Article
Thermodynamics
Geng Di Sia, Chang Sheng Lim, Ming Kwang Tan, Gooi Mee Chen, Yew Mun Hung
Summary: A study investigates subcooled flow boiling in a microchannel heat sink with superhydrophilic and superhydrophobic graphene nanoplatelets (GNPs) composite coatings. The superhydrophobic coating significantly enhances the flow boiling performance, with improved critical heat flux and heat transfer coefficient.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2023)
Article
Chemistry, Physical
Agnieszka Kujawska, Robert Mulka, Samah Hamze, Gawel Zyla, Bartosz Zajaczkowski, Matthias H. Buschmann, Patrice Estelle
Summary: Thermosyphons are efficient heat transfer devices that can be enhanced by using nanofluids. The impact of nanofluids is most significant in the boiling process in the evaporator section, where nanoparticles tend to deposit on the heater's surface, altering the characteristics of the nanofluid.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2021)
Article
Thermodynamics
Yong Guo, Chuan-Yong Zhu, Liang Gong, Zong-Bo Zhang
Summary: The effect of surface roughness on the thermal-hydraulic performance of flow boiling in microchannel was investigated using the Fourier series method to generate a surface with random roughness, and the VOF model and Lee model were used for simulation. The results showed that increasing relative roughness initially increased and then decreased Nu and fRe. Microchannels with rough surfaces achieved better thermal-hydraulic performance than those with smooth surfaces. The best thermal-hydraulic performance was observed at a relative roughness of 0.304%. Additionally, increasing the mean width of roughness elements resulted in gentler surface undulation, slower growth rate of Nu, and monotonously increasing fRe. Furthermore, decreasing inlet velocity led to drying up of the liquid film at the bottom of bubbles, resulting in drought spots on the bottom wall and deteriorated heat transfer performance.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Thermodynamics
Xiao Cheng, Junjun Wu
Summary: This study investigates the role of the inlet valve in microchannel flow boiling, particularly its flow reversal suppression (FRS) functionality. The results reveal that small valve openings contribute to stabilizing flow boiling and enhancing critical heat flux at a given mass flux. This study unravels the intricate role of the seemingly simple inlet valve in microchannel flow boiling and emphasizes the importance of incorporating its effects into experimental setups.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2022)
Article
Energy & Fuels
Sadegh Aberoumand, Deepak Dubal, Peter Woodfield, Seyed Masoud Parsa, Kiran Mahale, Hong Duc Pham, Tran Tung, Hong-Quan Nguyen, Dzung Viet Dao
Summary: This study aims to experimentally investigate the long-term effect of using reduced graphene oxide (rGO) nanofluidic electrolyte on vanadium redox flow battery performance. The results show that the optimum concentration of nanofluidic electrolyte (0.1 wt%) can significantly improve the oxidation/reduction peaks, charge transfer resistance, and redox reactions reversibility of the battery. The active surface area of the electrodes is also increased by a significant percentage.
JOURNAL OF ENERGY STORAGE
(2023)
Article
Thermodynamics
Mohammad Jamshidmofid, Abbas Abbassi, Mehdi Bahiraei
Summary: The study focuses on the utilization of graphene quantum dots nanofluid in microchannel heat exchangers. It is found that using nanofluid significantly improves heat transfer rate at Reynolds numbers of 50 and 100 with only a slight increase in pressure drop, while at Reynolds numbers of 150 and 200, a large pressure drop is imposed when using the nanofluid.
APPLIED THERMAL ENGINEERING
(2021)
Article
Thermodynamics
Ritunesh Kumar, Gurjeet Singh, Dariusz Mikielewicz
Summary: Flow maldistribution in microchannel heat sink has negative effects on the boiling process, leading to temperature non-uniformity. The intensity of flow boiling and flow reversal increases with the increase of heat flux. At high heat fluxes, vapor backflow from side microchannels blocks the flow in central microchannel, aggravating boiling in the central channel.
APPLIED THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Xiao Cheng, Junjun Wu
Summary: This study designed microchannels of different widths to investigate the influence of geometry on flow boiling characteristics. It was found that the flow patterns and heat transfer coefficient varied with microchannel widths, and the narrow 50 μm microchannel was highly susceptible to triggering the critical heat flux. Flow instability showed less dependence on microchannels but strong relevance to the mass flux.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
D. D. Ma, Y. X. Tang, G. D. Xia
Summary: The sinusoidal wavy microchannels with secondary channels (SWSC) show better heat removal performance in flow boiling studies compared to conventional microchannels, thanks to increased bubble nucleation induced by enlarged surface area and continuous development of thin liquid film due to the introduction of secondary channels. However, the SWSC microchannels suffer from a higher pressure drop penalty.
APPLIED THERMAL ENGINEERING
(2021)
Article
Thermodynamics
Nishant Tiwari, Manoj Kumar Moharana
Summary: A three-dimensional numerical study on two-phase flow boiling in a rectangular microchannel with wavy vertical wall configuration was conducted for heat dissipation in high flux electronics devices. The study compared straight and wavy microchannels and investigated the behavior of bubble growth rate and two-phase flow pattern in both. The results showed that smaller bubbles were formed in the wavy microchannel while confined and elongated bubbles were formed in the straight microchannel, leading to flow clogging and premature dryout.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Thermodynamics
Yanhong Sun, Ao Huang, Jinli Lu, Yuyan Jiang
Summary: This study experimentally investigated the heat transfer characteristics and dynamic flow boiling instabilities of ethanol in a rectangular microchannel. The results showed that the inhibition of bubble nucleation caused by large bubbles in the confined space led to a deterioration in heat transfer performance. Higher mass flux resulted in more effective bubble nucleation and better heat transfer. The triggering of flow boiling instability in the microchannel was strongly dependent on quasi-periodical flow phenomenon and multiphase alternation. The thermophysical properties of the working liquid significantly affected the fluctuation amplitude.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Yi Yuan, Li Chen, Chuangde Zhang, Xiaoyu Li, Wen-Quan Tao
Summary: This study numerically investigates the subcooling flow boiling heat transfer characteristics in a manifold microchannel (MMC) using a phase change model. The results show that a lower subcooling promotes nucleate boiling but leads to earlier increase in thermal resistance. Optimal channel height and outlet/inlet width ratio optimize the heat transfer performance. Moreover, a new heat transfer correlation is developed, which significantly improves the prediction accuracy of nucleate boiling in MMC compared to existing correlations.
APPLIED THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Gaurav Hedau, Mohammed Qadeer, N. P. Gulhane, Rishi Raj, Sandip K. Saha
Summary: This study proposes simple design modifications of inlet and outlet plenum and port orientations to suppress instabilities in two-phase microchannel heat sinks. Three different designs were investigated along with four orientations. The results show that the size of the inlet and outlet plenums and their orientations have a significant impact on vapor backflow and stability. Based on these findings, simple guidelines for the design of inlet and outlet plenums and port orientations are proposed to suppress the instability in two-phase microchannel heat sinks.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Engineering, Chemical
Meng Wang, Phillip S. Dobson, Manosh C. Paul
Summary: This paper conducts a numerical study to identify the best working conditions to prevent deposition of nanofluids in a microchannel cooling system. The results indicate that large nanoparticles, high velocity, low inlet temperature, high nanoparticle density, low nanofluid density, and high base fluid viscosity are the best working conditions for improving nanofluid stability. However, heat transfer rates and pressure drop must also be taken into account when designing systems.
Article
Thermodynamics
Rishi L. Ramakrishnan, Prasanna Jayaramu, Sateesh Gedupudi, Sarit K. Das
Summary: This study experimentally investigated the effect of copper surface ageing on heat transfer and critical heat flux during flow boiling. The results showed that ageing significantly reduces the heat transfer coefficient on the copper surface, while having an insignificant impact on the critical heat flux. Surface morphology and wettability of copper were found to change after ageing.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Thermodynamics
Cong Li, Jiali Wang, Chenhui Wang, Yanke Jin, Yina Yao, Rui Yang
Summary: This study investigates the impact of NaCl water droplets with various concentrations on a heated surface. The results show that the impact patterns can be categorized into different types, and models are established to predict the spreading behavior of droplets with different concentrations. Additionally, high concentration droplets exhibit more violent boiling and have lower residual energy and rebound time.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
C. Barrera, V. Castro, F. Escudero, J. J. Cruz, I. Verdugo, J. Yon, A. Fuentes
Summary: This study focuses on the characterization of soot maturity and sooting propensity of anisole fuel in a controlled laminar coflow diffusion flame. The results show that the spatial distribution of soot volume fraction is enhanced near the flame centerline, while soot production is promoted near the flame wings. The temperature increase also affects the maturity of soot particles.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Roman W. Morse, Jason Chan, Tiago A. Moreira, Jared J. Valois, Evan T. Hurlburt, Jean-Marie Le Corre, Arganthael Berson, Kristofer M. Dressler, Gregory F. Nellis
Summary: This study investigates the dryout of liquid film and the role of disturbance wave frequency. Experimental results indicate that the heat transfer coefficient associated with optimal boiling conditions is maximized when the surface is dry 5% of the time, independent of pulse amplitude and frequency. Liquid-film measurements, dryout statistics, and direct observation suggest that disturbance-wave frequency can be manipulated by density-wave oscillations in the flow field.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
E. J. Vega, J. M. Montanero
Summary: In this study, we experimentally investigated the bursting of a bubble covered with a surfactant. We found that the bubble bursting time is longer compared to a surfactant-free bubble due to interfacial elasticity. Furthermore, the Marangoni stress drives liquid flow that allows the jet to escape from the end-pinching mechanism within a certain surfactant concentration range.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Guofu Sun, Yi Zhan, Tomio Okawa, Mitsuhiro Aoyagi, Akihiro Uchibori, Yasushi Okano
Summary: Experiments were conducted on liquid jets ejected from oval nozzles to investigate the effects of nozzle orifice shape on jet behavior. The study found that the liquid jet exhibited different characteristics at different liquid flow rates. Correlations were established to predict the liquid jet state and characteristics of the secondary droplets produced during jet impact onto a solid surface. This research extended the available knowledge on liquid jet behavior.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Jeonghoon Lee, Laurent Zimmer, Takeshi Saito, Shinji Nakaya, Mitsuhiro Tsue
Summary: This study investigates the effects of spatial resolution on DMD amplitudes and spatial mode strengths, and proposes scaling factors to correct for the resolution differences. The results show that the proposed scaling factors successfully normalize the amplitudes and spatial modes, allowing for quantitative comparison of data obtained with different spatial resolutions. This study is significant for analyzing spatiotemporal data in various fields.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Yanli Zhao, Shibing Kuang, Xiaoliang Zhang, Mingjun Xu
Summary: This study experimentally investigates the dynamic process of water droplet impacting different wood surfaces and analyzes and discusses the impacting phenomena, phenomena distribution, droplet spreading dynamics, and maximum spread factor. The results show that the impacting process can be distinguished by Weber numbers and Reynolds numbers, and can be predicted by mathematical expressions.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Aakhash Sundaresan, Atul Srivastava, Callum Atkinson
Summary: This study presents the first-ever application of an advanced methodology, combining two-color laser-induced phosphorescence and particle image velocimetry, to investigate the heat transfer mechanisms on the surface of a cylinder placed inside a confined square duct. The technique allows for simultaneous measurement of velocity and temperature fields, reducing the complexity and costs associated with separately measuring temperature distributions. Experimental observations show that increasing the mass flow rate enhances heat removal from the cylinder surface, and increasing the cylinder heat input enhances heat transfer in the rear portion of the cylinder.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Harish K. Patel, Sukhjeet Arora, Rutuja Chavan, Bimlesh Kumar
Summary: This study experimentally analyzed the multiscale statistical assessment of scour depth surrounding spur dikes with downward seepage. The research found that seepage affects the morphological behavior and hydrodynamic characteristics of the channel bed, leading to changes in scour formation. The rate of scour depth changes initially increases with higher seepage velocity but eventually becomes constant over time.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Justas Sereika, Paulius Vilkinis, Gediminas Skarbalius, Algis Dziugys, Nerijus Pedisius
Summary: This study experimentally investigated the pulsatile flow structure based on a transitional-type cavity. It was found that the pulsation amplitude has a more significant effect on the dynamics of recirculation zone than the pulsation frequency. Pulsatile flow can reduce the size of the recirculation zone.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Merav Arogeti, Eran Sher, Tali Bar-Kohany
Summary: This study provides a detailed exploration of the events that occur when a droplet hits a dry solid surface of various small sizes, with a focus on the deposition, receding breakup, and prompt splash phases. By utilizing non-dimensional analysis and graphical representation, the boundaries between different events are defined, and criteria for differentiation based on target-to-drop ratio, Reynolds, and Webber numbers are presented.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Tianxiong Li, Fei Wen, Yingchun Wu, Botong Wen, Lei Wang, Jinxin Guo, Xuecheng Wu
Summary: This study investigates the structure of the flow field induced by a strut in a scramjet and its influence on flame stabilization. Experimental and numerical analyses reveal that the flow field exhibits features beneficial for flame stabilization, but the asymmetry of the flow poses a challenge to flame establishment.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Syed Ehtisham Gillani, Yasir M. Al-Abdeli
Summary: This study investigates the asymmetry in bluff-body stabilised annular jets and finds that swirl can significantly mitigate the asymmetry and restore the symmetry of the jets. Moreover, increasing the Reynolds number and the swirl intensity can both decrease the asymmetry of the jets.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Utsav Bhardwaj, Rabindra Kumar, Shyama Prasad Das
Summary: This study presents an experimental investigation on flooding phenomenon in a pulsating heat pipe (PHP) unit cell, and analyzes the impact of flooding on the performance of PHP. The study recognizes three different flooding mechanisms and finds that currently accepted correlations for predicting flooding velocity are inaccurate. The study emphasizes the need for further research on flooding in PHPs.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Thermodynamics
Yunpeng Xue, Yongling Zhao, Shuo-Jun Mei, Yuan Chao, Jan Carmeliet
Summary: This study investigates the impact of building morphology on local climate, air quality, and urban microclimate. The researchers conducted an experimental investigation in a large-scale water tunnel, analyzing heat and flow fields using Laser-induced Fluorescence (LIF) and Particle Image Velocimetry (PIV). The findings show that factors such as canyon configuration, buoyant force, and approaching flow magnitude significantly influence fluid flow in street canyons, and the morphology of the street canyon dominates ventilation rate and heat flux. For example, changing the aspect ratio of a street canyon can lead to a significant change in air ventilation rate, ranging from 0.02 to 1.5 under the same flow conditions.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)