CFD를 활용한 태양열 공기가열기 내 사각저항체 설치 조건에 따른 열전달 및 압력강하에 관한 연구

최휘웅,김영복,손창효,윤정인,최광환 한국태양에너지학회 2019 한국태양에너지학회 논문집 Vol.39 No.1

태양열 공기 가열기의 경우 덕트 내 저항체 설치에 따라 성능에 많은 차이를 보이게 된다. 따라서, 이와 관련된 많은 연구가 진행된 바 있으나 제작이 다소 어려운 흡수판에 저항체를 부착하는 방식을 주로 조사되어왔다. 따라서 본 연구에서는 제작이 용이하면서 상대적으로 설치가 쉬운 사각저항체가 태양열 공기 가열기 공기채널 내 설치된 경우 사각저항체 형상 조건에 따른 열전달 및 압력강하 성능을 전산열유체해석을 통해 확인해보고자 하였다. 그 결과, 열전달 성능은 사각저항체 설치 조건에 따라 최소 1.2배에서 최대 3.32배까지 향상되는 것을 확인할 수 있었다. 반면, 열전달 성능 향상과 함께 압력강하 또한 증가하는 모습을 보였고, 최소 2.8배에서 최대 180배까지 그 값이 증가하는 것을 확인할 수 있었다. 따라서 압력강하 증가 대비 열전달 성능 향상 정도에 대한 평가가 필요하며, 이를 위해 본 연구에서는 성능계수를 이용하였다. 성능 계수의 경우 최대 값 0.828정도를 보였으며, 열전달 성능이 향상될수록 해당 값이 적어지는 것을 알 수 있었다. 즉, 사각저항체 설치 및 형상 변경을 통한 열전달 성능 향상에 이보다 더 큰 압력강하 증가가 수반된다는 것을 확인할 수 있었으며, 향후 실제 태양열 공기가열기 적용을 위한 사각저항체 형상 조건 선정 시 필요 열전달 성능 향상 정도와 허용 압력강하에 대한 추가적인 고려가 수반될 필요가 있을 것으로 사료되었다. The solar air heater has various performances according to an obstacle installed in the air duct. Many studies on thermal performance have been conducted. But many of these studies were using a kind of rib type obstacle attached at the bottom of absorbing plate, but they are so hard to be manufactured. In this study, characteristics of the heat transfer and pressure drop in the solar air heater with various horizontal rectangular obstacles was investigated by CFD(Computational Fluid Dynamics) analysis. As a result, the heat transfer performance was improved from 1.2 to 3.32 times depending on installation conditions of rectangular obstacle. The pressure drop, however, also increased with increment of heat transfer performance from 2.8 to 180 times only by changing installation conditions of rectangular obstacle. Thus, the performance factor presenting the thermal performance enhancement on the same pressure drop was also confirmed. As a result, the highest value of 0.828 as better performance factor was obtained at the lower height of rectangular obstacle and this value has started to decrease with increment of heat transfer performance. In the end, it could be confirmed that the pressure drop was carried higher than the quantity of improvement of the heat transfer performance when the heat transfer performance was increased by change of installation conditions of rectangular obstacle. Both heat transfer enhancement and pressure drop to be required for system need to be considered before the rectangular obstacles are applied to the solar air heater.

외기온도 변화에 대한 공기식 태양열 집열기의 열성능 신뢰성 검토 연구

김유진(Kim Yu Jin),왕은석(Wang Eun Seok),이범준(Lee Beom Joon),신형기(Shin Hyung Ki),이의준(Lee Euy Joon),강은철(Kang Eun Chul) 한국태양에너지학회 2021 한국태양에너지학회 논문집 Vol.41 No.3

Solar air collector is a technology that uses the solar radiation heat energy as a heat source for the ventilation and heating of buildings to reduce energy consumption. According to ISO 9806 solar air collector thermal performance evaluation, an indoor performance evaluation method uses a solar radiation simulator in indoor chambers, and an outdoor performance evaluation method uses natural solar radiation in outdoors. The thermal performance evaluation has to ensure the reliability of the thermal performance of the collector using the outdoor performance evaluation method that is affected by the changes in the seasonal outside air temperature. This study compared and analyzed the thermal performance of the glazed solar air collector depending on ambient temperature variations in February, March, and April. The average outside air temperature was -0.5°C in February, 13.4°C in March, and 21.1°C in April. The experiment indicated that the solar air collector thermal performance was 68.1% in February, 68.5% in March, and 63.8% in April and the temperature difference between the inlet and outlet with 1000 W/m² condition was 29.2°C in February, 27.5°C in March, and 29.0°C in April. These results indicated that seasonal ambient temperature variations had a small effect on the solar air collector thermal performance evaluation. Therefore, the result of the outdoor solar air collector thermal performance evaluation was reliable irrespective of the seasonal ambient temperature changes.

Facade 일체형 태양열 집열기를 갖는 태양열/지열 하이브리드 시스템의 태양열 집열시스템 작동특성 연구

백남춘(Baek Nam-Choon),이진국(Lee Jin-Kook),유창균(Yu Chang-kyun),윤응상(Yoon Eung-Sang),윤종호(Yoon Jong-Ho) 한국태양에너지학회 2010 한국태양에너지학회 논문집 Vol.30 No.5

In this study, the solar thermal and geo-source heat pump(GSHP) hybrid system for heating and cooling of Zero Energy Solar House(ZESH) was analyzed by experiment. The GSHP in this hybrid system works like as aback-up device for solar thermal system. This hybrid system was designed and installed for Zero Energy Solar House (KIER ZeSH) in Korea Institute of Energy Research. The purpose of this study is to find out that this system is optimized and operated normally for the heating load of ZeSH. The analysis was conducted as followings ; -the thermal performance of facade integrated solar collector -the on/off characteristics of solar system and GSHP -the contribution of solar thermal system. -the performance of solar thermal and ground source heat pump system respectively. -the meet of thermal load (space and water heating load). This experimental study could be useful for the optimization of this system as well as its application in house. This hybrid system could be commercialized for the green home if it is developed to a package type.

실외 시험결과를 이용한 평판형 태양열 집열기의 집열효율 측정

김원욱(Wonuk Kim),김용기(Yong Ki Kim) 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.11

The use of renewable energy is increasing to reduce global warming. Solar energy is the biggest renewable energy source, used in the form of solar thermal and photovoltaic system. Solar thermal system is used as a good alternative to heating systems using fossil fuels, but it has a weakness that solar thermal energy is changing with weather conditions. Therefore, to use solar energy for heating, it is very important not only determining thermal efficiency of solar collector, but also predicting the amount of solar thermal energy. In this study, thermal efficiency of flat-plate solar thermal collectors from three manufacturers was investigated using outdoor steady-state thermal performance test with three water flow rates and various inlet water temperatures in Goyang city of Gyeonggi-do. As a results, the higher water flow rate showed the higher thermal efficiency and the small deviations of collector efficiency between manufacturers are observed.

The study on the comparison of the operation performance of different type of solar collectors

김휘동(Kim, Huidong),백남춘(Baek, Namchoon),이진국(Lee, Jinkook),주문창(Joo, Moonchang) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.11

The objective of this study is to make a comparative study of the operation performance of different type of solar collectors. A flat-plate collector, a single-glazed evacuated collector and a double-glazed evacuated collector are used in this study. These 3 type of collectors are connected in series in the order of a flat-plate collector, a single-glazed evacuated collector and a double-glazed evacuated collector. This experimental facility is a kind of a solar system with a controller, a heat exchanger, a storage tank and a circulation pump. Each collector has a different collection area(flat-plate collector-6.00m² total area/5.61m² aperture area, double-glazed evacuated collector-6.04m² total area/4.92m² aperture area, single-glazed evacuated collector-7.65m² total area/5.61m² aperture area) and its performance characteristic respectively. The experiments have been demonstrated at around 70?C operating temperature(flat-plate collector inlet temperature). The thermal collecting efficiencies of each collector are obtained under the different insolation and operation condition as a result.

태양열 이용 난방용 공기가열기 개발을 위한 기초 운전 특성

김종열(Kim,Jong-Ryeol),홍부표(Hong,Boo-Pyo),우종수(Woo,Jong-Soo),최광환(Choi,Kwang-Hwan) 한국태양에너지학회 2011 한국태양에너지학회 논문집 Vol.31 No.4

To develop the solar air heater, prototype of solar heater with test room set up on the roof of test chamber and operation characteristics were examined with solar radiation. Air induced from outside was supplied by a blower and also heated air was supplied to the test chamber(size of 1,000㎜(in width)*2,000㎜(in length)*2,000㎜(in depth)) established already for performance. It was clear that almost 30% of solar radiation was converted into effective heating energy at maximum and the highest air temperature was 46℃, and thus solar air heater in winter could be used as an possible alternative heating system in building. Furthermore, heat energy obtained from solar air heater can be applied to regenerate absorber in the solar desiccant cooling system.

핀-튜브 열교환 구조를 갖는 복합집열기에서 핀 높이 및 간격에 따른 공기열 이용 액체 가열 성능에 관한 수치해석 연구

최휘웅(Choi Hwi-Ung),파쿠르 로커만(Fatkhur Rokhman),류남진(Lyu Nam-Jin),윤정인(Yoon Jung-In),손창효(Son Chang-Hyo),최광환(Choi Kwang-Hwan) 한국태양에너지학회 2016 한국태양에너지학회 논문집 Vol.36 No.3

Solar assisted heat pump system uses solar thermal energy as a heat source of evaporator of heat pump. So, COP can be enhanced as well as collector efficiency. For improving performance of this system, some research about hybrid solar collector that has fin-and-tube heat exchanger has been conducted. This collector can get a thermal energy from ambient air for liquid heating, so heated liquid can be used as a heat source of evaporator in heat pump even the solar radiation is not enough. In this study, numerical analysis was conducted for confirming heat gain of liquid according to fin height and pitch of fin-and-tube heat exchanger in collector. As a result, higher heat gain was obtained on lower fin height and narrow fin pitch, but the pressure drop also increased with increment of heat gain. Thus the JF factor considering both heat transfer enhancement and pressure drop was investigated and the maximum value was shown when the fin height and pitch were 40mm and 45mm. So it is considered that this installation condition has a highest heat transfer improvement when comparing with pressure drop. However heat gain of liquid at this condition was less than the other installation conditions of fin pitch on same height. Then, after establishing a proper minimum heat gain of liquid, actual production and experiment of collector will be conducted with fin height and pitch showing maximum JF factor and satisfying selected minimum heat gain of liquid on the basis of results of this study.

태양열 집열기 히트파이프 효율 향상을 위한 에탄올-산화탄소나노유체의 특성 비교 연구

안응진(An, Eoungjin),박성식(Park, Sungseek),김남진(Kim, Nmajin) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11

최근 급격한 경제성장과 고도 산업사회로의 전환에 따라 에너지 수요가 크게 증가하고 있다. 이에 따라 석유, 가스 등 화석에너지의 소비량과 온실가스 배출량이 급격히 늘어나고 있는 실정이다. 따라서 화석에너지의 소비와 온실가스 배출을 저감시키기 위해 친환경적인 에너지를 이용하기 위한 많은 연구가 이루어지고 있다. 이와 같은 노력 중 하나가 바로 태양열에너지를 이용하는 방법이다. 태양열에너지는 자원 고갈의 우려가 없고, 에너지의 이용 과정에서 공해 물질을 배출하지 않아 대체 에너지원으로 각광을 받고 있다. 하지만 에너지 밀도가 낮고 에너지의 공급이 기상조건에 따라 큰 영향을 받으므로 태양열에너지를 이용하기 위해서는 효율적인 집열시스템이 필요하다. 따라서 본 연구에서는 우수한 열적특성을 가진 탄소나노유체를 히트파이프 작동유체에 적용하여, 태양열 집열기의 효율을 향상시키기 위해 탄소나노유체의 열전도도 및 점도특성을 비교분석하였다. 나노유체는 에탄올에 산화 다중벽 탄소나노튜브(Oxidized Multi-walled Carbon Nanotubes, OMWCNTs)를 혼합하고, 초음파 분산하여 제조하였다. 에탄올-산화탄소나노유체의 열전도도와 점도는 저온(10?C), 상온(25?C), 고온(70?C)에서 측정하여 비교분석하였으며, 열전도도는 전기 전도성 유체의 비정상 열선법(Transient Hot-wire Method)을 이용하여 측정하였고, 점도는 회전형 디지털 점도계를 이용하였다. 실험 결과 0.1 vol%의 에탄올-산화탄소나노유체의 열전도도는 기본 유체 대비 33.72%(10?C), 33.14%(25?C), 32.26%(70?C)가 향상되었으며, 점도 또한 기본유체보다 크게 증가하지 않아 히트파이프 작동유체로서 우수한 효과를 나타낼 수 있음을 확인하였다. 본 연구의 결과는 태양열 집열기 히트파이프의 효율 향상을 위한 기초자료로써 유용한 정보를 제공할 것이라 판단된다.

에너지 저장기술 기반 태양열 시스템 효율 개선 연구 동향 고찰 및 국내 활성화 방안 제안

최상호,박명군,이호석,오광철,최은택,정수광 한국건축친환경설비학회 2023 한국건축친환경설비학회 논문집 Vol.17 No.6

The rapid technological advancement post-industrialization and the global population surge necessitate urgent improvements in energy efficiency and the widespread adoption of renewable energy sources. This study examines research trends aimed at activating the domestic solar thermal system market. It scrutinizes the composition and characteristics of various solar thermal systems, focusing on non-concentrating and concentrating collectors. A key research trend explored is the application of phase change material (PCM) in energy storage systems. Additionally, ongoing research aims to enhance collector efficiency through nanoparticle integration. These technologies find active applications in diverse solar thermal systems like hot water systems, solar air heaters, solar stills, solar cookers, and solar ponds. The study observes research on seasonal thermal storage for solar thermal systems. However, practical market expansion requires addressing fundamental issues in current systems beyond energy storage materials and fin applications. From this standpoint, the study proposes a solar heat pump station technology, utilizing heat circulation and hot water circulation modules to overcome traditional system limitations.

국제 기준 공기식 태양열 집열기 열 성능 평가 연구

김유진(Kim Yu-Jin),김기봉(Kim Ki-Bong),이의준(Lee Euy-Joon),강은철(Kang Eun-Chul) 한국태양에너지학회 2021 한국태양에너지학회 논문집 Vol.41 No.1

Solar air thermal collectors are one of the technologies used to improve the efficiency of fresh air heating system in building spaces. Solar air collectors have the advantage of preventing freezing and overheating problems when compared with solar water collectors. However, thus far, there have been no harmonized thermal performance test facilities or round robin tests (RRT) based on the international standard ISO 9806 in Korea. In this study, an ISO 9806 thermal performance test facility was introduced and designed. In addition, an RRT was conducted based on ISO 9806 and compared to RRT sample Exova performance test results to verify the consistency of the thermal performance. The thermal efficiency ranged 36.06% ~ 72.02% depending on a change flow rate change of 36.6 ~ 182.9 m3/(hr·m2), respectively. The RRT was successfully conducted to compare the results of the Exova thermal performance test. A comparison between the Exova and KIER tests showed a relative error of 5.51% and 6.42% for ambient wind velocities of 1.0 and 1.8 m/s, respectively.