18 research outputs found
Experimental investigation of thermal and kinetic impacts of surface acoustic waves on water droplet
Get PDFAn analysis model for investigation of the coupling of kinetic and thermal impacts of
surface acoustic wave (SAW) on a microscale droplet is proposed. The model is based on
mass, momentum, and energy conservation principles with assistance from experimental
observations. The investigation is carried out on a 25 µl water droplet placed on the SAW
device fabricated on an aluminium (Al) plate substrate with deposition of 5 µm thick zinc
oxide (ZnO) as a top layer. The devices have a thickness of 200 µm and 600 µm with the
wavelength (λ) of 100 µm and 200 µm using Rayleigh, Sezawa, and a Lamb and Rayleigh
hybridized mode. The SAW input power values are from 0.30 W to 4.0 W with a
temperature range of 5-30 °C in this study.
A charged-coupled device (CCD) camera has been employed to monitor streaming inside
the droplet. To visualise the streaming, 10 µm red polystyrene particles have been used
whereas the velocity of particles estimated using particle image velocimetry (PIV). An
infrared (IR) thermal camera has been used to detect the droplet surface temperature.
However, temperature distributions of fluid layers of the droplet are estimated by
developing a MATLAB code. The data has been used in the implementation of the
analysis model to interpret the coupling mechanism inside the droplet. The thermal
impact includes energy absorbed by the droplet, heat transfer from the substrate to the
droplet, from the droplet to the air and the waves penetrated to the droplet (radiation).
Whereas kinetic impact involves energy transferred by the streaming and friction inside
the droplet.
Since this study is based on temperatures much lower than the boiling temperature, no
phase change or evaporation observed, therefore, no significant mass transfer has been
observed either with Rayleigh or Sezawa. However, at input power (Pin) of 4.0 W using
Rayleigh wave (R-wave) where the droplet slightly moves away on the surface in the
direction of the waves. Since Sezawa waves (S-waves) travel in the interlayers, they have
less SAW force because of which droplet sticks to the surface and does not move away
even at higher input power.
It has been observed that the thermal impacts of the SAW are more dominant than the
kinetic when considering both Rayleigh and Sezawa wave modes. However, the
streaming plays a key role in enhancing the heat transfer inside the droplet by internal convection. The major source of thermal impact is the radiation of SAW power (~ 0.05 W
to 0.20 W) penetrated to the droplet at input power (Pin) ranging from 0.96 W to 3.2 W,
while, at the power of 0.38 W or lower, is from both the SAW radiation (~0.025 W) and
hot substrate (~0.01 W) using Rayleigh waves.
Inverse heat flux from droplet to the substrate is observed after ‘reverse time’ at Pin >
0.50 W and Pin > 1.0 W for Rayleigh and Sezawa, respectively. Heat always transfers
from droplet to the air since this is the heat leaving the system.
The thermal impacts of both Rayleigh and Sezawa modes on the droplet showed an
exactly similar trend when compared to each other based on the results from the analysis
model and experimental data. However, the thermal impacts of SAW on the droplet with
a Sezawa wave is slightly less as compared to the Rayleigh. The thermal energy absorbed
by the droplet using Rayleigh waves is 4% more as compared to the Sezawa at an input
power of 0.96 W. However, this dropped to 1.5% at a higher input power of 3.2 W after
the same time frame.
It has been found that using the same wave mode, temperature rise inside the droplet is
directly proportional to the resonant frequency of the device. Furthermore, Lamb and
Rayleigh hybridized waves generate intense thermal impacts, showed 3.5 times and 2.5
times higher temperature as compared to the pure Rayleigh mode at Pin of 2.2 W and 3.2
W, respectively. The same trend and difference have been observed when the hybridized
mode is compared with pure Sezawa mode
Solar photovoltaic (PV) applications in Libya:Challenges, potential, opportunities and future perspectives
No full textThe solar photovoltaic (PV) is one way of utilising incident solar radiation to produce electricity without carbon dioxide (CO2) emission. It's important here to give a general overview of the present situation of Libyan energy generation. This paper aimed to highlight the energy challenges that faced the Libyan state, and the possibility to diagnose and suggest a strategy to develop and finding solutions. The residential building loads represent the largest energy consumption in the country, which presents approximately 36%. A wide range of critical literature review takes place to understand the energy system situations. This study addresses the current situation of solar photovoltaic power in Libya, the use of solar energy, and proposes strategies adopted by Libya to encourage future applications of solar photovoltaic energy and electricity generation. Furthermore, this study investigates an opportunity to exploit solar photovoltaics to meet the deficiency in energy demand and by the affordable way. Lastly, we presented solar photovoltaics application in Libya; thus, it has tremendous opportunities and possibilities. Besides, available potential, reality challenges and drawn up future perspectives.</p
Green hydrogen revolution and its pathway towards sustainable development
Get PDFThe demand surge for clean and sustainable energy has risen globally to gain a cleaner environment. Therefore, the global energy transition emphasizes hydrogen energy, particularly green hydrogen energy, as an essential energy source that emits no carbon dioxide. Green hydrogen has been prosperous in the last few years and has revolutionized the green energy sector needs. Green hydrogen energy could be employed as long-term energy storage to integrate energy from renewable energy sources with unexpected and variable characteristics in the future energy system largely comprised of renewable resources. Hence, it can enhance the electricity system’s dependability and increase the reliability of renewable energy; conversely, green hydrogen energy might help lower carbon emissions. This study gives insight through analysis of the overview and prospects of hydrogen energy. Besides, a thorough analysis is conducted on the present scenario of green hydrogen production technologies, their advancement trends, and the potential uses and roles of green hydrogen energy. The state-of-the-art green hydrogen has been highlighted, thus the developed approaches in the domain. Also, it gives an overview of the latest technologies used to produce/store/distribute green hydrogen. Moreover, a detailed description of green hydrogen utilization, distribution infrastructure, and storage technologies is given. This will help to achieve global Sustainable Development Goals in the near future. Accordingly, 6 of 17 global Sustainable Development Goals strategy clauses were met by adopting green hydrogen as a clean energy source
Green hydrogen energy production: current status and potential
No full textThe technique of producing hydrogen by utilizing green and renewable energy sources is called green hydrogen production. Therefore, by implementing this technique, hydrogen will become a sustainable and clean energy source by lowering greenhouse gas emissions and reducing our reliance on fossil fuels. The key benefit of producing green hydrogen by utilizing green energy is that no harmful pollutants or greenhouse gases are directly released throughout the process. Hence, to guarantee all of the environmental advantages, it is crucial to consider the entire hydrogen supply chain, involving storage, transportation and end users. Hydrogen is a promising clean energy source and targets plan pathways towards decarbonization and net-zero emissions by 2050. This paper has highlighted the techniques for generating green hydrogen that are needed for a clean environment and sustainable energy solutions. Moreover, it summarizes an overview, outlook and energy transient of green hydrogen production. Consequently, its perspective provides new insights and research directions in order to accelerate the development and identify the potential of green hydrogen production
Design, simulation and performance analysis of photovoltaic solar water pumping system
Get PDFThe solar photovoltaic system is one of the technologies which is used to pump water in rural, isolated and desert areas where electric connection to the main grid is a problem. The study area is selected because of its higher natural resources of solar radiation over the year. Thus, that encourages us to adopt this study in order to understand the effects of various operating parameters on performance behaviour, which leads to enhancing the system design. This paper aims to assess the solar water pump system's design and estimated performance in real environmental conditions. The PVsyst has been used to design and simulate a system which allows us to analyse the operating behaviour of a photovoltaic solar water pumping system. The solar PV pumping system design is considered; the photovoltaic module has characteristics and the pumping system characteristics. The photovoltaic array losses due to temperature were estimated about -14.3% and the soiling losses represented approximately -5%. The results showed that performance losses were significant variance in the months of the summer season from May to July. Therefore, their implication on the water flow rates significantly decreases throughout the months of the summer season from May to July, respectively.</p
Tracking Multiphase Flows through Steep Reservoirs with External Constraint
No full textProblem statement: The study offers theoretical formulations for high-viscosity particulate flows in inclined reservoirs, taking into account the presence of homogeneous spheroidal particles of various types to produce discrete two-phase suspensions. Purpose: The primary objective of this analytical and comparative study is to identify the most dependable nanoparticles among hafnium and crystal metals that are suspended in an Eyring–Powell fluid through an inclined channel while being subjected to external magnetic and gravitational forces. Solution methodology: The flow dynamics of multiphase flows are formulated utilizing the stress tensor of the base fluid. The regular perturbation method (RPM) is employed to attain a more closed-form solution. The perturbation method is frequently employed in engineering problems to obtain an approximated solution, even when demonstrating the convergence of the solution is challenging. The rough solution is also validated through a thorough parametric analysis that shows the role of relevant parameters that contribute to the multiphase flow. Results: A concise parametric study is carried out against some of the most pertinent parameters and reveals that additional particles have promising effects on the momentum of each multiphase flow, whereas Eyring–Powell multiphase suspensions lessen in momentum due to strong internal viscous forces. The velocity of fluid and particle phases diminish with Hartmann number M and Froude number Fr. The second-order material constant B and concentration of nanoparticles C boost the motion of the fluid. The velocities of the particulate phase are quicker than the fluid phase. The hafnium particle is more reliable than crystal particles. Solution benchmark: Numerical and graphical findings have also been compared with the existing literature for the limiting case and found to be fully in agreement. Applications: This study’s findings provide a wider understanding of subterranean flows, specifically within the petroleum sector, with a focus on multiphase flows. Originality: The current study represents the authors’ original work and has not been previously submitted or published elsewhere.Environmental Fluid Mechanic
Simulations of surface acoustic wave interactions on a sessile droplet using a three-dimensional multiphase lattice Boltzmann model
Get PDFThis study reports the development of a three-dimensional (3D) numerical model for acoustic interactions with a microscale sessile droplet under surface acoustic wave (SAW) excitation using the lattice Boltzmann method (LBM). We first validate the model before SAW interactions are added. The results demonstrate good agreements with the analytical results for thermodynamic consistency, Laplace law, static contact angle on a flat surface, and droplet oscillation. We then investigate SAW interactions on the droplet, with resonant frequencies ranging 61.7 MHz to 250.1 MHz. According to our findings, an increase in wave amplitude elicits an increase in streaming velocity inside the droplet, causing internal mixing, and further increase in wave amplitude leads to pumping and jetting. The boundaries of wave amplitude at various resonant frequencies are predicted for mixing, pumping and jetting modes. The modelling predictions on the roles of forces (SAW, interfacial tension, inertia and viscosity) on the dynamics of mixing, pumping and jetting of a droplet are in good agreement with observations and experimental data. The model is further applied to investigate the effects of SAW substrate surface wettability, viscosity ratio, and interfacial tension on SAW actuation onto the droplet. This work demonstrates the capability of the LBM in the investigation of acoustic wave interactions between SAW and a liquid medium
Theoretical study of silver nanoparticle suspension in electroosmosis flow through a nonuniform divergent channel with compliant walls: A therapeutic application
No full textThis study explores the effect of silver nanoparticles on heat transfer and flow behavior within the context of the Ellis fluid model. It specifically considers electroosmotic forces in a nonuniform divergent channel with compliant walls. The analysis involves studying thermal transport in silver-blood nanofluid flow, using MATHEMATICA 13.2 software to obtain exact solutions for velocity and temperature distribution. Findings reveal that certain parameters, such as wall damping and wall elastic properties, increase skin friction, while compliant wall parameters generally reduce flow velocity. Additionally, wall rigidity and tension parameters lead to larger trapped boluses. Notably, a 1% concentration of nanoparticles enhances heat transfer by up to 13.75%, offering control over heat transfer rates. This research introduces a novel perspective by examining compliant wall impacts on heat transfer analysis in the context of electroosmotic flow within the Ellis fluid model, incorporating silver nanoparticles with potential therapeutic applications due to their antibacterial properties.Environmental Fluid Mechanic
Performance simulation of single and dual-junction GaInP/GaAs tandem solar cells using AMPS-1D
No full textThe solar cell is a semiconductor device that converts sunlight into electricity. In this study, we used Analysis Microelectronic and Photonic Structures (AMPS-1D) simulator to show the performance analysis of Gallium Arsenide (GaAs) based solar cell model. A balance between semiconductor compositions, layer thickness and temperature dependence on the efficiency have been investigated as the layer thickness of the top Gallium Indium Phosphide (GaInP) in double junction solar cells decreases, the efficiency increases. Meanwhile, increasing the n-doped GaAs layer thickness will lead to slight increases in cell efficiency. However, the limitation would be the practical cost of utilising high layer thickness in exchange for a slight increase in high efficiency. The range of thickness from 500 nm to 3500 nm, which gives a variation in the efficiency of approximately 1.3%. However, the simulation results have shown, the temperature increase will lower the efficiency of the solar cell. In double-junction cells, the thickness variation of p-GaInP and n-GaInP significantly change the efficiency of the solar cell. The optimisation achieved here indicates some model structures for practical usage to achieve high-efficiency GaAs based on solar cells.</p
Numerical simulation of MHD flow of micropolar fluid inside a porous inclined cavity with uniform/non-uniform heated bottom wall
Get PDFBuoyancy-driven, incompressible, two-dimensional flow of a micropolar fluid inside an inclined porous cavity in the presence of magnetic field is investigated. The nonlinear partial differential equations are solved by employing a robust Galerkin finite element scheme. The pressure term in this scheme is eliminated by using the penalty method. The results are exhibited in the form of streamlines, isotherms, and local and average Nusselt numbers for two cases, namely, the constant and the sinusoidal heated lower wall of the conduit. In both cases, the side walls of the cavity are cold and the upper side is insulated. The main difference between the two cases is observed from temperature contours. For constant heated bottom wall a finite discontinuity appears in the temperature distribution at the corners of the bottom wall. In contrast, no such discontinuity appears in the temperature distribution for non-uniform heated bottom wall. The quantitative changes in temperature contours in different portions of the cavity are identified by comparing the results for both cases. The code is also validated and benchmarked with the previous numerical data available in the literature. It is found that the magnetic field inclined at a certain angle either suppresses or enhances the intensity of primary circulations depending on the inclination of the cavity. Further, the average Nusselt number at the bottom wall is higher when magnetic field is applied vertically irrespective of the inclination of cavity. The analysis presented here has potential application in solar collectors and porous heat exchangers.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
