Article
Thermodynamics
Hyeon Taek Nam, Hyung Hee Cho, Seungro Lee, Donghwi Lee
Summary: The study investigated the impact of surface roughness on wicking performance and critical heat flux (CHF) enhancement using micropillar structures. The results showed that the highly-rough surface exhibited better wicking performance and significantly improved CHF due to delayed vapor film formation. A new correlation model was proposed based on experimental data, which accurately predicted CHF within a 9% error.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2023)
Article
Thermodynamics
Youngsup Song, Lenan Zhang, Carlos D. Diaz-Marin, Samuel S. Cruz, Evelyn N. Wang
Summary: This study investigates the role of structured surfaces in enhancing critical heat flux (CHF) during pool boiling. The results show that CHF enhancement on structured surfaces cannot be solely explained by roughness or wickability. A unified descriptor, representing the combined effects of thin film density and volumetric wicking rate, is derived and shows a reasonable correlation with CHF values.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Gangtao Liang, Han Yang, Jiajun Wang, Shengqiang Shen
Summary: This study assesses the pool boiling critical heat flux (CHF) of nanofluids, demonstrating that the maximum CHF ratio of nanofluid to base fluid can reach 4 and 4.6 for different orientations of heaters. The type of heater (wire or block) has a significant impact on CHF, with direct electric-heating wire heaters accelerating nanoparticle deposition. Pressure and nanoparticle size affect CHF, but dispersion level of particles in base fluid plays a more crucial role in determining CHF ratio.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Engineering, Mechanical
Dong Il Shim, Wei-Ting Hsu, Maroosol Yun, Dongwhi Lee, Beom Seok Kim, Hyung Hee Cho
Summary: Surface manipulations have been used to enhance boiling performance by improving the heat transfer coefficient and critical heat flux. In this study, artificially patterned super-biphilic (SBPI) surfaces were utilized to overcome the limitation of liquid supply in hydrophobic regions and enhance boiling performance. The results highlight the importance of considering both wettability and bubble behaviors in designing structured surfaces for boiling.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Nanoscience & Nanotechnology
Youngsup Song, Shuai Gong, Geoffrey Vaartstra, Evelyn N. Wang
Summary: Boiling is a fundamental process in many applications where surfaces with microcavities or biphilic wettability can enhance heat transfer efficiency. This study investigated microtube structures to simultaneously enhance heat transfer coefficient and critical heat flux, achieving significant improvements compared to smooth surfaces. The combination of micropillars and microtubes further increased critical heat flux by separating nucleating bubbles and rewetting liquids.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Thermodynamics
Mayowa I. Omisanya, Zhihao Chen, Yoshio Utaka
Summary: Flow boiling heat transfer was studied using a different-mode-interacting boiling (DMIB) method to enhance critical heat flux (CHF) and heat transfer coefficient (HTC). The nonuniform surfaces were found to significantly improve CHF under certain conditions, showing the potential for enhanced performance.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Zhen Cao, Bengt Sunden, Zan Wu
Summary: The present study investigates boiling heat transfer enhancement on coated surfaces using mechanistic models. The results show that the coatings on copper surfaces significantly increase the critical heat flux and heat transfer coefficient of deionized water, with the coated surface providing more active nucleation sites. Based on these insights, a heat transfer model is established and the critical heat flux is explored experimentally and theoretically.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Chemistry, Multidisciplinary
Jiaqi Li, Yongyi Zhao, Jingcheng Ma, Wuchen Fu, Xiao Yan, Kazi Fazle Rabbi, Nenad Miljkovic
Summary: This study investigates the degeneration of wicking capability on structured surfaces and emphasizes the importance of environmental volatile organic compound adsorption. The authors design a hierarchical structure with superior wicking capability and anti-degeneration performance, demonstrating a 4100% increase in durability compared to single-tier structures. The research also reveals the coexistence of dry areas underneath individual bubbles during boiling on highly wicking surfaces, leading to significant augmentation of the three-phase contact line length.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Thermodynamics
Atul Ranjan, Israr Ahmad, Rinku Kumar Gouda, Manabendra Pathak, Mohd Kaleem Khan
Summary: This study reports the creation of Cu(OH)2 nanoneedles on a copper surface using an anodization process, which can enhance critical heat flux (CHF) limit in pool boiling applications by improving surface wettability and wickability. Results show that the anodized surface requires higher wall superheat for nucleation and exhibits a higher CHF value compared to the plain surface.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2022)
Article
Chemistry, Multidisciplinary
Qun Cao, Zirui Li, Zheng Cui
Summary: This paper investigates the effect of surface roughness on liquid-vapor phase change heat transfer and its microscopic mechanism using molecular dynamics simulation. The results show that pits on rough surfaces provide stable nucleation sites for bubbles, and as the surface roughness increases, bubble generation, merging, and growth are advanced.
Article
Thermodynamics
Seyed Moein Rassoulinejad-Mousavi, Firas Al-Hindawi, Tejaswi Soori, Arif Rokoni, Hyunsoo Yoon, Han Hu, Teresa Wu, Ying Sun
Summary: This research explores how deep learning can adapt to new datasets with limited data, studying convolutional neural networks and transfer learning. The study found that transfer learning outperforms convolutional neural networks in cases of data scarcity, demonstrating higher accuracy and lower false negative rates.
APPLIED THERMAL ENGINEERING
(2021)
Article
Thermodynamics
Lin Lin, Yanxin Hu, Zipei Su, Minghan Zhu, Jin Huang, Changxiang Fan
Summary: The preparation of micro-nano hybrid structured copper surfaces through sandblasting and ultrasonic wet etching techniques has been investigated for its impact on nucleate pool boiling. The study found that the hybrid structure exhibits improved critical heat flux and heat transfer coefficient compared to smooth and individual micro or nano structured surfaces. The enhancement mechanisms are attributed to the combined effects of roughness, surface area ratio, and wettability.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Physics, Applied
Madhumitha Ravichandran, Guanyu Su, Chi Wang, Jee Hyun Seong, Artyom Kossolapov, Bren Phillips, Md Mahamudur Rahman, Matteo Bucci
Summary: A neural network model was developed to predict the departure from nucleate boiling ratio (DNBR) using high-resolution infrared measurements of bubble dynamics on different surfaces. The importance of fundamental boiling parameters such as nucleation site density, bubble departure frequency, growth time, and footprint radius in predicting the boiling crisis was elucidated. The study concluded that these parameters are equally necessary and important, undermining the general validity of models attempting to predict critical heat flux based on single boiling parameters.
APPLIED PHYSICS LETTERS
(2021)
Article
Thermodynamics
Pulak Sen, Sanjib Kalita, Dipak Sen, Ajoy Kumar Das, Bidyut Baran Saha
Summary: In this study, hydrophobic copper micro-structured surfaces were prepared through chemical etching and heat treatment, resulting in different micro-structural features. The experimental results showed that the prepared hydrophobic surfaces have a higher heat transfer coefficient, although the critical heat flux is slightly smaller compared to the bare copper surface. Additionally, the micro-porous surface prepared by a combination of two conventional processes significantly improves heat transfer.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
W. J. Van den Bergh, H. R. Moran, J. Dirker, C. N. Markides, J. P. Meyer
Summary: The study investigated flow boiling of R-245fa at low mass and heat fluxes. It was found that the heat transfer coefficient was influenced by both mass and heat fluxes, with an increase in mass flux leading to an increase in heat transfer coefficient. Higher vapor quality cases were more sensitive to mass flux, except at low heat flux conditions.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Engineering, Mechanical
Taehyun Kim, Eui Yeop Jung, Minho Bang, Changyong Lee, Hee Koo Moon, Hyung Hee Cho
Summary: Impingement cooling is an effective cooling method for high-temperature devices. This study investigates the reduction of crossflow effect in impingement cooling by using a castellated hole plate. Experimental results show that both castellated cases with and without rib structures effectively reduce the crossflow and improve the heat/mass transfer performance.
JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME
(2022)
Article
Thermodynamics
Wei-Ting Hsu, Namkyu Lee, Donghwi Lee, JeongJu Kim, Maroosol Yun, Hyung Hee Cho
Summary: Recent research has focused on anisotropic wicking surfaces, which show improved boiling heat transfer by using bent polymerized pillar arrays compared to surfaces with vertically polymerized pillars. Experimental results confirmed the enhancements of critical heat flux and heat transfer coefficient on anisotropic wicking surfaces, and the relationship between liquid pinning forces and polymerized pillar surfaces was theoretically analyzed for a better understanding of the enhanced boiling heat transfer during subcooled flow boiling.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Energy & Fuels
Seok Min Choi, Hyun Goo Kwon, Taehyun Kim, Hee Koo Moon, Hyung Hee Cho
Summary: This study analyzes the effect of acoustic excitation on the cooling performance of internal channels in a solar PV cell system. The experiments showed that a specific frequency of acoustic excitation significantly enhanced the cooling performance.
Article
Thermodynamics
Seungyeong Choi, Maroosol Yun, Kiwoong Kim, Yong-Ki Park, Hyung Hee Cho
Summary: This study investigates an energy-efficient design of a circulating fluidized bed reactor using numerical simulation and experimental verification. An innovative design with junctions improves the heat transfer performance and has a large thermal margin, making it suitable for continuous CO2 capture.
Article
Thermodynamics
JeongJu Kim, Ho-Seong Sohn, Ho Seop Song, Ju Hyun Im, Hee Koo Moon, Hyung Hee Cho
Summary: The efficiency of the gas turbine engine has been improved by enhancing aerodynamic performance and reducing heat load through control of secondary vortices. This study investigates the heat transfer characteristics of flat and profiled endwalls under different turbulence intensities. The results show that the profiled endwall can significantly decrease the intensity of the horseshoe vortex compared to the flat endwall.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Wei-Ting Hsu, Namkyu Lee, Maroosol Yun, Donghwi Lee, Hyung Hee Cho
Summary: The energy management issues of data center cooling systems have become more severe due to the miniaturization of electronic components. Two-phase immersion cooling is the most potential cooling method for resolving the energy consumption issues. By using polymerized surfaces with anisotropic pillar structures, the overall heat transfer performance can be further improved.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Multidisciplinary Sciences
Beom Seok Kim, Suk-Ho Hong, Keeman Kim
Summary: This paper examines the safety factors and feasibility of nuclear fusion technology under the current legislative environment, using the Korean Fusion Demonstration Reactor (K-DEMO) as a case study. By analyzing precedent licenses and lessons learned, the study proposes methods to ensure regulatory compliance and discusses relevant aspects of regulatory framework.
SCIENTIFIC REPORTS
(2022)
Article
Materials Science, Multidisciplinary
Namkyu Lee, Joon-Soo Lim, Injoong Chang, Hyung Mo Bae, Juyeong Nam, Hyung Hee Cho
Summary: This paper introduces a flexible assembled metamaterial (FAM) for multispectral camouflage by assembling infrared emitters and microwave absorbers. By controlling the wavelengths of infrared radiation and microwave absorption, effective camouflage in the infrared and microwave regimes is achieved.
ADVANCED OPTICAL MATERIALS
(2022)
Article
Thermodynamics
Geehong Choi, Maroosol Yun, Wei-Ting Hsu, Dong Il Shim, Donghwi Lee, Beom Seok Kim, Hyung Hee Cho
Summary: In this study, a new nucleation patterned surface was proposed by embedding micropillar-free cavities in a micropillar array and coating them with rGO to suppress bubble coalescence and enhance boiling heat transfer. High heat transfer performance was achieved by constructing toned rGO layers on the patterned micropillar surfaces.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Chemistry, Physical
Namkyu Lee, Joon-Soo Lim, Juyeong Nam, Hyung Mo Bae, Hyung Hee Cho
Summary: This article introduces durable camouflage materials for infrared waves, which coat the micro-nano structures with polyimide nanofilm. The research findings show that this material performs well in terms of mechanical properties and can maintain its infrared camouflage performance.
APPLIED SURFACE SCIENCE
(2023)
Article
Thermodynamics
Minho Bang, Seungyeong Choi, Seok Min Choi, Hee Koo Moon, Hyung Hee Cho
Summary: In this study, the effect of cooling slot location on film cooling effectiveness and flow characteristics of the blade tip with slot cooling was investigated, considering the application of additive manufacturing. The experimental results showed that the PS slot configuration provided superior blade tip cooling performance under most operating conditions, while the SS slot configuration only provided outstanding cooling performance at a large amount of coolant mass flow rate.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Thermodynamics
Seon Ho Kim, Chul Park, Hee Seung Park, Hee Koo Moon, Hyung Hee Cho
Summary: A wing-shaped structure design is proposed to improve impingement jet array heat transfer in a corrugated channel by weakening crossflow degradation. Local heat/mass transfer distributions were measured using the naphthalene sublimation method, and pressure drop characteristics were examined through pressure measurements. Detailed flow structures were analyzed through numerical simulations.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Biochemical Research Methods
Sangwoo Shin
Summary: DC electrokinetics enables the manipulation and assembly of colloidal particles, contributing to the understanding of life origin and the synthesis of new materials for various applications.
Article
Mechanics
Jesse T. Ault, Sangwoo Shin, Allan Garcia, Antonio Perazzo, Howard A. Stone
Summary: Glycerol is hygroscopic and its viscosity decreases as it absorbs water vapour from the atmosphere. Experimental measurements of glycerol viscosity in a rheometer show that it decreases with time as water is absorbed and transported within the glycerol. The rate of viscosity decrease has a non-monotonic relationship with the rheometer gap height.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Fluids & Plasmas
Viet Sang Doan, Dong-Ook Kim, Craig Snoeyink, Ying Sun, Sangwoo Shin
Summary: We study the diffusion and aggregation of ellipsoidal particles induced by ionic solute gradients. Contrary to the common assumption that diffusion and aggregation are independent of particle shape, we experimentally show that the shape of the particles can affect these processes when the thin Debye layer approximation is relaxed. By tracking the translation and rotation of different ellipsoids, we find that the phoretic mobility of ellipsoids is sensitive to their eccentricity and orientation relative to the solute gradient, and can exhibit nonmonotonic behavior under strong confinement. We demonstrate that modifying theories for spheres can easily capture the shape- and orientation-dependent diffusion and aggregation of colloidal ellipsoids.
