• 설비공학논문집
• /
• 제9권2호
• /
• pp.104-111
• /
• 1997

The freezing phenomenon of saturated water with the supercooled region in a horizontal circular cylinder has been studied experimentally by using the holographic real time interferometry technique. From the experiments, it was found that there were three types of freezing patterns. The first is the annular ice layer growing from the cylinder surface at a high cooling rate; the next is the asymmetric ice layer at a moderate cooling rate; and the last is the instantaneous ice layer growth over the full region at lower cooling rate. As the water was coolde from room temperature to the subfreezing point passing through the density inversion point, the freezing pattern was largely affected by the inversion phenomenon, which had much effected the free convection and was susceptible to influences from the cooling rate. When the cooling rate is high, supercooling energy is released before the water is sufficientry mixed by free convection. On the other hand, when the cooling rate is low, there is much time for the water to be mixed by free convection. This seems to be the reason why the different ice layer growths occur.

• 한국기계가공학회지
• /
• 제17권6호
• /
• pp.144-150
• /
• 2018

In this study, the freezing process of L-shaped pipe exposed to the outside was investigated numerically by considering the mushy zone of freezing water. From the numerical results, it was found that the flow was outwardly directed due to the influence of the L-shaped bending part in the outside exposed part of the pipe, and the ice was formed in the shape of longitudinal corrugation on the wall surface of the pipe after the bending part. It is confirmed that this phenomenon is caused by the venturi effect due to the freezing as seen in connection with the velocity distribution in the pipe. It is found that the remelting phenomenon at the end of the freezing section occur simultaneously during the process of forming the ice in the pipe section. In regard of the factors affecting freezing, it was found that the thickness of the freezing layer is increased as the exposed pipe surface temperature is decreased, and the pipe surface temperature had a significant effect on the change of the freezing layer thickness. At the same time, it was found that the freezing layer becomes relatively thin when the water inflow rate is increased. This phenomenon was caused by reducing the exposure time of freezing water due to the vigorous flow convection of the water fluid.

• 대한기계학회논문집B
• /
• 제21권7호
• /
• pp.862-872
• /
• 1997

Ice formation in a horizontal circular cylinder has been studied numerically. From the numerical analysis results, it was found that there were three types of freezing pattern and that freezing phenomenon was affected largely by density inversion and cooling rate. The type of freezing pattern largely depends on the secondary flow which is generated by density inversion. When supercooling energy is released before the development of the secondary flow, the annular ice layer grows. If the energy is released when the secondary flow is considerably developed and the supercooled region is removed to the upper half part of the cylinder, an asymmetric ice layer grows. And if the energy is released after perfect development of the secondary flow, instantaneous dendritic ice formation over the full region occurs. Furthermore, this secondary flow was found to have an effect on heat transfer characteristics. The heat transfer rate becomes small at the instant when the secondary flow is generated, but becomes large with the development of the flow. It's concluded that for the facilitation of heat transfer it is desirable to keep water in liquid phase until the secondary flow is perfectly developed. This study gave an instruction of performance improvement of capsule type ice storage tank.

• 한국과학교육학회지
• /
• 제25권2호
• /
• pp.88-97
• /
• 2005

이 연구에서는 어는점 내림에 대한 과학교과서의 설명 방식과 과학 교사들의 개념을 조사하였다. 분석한 교과서는 7차 교육과정에 근거하여 개발된 중학교 2학년 과학교과서 7종과 고등학교 화학 II 교과서 5종이었다. 교사들의 개념은 설문지를 통해 얻었으며, 연구 대상 교사의 수는 146명이었다. 교과서의 설명 유형은 '현상을 묘사' 하는 것과 '증기압 내림으로 설명' 하는 유형으로 구분하였다. 대부분의 중학교 교과서와 고등학교 교과서에서는 현상을 묘사하는 수준으로 어는점 내림을 설명하였으며, 이러한 현상이 일어나는 이유에 대한 설명은 없었다. 또한 어는점 내림을 설명하는 그래프의 내용도 교과서마다 달랐다. 교사들 역시 어는점 내림에 대해 제대로 이해하지 못하는 것으로 나타났다. 용질의 방해로 어는점 내림 현상을 이해하는 교사들도 많았다. 그러나 끓는점 오름 현상을 설명할 때 도입되는 이러한 개념이 어는점 내림에서는 어떻게 관련되는지 명확하게 설명하지 못하였다. 이 연구에서는 어는점 내림 현상을 설명하기 위하여 엔트로피의 개념을 도입할 필요성에 대해 주장하였다.

• 한국초등과학교육학회지:초등과학교육
• /
• 제32권2호
• /
• pp.206-224
• /
• 2013

The purpose of this study is to investigate the elementary pre-service teachers' conceptions on 'the freezing point depression' focusing on the survey from a National University of Education. Eighteen pre-service teachers who had completed high school Chemistry II coursework were selected to participate in the study. Participants answered a four question survey to measure their scientific knowledge and conceptions of this phenomenon. Each answer was qualitatively analyzed to determine whether they have 'scientific conceptions' or 'quasi-scientific conceptions' or 'misconceptions'. The results from the study are as follows: First, it was showed that none of the eighteen participants had 'scientific conceptions', six had 'quasi-scientific conceptions' and eight had 'misconceptions' about the caused effect when $CaCl_2$ is scattered on the ice. Second, it was found that three participants had 'scientific conceptions', eight had 'quasi-scientific conceptions' and two had 'misconceptions' for the second survey question. Third, ten out of eighteen participants demonstrated 'scientific conceptions' about the phenomenon of salt water freezing. Fourth, only three of eighteen participants illustrated appropriate 'scientific conceptions' for the fourth survey question. Fifth, of all participants, none answered more than three questions correctly, and only three participants answered any combination of two questions correctly. Based on the findings of this study, five explanatory models were developed. And the models were proposed for pre-service teachers to enhance their understanding of the freezing point depression phenomenon.

• Journal of Advanced Marine Engineering and Technology
• /
• 제23권3호
• /
• pp.275-283
• /
• 1999

• 한국지열·수열에너지학회논문집
• /
• 제6권1호
• /
• pp.17-22
• /
• 2010

A sliding accident on the road have a high percentage by road freezing, especially, it is often appeared at bridges and tunnel of freezing areas. Thus, the stability of road operations is enhanced by preventing a partial freezing phenomenon. According to the geothermal snow melting system analysis, a pattern of thermal conductivity is found out about pavement materials of concrete and asphalt when it is buried. For the feasibility study on geothermal snow melting system, analysis of the ground melting point when operating system, life evaluation of pavements and safety evaluation of pipes are performed.

• 한국해양공학회지
• /
• 제27권6호
• /
• pp.106-111
• /
• 2013

In this study, numerical simulations and performance evaluation has been carried out to investigate performance characteristics of air-type high pressure piston pump. ANSYS and CFX were applied for analyzing the structure and flow behavior of air-type high pressure piston pump, respectively. The performance evaluation of high pressure piston pump was performed experimentally, the results were compared with simulation. It was found that the freezing phenomenon was improved by 20% and the pressure fluctuation decreased by 50%, compared with the previous pump.

• 한국지역지리학회지
• /
• 제7권1호
• /
• pp.97-106
• /
• 2001

한국에는 하계 동결현상이라는 특수기상이 나타나는 곳이 수 군데 존재한다. 특히 경남 밀양의 천황산 얼음골과 경북 의성 법계계곡의 빙혈 그리고 경북 청송의 얼음골은 이러한 기상적 특성 때문에 관광지로 유명한 곳이다. 본 연구에서는 한국 하계 동결현상 3대 분포지로 볼 수 있는 상기의 지역들을 대상으로 기존의 미기상학적 수문학적 연구를 참고하여 지형학적 지질학적 측면에서 접근하여 다음의 연구결과를 얻었다. 첫째, 하계 동결현상 분포지에서 볼 수 있는 지형 및 지질적특성은 두터운 거력 퇴적물로 구성된 애추사면의 존재, 일사량이 적은 북향사면이거나 또는 비교적 깊은 곡벽으로 둘러 쌓여 상대적으로 일사량이 적은 지역, 안산암 또는 유문암 등의 화산암 질로 구성되는 거력 퇴적물의 특성 등이다. 둘째, 하계 동결현상을 야기시키는 시스템으로서 얼음굴은 공기의 유통이 자유로움 공간이 많이 존재하며, 일부 공간은 매우 넓어 동굴을 형성하며 부분적으로 지하수계와 연결되어 있는 경우를 가정할 수 있다. 넷째, 하계 동결현상이 나타나기 위해서는 얼음굴 내에 있는 지하수제의 부분적 동결이 필요하며, 이를 위해서는 두 가지의 가정이 요구된다. 하나는 외부로부터 얼음굴로 유입된 공기의 기화열에 의한 지하수제의 급랭이며, 또 다른 하나는 지난 겨울 동안 동결된 지하수제가 특수한 지형적 영향으로 동결상태가 장기간 지속되어야 한다. 그러나 명확한 원인은 얼음굴에 대한 시추작업을 통해서 만이 가능할 것이다.

• 한국환경과학회지
• /
• 제26권7호
• /
• pp.827-836
• /
• 2017

Freezing rain is a phenomenon when precipitation falls as a liquid rain drop, but freezes when it comes into contact with surfaces or objects. In this study, we investigated the predictability of freezing rain and its characteristics, which are strongly related with the occurrence of black ice using synoptic scale meteorological observation data. Two different cases occurred at 2012 were analyzed and in the presented cases, freezing rain often occurs in the low-level low pressure with the warm front. The warm front due to the lower cyclone make suitable environment in which snow falling from the upper layer can change into supercooled water. The $0^{\circ}C$ temperature line to generate supercooling water is located at an altitude of 850 hPa in the vertical temperature distribution. And the ground temperature remained below zero, as is commonly known as a condition for black ice formation. It is confirmed that the formation rate of freezing rain is higher when the thickness after 1000-850 hPa is 1290-1310 m and the thickness of 850-700 hPa layer is larger than 1540 m in both cases. It can also be used to predict and estimate the generation of freezing rain by detecting and analyzing bright bands in radar observation.