• 제목/요약/키워드: Boiling Channel

검색결과 79건 처리시간 0.02초

CFD 코드의 기포류 유동 예측을 위한 기포크기모델 평가 (Evaluation of Bubble Size Models for the Prediction of Bubbly Flow with CFD Code)

  • 박진영;윤병조
    • 에너지공학
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    • 제25권1호
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    • pp.69-75
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    • 2016
  • 기포크기는 다차원 이상유동에서 정확한 기포거동의 예측을 위해 중요한 인자이다. 현재 CFD 코드인 STAR CCM+에서는 유동채널에서 기포크기예측을 위해 역학적인 기포크기모델인 $S{\gamma}$ 모델을 제공하고 있다. 기포크기 예측을 위한 또 다른 모델로써 고압조건의 과냉 비등 실험인 DEBORA 실험을 바탕으로 개발된 Yun 모델이 있다. 본 연구에서는 상용 CFD 코드인 STAR CCM+ ver. 10.02를 이용하여 물-공기 이상유동에 대한 수치해석을 통해 $S{\gamma}$ 모델과 Yun 모델의 성능을 확인하고 평가하였다. 이를 위해 두 모델은 수직관에서의 물-공기 실험인 DEDALE 실험과 Hibiki 등의 실험에 대하여 평가되었다. 해석 결과 $S{\gamma}$ 모델은 이상유동 인자들을 합리적으로 예측하였으며, Yun 모델은 저압조건의 물-공기 유동에는 적합하지 않음을 확인하였다.

수직 상향유동 배관에서 비뉴톤유체에 의한 2상류의 유동특성 (The Characteristics of Two Phase Flow by Non-Newtonian Fluid for Vertical Up-ward in a Tube)

  • 차경옥;김재근;최경석
    • 한국가스학회지
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    • 제2권4호
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    • pp.53-59
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    • 1998
  • 기-액 2상유동장에서 유동양식은 압력강하, 보이드율분포, 유동장의 기하학적 형상과 밀접한 관계가 있다. 한편 원유수송, 비등이 발생하는 유동, 펌프에서 발생하는 케비테션 현상, 그리고 화학 반응로와 같은 상변화 장치 등의 2상유동에서 고분자물질에 의한 저항감소 현상의 적용이 가능할 것으로 예상된다. 그러나 2상유동장에서 고분자물질에 의한 저항감소에 관한 연구는 매우 미비하다. 그래서 본 연구는 2상유동장에 합성고분자물질(A611p)에 의한 저항감 소율을 실험을 통하여 계측 및 분석하였다. 본 연구에서는 고분자물질의 농도를 증가시킬수록 국부보이드율의 최고치가 관의 중심에서 관의 벽쪽으로 이동하며 2상유동의 유동양식이 변화됨을 규명하였다. 그래서 저항감소율과 유동양식과 밀접한 관계가 있음을 예측할 수 있었다.

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가압경수로의 운전변수 변화에 대한 DNBR의 민감도 (DNBR Sensitivities to Variations in PWR Operating Parameters)

  • Hyun Koon Kim;Ki In Han
    • Nuclear Engineering and Technology
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    • 제15권4호
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    • pp.236-247
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    • 1983
  • 한국원자력 1호기(KNU-1)의 설계 및 운전자료를 이용하여 가압경수로 운전변수들의 변화에 대한 DNBR의 민감도를 분석하였다. 본 민감도 분석에는 원자로 출력, 압력, 냉각수 주입유량, 냉각수 주입온도, 반경방향 및 축방향 출력분포 그리고 축방향 출력편차 등의 운전변수가 고려되었다. 민감도 분석을 위하여는 노심의 열수력 해석용 전산코드인 COBRA-IV-K를 사용하였는데 본 코드는 COBRA-IV-i의 수정판으로써 한국에너지연구소에서 일부 프로그램을 수정하였고 또한 신뢰도도 확인하였다. 민감도 분석을 수행하기 전에 KNU-1 원자로심의 설계 및 운전조건을 근거로 하여 기초 계산을 수행하고 이 결과를 본 민감도 분석의 기본자료로 삼았다. 민감도 분석결과 원자로의 DNBR 열설계에 있어서 가장 민감한 운전변수는 냉각수 주입온도이고 가장 둔감한 변수는 축방향 출력분포라는 것이 밝혀졌다.

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CORE DESIGN FOR HETEROGENEOUS THORIUM FUEL ASSEMBLIES FOR PWR (II) - THERMAL HYDRAULIC ANALYSIS AND SPENT FUEL CHARACTERISTICS

  • BAE KANG-MOK;HAN KYU-HYUN;KIM MYUNG-HYUN;CHANG SOON-HEUNG
    • Nuclear Engineering and Technology
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    • 제37권4호
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    • pp.363-374
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    • 2005
  • A heterogeneous thorium-based Kyung Hee Thorium Fuel (KTF) assembly design was assessed for application in the APR-1400 to study the feasibility of using thorium fuel in a conventional pressurized water reactor (PWR). Thermal hydraulic safety was examined for the thorium-based APR-1400 core, focusing on the Departure from Nucleate Boiling Ratio (DNBR) and Large Break Loss of Coolant Accident (LBLOCA) analysis. To satisfy the minimum DNBR (MDNBR) safety limit condition, MDNBR>1.3, a new grid design was adopted, that enabled grids in the seed and blanket assemblies to have different loss coefficients to the coolant flow. The fuel radius of the blanket was enlarged to increase the mass flow rate in the seed channel. Under transient conditions, the MDNBR values for the Beginning of Cycle (BOC), Middle of Cycle (MOC), and End of Cycle (EOC) were 1.367, 1.465, and 1.554, respectively, despite the high power tilt across the seed and blanket. Anticipated transient for the DNBR analysis were simulated at conditions of $112\%$ over-power, $95\%$ flow rate, and $2^{\circ}C$ higher inlet temperature. The maximum peak cladding temperature (PCT) was 1,173K for the severe accident condition of the LBLOCA, while the limit condition was 1,477K. The proliferation resistance potential of the thorium-based core was found to be much higher than that of the conventional $UO_2$ fuel core, $25\%$ larger in Bare Critical Mass (BCM), $60\%$ larger in Spontaneous Neutron Source (SNS), and $155\%$ larger in Thermal Generation (TG) rate; however, the radio-toxicity of the spent fuel was higher than that of $UO_2$ fuel, making it more environmentally unfriendly due to its high burnup rate.

수족한(手足汗)의 원인(原因)과 치료법(治療法)에 대한 동(東).서의학적(西醫學的) 고찰(考察) (A Comparative Study of the Oriental and the Occidental Medical Literature on the Etiologies & Treatments for Palmoplantar Hyperhidrosis)

  • 고영철;신조영
    • 대한한방내과학회지
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    • 제18권2호
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    • pp.268-295
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    • 1997
  • Sweating is natural phenomenon necessary for the regulation of an individual's body-temperature. The secretion of sweat is mediated by a portion of our vegetative nervous system(the sympathetic nervous system). In some people, this system is working at a very high activity level, far higher than needed to keep a constant temperature. This condition is referred to as hyperhidrosis. Especially excessive sweating of the hands and the feet is palmoplantar hyperhidrosis or volar hyperhidrosis. This is by far the most distressing condition. It was founded that the first important cause of this was emotional factor. The hands are much more exposed in social and prefessional activities than any other part of our body. Many individuals with palmoplantar hyperhidrosis are limited in their choice of proffession, because unable to manipulate materials sensitive to humidity or reluctant to shake hands; some patients arrive to the point to avoid social contact. The occidental medical treatments for palmoplantar hyperhidrosis include application of topical agents(chemical antiperspirants such as aluminum chloride), iontophoresis(treatment with electrical current), or surgery(thoracic sympathectomy). It was reported that the most effective treatment was thoracic sympathectomy. So this study was started to find the easy and effective oriental medical treatments against the occidental medical treatments through the oriental medical literature. The occidental medical idea for palmoplantar hyperhidrosis is only limited in neurologic system, so surgery is the best treatment. But the oriental medical idea for palmoplantar hyperhidrosis is much wider, so the oriental medical causes and treatments for this are able to be veriety. And the oriental medical teatment is freely in treating the patients of palmoplantar hyperhidrosis, because entire idea including pulse, facial color, mental condition, constitution and other symptom exists in the oriental medicine. The results of a bibliographic study of causes and treatments for palmoplantar are as follows; 1. The main causes of pa1moplantar hyperhidrosis are heat in the stomach, damp-heat in the spleen and the stomach, insufficiency of the spleen-qi and the stomach-qi, deficiency of the spleen-yin and the stomach-yin, and the others are the stomach-cold syndrome, stasis of blood and dyspepsia in the stomach, disorder of the liver-qi, deficiency of the heart-yin and the kidney-yin, deficiency of the heart-yang and the kidney-yang, stagnated heat in the liver and the spleen, the lung channel-heat etc. 2. The main methods of medical treatments for palmoplantar hyperhidrosis are clearing out the stomach-heat, eliminating dampness and heat in the spleen and the stomach, invigorating the spleen-qi and the stomach-qi, reinforcing the spleen-yin and the stomach-yin, warming the stomach, relaxing the liver and alleviating of mental depression and tonifying the heart and the kidney etc. 3. The main prescriptions of palmoplantar hyperhidrosis are Taesihotang, Palmultang-kakam, Samyeongbaechusan, Chongbisan, Sasammaekmundongtang, the others are Leejungtang, Hwangkikonjungtang, Seungkitang, Boyumtang, Baekhotang, Chongsimyonjayum, Moyrosan, etc. 4. Local medicine for external use are liquid after boiling alum in water for about 1 or 2 hours, liquid after boiling alum and pueraria root in water and liquid after boiling stragalus root, pueraria root, ledebouriella root and schizonepeta in water, etc. 5. The methods of acupuncture therapy include invigorating Bokyru, Yumkuk and purgating Hapkouk, or invigorating Bokyru, Kihae and purgating Hapkouk, or steadying Hapkouk, Nokung.

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설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제27권7호
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

설비공학 분야의 최근 연구 동향 : 2012년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2012)

  • 한화택;이대영;김사량;김현정;최종민;박준석;김수민
    • 설비공학논문집
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    • 제25권6호
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    • pp.346-361
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    • 2013
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2012. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. The conclusions are as follows : (1) The research works on thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and valves, fuel cells and power plants, ground-coupled heat pumps, and general heat and mass transfer systems. Research issues are mainly focused on new and renewable energy systems, such as fuel cells, ocean thermal energy conversion power plants, and ground-coupled heat pump systems. (2) Research works on the heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, and industrial heat exchangers. Researches on heat transfer characteristics included the results for natural convection in a square enclosure with two hot circular cylinders, non-uniform grooved tube considering tube expansion, single-tube annular baffle system, broadcasting LED light with ion wind generator, mechanical property and microstructure of SA213 P92 boiler pipe steel, and flat plate using multiple tripping wires. In the area of pool boiling and condensing heat transfer, researches on the design of a micro-channel heat exchanger for a heat pump, numerical simulation of a heat pump evaporator considering the pressure drop in the distributor and capillary tubes, critical heat flux on a thermoexcel-E enhanced surface, and the performance of a fin-and-tube condenser with non-uniform air distribution and different tube types were actively carried out. In the area of industrial heat exchangers, researches on a plate heat exchanger type dehumidifier, fin-tube heat exchanger, an electric circuit transient analogy model in a vertical closed loop ground heat exchanger, heat transfer characteristics of a double skin window for plant factory, a regenerative heat exchanger depending on its porous structure, and various types of plate heat exchangers were performed. (3) In the field of refrigeration, various studies were executed to improve refrigeration system performance, and to evaluate the applicability of alternative refrigerants and new components. Various topics were presented in the area of refrigeration cycle. Research issues mainly focused on the enhancement of the system performance. In the alternative refrigerant area, studies on CO2, R32/R152a mixture, and R1234yf were performed. Studies on the design and performance analysis of various compressors and evaporator were executed. (4) In building mechanical system research fields, twenty-nine studies were conducted to achieve effective design of mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, renewable energy systems, and lighting systems in buildings. New designs and performance tests using numerical methods and experiments provide useful information and key data, which can improve the energy efficiency of buildings. (5) In the fields of the architectural environment, studies for various purposes, such as indoor environment, building energy, and renewable energy were performed. In particular, building energy-related researches and renewable energy systems have been mainly studied, reflecting interests in global climate change, and efforts to reduce building energy consumption by government and architectural specialists. In addition, many researches have been conducted regarding indoor environments.

설비공학회 분야의 최근 연구 동향 : 2015년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2015)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제28권6호
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    • pp.256-268
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    • 2016
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2015. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering were carried out in the areas of flow, heat and mass transfer, cooling and heating, and air-conditioning, the renewable energy system and the flow inside building rooms. Research issues dealing with air-conditioning machines and fire and exhausting smoke were reduced. CFD seems to be spreading to more research areas. (2) Research works on heat transfer area were carried out in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the economic analysis of GHG emission, micro channel heat exchanger, effect of rib angle on thermal performance, the airside performance of fin-and-tube heat exchangers, theoretical analysis of a rotary heat exchanger, heat exchanger in a cryogenic environment, the performance of a cross-flow-type, indirect evaporative cooler made of paper/plastic film. In the area of pool boiling and condensing, the bubble jet loop heat pipe was studied. In the area of industrial heat exchangers, researches were performed on fin-tube heat exchanger, KSTAR PFC and vacuum vessel at baking phase, the performance of small-sized dehumidification rotor, design of gas-injection port of an asymmetric scroll compressor, effect of slot discharge-angle change on exhaust efficiency of range hood system with air curtain. (3) In the field of refrigeration, various studies were carried in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, a cold-climate heat pump system, $CO_2$ cascade systems, ejector cycles and a PCM-based continuous heating system were investigated. In the alternative refrigeration/energy system category, a polymer adsorption heat pump, an alcohol absorption heat pump and a desiccant-based hybrid refrigeration system were investigated. In the system control category, turbo-refrigerator capacity controls and an absorption chiller fault diagnostics were investigated. (4) In building mechanical system research fields, eighteen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the user and location awareness technology applied dimming lighting control system, the lighting performance evaluation for light-shelves, the improvement evaluation of air quality through analysis of ventilation efficiency and the evaluation of airtightness of sliding and LS window systems. The subjects of building energy were worked on the energy saving estimation of existing buildings, the developing model to predict heating energy usage in domestic city area and the performance evaluation of cooling applied with economizer control. The studies were also performed related to the experimental measurement of weight variation and thermal conductivity in polyurethane foam, the development of flame spread prevention system for sandwich panels, the utilization of heat from waste-incineration facility in large-scale horticultural facilities.

주 에티오피아 열곡대 내 온천수의 산출특성 및 천열수형 광상의 부존 잠재성 (Occurrences of Hot Spring and Potential for Epithermal Type Mineralization in Main Ethiopian Rift Valley)

  • 문동혁;김의준;고상모
    • 자원환경지질
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    • 제46권3호
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    • pp.267-278
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    • 2013
  • 동아프리카 열곡계는 천열수 금-은 광상을 배태하고 있는 것으로 알려져 있으며, 그 대표적인 예로서 에티오피아에 발달된 열곡대는 제 4기 복마그마 화산활동과 관련하여 광화작용이 수반된다. 주 에티오피아 열곡대의 형성과정 동안 발달된 대규모의 지루-지구 구조는 마그마의 관입과 열수유체의 순환을 위한 열린 공간을 제공하였다. 최근 들어, 에티오피아 열곡대 및 다나낄 함몰지 내 천열수형 광화작용이 보고되고 있어, 주 에티오피아 열곡대 내 대규모 열수변질대의 발달(샬라, 랑가노, 알라로베다)과 온천수에 대한 관심이 높아지고 있다. 온천수의 지표산출은 주로 비등천(샬라) 또는 간헐천(알라로베다)의 형태로 이루어지고 있으나, 일부 지역은 지하수면의 하강으로 폭발적인 비등과 분출이 관찰되지 않는다. 온천수의 지표 분출과 관련하여 주변 암석들은 주로 석영, 카올리나이트, 일라이트, 스멕타이트, 녹니석의 광물조합을 갖는 암석으로 변질되어 있다. 온천수는 중성 내지 약한 알카리(pH 7.88~8.83)의 특성을 보이고, 대체적으로 중탄산염 유체로 분류된다. 온천수 내 금과 은 및 기타 수반원소들의 함량은 상당히 낮으나, Se의 함량이 최대 26.7 ppm으로 나타났다. 반면에 온천수 주변 규질 퇴적물들은 Pb(최대 33 ppm, 샬라), Zn(최대 313 ppm, 샬라), Cu(53.1 ppm, 데마에고나), Mn(최대 0.18 wt%, 샬라) 등으로 다소 부화되어 있다. 결론적으로 온천수내 높은 Se 함량과 규질 암석내 Pb, Zn, Cu, Mn 이상 및 최근 천열수형 광화작용의 발견은 주 에티오피아 열곡대내 천열수형 광상의 부존 가능성에 관한 기대를 높인다.