scholarly journals Visualization and Sound Measurements of Vibration Plate in a Boiling Bubble Resonator

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 443
Author(s):  
Junichiro Ono ◽  
Noriyuki Unno ◽  
Kazuhisa Yuki ◽  
Jun Taniguchi ◽  
Shin-ichi Satake
Keyword(s):  
High Speed ◽  
Plate Motion ◽  
Transfer Enhancement ◽  
Design Specification ◽  
Led Lighting ◽  
Peak Point ◽  
Flow Motion ◽  
Enhancement Method ◽  
Electrical Source ◽  
Flux State

We developed a boiling bubble resonator (BBR) as a new heat transfer enhancement method aided by boiling bubbles. The BBR is a passive device that operates under its own bubble pressure and therefore does not require an electrical source. In the present study, high-speed visualization of the flow motion of the microbubbles spouted from a vibration plate and the plate motion in the BBR was carried out using high-speed LED lighting and high-speed cameras; the sounds in the boiling chamber were simultaneously captured using a hydrophone. The peak point in the spectrum of the motion of the vibration plate and the peak point in the spectrum of the boiling sound were found to be matched near a critical heat-flux state. Therefore, we found that it is important to match the BBR vibration frequency to the condensation cycle of the boiling bubble as its own design specification for the BBR.

scholarly journals Droplet impact onto a spring-supported plate: analysis and simulations

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Michael J. Negus ◽  
Matthew R. Moore ◽  
James M. Oliver ◽  
Radu Cimpeanu
Keyword(s):  
High Speed ◽  
Flexible Substrate ◽  
Practical Importance ◽  
Hybrid Approach ◽  
Hydrodynamic Pressure ◽  
Analytical Framework ◽  
Canonical System ◽  
Linear Process ◽  
Plate Motion ◽  
The Impact

AbstractThe high-speed impact of a droplet onto a flexible substrate is a highly non-linear process of practical importance, which poses formidable modelling challenges in the context of fluid–structure interaction. We present two approaches aimed at investigating the canonical system of a droplet impacting onto a rigid plate supported by a spring and a dashpot: matched asymptotic expansions and direct numerical simulation (DNS). In the former, we derive a generalisation of inviscid Wagner theory to approximate the flow behaviour during the early stages of the impact. In the latter, we perform detailed DNS designed to validate the analytical framework, as well as provide insight into later times beyond the reach of the proposed analytical model. Drawing from both methods, we observe the strong influence that the mass of the plate, resistance of the dashpot, and stiffness of the spring have on the motion of the solid, which undergo forced damped oscillations. Furthermore, we examine how the plate motion affects the dynamics of the droplet, predominantly through altering its internal hydrodynamic pressure distribution. We build on the interplay between these techniques, demonstrating that a hybrid approach leads to improved model and computational development, as well as result interpretation, across multiple length and time scales.

Phenomenon and Mechanism of Spray Cooling on Nanowire Arrayed and Hybrid Micro/Nanostructured Surfaces

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Jian-nan Chen ◽  
Rui-na Xu ◽  
Zhen Zhang ◽  
Xue Chen ◽  
Xiao-long Ouyang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
High Speed ◽  
Spray Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Enhancement ◽  
Nanostructured Surfaces ◽  
New Energy ◽  
Dry Out

Enhancing spray cooling with surface structures is a common, effective approach for high heat flux thermal management to guarantee the reliability of many high-power, high-speed electronics and to improve the efficiency of new energy systems. However, the fundamental heat transfer enhancement mechanisms are not well understood especially for nanostructures. Here, we fabricated six groups of nanowire arrayed surfaces with various structures and sizes that show for the first time how these nanostructures enhance the spray cooling by improving the surface wettability and the liquid transport to quickly rewet the surface and avoid dry out. These insights into the nanostructure spray cooling heat transfer enhancement mechanisms are combined with microstructure heat transfer mechanism in integrated microstructure and nanostructure hybrid surface that further enhances the spray cooling heat transfer.

scholarly journals Design and Evaluation of Uniform LED Illumination Based on Double Linear Fresnel Lenses

2020 ◽  
Vol 10 (9) ◽  
pp. 3257
Author(s):  
Hoang Vu ◽  
Ngoc Minh Kieu ◽  
Do Thi Gam ◽  
Seoyong Shin ◽  
Tran Quoc Tien ◽  
...  
Keyword(s):  
High Speed ◽  
Field Experiments ◽  
Numerical Control ◽  
Free Form ◽  
Light Sources ◽  
Cnc Machine ◽  
Led Lighting ◽  
Positive Effects ◽  
Fresnel Lenses ◽  
Linear Fresnel Lenses

Redistribution of LED radiation in lighting is necessary in many applications. In this article, we propose a new optical component design for LED lighting to achieve a higher performance. The design consists of a commercial collimator and two linear Fresnel lenses. The LED radiation is collimated by a collimator and redistributed by double linear Fresnel lenses to create a square-shaped, uniform distribution. The linear Fresnel lenses design is based on Snell’s law and the “edge-ray principle”. The optical devices are made from poly methyl methacrylate (PMMA) using a high-speed computer numerical control (CNC) machine. The LED prototypes with complementary optics were measured, and the optical intensity distribution was evaluated. The numerical results showed we obtained a free-form lens that produced an illumination uniformity of 78% with an efficiency of 77%. We used the developed LED light sources for field experiments in agricultural lighting. The figures of these tests showed positive effects with control flowering criteria and advantages of harvested products in comparison with the conventional LED sources. This allows our approach in this paper to be considered as an alternative candidate for highly efficient and energy-saving LED lighting applications.

scholarly journals Application of life-cycle assessment to the eco-design of LED lighting products

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Shuyi Wang ◽  
Daizhong Su ◽  
You Wu ◽  
Zijian Chai
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Environmental Impact ◽  
Product Design ◽  
Environmental Performance ◽  
New Product ◽  
Design Features ◽  
Design Specification ◽  
Led Lighting ◽  
Lca Results

Abstract An approach for integrating life-cycle assessment (LCA) into the eco-design of lighting products was developed, and LCAs of five lighting products that are currently on the market were then carried out using this approach. Based on the results of these LCAs, the sustainability requests for lighting products were derived and embedded into the product design specification (PDS), thus ensuring that any product developed according to the PDS would have the desired eco-design features. A new sustainable lighting product was then designed according to the PDS and manufactured, after which the new product underwent LCA. Upon comparing the results of the LCA of the new product with the LCA results for the existing lighting products, the newly designed product was found to provide better environmental performance than the existing products (a 27–58% reduction in environmental impact).

scholarly journals Hydroelastic effects during the fast lifting of a disc from a water surface

2019 ◽  
Vol 869 ◽  
pp. 726-751 ◽  
Author(s):  
P. Vega-Martínez ◽  
J. Rodríguez-Rodríguez ◽  
T. I. Khabakhpasheva ◽  
A. A. Korobkin
Keyword(s):  
Water Surface ◽  
High Speed ◽  
Hydrodynamic Force ◽  
Early Stage ◽  
The Body ◽  
Plate Motion ◽  
Elastic Behaviour ◽  
Simple Extension ◽  
Wetted Area ◽  
Water Exit

Here we report the results of an experimental study where we measure the hydrodynamic force acting on a plate which is lifted from a water surface, suddenly starting to move upwards with an acceleration much larger than gravity. Our work focuses on the early stage of the plate motion, when the hydrodynamic suction forces due to the liquid inertia are the most relevant ones. Besides the force, we measure as well the acceleration at the centre of the plate and the time evolution of the wetted area. The results of this study show that, at very early stages, the hydrodynamic force can be estimated by a simple extension of the linear exit theory by Korobkin (J. Fluid Mech., vol. 737, 2013, pp. 368–386), which incorporates an added mass to the body dynamics. However, at longer times, the measured acceleration decays even though the applied external force continues to increase. Moreover, high-speed recordings of the disc displacement and the radius of the wetted area reveal that the latter does not change before the disc acceleration reaches its maximum value. We show in this paper that these phenomena are caused by the elastic deflection of the disc during the initial transient stage of water exit. We present a linearised model of water exit that accounts for the elastic behaviour of the lifted body. The results obtained with this new model agree fairly well with the experimental results.

Prevention of Material Deterioration in ECM of Sintered Carbide with Iron Ions

2017 ◽  
Vol 11 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Akihiro Goto ◽  
◽  
Atsushi Nakata ◽  
Sicong Wang ◽  
Nagao Saito ◽  
...  
Keyword(s):  
High Speed ◽  
Electrochemical Machining ◽  
High Speed Machining ◽  
Conductive Liquid ◽  
Sintered Carbide ◽  
High Speeds ◽  
Quality Degradation ◽  
Fe Ions ◽  
Electrical Source

This study focuses on electrochemical machining as a method of processing sintered carbide at high speeds. Previous studies have suggested the possibility of using electrochemical machining to achieve high-speed machining of sintered carbide. However, there has been strong resistance in industry against bringing sintered carbide into contact with a conductive liquid. This is because the material quality of sintered carbide is degraded by the elution of Co when it is brought into contact with a conductive liquid.In previous reports, the authors have shown that it is possible to control two modes of Co elution occurring during electrochemical machining: the elution from sintered carbide when it comes into contact with an electrolyte, and the selective elution of Co due to difference in the speeds of WC dissolution and elution of Co when sintered carbide is connected to an electrical source for processing. It was shown that it is possible to control the elution Co in sintered carbide when it comes into contact with an electrolyte by adding Co ions to the electrolyte to increase the concentration of Co ion, and that it is possible to prevent the excessive elution of Co by using a bipolar electrical source for machining. Although we showed that it is possible to carry out electrochemical machining of sintered carbide without degrading its quality, adding of large amounts of Co ions to the electrolyte entails a high cost. In this report, therefore, we describe the addition of Fe ions instead of Co ions to perform electrochemical machining of sintered carbide without quality degradation.

Prevention of Material Deterioration in ECM of Sintered Carbide with Iron Ions (2ndReport)

2017 ◽  
Vol 11 (5) ◽  
pp. 829-834
Author(s):  
Sicong Wang ◽  
Akihiro Goto ◽  
Atsushi Nakata ◽  
◽  
Keyword(s):  
High Speed ◽  
Present Report ◽  
Electrochemical Machining ◽  
Ion Concentration ◽  
Iron Ions ◽  
Conductive Liquid ◽  
Sintered Carbide ◽  
Fe Ions ◽  
Electrical Source

This study focuses on electrochemical machining as a method of processing sintered carbide at high speed. Previous studies have suggested the possibility of using electrochemical machining to achieve the high-speed machining of sintered carbide. However, there has been strong resistance from industry against bringing sintered carbide into contact with a conductive liquid. This is because the material quality of sintered carbide is degraded by the elution of Co when in contact with a conductive liquid. In previous reports, the authors have shown that it is possible to control the two modes of Co elution occurring during electrochemical machining: the elution from sintered carbide in contact with an electrolyte and the selective elution of Co arising from differences in the speeds of the dissolution of tungsten carbide and the elution of Co when sintered carbide is connected to an electrical source for processing. It is possible to control the elution of Co from sintered carbide in contact with an electrolyte by adding Co ions to the electrolyte, which increases the Co ion concentration. In addition, the excessive elution of Co can be prevented by using a bipolar electrical source for machining. Although we have shown that it is possible to carry out the electrochemical machining of sintered carbide without degrading its quality, the addition of large amounts of Co ions to the electrolyte is expensive. Therefore, we attempted to prevent the degradation in the quality of sintered carbide by adding iron ions instead of Co ions, and we confirmed that the addition of Fe ions has the desired effect. However, the Fe2+ions in the solution are easily oxidized to Fe3+ions with time, and the Fe3+ions yield no protective effect for sintered carbide. In our previous report, we discussed a method to bring the electrolyte into contact with Fe to prevent the oxidation of Fe2+ions to Fe3+ions and proposed the use of an iron filter. In the present report, we verify the effect of the iron filter.

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