편미분 연산자인 FEMLAB을 이용하여 전산모사를 수행하였다. 전류밀도를 5 $A/m^2$에서 25 $A/m^2$까지 증가시켜 계산을 수행한 결과, 전류밀도가 증가함에 따라 전극표면에서 고체상 리튬의 소모량이 증가되는 것으로 나타났다. 이로 인한 확산제한의 발생시점이 단축되었으며, 동시에 리튬이온전지의 내부 전위가 컷오프 전위에 도달하는 시점에서 열발생 속도가 급격하게 증가되는 현상을 보여주었다.

• 전력전자학회논문지
• /
• 제6권6호
• /
• pp.572-581
• /
• 2001

최대 1800W의 열부하를 발생하는 전력반도체를 냉각하는 히트파이프 히트싱크를 설계하고 제작하였다. 히으파이프 냉각장치는 4개의 외경 22.23mm 인 FC-72 히트파이프, 알루미늄 블록 (130${\times}$160${\times}$35mm) 및 126개의 알루미늄핀 (250${\times}$58${\times}$0.8mm)으로 구성되어 있다. 성능 실험결과 총열저항은 1~2kW의 열부하일때 2~3m/s의 풍속에 풍속의 증가에 따라 0.02~0.018$^{\circ}C$/W 를 나타냈다. 이 결과는 3 m/s의 풍속에서 1800W의 열부하가 주어질 때 $40^{\circ}C$미만의 온도상승을 나타내는 것으로 설계 목표를 잘 만족하였다. 이 외로 대류 및 히트파이프의 열저항의 실험값은 몇가지 상관식에 의한 예측값과 비교적 잘 일치하였다.

• 신재생에너지
• /
• 제18권4호
• /
• pp.12-21
• /
• 2022

The pyrolysis characteristics of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) were analyzed numerically using a 1D plug flow reactor (PFR) model. A lumped kinetic model was selected to simplify the pyrolysis products as wax, oil, and gas. The simulation was performed in the 400-600℃ range, and the plastic pyrolysis and product generation characteristics with respect to time were compared at various temperatures. It was found that plastic pyrolysis accelerates rapidly as the temperature rises. The amounts of the pyrolysis products wax and oil increase and then decrease with time, whereas the amount of gas produced increases continuously. In LDPE pyrolysis, the pyrolysis time was longer than that observed for other plastics at a specified temperature, and the amount of wax generated was the greatest. The maximum mass fraction of oil was obtained in the order of HDPE, PP, and LDPE at a specified temperature, and it decreased with temperature. Although the 1D model adopted in this study has a limitation in that it does not include material transport and heat transfer phenomena, the qualitative results presented herein could provide base data regarding various types of plastic pyrolysis to predict the product characteristics. These results can in turn be used when designing pyrolysis reactors.