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Impact of fin Arrangement on Heat Transfer and Melting Characteristics of Phase Change Material

Journal of Thermal Science 2024年第2期33卷 435-456页

作者： Arun UNIYAL Yogesh K.PRAJAPATI Department of Mechanical Engineering National Institute of Technology UttarakhandSrinagar(Garhwal)246174India Department of Mechanical Engineering BIT SindriDhanbadJharkhand828123India

Present work investigates the heat transfer and melting behaviour of phase change material(PCM) in six enclosures(enclosure-1 to 6) filled with paraffin wax.Proposed enclosures are equipped with distinct arrangements of the fins while keeping the fin's surface area equal in each case.Comparative analysis has been presented to recognize the suitable fin arrangements that facilitate improved heat transfer and melting rate of the PCM.Left wall of the enclosure is maintained isothermal for the temperature values 335 K,350 K and 365 K.Dimensionless length of the enclosure including fins is ranging between 0 and 1.Results have been illustrated through the estimation of important performance parameters such as energy absorbing capacity,melting rate,enhancement ratio,and Nusselt number.It has been found that melting time(to melt 100% of the PCM) is 60.5%less in enclosure-2(with two fins of equal length) as compared to the enclosure-1,having no fins.Keeping the fin surface area equal,if the longer fin is placed below the shorter fin(enclosure-3),melting time is further decreased by 14.1% as compared to enclosure-2.However,among all the configurations,enclosure-6 with wire-mesh fin structure exhibits minimum melting time which is 68.4% less as compared to the enclosure-1.Based on the findings,it may be concluded that fins are the main driving agent in the enclosure to transfer the heat from heated wall to the PCM.Proper design and positioning of the fins improve the heat transfer rate followed by melting of the PCM in the entire area of the enclosure.Evolution of the favourable vortices and natural convection current in the enclosure accelerate the melting phenomenon and help to reduce charging time.

关键词： phase change material enclosure fin melting fraction energy storage heat transfer

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Thermal Analysis of Melting Occurring Inside a finned Rectangular Enclosure Equipped with Discrete Pulsed Protruding Heat Sources

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Fluid Dynamics & Materials Processing 2022年第5期18卷 1539-1549页

作者： Brahim Amahan Hamid El Qarnia Ali El Afif Faculty of Sciences Department of PhysicsLaboratory of Innovation in Sciences Technology and ModelingChouaib Doukkali UniversityEl JadidaMorocco Faculty of Sciences Semlalia Fluid Mechanics and Energetic LaboratoryDepartment of PhysicsCadi Ayyad UniversityMarrakeshMorocco

This paper numerically investigates the effect of the location of a horizontal fin on the melting of a phase change material(PCM)inside a rectangular enclosure heated by multiple discrete pulsed protruding heat sources.The fin and the phase change material filling the enclosure store the thermal energy extracted from the heat sources,in sensible and latent forms.The heat sources are assumed to simulate electronic components undergoing a superheating technical issue.By extracting heat from the electronics,the PCM plays the role of a heat sink.To analyze the thermal behavior and predict the cooling performance of the proposed cooling system,we derive a nonlinear mathematical model based on mass,momentum and energy conservation laws.Several numerical investigations are conducted to quantify the influence of the fin position on the thermal behavior and the cooling performance of the heat sink.Predictions include the transient maximum temperature occurring inside the heat sources and the liquid volume.A comparison between our numerical results and experimental data selected from the literature shows a good agreement.The main conclusion is that the presence of the fin leads to a slight increase in the melting time.

关键词： Phase change material melting heat transfer pulsed heating electronics cooling heat storage fin

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Depressed female cynomolgus monkeys(Macaca fascicularis) display a higher second-to-fourth(2D:4D)digit ratio

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Zoological Research 2019年第3期40卷 219-225页

作者： Wei Li Ling-Yun Luo Xun Yang Yong He Bin Lian Chao-Hua Qu Qing-Yuan Wu Jian-Guo Zhang Peng Xie Department of Neurology Army Medical Center of PLAChongqing 400042China Institute of Neuroscience Chongqing Medical UniversityChongqing 400016China Chongqing Key Laboratory of Neurobiology of Chongqing Medical University Chongqing 400016China Department of Neurology the Third Affiliated Hospital of Sun Yat-Sen University Yuedong HospitalGuangzhou Guangdong 514700China

This research aimed to provide evidenee of a relationship between digit ratio and depression status in the cynomolgus monkey(Macaca fascicularis).In stable cyno molgus mon key social groups,we selected 15 depressed monkeys based on depressive-like behavioral criteria and 16 normal control mon keys.All animals were video recorded for two weeks,with the duration and frequency of the core depressive behaviors and 58 other behaviors in 12 behavioral categories then evaluated via behavioral analysis.fin ger len gths from the right and left forelimb hands of both groups were measured by X-ray imagi ng.fin ger length and digit ratio comparisons between the two groups were con ducted using Stude nt's Mest.In terms of the durati on of each behavior,signifies nt differences emerged in“Huddling”and five other behavioral categories,including Ingestive,Amicable,Parental,Locomotive,and Resting.In addition to the above five behavioral categories,we found that depressed mon keys spent less time in parental and rubbing back and forth behaviors than the control group.Furthermore,the 4th fin gers were significantly Ion ger in the left and right hands in the control group relative to the depressed mon keys.The sec ond?to?fourth(2D:4D)digit ratio in the left and right forelimb hands was significantly lower in the control group tha n that in the depressed group.Our fin dings revealed significant differences in finger lengths and digit ratios between depressed mon keys and healthy controls,which concords with our view that relatively high fetal testosterone exposure may be a protective factor against developing depressive symptoms(or that low fetal testosterone exposure is a risk factor).

关键词： fin ger length Digit ratio Major depressive disorder Cynomolgus mon key

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fin characteristics of aerator devices with lateral deflectors

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Journal of Hydrodynamics 2013年第2期25卷 258-263页

作者：吴建华李丹马飞钱尚托 College of Water Conservancy and Hydropower Engineering Hohai University

The fins will be formed if the lateral deflectors in the side-walls with a bottom aerator device are improperly designed, and the flow regime downstream of the aerator device will be worsened. In this paper, the height and the length of the fins induced by the lateral deflectors are theoretically analyzed along with their influencing factors, and the fin characteristics are experimentally investigated on the basis of the theoretical analysis. It is shown that the intensities of the fins are strongly dependent on the ratio of the lateral cavity length to the bottom cavity length, and other factors, like the working head, the height and the angle of the lateral deflector, the flow Froude number around the aerator device, affect the fins indirectly through the changes of the lateral cavity length. When an aerator device with lateral deflectors is designed, it is crucial to match the above mentioned ratio, and to make the ratio of the two cavity lengths less than 1.0 in order to avoid the generation of the fins.

关键词： aerator cavity length fin lateral deflector

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Bionic Flapping Pectoral fin with Controllable Spatial Deformation

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Journal of Bionic Engineering 2019年第5期16卷 916-930页

作者： Yueri Cai Lingkun Chen Shusheng Bi Guoyuan Li Houxiang Zhang Robotics Institute Beihang UniversityBeijing 100191China Department of Ocean Operations and Civil Engineering Norwegian University of Science and TechnologyAalesund 6025Norway

This paper presents the design of a bionic pectoral fin with fin rays driven by multi-joint mechanism.Inspired by the cownose ray,the bionic pectoral fin is modeled and simplified based on the key structure and movement parameters of the cownose ray's pectoral fin.A novel bionic propulsion fin ray composed of a synchronous belt mechanism and a slider-rocker mechanism is designed and optimized in order to minimize the movement errors between the designed fin rays and the spanwise curves observed from the cownose ray,and thereby reproducing an actively controllable flapping deformation.A bionic flapping pectoral fin prototype is developed accordingly.Observations verify that the bionic pectoral fin flaps consistently with the design rule extracted from the cownose ray.Experiments in a towing tank are set up to test its capability of generating the lift force and the propulsion force.The movement parameters within the usual propulsion capabilities of the bionic pectoral fm are utilized:The flapping frequency of 0.2 Hz-0.6 Hz,the flapping amplitude of 3°-18°,and the phase di^rence of 10°-60°.The results show that the bionic pectoral fin with actively controllable spatial deformation has expected propulsion performance,which supports that the natural features of the cownose ray play an important role in designing and developing a bionic prototype.

关键词： cownose ray bionic pectoral fin controllable deformation multiple fin rays propulsion perfonnance

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Histological observation on unique phenotypes of malformation induced in Xenopus tropicalis larvae by tributyltin

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Journal of Environmental Sciences 2012年第2期24卷 195-202页

作者： Junqi Liu Qinzhen Cao Jing Yuan Xiaoli Zhang Lin Yu Huahong Shi Key Laboratory of Urbanization and Ecological Restoration Department of Environmental Science East China Normal University Shanghai State Key Laboratory of Estuarine and Coastal Research ＇East China Normal University Shanghai 200062 China

Tributyltin（TBT）,a biocide used in antifouling paints,has shown strong teratogenic effects on Xenopus tropicalis embryos at environmentally relevant concentrations.X.tropicalis embryos were exposed to 50,100 and 200 ng/L tributyltin chloride for 72 hr.The histological changes were further observed on abnormal eyes,enlarged trunks,enlarged proctodaeums and absence of fins induced by TBT.The lens and the retinal layers of abnormal eyes were slightly or barely differentiated,and that the pigment epithelium was neither continuous nor smooth.The abdomens were full of undifferentiated gut tissue with yolk-rich inclusions in the tadpoles with enlarged trunks.The proctodaeums formed a bump-like or columnar structure.The mass of yolk-rich cells occupied the lumen,blocked the opening and even turned inside out of the proctodaeum.Both the ventral and dorsal fins in trunks and tails became narrow or even disappeared totally.Our results suggest that great changes of histology took place corresponding to the unique phenotypes.The gut tissue was poorly differentiated,which led to the failed elongation of the guts and subsequently the enlarged trunks.The enlarged proctodaeums were due to the undifferentiation of inner layer,the expansion of outer epidermal part and the absence of fins around them.In brief,the histological observations provided insights into the reason of the unique external malformations in some degree.

关键词： Xenopus tropicalis tributyltin teratogenicity histology proctodaeum fin

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A swept fin-induced flow field with different height mounting gaps

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Chinese Journal of Aeronautics 2021年第1期34卷 148-162页

作者： Feng ZHANG Shihe YI Xiwang XU Haibo NIU Xiaoge LU College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China

In order to apply the air fin successfully and ensure the maneuverability of hypersonic vehicle, a key problem to be studied urgently is the heat flux brought by the fin mounting gap.The appearance of mounting gap and fin shaft can induce many complex flow structures which need more attentions to be investigated. Under Ma 6, Nano-tracer-based Planar Laser Scattering(NPLS)and Temperature Sensitive Paints(TSP) were applied to visualize and measure transient flow structures and heat flux distribution of a swept fin-induced flow field with different height mounting gaps. Complementarily, Reynolds-averaged N-S equations were solved with k-x SST turbulent model. The heat flux distribution results of numerical simulation and TSP observed the change of high heat flux region with different mounting gap, both in position and magnitude. The streamlines based on Computational Fluid Dynamics(CFD) and flow visualization results obtained by NPLS revealed the cause of high heat flux region. The high heat flux region in this flow field is mainly related to the reattachment of vortex and flow stagnation. The increase of gap height can lead to stronger gap overflow and shaft-induced horseshoe vortex, which are source of the high heat flux around the fin. The case with the highest mounting gap(4 mm) en-counters the most severe aerodynamic heating, both on the surface of fin and plate. Thus, under the premise of ensuring the flexibility of the fin, the gap should be set as small as possible.

关键词： fin Flow visualization Heat flux Hypersonic Shock/boundary layer interaction Temperature sensitive paint

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A Flexible fin with Bio-Inspired Stiffness Profile and Geometry

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Journal of Bionic Engineering 2011年第4期8卷 418-428页

作者： T. Salumae M. Kruusmaa Centre for Biorobotics Tallinn University of Technology Akadeemia tee 15A-111 12618 Tallinn Estonia

Biological evidence suggests that fish use mostly anterior muscles for steady swimming while the caudal part of the body is passive and, acting as a carrier of energy, transfers the momentum to the surrounding water. Inspired by those findings we hypothesize that certain swimming patterns can be achieved without copying the distributed actuation mechanism of fish but rather using a single actuator at the anterior part to create the travelling wave. To test the hypothesis a pitching flexible fin made of silicone rubber and silicone foam was designed by copying the stiffness distribution profile and geometry of a rainbow trout. The kinematics of the fin was compared to that of a steadily swimming trout. fin＇s propulsive wave length and tail-beat am- plitude were determined while it was actuated by a single servo motor. Results showed that the propulsive wave length and tail-beat amplitude of a steadily swimming 50 cm rainbow trout was achieved with our biomimetic fin while stimulated using certain actuation parameters （frequency 2.31 Hz and amplitude 6.6 degrees）. The study concluded that fish-like swimming can be achieved by mimicking the stiffness and geometry of a rainbow trout and disregarding the details of the actuation mechanism.

关键词： biomimetics stiffness profile fin robotics fish

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Linear Acceleration of an Undulatory Robotic Fish with Dynamic Morphing Median fin under the Instantaneous Self-propelled Condition

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Journal of Bionic Engineering 2020年第2期17卷 241-253页

作者： Wenguang Sun Zemin Liu Ziyu Ren Gang Wang Tao Yuan Li Wen School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China AECC Hunan Aviation Powerplant Research Institute Zhuzhou 412000China

Fish commonly execute rapid linear accelerations initiated during steady swimming,yet the function of the median fins during this process is less understood.We find that the erection/folding time(from the starting time of the linear acceleration(0 s)to the starting time of the folding movement of the fin),as well as the spreading area of the median fins,actively change during the linearacceleration of the live largemouth bass(Micropterus salmoides).To better understand the influence of the folding time and the area change of the median fins on the linear acceleration,we implemented an undulatory biomimetic robotic fish with soft median fins that can be programmed to erect and fold,just like a live fish.To characterize the acceleration performance of the robotic fish,we developed a"self-propelled"experiment technique based on the Kalman filter and Proportional-Integral-Derivative(PID)control algorithm.The experiments on the robotic fish show the acceleration induced by fully-erected median fins increases by 46.3%.Fully-erected median fins positively contribute to propulsion primarily at the onset stage of the linear acceleration while result in a significant decrease in steady swimming speed by 25%,which suggests a large drag force is induced at the steady swimming stage due to the enlarged wetted area.Parametric sweeping experiments on erection/folding time and spreading area demonstrate a proper combination of the erection/folding time and the spreading area enhances the mean linear acceleration by up to 85%.Particle Image Velocimetry(PIV)results reveal that the vortexes shed by the erected dorsal fin are stronger than those shed by the folded fin.As the acceleration process progresses,the thrust generated by the dorsal fins gradually is weakened until only resistance is generated in the end.Our findings may shed light on the realization of controllable surfaces on high performance fish-inspired robotic systems in the future.

关键词： robotic fish linear acceleration median fin instantaneous self-propelled system

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HEATING CHARACTERISTICS OF BLUNT SWEPT fin-INDUCED SHOCK WAVE TURBULENT BOUNDARY LAYER INTERACTION

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Acta Mechanica Sinica 1998年第2期14卷 139-146页

作者：唐贵明 LHD Institute of Mechanics Chinese Academy of Sciences Beijing China 100080

An experimental study was conducted on shock wave turbulent boundary layer interactions caused by a blunt swept fin-plate configuration at Mach numbers of 5.0, 7.8, 9.9 for a Reynolds number range of (1.***.similar to 4.7) x 10(7)/m. Detailed heat transfer and pressure distributions were measured at fin deflection angles of up to 30 degrees for a sweepback angle of 67.6 degrees. Surface oil flow patterns and liquid crystal thermograms as well as schlieren pictures of fin shock shape were taken. The study shows that the flow was separated at deflection of 10 degrees and secondary separation were detected at deflection of theta greater than or equal to 20 degrees. The heat transfer and pressure distributions on flat plate showed an extensive plateau region followed by a distinct dip and local peak close to the fin foot. Measurements of the plateau pressure and heat transfer were in good agreement with existing prediction methods, but pressure and heating peak measurements at M greater than or equal to 6 were significantly lower than predicted by the simple prediction techniques at lower Mach numbers.

关键词： fin shock wave boundary layer interaction hypersonic flow heat transfer

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