Numerical study on conjugate heat transfer in a liquid-metal-cooled pipe based on a four-equation turbulent heat transfer model

Li Xian-Wen,Su Xing-Kang,Gu Long,Wang Xiang-Yang,Fan Da-Jun 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.5

Conjugate heat transfer between liquid metal and solid is a common phenomenon in a liquid-metalcooled fast reactor's fuel assembly and heat exchanger, dramatically affecting the reactor’s safety and economy. Therefore, comprehensively studying the sophisticated conjugate heat transfer in a liquidmetal-cooled fast reactor is profound. However, it has been evidenced that the traditional Simple Gradient Diffusion Hypothesis (SGDH), assuming a constant turbulent Prandtl number (Prt, usually 0.85 - 1.0), is inappropriate in the Computational Fluid Dynamics (CFD) simulations of liquid metal. In recent decades, numerous studies have been performed on the four-equation model, which is expected to improve the precision of liquid metal’s CFD simulations but has not been introduced into the conjugate heat transfer calculation between liquid metal and solid. Consequently, a four-equation model, consisting of the Abe k ε turbulence model and the Manservisi kq εq heat transfer model, is applied to study the conjugate heat transfer concerning liquid metal in the present work. To verify the numerical validity of the four-equation model used in the conjugate heat transfer simulations, we reproduce Johnson’s experiments of the liquid lead-bismuth-cooled turbulent pipe flow using the four-equation model and the traditional SGDH model. The simulation results obtained with different models are compared with the available experimental data, revealing that the relative errors of the local Nusselt number and mean heat transfer coefficient obtained with the four-equation model are considerably reduced compared with the SGDH model. Then, the thermal-hydraulic characteristics of liquid metal turbulent pipe flow obtained with the four-equation model are analyzed. Moreover, the impact of the turbulence model used in the four-equation model on overall simulation performance is investigated. At last, the effectiveness of the four-equation model in the CFD simulations of liquid sodium conjugate heat transfer is assessed. This paper mainly proves that it is feasible to use the four-equation model in the study of liquid metal conjugate heat transfer and provides a reference for the research of conjugate heat transfer in a liquidmetal-cooled fast reactor

유사 조성의 모재분말과 Ni기 삽입금속 혼합분말을 사용한 천이액상확산 접합 시 모재의 용해현상

송우영,예창호,강정윤,Song, Woo-Young,Ye, Chang-Ho,Kang, Chung-Yun 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.3

The dissolution phenomenon of the solid phase powder and base metal by liquid phase insert metal during Transient Liquid Phase bonding using the mixed powder composed of the modified GTD111(base metal) powder and the GNi3 (Ni-l4Cr-9.5Co-3.5Al-2.5B) powder was investigated. In case of the mixed powder contains modified GTD111 powder 50wt%, all of the powder was melted by liquid phase at 1423K. At the temperature between solidus and liquidus of GNi3, liquid phase penetrated into the boundary of the modified GTD111 powder and solid particle separated from powder was melted easily because area of reaction was increased. With increasing mixing ratio of the modified GTD111, it needed the higher temperature to melt all of the modified GTD111 powder. During Transient Liquid Phase bonding using the mixed powder composed of the modified GTD111 50wt% and GNi3 50wt% as insert metal, width of the bonded interlayer was increased with increasing bonding temperature by reaction of the base metal and liquid phase in insert metal. Dissolution of the base metal and modified powder by liquid phase progressed all together and after all of the powder was melted nearly, the dissolution of the base metal occurred quickly.

Experimental validation of simulating natural circulation of liquid metal using water

Lee, Min Ho,Jerng, Dong Wook,Bang, In Cheol Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.9

Liquid metal-cooled reactors use various passive safety systems driven by natural circulation. Investigating these safety systems experimentally is more advantageous by using a simulant. Although numerous experimental approaches have been applied to natural circulation-driven passive safety systems using simulants, there has been no clear validation of the similarity law. To validate the similarity law experimentally, SINCRO-V experiment was conducted using Wood's metal and water for simulant of the Wood's metal. A pair of SINCRO-V facilities with length-scale ratio of 14.1:1 for identical Bo' was investigated, which was the main similarity parameter in temperature field simulation. In the experimental range of 0.2-1.0% of decay heat, the temperature distribution characteristics of the small water facility were very similar to that of the large Wood's metal facility. The temperature of the Wood's metal predicted by the water experiment showed good agreement with the actual Wood's metal temperature. Despite some error factors like discordance of Gr' and property change along the temperature, the water experiment predicted the Wood's metal temperature with an error of 27%. The validity of the similarity law was confirmed by the SINCRO-V experiments.

Photolithography-Based Patterning of Liquid Metal Interconnects for Monolithically Integrated Stretchable Circuits

Park, Chan Woo,Moon, Yu Gyeong,Seong, Hyejeong,Jung, Soon Won,Oh, Ji-Young,Na, Bock Soon,Park, Nae-Man,Lee, Sang Seok,Im, Sung Gap,Koo, Jae Bon American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.24

<P>We demonstrate a new patterning technique for gallium-based liquid metals on flat substrates, which can provide both high pattern resolution (similar to 20 mu m) and alignment precision as required for highly integrated circuits. In a very similar manner as in the patterning of solid metal films by photolithography and lift-off processes, the liquid metal layer painted over the whole substrate area can be selectively removed by dissolving the underlying photoresist layer, leaving behind robust liquid patterns as defined by the photolithography. This quick and simple method makes it possible to integrate fine-scale interconnects with preformed devices precisely, which is indispensable for realizing monolithically integrated stretchable circuits. As a way for constructing stretchable integrated circuits, we propose a hybrid configuration composed of rigid device regions and liquid interconnects, which is constructed on a rigid substrate first but highly stretchable after being transferred onto an elastomeric substrate. This new method can be useful in various applications requiring both high-resolution and precisely aligned patterning of gallium-based liquid metals.</P>

Rewritable, Printable Conducting Liquid Metal Hydrogel

Park, Jung-Eun,Kang, Han Sol,Baek, Jonghyek,Park, Tae Hyun,Oh, Seunghee,Lee, Hyungsuk,Koo, Min,Park, Cheolmin American Chemical Society 2019 ACS NANO Vol.13 No.8

<P>The development of high-performance printable electrical circuits, particularly based on liquid metals, is fundamental for device interconnection in flexible electronics, motivating numerous attempts to develop a variety of alloys and their composites. Despite their great potential, rewritable and printable electronic circuits based on liquid metals are still manufactured on demand. In this study, we demonstrate liquid metal-based hydrogels suitable for rewritable, printable electrical circuits. Our liquid metal hydrogels are based on sedimentation-induced composites of eutectic gallium-indium (EGaIn) particles in poly(ethylene glycol) diacrylate (PEGDA). The EGaIn particles are vertically phase-segregated in the PEGDA. When a composite surface with high EGaIn content is gently scratched, the surface covering PEGDA is removed, followed by the rupture of the native oxide layers of the particles, and the exposed EGaIn becomes conductive. The subsequent water-driven swelling of PEGDA on the scratched surface completely erases the conductive circuit, causing the system to reset. Our friction-responsive liquid metal hydrogel exhibits writing-erasing endurance for 20 cycles, with a dramatic change in the electrical resistance from metal (∼1 Ω) to insulator (∼10<SUP>7</SUP> Ω). By employing surface friction pen printing, we demonstrate mechanically flexible, rewritable, printable electrical conductors suitable for displays.</P> [FIG OMISSION]</BR>

액체금속을 활용한 플렉서블 섬유상 전극 제조 및 도파민 센서로의 응용

임태환,이소희,여상영 한국섬유공학회 2022 한국섬유공학회지 Vol.59 No.4

Gallium-based liquid metals have gained significant attention as promisingmaterial platforms for flexible bioelectronics owing to their fluidic behavior but still metallic. However, low electrochemical stability owing to oxidation may limit the use of bioelectronicsthat typically operate under physiological conditions. Here, we developed a liquidmetal core/polymer shell fiber platform for flexibility. Then, nanostructured conductivepoly(3,4-ethylenedioxythiophene) (PEDOT) was encapsulated on the liquid metal surfaceto prevent oxidation. Mechanical property measurement demonstrated that the platformdisplayed high flexibility and low Young’s modulus that could minimize the mechanicalmismatch between the fiber platform and soft human tissues. PEDOT encapsulation on theliquid metal surface offered the fiber platform-based electrode considerably higher electrochemicalproperties, such as lower impedance and higher charge storage capacity. Theimproved electrochemical performance enables the liquid metal-based fiber electrode tobe used for electrochemical dopamine (DA) monitoring. This study demonstrated that thePEDOT structured flexible electrode had a sensitivity of 0.218±0.022 μA/μM and a limit ofdetection of 150 nM. Finally, the electrode could effectively detect DA under a plethora ofbyproducts produced by human metabolism. All the results confirmed the flexibility andremarkable electrochemical properties of the prepared liquid metal-based electrode,opening numerous design opportunities for next-generation liquid metal-based bioelectronics.

First Studies for the Development of Computational Tools for the Design of Liquid Metal Electromagnetic Pumps

Carlos O. Maidana,Juha E. Nieminen 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.1

Liquid alloy systems have a high degree of thermal conductivity, far superior to ordinary nonmetallic liquids and inherent high densities and electrical conductivities. This results in the use of these materials for specific heat conducting and dissipation applications for the nuclear and space sectors. Uniquely, they can be used to conduct heat and electricity between nonmetallic and metallic surfaces. The motion of liquid metals in strong magnetic fields generally induces electric currents, which, while interacting with the magnetic field, produce electromagnetic forces. Electromagnetic pumps exploit the fact that liquid metals are conducting fluids capable of carrying currents, which is a source of electromagnetic fields useful for pumping and diagnostics. The coupling between the electromagnetics and thermo-fluid mechanical phenomena and the determination of its geometry and electrical configuration, gives rise to complex engineering magnetohydrodynamics problems. The development of tools to model, characterize, design, and build liquid metal thermomagnetic systems for space, nuclear, and industrial applications are of primordial importance and represent a cross-cutting technology that can provide unique design and development capabilities as well as a better understanding of the physics behind the magneto-hydrodynamics of liquid metals. First studies for the development of computational tools for the design of liquid metal electromagnetic pumps are discussed.

Separation of Oxide Inclusions from Liquid Metal in an Applied Electrostatic Field

Kim, Jae H.,Lee, Jung M.,Shin, Ho C.,Paik, Young H. 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.6

It is known that oxide inclusions in liquid metal carry mostly positive charges on their surfaces. In an electrostatic field, therefore, such charged particles suspended in a liquid metal experience forces and accumulate in the region of the negatively charged surface, resulting in the separation of oxide inclusions from the liquid metal. In this study, this principle was experimentally demonstrated for the case of a capacitor cell by the imposition of a d.c. potential on electrodes. The capacitor cell consisted of a dielectric container of Pyrex tube, a high voltage d.c. source, and two electrodes, which were symmetrically attached onto the outer surface of the Pyrex tube. Experiments were carried out for suspensions of liquid tin/metal oxides, such as SnO₂, WO₃, and PbO under an applied potential of up to 12 kV. All experimental results were in good agreement with the theoretical prediction and showed that the degree of separation was significantly increased with the applied potential.

Functionalized 2D transition metal dichalcogenide inks via liquid‐phase exfoliation for practical applications

정연수,Samorì Paolo 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.2

Transition metal dichalcogenides (TMDs) are promising 2D materials which are attracting significant interest because of their distinctive physicochemical properties. The possibility of being exfoliated and dispersed in liquid solutions offers a viable pathway to scalable production. This personal account focuses on recent advancements in 2D TMD inks produced by liquid‐phase exfoliation (LPE) methods and intercalation‐based electrochemical exfoliation. In particular, different LPE production strategies, like ultrasonication LPE, high‐shear mixing exfoliation, and microfluidization, are introduced alongside a broad range of liquid media employed to provide functionalized TMD inks. The main advantage of TMD inks is its scalability, for practical applications in printed optoelectronics, energy storage, and conversion. Furthermore, the chemical functionalization of TMD inks can solve the poor electrical conductivity attributed to edge defects inherent in TMD inks. Finally, the ultimate orientations for future applications of chemically functionalized TMD devices are forecasted, with a specific focus on wearable and flexible printed electronics. Transition metal dichalcogenides (TMDs) are promising 2D materials which are attracting significant interest because of their distinctive physicochemical properties. The possibility of being exfoliated and dispersed in liquid solutions offers a viable pathway to scalable production. This personal account focuses on recent advancements in 2D TMD inks produced by liquid-phase exfoliation (LPE) methods and intercalation-based electrochemical exfoliation. In particular, different LPE production strategies, like ultrasonication LPE, high-shear mixing exfoliation, and microfluidization, are introduced alongside a broad range of liquid media employed to provide functionalized TMD inks. The main advantage of TMD inks is its scalability, for practical applications in printed optoelectronics, energy storage, and conversion. Furthermore, the chemical functionalization of TMD inks can solve the poor electrical conductivity attributed to edge defects inherent in TMD inks. Finally, the ultimate orientations for future applications of chemically functionalized TMD devices are forecasted, with a specific focus on wearable and flexible printed electronics.

The transfer characteristics of heavy metals in electronic cigarette liquid

Na, Chae-Jin,Jo, Sang-Hee,Kim, Ki-Hyun,Sohn, Jong-Ryeul,Son, Youn-Suk Academic Press 2019 Environmental research Vol.174 No.-

<P><B>Abstract</B></P> <P>In this research, the concentrations of six heavy metals (Zn, Pb, Ni, Fe, Cd, and Cr) in electronic cigarette (EC) solutions were determined to assess their association with EC use patterns. To this end, their contents were analyzed under three conditions: (1) ECL I: EC liquid was directly taken from EC liquid bottles as purchased from retail, (2) ECL II: EC liquid simply stored in the EC clearomizer for a certain period was collected without any puffing, and (3) ECL III: EC liquid remaining in the EC clearomizer after puffing. Each of all three types of electronic cigarette liquid (ECL) samples selected in this study was analyzed after being stored for up to seven days (at elapsed intervals of 1, 3, and 7 days). Zn and Pb were detected in all types of samples while Cd was all below method detection limit (MDL). Fe, Ni, and Cr were generally below MDL in ECL I, while it was not the case for ECL II and III samples. Especially, Zn, Pb, and Ni levels increased significantly with the use of EC. If the consumption of EC causes alterations in elemental content, such changes can be assessed in terms of ratio values such as “after/before use”. The maximum ratio values for each target, when assessed using ECL III samples, were seen in the following order: 463 (Zn) > 315 (Ni) > 131 (Fe) > 47.9 (Cr) > 36.0 (Pb). As such, EC use is clearly demonstrated as the transfer route of heavy metals.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study investigated heavy metals released into EC liquids through storage or use. </LI> <LI> Heavy metal components can be released by simply contacting the coil and device parts. </LI> <LI> It was confirmed that some of metals were released by the heat supply by the coil. </LI> <LI> All types of routes for metal releases into EC liquids are identified and described. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>