• 대한기계학회논문집B
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• 제21권5호
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• pp.670-678
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• 1997

A method to mitigate the thermal stratification phenomenon of pressurizer surge line is proposed by heating bottom outside of horizontal pipe. Unsteady two dimensional model has been used to numerically investigate an effect of heating the bottom of pipe. The dimensionless governing equations are solved by using the control volume formulation and SIMPLE algorithm. Temperature and streamline profiles of fluids and pipe walls with time are compared with the previous study result. The numerical result of this study shows that the outside heating can relaxate the thermal stratification flow of the pressurizer surge line. Maximum dimensionless temperature difference between hot and cold sections of the pipe inner wall which causes thermal stratification was reduced from 0.514 to 0.424 at dimensionless time 1, 632 and 1, 500 respectively.

• 설비공학논문집
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• 제1권1호
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• pp.55-63
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• 1989

A one dimensional analytic model for the prediction of the stratification coefficient of a liquid-based solar heating system is developed. The stratification coefficient, $K_s$, is defined as the ratio of the actual useful energy gain to the energy gain that would be achieved if there were no thermal stratification in the storage tank. Previous studies incorporated only collector-side effects, but in this study both the collector and load-side effects are included for the overall performance evaluation.

• 대한설비공학회지:설비저널
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• 제15권1호
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• pp.87-96
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• 1986

An experiment on the devices that enchance the stratification of storage tanks in a solar heat ins system has been carried out. The benefits of thermal stratification in sensible heat storage are to increase the system performance such as the collector efficiency or the fraction of the total load supplied by solar energy. Using the diffuser and the distributor as the stratification enchancement device, the expeliments were perfomed in the different condition of diameter and material of the distributor. As a result of experiments, there exists the diameter of distributor in which the stratification is made maximum under certain design and operation condition. Also it was identified that the kind of distributor material influenced the degree of stratification. Comparing the experimental result to the computational results calculated under the same conditions, the node number N(stratification index) was determined. The results of computer simulation that was performed about the actual solar heating system in Seoul for 24 hours show the relative advantage of stratified over well-mixed storage and the significant improvements in system performance.

• 에너지공학
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• 제6권2호
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• pp.119-128
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• 1997

수평배관의 열성층 유동을 완화하기 위하여 아래부분에 Heat Tracing을 한 수평배관의 외부 가열에 의한 열성층 유동과 열전달 특성을 수치적으로 해석하기 위하여 비정상 2차원 모델을 이용하였다. 무차원 지배방정식은 제어체적방법과 SIMPLE 알고리즘을 사용하여 해를 구하였다. Heat Tracing이 있는 수평배관 내부 열성층 유동의 등온선, 유선분포, Nusselt수, 온도 분포를 해석하였다. 무차원 시간 1,500에서 최대 무차원 온도차가 0.424로 계산되어졌고 무차원 시간 9,000 이후에는 열성층 현상이 없어졌다.

• 디지털융복합연구
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• 제19권6호
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• pp.285-292
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• 2021

최근 코로나19 사태로 캠핑 문화가 급속하게 많은 사람들에게 관심을 받고 있다. 많은 캠퍼들이 겨울철 사용하는 대류난방기구는 온도 성층화 문제를 가지고 있다. 이를 해결하기 위해 다양한 동력 서큘레이터가 활용되고 있다. 몇 가지 무동력 서큘레이터도 판매가 되고 있으나, 서큘레이터의 방향이 대류난방기구와 직각으로 디자인되어 있어 실제 공기 순환의 역할을 제대로 하지 못하고 있다. 이러한 문제점을 해결하고자 3D 프린터를 이용하여 대류난방기구의 방향과 같은 무동력 서큘레이터를 디자인하였다. 펠티어소자와, 세라믹페이퍼 등을 이용하여 무동력으로 전기를 만들어 냈으며, HTPLA-CF 필라멘트를 이용하여 열에 강하게 제작하였다. 3D 프린터를 이용하여 원가를 절감할 수 있었으며, 다양한 대류난방기구의 크기에 맞게 제작 할 수 있는 장점이 있다. 본 연구는 효율적인 대류순환을 통해 온도 성층화 문제를 해결할 수 있는 하나의 방법을 제시한다. 또한 3D 프린터를 이용하여 보다 저렴하게 제품을 제작하는 것이 본 연구의 목적이다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.304-309
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• 1997

A method to mitigate the thermal stratification flow of a horizontal pipe line is proposed by heating external bottom of the pipe with electrical heat tracing. Unsteady two dimensional model has been used to numerically investigate an effect of the external Denting to the thermally stratified flow. The dimensionless governing equations are solved by using the control volume formulation and SIMPLE algorithm. Temperature distribution, streamline profile and Nusselt numbers of fluids and pipe walls with time are analyzed in case of externally heating condition. no numerical result of this study shows that the maximum dimensionless temperature difference between the hot and the cold sections of pipe inner wall is 0.424 at dimensionless time 1,500 ann the thermal stratification phenomena is disappeared at about dimensionless time 9,000. This result means that external heat tracing can mitigate the thermal stratification phenomena by lessening $\Delta$ $T_{ma}$ about 0.1 and shortening the dimensionless time about 132 in comparison with no external heat tracing.rnal heat tracing.

• 설비공학논문집
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• 제26권1호
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• pp.8-14
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• 2014

We have performed experiments to enhance the stratification in a storage tank in order to raise the collector efficiency and solar fraction in solar thermal systems. The storage tank with a spiral jacket in the side wall has a scroll-shaped heat exchanger coil added to the upper part. The performance was compared between only the side and upper-side heating part through simulation using TRNSYS under the same weather conditions and initial conditions. As a result, the upper-side heating has a 4.2% advantage in solar fraction, but almost no increase in collector efficiency.

• 한국환경과학회지
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• 제6권6호
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• pp.579-588
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• 1997

In order to see the stratification related to the heat flux In Deukryang Bay, the oceanographic data on July 12, 1994 and the meteorological data of Kohung and Kwangju meteorological stations were analysed. The temperature durerences between the sea surface and the near bottom were 1~3 ton spring tide (July 12, 1994) In Deukryang Bay. The temperature anomalies were high about 3t during summer In 1994. These mean that the non mixing was not effective In destroying the stratification due to the sea surface heating by the solar radition, even though it was on spring tide. The maximum solar radiation was about 600 ly/day, which was the value of the same date of oceanographic observation. The sensible and the latent heat flux which are 0~100 ly/day were not so varied during summer. The absorbed heat flux through the sea surface was mostly lost by the back radiation. which ranges are about 0~-400 ly/day. The dimensionless mixing parameter related to the buoyancy flux was 5~150$\times$$10^{-5}$. The efficiency of tidal mixing to destroy the stratecation was 0.4~0.6%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.188-192
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• 2006

This study is conducted to improve efficiency of thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from solar or the others heat sources. However, it has difficulties in storing heat with uniform temperature through the entire tank with respect to vertical direction. This kind of maldistribution of the supplied heat to the storage tank effects on the system performance. In this study is focused on utilization of the thermal stratification to improve thermal comfort for people in the house. To enhance temperature stratification of the tank, a distributor was designed and Installed in the middle of the tank. The distributor is supplies hottest water to the top side of the tank which is very close to inlet of the supply line to the heating load. The hottest water that is accumulated on top side of the tank is firstly supplied to the load with higher temperature. Reminder water takes a little time to warming up until desired supply temperature reached. This kind alternating selection of the supply temperature is improve thermal comfort with moderated system performance.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.43-49
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• 2007

This study is conducted to improve the efficiency of a thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from the solar or the others heat sources. However, it has difficulties in storing heat with nonuniform temperature through the entire tank with respect to the vertical direction, This study is focused on the thermal stratification to improve thermal comfort for the resident in house. To enhance temperature stratification of the tank, a distributor was designed and installed in the middle of the storage tank vertically. The vertically designed distributor could supply the return water with stratified temperature in the storage tank with respect to the height. The water velocity from the distributor hole is the same with the other outlet in the distributor. However, gravity effect on the flow in the storage tank is much higher than that of the velocity effect due to that Froude Number is less than 1. During the heat charging process in the storage tank, temperature maintained with little difference with respect to the height. However the charging process takes long time to get a effective temperature for the heating or hot water supply because of all of water in the storage tank needs to be heated.