Preliminary design and performance analysis of a radial inflow turbine for ocean thermal energy conversion

Kim, Do-Yeop,Kim, You-Taek Elsevier 2017 RENEWABLE ENERGY Vol.106 No.-

<P><B>Abstract</B></P> <P>Ocean thermal energy conversion is an organic Rankine cycle for generating power using the temperature difference between surface seawater and deep seawater. The potential of ocean thermal energy is significant, and it is an environmentally friendly power system. However, its thermal efficiency is very low due to the low temperature difference between surface seawater and deep seawater. Hence, it is essential to develop a high efficiency turbine in order to improve the thermal efficiency of ocean thermal energy conversion. The precise preliminary design for the high efficiency radial inflow turbine requires selection of the appropriate flow and loading coefficients for the target efficiency. A new approach for the appropriate choice of flow and loading coefficients is proposed in this study. The meanline analysis and three-dimensional viscous simulations for the designed turbine are conducted in order to verify the proposed approach in design and off-design conditions. The results demonstrate that the optimum radial inflow turbine for the design conditions can be designed through applying the proposed model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study presents the preliminary design process of a 200 kW radial inflow turbine for ocean thermal energy conversion. </LI> <LI> A new approach that can calculate the appropriate flow and loading coefficients for the target efficiency is proposed. </LI> <LI> The meanline analysis and 3D viscous simulations for the designed turbine are conducted to verify the proposed model. </LI> <LI> The results demonstrate that the optimum radial inflow turbine can be designed through applying the proposed model. </LI> </UL> </P>

An evaluation of power conversion systems for land-based nuclear microreactors: Can aeroderivative engines facilitate near-term deployment?

D.P. Guillen,P.J. McDaniel 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.4

Power conversion cycles (Subcritical Steam, Supercritical Steam, Open Air Brayton, Recuperated AirBrayton, Combined Cycle, Closed Brayton Supercritical CO2 (sCO2), and Stirling) are evaluated for landbased nuclear microreactors based on technical maturity, system efficiency, size, cost and maintainability, safety implications, and siting considerations. Based upon these criteria, Air Brayton systems wereselected for further evaluation. A brief history of the development and applications of Brayton powersystems is given, followed by a description of how these thermal-to-electrical energy conversion systemsmight be integrated with a nuclear microreactor. Modeling is performed for optimized cycles operatingat 3 MW(e) with turbine inlet temperatures of 500 C, 650 C and 850 C, corresponding to: a) sodiumfast, b) molten salt or heat pipe, and c) helium or sodium thermal reactors, coupled with three types ofBrayton power conversion units (PCUs): 1) simple open-cycle gas turbine, 2) recuperated open-cycle gasturbine, and 3) recuperated and intercooled open-cycle gas turbine. Aeroderivative turboshaft enginesemploying the simple Brayton cycle and two industrial gas turbine engines employing recuperated airBrayton cycles are also analyzed. These engines offer mature technology that can facilitate near-termdeployment with a modest improvement in efficiency.

Experimental Study on Combined Ocean Thermal Energy Conversion with Waste Heat of Power Plant

Jung, Hoon,Jo, Jongyoung,Chang, Junsung,Lee, Sanghyup Korea Electric Power Corporation 2019 KEPCO Journal on electric power and energy Vol.5 No.3

This work is experimental study of 10 kW specialized Combined Ocean Thermal Energy Conversion. We propose a C-OTEC technology that directly uses exhaust thermal energy from power station condensers to heat the working fluid (R134a), and tests the feasibility of such power station by designing, manufacturing, installing, and operating a 10 kW-pilot facility. Power generation status was monitored by using exhaust thermal energy from an existing power plant located on the east coast of the Korean peninsula, heat exchange with 300 kW of heat capacity, and a turbine, which can exceed enthalpy efficiency of 45%. Output of 8.5 kW at efficiency of 3.5% was monitored when the condenser temperature and seawater temperature are $29^{\circ}C$ and $7.5^{\circ}C$, respectively. The evaluation of the impact of large-capacity C-OTEC technology on power station confirmed the increased value of the technology on existing power generating equipment by improving output value and reducing hot waste water. Through the research result, the technical possibility of C-OTEC has been confirmed, and it is being conducted at 200 kW-class to gain economic feasibility. Based on the results, authors present an empirical study result on the 200 kW C-OTEC design and review the impact on power plant.

Influence of organic acids and heat treatment on ginsenoside conversion

Jang, Gwi Yeong,Kim, Min Young,Lee, Yoon Jeong,Li, Meishan,Shin, Yu Su,Lee, Junsoo,Jeong, Heon Sang The Korean Society of Ginseng 2018 Journal of Ginseng Research Vol.42 No.4

Background: Heat treatments are applied to ginseng products in order to improve physiological activities through the conversion of ginsenosides, which are key bioactive components. During heat treatment, organic acids can affect ginsenoside conversion. Therefore, the influence of organic acids during heat treatment should be considered. Methods: Raw ginseng, crude saponin, and ginsenoside $Rb_1$ standard with different organic acids were treated at $130^{\circ}C$, and the chemical components, including ginsenosides and organic acids, were analyzed. Results: The organic acid content in raw ginseng was 5.55%. Organic acids were not detected in crude saponin that was not subjected to heat treatment, whereas organic acids were found in crude saponin subjected to heat treatment. Major ginsenosides ($Rb_1$, Re, and $Rg_1$) in ginseng and crude saponin were converted to minor ginsenosides at $130^{\circ}C$; the ginsenoside $Rb_1$ standard was very stable in the absence of organic acids and was converted into minor ginsenosides in the presence of organic acids at high temperatures. Conclusion: The major factor affecting ginsenoside conversion was organic acids in ginseng. Therefore, the organic acid content as well as ginsenoside content and processing conditions should be considered important factors affecting the quality of ginseng products.

Influence of organic acids and heat treatment on ginsenoside conversion

Gwi Yeong Jang,김민영,Yoon Jeong Lee,Meishan Li,Yu Su Shin,Junsoo Lee,Heon Sang Jeong 고려인삼학회 2018 Journal of Ginseng Research Vol.42 No.4

Background: Heat treatments are applied to ginseng products in order to improve physiological activities through the conversion of ginsenosides, which are key bioactive components. During heat treatment, organic acids can affect ginsenoside conversion. Therefore, the influence of organic acids during heat treatment should be considered. Methods: Raw ginseng, crude saponin, and ginsenoside Rb1 standard with different organic acids were treated at 130C, and the chemical components, including ginsenosides and organic acids, were analyzed. Results: The organic acid content in raw ginseng was 5.55%. Organic acids were not detected in crude saponin that was not subjected to heat treatment, whereas organic acids were found in crude saponin subjected to heat treatment. Major ginsenosides (Rb1, Re, and Rg1) in ginseng and crude saponin were converted to minor ginsenosides at 130C; the ginsenoside Rb1 standard was very stable in the absence of organic acids and was converted into minor ginsenosides in the presence of organic acids at high temperatures. Conclusion: The major factor affecting ginsenoside conversion was organic acids in ginseng. Therefore, the organic acid content as well as ginsenoside content and processing conditions should be considered important factors affecting the quality of ginseng products.

Dithienobenzodithiophene-Based Small Molecule Organic Solar Cells with over 7% Efficiency via Additive- and Thermal-Annealing-Free Processing

Song, Hyeng Gun,Kim, Yu Jin,Lee, Ji Sang,Kim, Yun-Hi,Park, Chan Eon,Kwon, Soon-Ki American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.50

<P>Here we introduce a novel small molecule based on dithienobenzodithiophene and rhodanine, DTBDT-Rho, developed to study the effect of the rhodanine substitutuent on small molecule bulk heterojunction (BHJ) solar cells. DTBDT-Rho possesses distinct crystalline characteristics, sufficient solubility in chlorinated solvents, and broad absorption properties. Therefore, solution-processed BHJ photovoltaic cells made with DTBDT-Rho:PC71BM blends showed an extremely high power conversion efficiency (PCE; 7.10%); notably, this PCE value was obtained without the use of additives or thermal treatments. To our knowledge, the PCE over 7% is a significantly powerful value among rhodanine-based small molecule BHJ solar cells without additives or thermal treatments.</P>

Structural evolution of the thermal conversion products of modified coal tar pitch

Qi Li,Dongyun Han,Haiyan Qiao,Weiwei Shi,Yuqi Zhang,Zubin Cao 한국탄소학회 2023 Carbon Letters Vol.33 No.1

Coal tar pitch is a product with high carbon content and aromatic compounds. Modified coal tar pitch is a high quality raw material for the preparation of intermediate phase pitch, needle coke, carbon microspheres, et al. In this paper, modified coal tar pitch was used as raw material, nitrogen was used as protective gas, and thermal conversion was carried out at constant temperatures (370, 390, 410, 420 °C). Polarized light microscopy, SEM, elemental analysis, FTIR spectroscopy, Raman spectroscopy and XRD diffraction combined with split-peak fitting were used to characterize the microstructures of the thermal transformation products. The results showed that the Iar and CH3/ CH2 contents of the products increased with the gradual increase of the thermal conversion temperature, and the aromatic content increased. And the higher the temperature at the same heating rate, the more the ideal graphite microcrystal content, and the defective graphite microcrystals are converted into ideal graphite microcrystals during the thermal conversion process. When the reaction temperature exceeds 390 °C, the microstructure of the thermal transformation products is anisotropic spheres, and the small spheres fuse with each other and tend to be basin-like and mosaic structure as the temperature increases.

Off-design performance analysis of a closed-cycle ocean thermal energy conversion system with solar thermal preheating and superheating

Aydin, H.,Lee, H.S.,Kim, H.J.,Shin, S.K.,Park, K. Pergamon Press 2014 RENEWABLE ENERGY Vol.72 No.-

This article reports the off-design performance analysis of a closed-cycle ocean thermal energy conversion (OTEC) system when a solar thermal collector is integrated as an add-on preheater or superheater. Design-point analysis of a simple OTEC system was numerically conducted to generate a gross power of 100 kW, representing a base OTEC system. In order to improve the power output of the OTEC system, two ways of utilizing solar energy are considered in this study: (1) preheating of surface seawater to increase its input temperature to the cycle and (2) direct superheating of the working fluid before it enters a turbine. Obtained results reveal that both preheating and superheating cases increase the net power generation by 20-25% from the design-point. However, the preheating case demands immense heat load on the solar collector due to the huge thermal mass of the seawater, being less efficient thermodynamically. The superheating case increases the thermal efficiency of the system from 1.9% to around 3%, about a 60% improvement, suggesting that this should be a better approach in improving the OTEC system. This research provides thermodynamic insight on the potential advantages and challenges of adding a solar thermal collection component to OTEC power plants.

인공위성 구조모듈의 열변형 해석을 위한 온도 자동 변환 전산프로그램 개발

김도형(Do Hyung Kim),임형은(Hyung Eun Im),이희남(Huinam Rhee),황도순(Do Soon Hwang) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.11

지구궤도 상에서 운용되는 인공위성의 구조체는 태양의 영향으로 각 부품들 위치마다 온도 분포가 다르고 이에 따라 열변형을 하게 되며, 따라서 카메라 및 여러 과학 탑재체에 열지향 오차가 발생하게 된다. 이러한 열지향 오차를 줄이기 위해 위성 구조 설계 단계에서 인공위성 열 변형 해석을 필수적으로 하는데, 상대적으로 덜 상세한 위성 열 해석 모델을 이용하여 구한 3차원 구조체의 온도 분포 데이터를 이용하여 상세한 위성 구조해석 모델에 적합한 온도 분포 입력 데이터로 변화하는 과정이 필요하며, 이것은 매우 복잡하고 어려운 과정이어서 오류를 유발하기 쉽다. 본 연구에서는 내삽 및 외삽법을 이용하여 체계적이고 정확하게 온도 분포 데이터를 자동 변환하여 주는 알고리즘을 개발하였고 이를 기반으로 윈도우 그래픽 기반의 전산프로그램을 개발하였다. 본 연구에서 개발한 방법을 이용하면 다양한 위성구조체의 열변형 해석 시간을 획기적으로 단축시키고 정확성을 대폭 높일 수 있는 장점이 있다. Artificial satellite structures undergo thermal deformation during operation in Earth orbit depending on the temperature distribution. The thermal deformation directly causes thermal pointing errors of cameras and other scientific payloads. Therefore, it is necessary to perform the thermal deformation analysis of satellite structures to minimize thermal pointing errors. Because the thermal model and structural models have different structures, the temperature data generated using the thermal model is not compatible with the structural model. Therefore, there is a need for a temperature-conversion process between two models. In this paper, an effective algorithm is proposed for the automatic conversion process. Finally, a computer program is successfully developed to perform the precise conversion in a relatively short time period.

열발전소자를 이용한 전력변환장치의 성능 평가

왕호,김해지,양영준 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.5

This study was performed to verify performance of power conversion device, which could product small scale power, using waste heat and thermoelectric generator. For this purpose, after conducting the analyses of thermal stress and thermal flow on power conversion device, experimental apparatus as well as power conversion device was manufactured and then its performance was tested. As for the results of analyses, it was confirmed that high temperature part of power conversion device was safe in case of maximum 160℃ for thermal stress. As for thermal flow, case of Input A was shown more vortex and large flow velocity than case of Input B due to influence of internal structure of power conversion device. As for experimental results, the power in case of water-cooling, which showed 5.31 volts as maximum power, was about 9∼13 times higher than case of air-cooling.