태양열원 난방기의 수축열조 효율개선에 관한 연구

류남진(Ryu Nam-Jin),한유리(Han Yury),박윤철(Park Youn Cheol) 한국태양에너지학회 2007 한국태양에너지학회 논문집 Vol.27 No.4

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.

태양열 시스템에 적용된 나선재킷형 축열조의 실증실험

김진홍,최봉수,홍희기,김용식 대한설비공학회 2005 설비공학 논문집 Vol.17 No.4

The simplification of solar thermal systems reduces the possibility of operating trouble and lowers the cost of the initial investment and maintenance. This also leads to increased competitiveness in the energy market. We proposed a spiral-jacketed storage tank that functions both as a heat exchanger and expansion tank, which removes the secondary piping and markedly simplifies the entire system. The new storage tank was designed and manufactured to maintain the same performance as the conventional system and the exiting system was remodelled by adopting the newly proposed storage tank. This experiment was conducted under real conditions over a period of several months. The retrofitted system with the spiral-jacketed storage tank showed good performance that is on a similar level as the previous system having a typical storage tank and heat exchanger.

Experimental verification of a solar hot water heating system with a spiral-jacketed storage tank

Douglas Reindl,김선국,강용태,홍희기 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.11

Simplifying solar thermal systems offers a number of potential benefits, including lower initial investment, lower maintenance costs, and reduced likelihood of operating faults. Reduced capital cost leads to increased competitiveness in the energy market. With appropriate care, a simplified solar thermal system design can maintain competitive energy performance with more complicated designs. We propose to simplify small-scale thermal storage systems by the use of a spiral-jacketed storage tank that combines the function of both the heat exchanger and storage tank. The new storage tank is designed and manufactured to maintain performance comparable to a conventional system, and its functional performance validated by retrofitting an existing system and operating it under real conditions over a multiple month period. The system retrofitted with a spiral-jacketed storage tank showed performance competitive with the previous system that utilized a typical storage tank and heat exchanger during a day with a good solar radiation but experienced somewhat diminished performance during a month that included cloudy days.

태양열 난방 일체형 복합시스템의 축열조 효율개선에 관한 연구

류남진(Lyu, Nam-Jin),고광수(Ko, Kwang-Soo),한유리(Han, Yu-Ri),박윤철(Park, Youn-Cheol) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11

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.

성층축열조의 성능에 대한 설계인자의 영향

정재동,박주혁,조성환 대한설비공학회 2004 설비공학 논문집 Vol.16 No.11

This study is to systematically analyze the effect of various kinds of design factors on the performance of stratified thermal storage tank. Taguchi method, known as a very reasonable tool in the parametric study, is employed in the present work. Three dimensional unsteady numerical experiment is conducted for 4 design parameters of stratified thermal storage tank: inlet Reynolds number, Froude number, diffuser size with 3 levels (Re=400, 800, 1200, Fr=0.5, 1.0, 2.0 and150mm, 200mm, 300mm) and diffuser shape with 2 levels. Orthogonal array L18(2×37) is adopted for the analysis of variance. The result gives quantitative estimation of the various design parameters affecting the performance and helps to select the main factors for the optimum design of stratified thermal storage tank. Reynolds number is found to be the most dominant parameter and the diffuser shape plays significant role on the performance of stratified thermal storage tank. Based on this finding, the prior questions on the contribution of the diffuser shape proposed by the authors become clear. The optimum condition for the performance is a set of300mm, Re=800, and radial regulated plate diffuser. Conformation test shows the repeatability in the analysis and 1.3% difference between the estimated thermocline thickness and that of numerical result.

집단에너지 공급 축열조의 디퓨져 형태별 성층화 연구

장철용(Jang Cheol-Yong),조수(Cho Soo),최석용(Seok-Yong Choi) 한국태양에너지학회 2008 한국태양에너지학회 학술대회논문집 Vol.- No.-

The stratification effect was investigated with four different types of diffuser shape in a thermal storage tank. For this study, experimental facility was constructed, which was composed of experimental thermal storage tank, hot and cold water storage tanks, boiler, chiller, data acquisition system, etc.. Visualization and lab scale experimental result showed that radial curved type diffuser was the highest degree of stratification among the four diffuser shapes.

태양열 시스템에 적용된 나선재킷형 축열조의 CFD 해석

남진현(Jin Hyun Nam),김민철(Min Cheol Kim),김찬중(Charn-Jung Kim),홍희기(Hiki Hong) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.10

Spiral-jacketed thermal storage tanks can greatly simplify solar heating systems while maintaining the thermal performance at a similar level as conventional systems with an external heat exchanger. Proper design of the spiral-jacket flow path is essential to make the most of solar energy, and thus to maximize the thermal performance. In the present work, computational fluid dynamics (CFD) analysis was carried out for a spiral-jacketed storage tank installed in a solar heating demonstration system. The results of the CFD analysis showed a good agreement with experimentally determined thermal performance indices such as the acquired heat, collector efficiency, and mixed temperature in the storage tank. This verified CFD modelling approach can be a useful design tool in optimizing the shape of spiral -jacket flow path and the flow rate of circulating fluid for better performance.

디퓨저 타입 계간 축열조 내부 열성층화에 대한 입구 유속 및 탱크 종횡비 영향 연구

김성근(Seong Keun Kim),정성용(Sung Yong Jung) 한국가시화정보학회 2021 한국가시화정보학회지 Vol.19 No.3

In this study, the thermal stratification in solar seasonal thermal storage tanks was numerically simulated. The effects of the aspect ratio (AR) and inlet velocity on the thermal stratification in the diffuser type heat storage tank were investigated. The temperature distributions inside the tank were similar with velocity fields. Jet flows from opposite diffusers encountered each other at the tank center region. Thereafter, the downward flows occurred, and this flows strongly affected the thermal stratification. When AR was smaller than 2, these downward flows influenced a further distance and enhanced mixing inside the tank. Thermal stratification was evaluated by thermocline thickness and degree of stratification, and AR of 3 had the highest degree of stratification. The inlet velocity effect was expressed with the ratio (Re/Ri) of Reynolds and Richardson numbers. The second-order approximation was found for the relationship between the thermocline thickness and log Re/Ri.

Consistent thermal analysis procedure of LNG storage tank

Jeon, Se-Jin,Jin, Byeong-Moo,Kim, Young-Jin,Chung, Chul-Hun Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.25 No.4

As the LNG (Liquefied Natural Gas) tank contains cryogenic liquid, realistic thermal analyses are of a primary importance for a successful design. The structural details of the LNG tank are so complicated that some strategies are necessary to reasonably predict its temperature distribution. The proposed heat transfer model can consider the beneficial effects of insulation layers and a suspended deck on temperature distribution of the outer concrete tank against cryogenic conditions simply by the boundary conditions of the outer tank model. To this aim, the equilibrium condition or heat balance in a steady state is utilized in a various way, and some aspects of heat transfer via conduction, convection and radiation are implemented as necessary. Overall thermal analysis procedures for the LNG tank are revisited to examine some unjustifiable assumptions of conventional analyses. Concrete and insulation properties under cryogenic condition and a reasonable conversion procedure of the temperature-induced nonlinear stress into the section forces are discussed. Numerical examples are presented to verify the proposed schemes in predicting the actual temperature and stress distributions of the tank as affected by the cryogenic LNG for the cases of normal operation and leakage from the inner steel tank. It is expected that the proposed schemes enable a designer to readily detect the effects of insulation layers and a suspended deck and, therefore, can be employed as a useful and consistent tool to evaluate the thermal effect in a design stage of an LNG tank as well as in a detailed analysis.

히트펌프 수배관시스템에서 믹싱밸브를 이용한 온도 성층화에 대한 고찰

한왕국(Wang Kook Han),임태훈(Tae Hun Lim),안영철(Young Chul Ahn) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6

A mismatch between heat production and heat demand can not be avoided even undesirable effect. Thermal storage system has been widely used to resolve this problem. This study is focusing on water storage system because water has excellent heat storage characteristics than other substances on earth. Recently, There is a demand for the use of highly efficient equipment for heating and hot water system. The system using electric heater has been used for a long time and now is changing to a heat pump system. Thermal stratification review is required by changing heat source system. Previous research has been confined to factors relating to internal parts of the storage tank. In this study, The influence of water storage tank stratification is investigated experimentally by installing mixing valve in heat pump system.