• 태양에너지
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• 제9권3호
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• pp.37-43
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• 1989

This paper dealt with thermal storage efficiency due to difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank [$0.5m{\times}0.5m{\times}1.0m$] and the temperature of water flowing into the tank, flow rate of water flowing into the tank and shape of porous manifold which water flow into the tank through. As results of experiments; (1) When the flow rate was constant and the diameter of porous section decreased by 8mm, 6mm, and 4mm, the thermal storage efficiency increased. (2) When the diameter of porous section was constant and the difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank and the temperature of water flowing into the tank increased by -30, -20, -10, 5, 10, 15 ($^{\circ}C$), the thermal storage efficiency increased. (3) When the($T_{\infty}-Ti$) was constant and the flow rate decreased by 0.8, 0.4, 0.25(LPM), the thermal storage efficiency increased. (4) When the shape of porous section was rigid, the thermal storage efficiency was the most effective, and with establishing flexible porous section or mesh, the effective thermal storage efficiency was obtained.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.158-164
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• 2004

In the present work, the numerical model was refined to predict the thermal analysis of energy storage in a fixed beds during charging mode. The governing energy equations of both fluid and the solid particles along with their initial and boundary conditions are derived using a two-phase, one dimensional model. The refined model is carried out by taking into account change of (air density , air specific heat) with air temperature and also by taking into considerations heat losses from bed to surrounding. Finite difference method was used to obtain solution of two governing energy equations of both fluid and solid particles through a computer program especially constructed for this purpose. The temperature field for the air and the solid are obtained, also energy stored inside the bed is computed. A comparison between refined model and non refined model is done. Finally using refined model the effect of bed material (Glass, Fine clay ,and aluminum ), and air flow rate per unit area Ga (0.3, 0.4, and 0.5 kg/$m^2$-s) on energy storage characteristics was studied.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3581-3590
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• 2023

High-temperature design evaluations were conducted on Type 316L stainless steel piping for a 700 ℃ large-capacity thermal energy storage verification test loop (TESET) under construction at KAERI. The hot leg piping with sodium coolant at 700 ℃ connects the main components of the loop heater, hot storage tank, and air-to-sodium heat exchanger. Currently, the design rules of ASME B31.1 and RCC-MRx provide design procedures for high-temperature piping in the creep range for Type 316L stainless steel. However, the design material properties around 700 ℃ are not available in those rules. Therefore, a number of material tests, including creep tests at various temperatures, were conducted to determine the insufficient material properties and relevant design coefficients so that high-temperature design on the 700 ℃ piping may be possible. It was shown that Type 316L stainless steel can be used in a 700 ℃ high-temperature piping system of Generation IV reactor systems or a renewable energy systems, such as thermal energy storage systems, for a limited operation time.

• 터널과지하공간
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• 제22권3호
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• pp.188-195
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• 2012

본 연구에서는 전산유체역학 코드인 FLUENT를 이용하여 열에너지 지하 저장을 위한 최초의 대규모 암반공동인 스웨덴 Lyckebo 저장소의 열성층화 거동을 분석하였다. 열에너지의 반복적인 저장 및 생산으로 인한 주변 암반의 히팅이 열성층화와 열손실에 미치는 영향을 분석하기 위해 암반의 온도조건을 달리하여 열전달 해석을 수행하였으며, 성층화 지수를 토대로 열에너지 저장 후 시간경과에 따른 열성층화의 변화를 정량적으로 분석하였다. 분석결과, 주변 암반이 히팅되지 않은 저장공동의 초기 운영단계에서는 시간경과에 따라 저장된 열에너지의 성층화가 빠르게 저하되는것으로 나타났으며, 저장공동의 운영기간이 늘어남에 따라 주변 암반의 히팅으로 인해 열성층화의 변화 및 열손실이 줄어드는 것을 확인하였다.

• 한국농촌건축학회논문집
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• 제19권4호
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• pp.49-56
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• 2017

Each country in the world currently concentrates on shifting into clean energy, which can be alternative energy, for global environment protection and solution to the problem of fossil fuel depletion. The Korean government is predicted to develop renewable energy, such as solar power, ground power, and offshore wind power, and to increase their supply ratios by ending the use of coals and nuclear power plants. This study conducted experiments on thermal storage performance of Trombe wall thermal storage materials using solar power and simulations in order to offer baseline data for the development of a hybrid air circulation system for heating that can maximize efficiency by simultaneously using solar and geothermal power. The study results are as follows: (1) In all the specimens with 3m, 5m, and 7m in the length of thermal storage pipe, $5.7^{\circ}C$, $7.8^{\circ}C$, and $10.5^{\circ}C$ rose, respectively, as the thermal storage effect of the specimens attaching insulation film and black tape to the general funnel. They were most excellent in terms of thermal storage effect. (2) As a result of thermal performance evaluation on the II type specimens, II-3 ($7.8^{\circ}C$ rise) > II-4 ($5.3^{\circ}C$ rise) > II-1 ($3.9^{\circ}C$ rise) > II-2 ($2.3^{\circ}C$ rise) was revealed, and thus II-3 (insulation film + black tape) was most effective as shown in the I type. (3) This study analyzed air current and temperature distribution inside of the greenhouse by linking actually measured values and simulation interpretation results through the interpretation of CFD (computational fluid dynamics). As a result, the parts absorbing heat and discharging heat around the thermal storage pipe could be visibly classified, and temperature distribution inside of the greenhouse around the thermal storage pipe could be figured out.

• Journal of Biosystems Engineering
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• 제16권4호
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• pp.399-407
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• 1991

In Korea, the cultivation area under the plastic greenhouse was 1,746 ha in 1975, and 36,656 ha in 1989, it shows that the greenhouse cultivation area was increased by 21 times during last 14 years. The greenhouse cultivation area of 90~93% has been kept warm with double layers of plastic film and thermal curtain knitted with rice straw, and the rest area of 7~10% has been heated by fossil fuel energy. The use of rice straw thermal curtain is inconvenient to put it on and off, on the other hand the use of fossil fuel heating system results in the increase of production cost. To solve these problems, at first the heating load and the storable solar energy in greenhouse during the winter season were predicted to design solar utilization system, secondly a solar thermal storage system filled with latent heat storage materials was developed in this study. And then finally the thermal performance of greenhouse-solar energy storage system was analyzed theoretically and experimentally.

• 한국태양에너지학회 논문집
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• 제33권5호
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• pp.82-88
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• 2013

There are the stirring test and drain test in the daily performance test to determine the thermal performance of a domestic solar hot water system. The drain test is a test that measures the discharge heating rate while drain the hot water from the top of the storage tank and supply the city water to the bottom of the tank. From the perspective of the user, this drain test is more effective than the stirring test. In this study, the thermal performance were compared through the drain test for a passive type and an active type domestic solar hot water systems consisting of the same storage tank and collectors. At this point, a passive type was used the horizontal storage tanks, and an active type was used vertical storage tank. In the drain test, when the hot water drained up to the reference hot water temperature, an active type which have vertical storage tank represents excellent daily performance than a passive type which have horizontal storage tank regardless of weather conditions. The reason for this is because the vertical storage tank is advantageous to thermal stratification in the tank. After the drain test, the residual heat for the horizontal storage tank was much more than the vertical storage tank, but in the next day the amount of discharged heat were less than the those of vertical storage tank neither. Thus, the solar water heating system which have horizontal storage tank should be adopted preheating control method rather than separate using control method when connected with auxiliary heat source device.

• 설비공학논문집
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• 제28권8호
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• pp.305-310
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• 2016

A thermal storage systems was designed to correspond to the temporal or quantitative variation in the thermal energy demand, and most of its heat is stored using the latent and sensible heat of the heat storage material. The heat storage method using latent heat has a very complex phenomenon for heat transfer and thermal behavior because it is accompanied by a phase change in the course of heating/cooling of the heat storage material. Therefore, many studies have been conducted to produce an experimentally accessible as well as numerical approach to confirm the heat transfer and thermal behavior of phase change materials. The purpose of this study was to investigate the problems encountered during the actual heat transfer from an internal storage tank through simulation of the process of storing and utilizing thermal energy from the thermal storage tank containing charged PCM. This study used analysis methods to investigate the heat transfer characteristics of the PCM with simultaneous heating/cooling conditions in the rectangular space simulating the thermal storage tank. A numerical analysis was carried out in a state considering natural convection using the ANSYS FLUENT(R) program. The result indicates that the slope of the liquid-solid interface in the analysis field changed according to the temperature difference between the heating surface and cooling surface.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.169-170
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• 2022

Due to the higher use of nonrenewable fossil fuel energy, environment friendly sustainable energy from waste materials is attracting attention of the researchers. Considering that, jute stick (JS) biochar has been considered for this study for ecofriendly and sustainable thermal energy storage application. Waste jute sticks (JS), which are being mainly used as a fuel for cooking purpose, have been pyrolyzed to produce porous biochar and have been used for shape stabilization of stearic acid (SA) as phase change material (PCM). SA at 1:1 ratio has been incorporated into the activated JS biochar to concoct shape-stabilized phase change composite (SAJS). The SAJS has been evaluated by different techniques such as Fourier transform-infrared spectroscope (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The obtained composite PCM has shown excellent shape stability with a high latent heat storage, suggesting its suitability for thermal energy storage applications.

• 한국태양에너지학회 논문집
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• 제21권3호
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• pp.51-60
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• 2001

A greenhouse equipped with latent heat storage system was built to obtain various thermal properties, such as greenhouse air temperature, soil surface temperature, energy flow in latent heat storage, etc., which could be used in validation of greenhouse numerical model to be developed in this study. This numerical model expressed with Newton-Raphson method was programed by C-language and utilized to simulate greenhouse thermal behavior. Greenhouse air temperature and soil surface temperature predicted by the greenhouse model developed in this study were very close to the measured data obtained through almost 3 years of experiment. Therefore, it is concluded that the greenhouse model developed and verified by measured data could be utilized for simulating various thermal behaviors of greenhouses equipped with latent heat storage system to be used for energy saving purposes.