Articoli di riviste: "Microchannel absorber"

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Goel, Nitin, e D. Yogi Goswami. "Experimental Verification of a New Heat and Mass Transfer Enhancement Concept in a Microchannel Falling Film Absorber". Journal of Heat Transfer 129, n. 2 (26 maggio 2006): 154–61. http://dx.doi.org/10.1115/1.2402182.

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This paper presents an experimental study of a new concept of using a screen mesh to enhance heat and mass transfer in a microchannel falling film absorber. Results of the experiments on the conventional and mesh-enhanced microchannel absorber designs are then reported. The experimental study shows that the absorber heat load for the mesh-enhanced design is about 17%±3.4%-26%±3.8% higher than a conventional microchannel design. The paper also presents a comparison of the experimental results with a numerical model. A finite difference scheme is used to model the heat and mass transfer processes in a falling film absorber. The numerical model agrees well with experimental results with some deviation at low temperature of coolant and high flow rate of weak solution.

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Alston, Mark E. "Optimal Microchannel Planar Reactor as a Switchable Infrared Absorber". MRS Advances 2, n. 14 (2017): 783–89. http://dx.doi.org/10.1557/adv.2017.112.

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ABSTRACTThis paper will propose methods to use leaf vasculature formations to advance a material to act as an infrared block. The research shows the use of microfluidics based flows to direct the structural assembly of a polymer into a thermally functional material. To manage IR radiation stop-band to lower a polymer device phase transition temperature. This paper will determine this functionality by hierarchical multi microchannel network scaling, to regulate laminar flow rate by analysis as a resistor circuit.Nature uses vasculature formations to modulate irradiance absorption by laminar fluidic flow, for dehydration and autonomous self-healing surfaces as a photoactive system. This paper will focus specifically on pressure drop characterization, as a method of regulating fluidic flow. This approach will ultimately lead to desired morphology, in a functional material to enhance its ability to capture and store energy. The research demonstrates a resistor conduit network can define flow target resistance, that is determined by iterative procedure and validated by CFD. This algorithm approach, which generates multi microchannel optimization, is achieved through pressure equalization in diminishing flow pressure variation. This is functionality significant in achieving a flow parabolic profile, for a fully developed flow rate within conduit networks. Using precise hydrodynamics is the mechanism for thermal material characterization to act as a switchable IR absorber. This absorber uses switching of water flow as a thermal switching medium to regulate heat transport flow. The paper will define a microfluidic network as a resistor to enhance the visible transmission and solar modulation properties by microfluidics for transition temperature decrease.

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Sui, Zengguang, Wei Wu, Tian You, Zhanying Zheng e Michael Leung. "Performance investigation and enhancement of membrane-contactor microchannel absorber towards compact absorption cooling". International Journal of Heat and Mass Transfer 169 (aprile 2021): 120978. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2021.120978.

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Kim, Yoon Jo, Yogendra K. Joshi e Andrei G. Fedorov. "Performance analysis of air-cooled microchannel absorber in absorptionbased miniature electronics cooling system". Journal of Mechanical Science and Technology 22, n. 2 (febbraio 2008): 338–49. http://dx.doi.org/10.1007/s12206-007-1034-5.

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García-Hernando, N., M. Venegas e M. de Vega. "Experimental performance comparison of three flat sheet membranes operating in an adiabatic microchannel absorber". Applied Thermal Engineering 152 (aprile 2019): 835–43. http://dx.doi.org/10.1016/j.applthermaleng.2019.02.129.

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Sui, Zengguang, Chong Zhai e Wei Wu. "Swirling flow for performance improvement of a microchannel membrane-based absorber with discrete inclined grooves". International Journal of Refrigeration 130 (ottobre 2021): 382–91. http://dx.doi.org/10.1016/j.ijrefrig.2021.05.039.

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Sui, Zengguang, Chong Zhai e Wei Wu. "Parametric and comparative study on enhanced microchannel membrane-based absorber structures for compact absorption refrigeration". Renewable Energy 187 (marzo 2022): 109–22. http://dx.doi.org/10.1016/j.renene.2022.01.052.

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Motamedi, Mahdi, Chia-Yang Chung, Mehdi Rafeie, Natasha Hjerrild, Fan Jiang, Haoran Qu e Robert A. Taylor. "Experimental Testing of Hydrophobic Microchannels, with and without Nanofluids, for Solar PV/T Collectors". Energies 12, n. 15 (6 agosto 2019): 3036. http://dx.doi.org/10.3390/en12153036.

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Solar energy can be converted into useful energy via photovoltaic cells or with a photothermal absorber. While these technologies are well-developed and commercially viable, significant benefits can be realised by pulling these two technologies together in photovoltaic/thermal (PV/T) systems which can provide both heat and electricity from a single collector. Emerging configurations in the PV/T field aim to incorporate micro and/or nanotechnology to boost total solar utilisation even further. One example of this is the nanofluid-based PV/T collector. This type of solar collector utilises nanofluids—suspensions of nanoparticles in traditional heat transfer fluids—as both an optical filter and as a thermal absorber. This concept seeks to harvest the whole solar spectrum at its highest thermodynamic potential through specially engineered nanofluids which transmit the portion of solar spectrum corresponding to the PV response curve while absorbing the rest as heat. Depending on the nanoparticle concentration, employing nanofluids in a flowing system may come with a price—an efficiency penalty in the form of increased pumping power (due to increased viscosity). Similarly, microchannel-based heat exchangers have been shown to increase heat transfer, but they may also pay the price of high pumping power due to additional wall-shear-related pressure drop (i.e., more no-slip boundary area). To develop a novel PV/T configuration which pulls together the advantages of these micro and nanotechnologies with minimal pumping power requirements, the present study experimentally investigated the use of nanofluids in patterned hydrophobic microchannels. It was found that slip with the walls reduced the impact of the increased viscosity of nanofluids by reducing the pressure drop on average 17% relative to a smooth channel. In addition, flowing a selective Ag/SiO2 core–shell nanofluid over a silicon surface (simulating a PV cell underneath the fluid) provided a 20% increase in solar thermal conversion efficiency and ~3% higher stagnation temperature than using pure water. This demonstrates the potential of this proposed system for extracting more useful energy from the same incident flux. Although no electrical energy was extracted from the underlying patterned silicon, this study highlights potential a new development path for micro and nanotechnology to be integrated into next-generation PV/T solar collectors.

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Sui, Zengguang, Yunren Sui e Wei Wu. "Multi-objective optimization of a microchannel membrane-based absorber with inclined grooves based on CFD and machine learning". Energy 240 (febbraio 2022): 122809. http://dx.doi.org/10.1016/j.energy.2021.122809.

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Wei, Xinghua, Rijing Zhao, Siyuan Wu, Shouzhen Wang e Dong Huang. "Effect of rhombus mesh on 3D falling film flow characteristics over microchannel flat tube for LiBr (Lithium bromide) absorber". International Journal of Heat and Mass Transfer 209 (agosto 2023): 124097. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2023.124097.

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Zhai, Chong, Yunren Sui e Wei Wu. "Machine learning-assisted correlations of heat/mass transfer and pressure drop of microchannel membrane-based desorber/absorber for compact absorption cycles". International Journal of Heat and Mass Transfer 214 (novembre 2023): 124431. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2023.124431.

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de Vega, Mercedes, María Venegas e Néstor García-Hernando. "Modeling and performance analysis of an absorption chiller with a microchannel membrane-based absorber using LiBr-H2 O, LiCl-H2 O, and LiNO3 -NH3". International Journal of Energy Research 42, n. 11 (15 maggio 2018): 3544–58. http://dx.doi.org/10.1002/er.4098.

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Kurniawati, Ischia, e Yonmo Sung. "A Review of Heat Dissipation and Absorption Technologies for Enhancing Performance in Photovoltaic–Thermal Systems". Energies 17, n. 7 (3 aprile 2024): 1721. http://dx.doi.org/10.3390/en17071721.

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With the growing demand for photovoltaic (PV) systems as a source of energy generation that produces no greenhouse gas emissions, effective strategies are needed to address the inherent inefficiencies of PV systems. These systems typically absorb only approximately 15% of solar energy and experience performance degradation due to temperature increases during operation. To address these issues, PV–thermal (PVT) technology, which combines PV with a thermal absorber to dissipate excess heat and convert it into additional thermal energy, is being rapidly developed. This review presents an overview of various PVT technologies designed to prevent overheating in operational systems and to enhance heat transfer from the solar cells to the absorber. The methods explored include innovative absorber designs that focus on increasing the heat transfer contact surface, using mini/microchannels for improved heat transfer contiguity, and substituting traditional metal materials with polymers to reduce construction costs while utilizing polymer flexibility. The review also discusses incorporating phase change materials for latent heat absorption and using nanofluids as coolant mediums, which offer higher thermal conductivity than pure water. This review highlights significant observations and challenges associated with absorber design, mini/microchannels, polymer materials, phase change materials, and nanofluids in terms of PV waste heat dissipation. It includes a summary of relevant numerical and experimental studies to facilitate comparisons of each development approach.

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Oyinlola, M. A., G. S. F. Shire e R. W. Moss. "Thermal analysis of a solar collector absorber plate with microchannels". Experimental Thermal and Fluid Science 67 (ottobre 2015): 102–9. http://dx.doi.org/10.1016/j.expthermflusci.2014.10.014.

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Guan, Dong, Jiu Hui Wu, Li Jing e Kuan Lu. "Lattice Boltzmann simulation of acoustic resistance in microchannels". International Journal of Modern Physics B 29, n. 16 (23 giugno 2015): 1550104. http://dx.doi.org/10.1142/s0217979215501040.

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Lattice Boltzmann method (LBM) is utilized to model the acoustic resistance in microchannels at mesoscopic scale in this paper. Sound pressure distribution at different positions are studied. A number of physical parameters, such as the wavelength, channel number, channel width and length are investigated to find their effects on pressure variation. Simulation results are compared with those obtained by traditional methods and demonstrate that the LBM is a helpful approach to study sound attenuation in microchannels at mesoscopic scale. These results have potential application for designing the high-efficiency sound absorbers.

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Tabatabaei, Seyed Ali, Mohammad Zabetian Targhi, Javane Javaherchian e Marzieh Yaghoubi. "Basic concepts of biological microparticles isolation by inertia spiral microchannels in simple terms: a review". Journal of Micromechanics and Microengineering 32, n. 1 (26 novembre 2021): 013001. http://dx.doi.org/10.1088/1361-6439/ac388c.

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Abstract The microfluidics separation has absorbed wide-ranging attention in recent years due to its outstanding advantages in biological, medical, clinical, and diagnostical cell studies. While conventional separation methods failed to render the acceptable performance, microfluidics sorting methods offer many privileges such as high throughput, user-friendliness, minimizing sample volumes, cost-efficiency, non-invasive procedures, high precision, improved portability, quick processing, etc. Among the inertial microfluidics approaches such as the straight and curved microchannels, although the spiral microchannels, which are the sorts of passive separations, are complicated in concepts and geometries, they have demonstrated auspicious benefits for this purpose. Thus, numerous studies have strived to explain the principle of particle migrating and forces in these complex microchannels. However, a comprehensive understanding is still necessary. On the other side, it is manifest that the diagnosis and separation of circulating tumor cells (CTCs) from the blood are significant for targeted treatments of this detrimental disease. Therefore, this study aims to review the previous investigations and developments for understanding the CTC separation using the spiral microchannels straightforwardly and profoundly. After elucidating the inertial microfluidics and their governing physics in simple terms, we provide insights about spiral microchannels’ mechanism and concepts, the secondary flow, the cross-section effects on the separation processes, the investigation about CTCs in the spiral microchannels specifically, and finally, the future applications and challenges of this kind of inertial microfluidics. The analyses reveal that new approaches should be conducted to use spiral microchannels with combined cross-sections. These kinds of microchannels with optimum size and shape of cross-sections can improve performance efficiently.

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Mihai, Ioan, Cornel Suciu e Claudiu Marian Picus. "Particularities of R134a Refrigerant Temperature Variations in a Transient Convective Regime during Vaporization in Rectangular Microchannels". Micromachines 13, n. 5 (13 maggio 2022): 767. http://dx.doi.org/10.3390/mi13050767.

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An analysis of the R134a (tetrafluoroetane) coolant’s non-stationary behavior in rectangular microchannels was conducted with the help of a newly proposed miniature refrigerating machine of our own design and construction. The experimental device incorporated, on the same plate, a condenser, a lamination tube and a vaporizer, all of which integrated rectangular microchannels. The size of the rectangular microchannels was determined by laser profilometry. R-134a coolant vapors were pressurized using a small ASPEN rotary compressor. Using the variable soft spheres (VSS) model, the mean free path, Knudsen and Reynolds numbers, as well as the dimensionless velocity profile can be assessed analytically. In order to determine the average dimensionless temperature drop in the vaporizer’s rectangular microchannels, in non-stationary regime, an analytical solution for incompressible flow with slip at the walls, fully developed flow and laminar regime was used, by aid of an integral transform approach. In the experimental study, the transitional distribution of temperature was tracked while modifying the R134a flow through the rectangular microchannels. Coolant flow was then maintained at a constant, while the amount of heat absorbed by the vaporizer was varied using multiple electric resistors. A comparative analysis of the analytical and experimental values was conducted.

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Kono, Ippei, Naohiko Sugita e Mamoru Mitsuishi. "Simulation of Laser Micromachining in Silica Glass with Absorbent Slurry". International Journal of Automation Technology 4, n. 3 (5 maggio 2010): 284–90. http://dx.doi.org/10.20965/ijat.2010.p0284.

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The authors are studying a method of machining a 3D microchannel in silica glass using a UV nanosecond pulsed laser and an absorbent slurry. 3D microstructures in glass materials are required for optical waveguides, microfluidic chips, etc. The depths of the grooves and holes produced in the silica glass have been proportional to the number of laser pulses. The paper reports the results of a simulation of laser micro machining in silica class with absorbent slurry. The results are that the material removal process in the proposed method is the melting of the glass by heat transfer from the absorbent particles, which are attached to the surface of the glass, providing for strong laser absorption.

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Moss, R. W., G. S. F. Shire, P. Henshall, P. C. Eames, F. Arya e T. Hyde. "Optimal passage size for solar collector microchannel and tube-on-plate absorbers". Solar Energy 153 (settembre 2017): 718–31. http://dx.doi.org/10.1016/j.solener.2017.05.030.

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Liu, Chao, Kevin Hong, Xiao Sun, Avi Natan, Pengcheng Luan, Yang Yang e Hongli Zhu. "An ‘antifouling’ porous loofah sponge with internal microchannels as solar absorbers and water pumpers for thermal desalination". Journal of Materials Chemistry A 8, n. 25 (2020): 12323–33. http://dx.doi.org/10.1039/d0ta03872e.

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We found that a type of fruiting body, the loofah, can enable efficient solar-driven steam generation based on the integrated bilayers and microchannels. Under illumination of one Sun, the steam generation rate and efficiency achieved 1.42 kg m⁻² h⁻¹ and 89.9%, respectively.

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Glawdel, Tomasz, Zeyad Almutairi, Shuwen Wang e Carolyn Ren. "Photobleaching absorbed Rhodamine B to improve temperature measurements in PDMS microchannels". Lab Chip 9, n. 1 (2009): 171–74. http://dx.doi.org/10.1039/b805172k.

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Costa Pena, Liz, e Cristina Rech Feldmann. "NECK TISSUE REJUVENATION WITH PERCUTANEOUS COLLAGEN INDUCTION, DRUG DELIVERY AND HOME CARE". Health and Society 2, n. 04 (21 dicembre 2022): 140–54. http://dx.doi.org/10.51249/hs.v2i04.1040.

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Percutaneous collagen induction or microneedling is a procedure that, through the opening of microchannels on the surface of the skin, generates healing induced by platelets that increase the production of growth factors and cytokines, triggered by a controlled inflammation that stimulates the production of collagen and elastin. With the microneedling protocol and the use of drug delivery in mature skin, the results are optimized by the association of specific actives that will be more effectively absorbed by the microchannels. The objective of this work is to carry out a brief literature review and case report on the use of the percutaneous collagen induction method with the association of drug-delivery and home care in the neck region with the aim of superficial and deep tissue rejuvenation. The results found through clinical observation were a significant improvement in the appearance of aging, dryness, superficial flaccidity, fine rhytids, photoaging and devitalized appearance. Little or no results were observed in the improvement of deep flaccidity, horizontal wrinkles and central vertical bands of the neck after 4 sessions of the protocol.

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Jones, Ian, e Jonathan Griffiths. "Preparation and Sealing of Polymer Microchannels Using Electron Beam Lithography to Pattern Absorber for Laser Welding". MATERIALS TRANSACTIONS 56, n. 7 (2015): 997–1001. http://dx.doi.org/10.2320/matertrans.mi201402.

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Sehgal, Shitiz, Jorge L. Alvarado, Ibrahim G. Hassan e Sambhaji T. Kadam. "A comprehensive review of recent developments in falling-film, spray, bubble and microchannel absorbers for absorption systems". Renewable and Sustainable Energy Reviews 142 (maggio 2021): 110807. http://dx.doi.org/10.1016/j.rser.2021.110807.

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Gao, Dan, Youwei Qi, Jiaxi Yang e Heng Zhang. "Experimental study of carbon dioxide desorption from ethanolamine/non-aqueous CO2-rich absorbent solvent using microchannel". Separation and Purification Technology 331 (marzo 2024): 125651. http://dx.doi.org/10.1016/j.seppur.2023.125651.

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Gekle, Stephan. "Dispersion of solute released from a sphere flowing in a microchannel". Journal of Fluid Mechanics 819 (18 aprile 2017): 104–20. http://dx.doi.org/10.1017/jfm.2017.177.

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A solute is released from the surface of a sphere flowing freely in a cylindrical channel mimicking a modern drug delivery agent in a blood vessel. The solute then disperses by the combined action of advection and diffusion. We consider reflecting boundary conditions on the sphere and absorbing boundary conditions on the channel surface mimicking a biochemical reaction between the drug and endothelial cells on the vessel surface. The drug is released either instantaneously or continuously in time. The two key observables are the mean residence time in the flow before the drug is absorbed and the width over which it is spread on the vessel surface upon reaction. We numerically solve the Fokker–Planck equation for the time-dependent substance concentration combined with an analytical solution of the flow field. As expected, we find that the presence of the sphere leads to a substantial reduction in mean residence time and reaction width. Surprisingly, however, even in the limit of very large Péclet numbers (high velocities) the sphere-free case is not generally recovered. This observation can be attributed mainly to the small, but non-negligible radial flow component induced by the moving sphere. We further identify a strong influence of the release position which sharply separates two qualitatively different regimes. If the release position is between $\unicode[STIX]{x1D703}_{0}=0$ (front) and a critical $\unicode[STIX]{x1D703}_{c}$ the substance is quickly advected away from the sphere and its overall behaviour is similar to free diffusion in an empty channel. For release between $\unicode[STIX]{x1D703}_{c}$ and $\unicode[STIX]{x1D703}_{0}=\unicode[STIX]{x03C0}$ (tail), on the other hand, the substance is pushed towards the sphere leading to behaviour reminiscent of confined diffusion between two infinitely long cylinders. The critical position $\unicode[STIX]{x1D703}_{c}$ is generally smaller than $\unicode[STIX]{x03C0}/2$ which would correspond to an equatorial release position.

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Akkarawatkhoosith, Nattee, Wannarak Nopcharoenkul, Amaraporn Kaewchada e Attasak Jaree. "Mass Transfer Correlation and Optimization of Carbon Dioxide Capture in a Microchannel Contactor: A Case of CO2-Rich Gas". Energies 13, n. 20 (19 ottobre 2020): 5465. http://dx.doi.org/10.3390/en13205465.

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This work focused on the application of a microchannel contactor for CO2 capture using water as absorbent, especially for the application of CO2-rich gas. The influence of operating conditions (temperature, volumetric flow rate of gas and liquid, and CO2 concentration) on the absorption efficiency and the overall liquid-side volumetric mass transfer coefficient was presented in terms of the main effects and interactions based on the factorial design of experiments. It was found that 70.9% of CO2 capture was achieved under the operating conditions as follows; temperature of 50 °C, CO2 inlet fraction of 53.7%, total gas volumetric flow rate of 150 mL min−1, and adsorbent volumetric flow rate of 1 mL min−1. Outstanding performance of CO2 capture was demonstrated with the overall liquid-side volumetric mass transfer coefficient of 0.26 s−1. Further enhancing the system by using 2.2 M of monoethanolamine in water (1:1 molar ratio of MEA-to-CO2) boosted the absorption efficiency up to 88%.

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Tan, Jinhao, Yushou Song, Jianrong Zhou, Wenqin Yang, Xingfen Jiang, Xiaojuan Zhou, Yuanguang Xia et al. "An energy resolved neutron imaging detector based on boron doped nMCP coupled with a time stamping optical camera". Journal of Instrumentation 19, n. 01 (1 gennaio 2024): P01015. http://dx.doi.org/10.1088/1748-0221/19/01/p01015.

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Abstract Energy resolved neutron imaging has developed rapidly due to its advantage on testing the inner structure of crystal samples. Neutron detector is one of the key components to determine the imaging results quality. The neutron sensitive microchannel plate (nMCP) has been widely used in energy resolved neutron imaging experiments because of the high spatial and timing resolution. However, the ability to adjust field-of-view (FOV) and spatial resolution has not been realized in the nMCP detector, which is an attractive capability in energy resolved neutron imaging experiments. In this paper, an energy resolved neutron imaging detector was developed by coupling nMCP with a time stamping camera. The neutrons were absorbed by nMCP and converted into light through a phosphor screen. Then the light was focused on the camera by optical lens. A data algorithm was designed to improve the data quality. By changing the magnification of the optical lens, large FOV (46mm diameter) and high spatial resolution (26 μm) were realized in the experiments at CSNS beamline 20. The energy resolved ability was demonstrated by a Bragg-edge transmission imaging experiment for aluminum and stainless-steel samples. The performance of this detector makes it a promising candidate used in energy resolved neutron imaging.

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Sano, Emi, Chihiro Mori, Naoki Matsuoka, Yuka Ozaki, Keisuke Yagi, Aya Wada, Koichi Tashima et al. "Tetrafluoroethylene-Propylene Elastomer for Fabrication of Microfluidic Organs-on-Chips Resistant to Drug Absorption". Micromachines 10, n. 11 (19 novembre 2019): 793. http://dx.doi.org/10.3390/mi10110793.

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Organs-on-chips are microfluidic devices typically fabricated from polydimethylsiloxane (PDMS). Since PDMS has many attractive properties including high optical clarity and compliance, PDMS is very useful for cell culture applications; however, PDMS possesses a significant drawback in that small hydrophobic molecules are strongly absorbed. This drawback hinders widespread use of PDMS-based devices for drug discovery and development. Here, we describe a microfluidic cell culture system made of a tetrafluoroethylene-propylene (FEPM) elastomer. We demonstrated that FEPM does not absorb small hydrophobic compounds including rhodamine B and three types of drugs, nifedipine, coumarin, and Bay K8644, whereas PDMS absorbs them strongly. The device consists of two FEPM layers of microchannels separated by a thin collagen vitrigel membrane. Since FEPM is flexible and biocompatible, this microfluidic device can be used to culture cells while applying mechanical strain. When human umbilical vein endothelial cells (HUVECs) were subjected to cyclic strain (~10%) for 4 h in this device, HUVECs reoriented and aligned perpendicularly in response to the cyclic stretch. Moreover, we demonstrated that this device can be used to replicate the epithelial–endothelial interface as well as to provide physiological mechanical strain and fluid flow. This method offers a robust platform to produce organs-on-chips for drug discovery and development.

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Montenegro, Miguel, e Francisco J. Galindo-Rosales. "On the Complex Flow Dynamics of Shear Thickening Fluids Entry Flows". Micromachines 15, n. 11 (22 ottobre 2024): 1281. http://dx.doi.org/10.3390/mi15111281.

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Due to their nature, using shear thickening fluids (STFs) in engineering applications has sparked an interest in developing energy-dissipating systems, such as damping devices or shock absorbers. The Rheinforce technology allows the design of customized energy dissipative composites by embedding microfluidic channels filled with STFs in a scaffold material. One of the reasons for using microfluidic channels is that their shape can be numerically optimized to control pressure drop (also known as rectifiers); thus, by controlling the pressure drop, it is possible to control the energy dissipated by the viscous effect. Upon impact, the fluid is forced to flow through the microchannel, experiencing the typical entry flow until it reaches the fully developed flow. It is well-known for Newtonian fluid that the entrance flow is responsible for a non-negligible percentage of the total pressure drop in the fluid; therefore, an analysis of the fluid flow at the entry region for STFs is of paramount importance for an accurate design of the Rheinforce composites. This analysis has been numerically performed before for shear-thickening fluids modeled by a power-law model; however, as this constitutive model represents a continuously growing viscosity between end-viscosity plateau values, it is not representative of the characteristic viscosity curve of shear-thickening fluids, which typically exhibit a three-region shape (thinning-thickening-thinning). For the first time, the influence of these three regions on the entry flow on an axisymmetric pipe is analyzed. Two-dimensional numerical simulations have been performed for four STFs consisting of four dispersions of fumed silica nanoparticles in polypropylene glycol varying concentrations (7.5–20 wt%).

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Shamsoddini, Rahim, Bahador Abolpour, Hanie Abbaslou e Hossein Yarahmadi. "SPH modeling and investigation of the effect of the carbon dioxide entry form on its absorption rate in a microchannel containing absorbent aqueous solution". Fuel 371 (settembre 2024): 132073. http://dx.doi.org/10.1016/j.fuel.2024.132073.

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Asim, Muhammad, Jassinnee Milano, Hassan Izhar Khan, Muhammad Hanzla Tahir, M. A. Mujtaba, Abd Halim Shamsuddin, Muhammad Abdullah e M. A. Kalam. "Investigation of Mono-Crystalline Photovoltaic Active Cooling Thermal System for Hot Climate of Pakistan". Sustainability 14, n. 16 (17 agosto 2022): 10228. http://dx.doi.org/10.3390/su141610228.

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Climate change is causing adverse and diverse effects on human beings in term of severe diseases, melting of ice, and increase temperatures, which are directly linked to the consumption of traditional fossil fuels. These fuels can only be replaced by exploring renewable energy technologies, and photovoltaic solar modules are the most promising choice among them. This paper investigates electrical output in term of efficiency and power of a monocrystalline photovoltaic module under climatic conditions of Lahore, Pakistan in an effort to enhance electrical performance based on laminar and turbulent flow boundary conditions. A computational model of a PV module was designed and investigated, when the solar irradiance was observed to be maximum at 920.64 W/m2. Initially, the total flux received and absorbed by PV module was observed to be at 179.37 W/m2 after ray tracing analysis in Trace Pro; thereafter, the module’s temperature increased to 65.86 °C, causing an electrical efficiency drops to 15.65% from 19.40% without applying active cooling schemes. A coupling of Ansys Fluent and Steady State Thermal Analysis was performed for thermal management of a PV module by selecting water and air as a coolant at inlet temperature of 25 °C through microchannels contingent upon varying Reynolds numbers. The results maintained that the optimum coolant outlet temperature (49.86 °C), average PV cell’s layer temperature (32.42 °C), and temperature uniformity (4.16 °C) are achieved by water at 224, 6710, and 4200 Reynolds numbers respectively. In addition, again water maintained 18.65% of electrical efficiency and 33.65 W power output at 6710 Reynolds number. On the other hand, air-based cooling lagged behind water by 14% in term of efficiency and power output at maximum Reynolds number (6710).

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Nagavarapu, Ananda Krishna, e Srinivas Garimella. "Comparative Assessment of Falling-film and Convective-flow Absorption in Microscale Geometries". Journal of Thermal Science and Engineering Applications, 11 aprile 2022, 1–34. http://dx.doi.org/10.1115/1.4054302.

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Abstract A comparative assessment between two modes for ammonia-water absorption, microchannel falling-film absorption and microscale convective-flow, is presented in this study. The microchannel falling-film absorber consists of an array of short microchannel tubes arranged parallel to each other, and stacked in several vertical rows to provide the necessary transfer area. Dilute solution flows in a falling-film mode around these cooled tubes, while absorbing the counter-current vapor. The microscale convective-flow absorber consists of an array of parallel, aligned alternating sheets with integral microscale features, enclosed between cover plates. Several absorber variants were designed for each flow configuration, and optimal prototypes were identified based on design and operational constraints for a 10.5 kW cooling capacity chiller. Comparative assessments of heat and mass transfer characteristics are presented while accounting for fabrication considerations. This work will guide the development of miniaturized absorption heat pump components.

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34

Nagavarapu, Ananda Krishna, e Srinivas Garimella. "Falling-Film Absorption Around Microchannel Tube Banks". Journal of Heat Transfer 135, n. 12 (27 settembre 2013). http://dx.doi.org/10.1115/1.4024261.

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An experimental investigation of heat and mass transfer in a falling-film absorber with microchannel tube arrays was conducted. Liquid ammonia–water solution flows in a falling-film mode around an array of small diameter coolant tubes, while vapor flows upward through the tube array counter-current to the falling film. This absorber was installed in a test facility consisting of all components of a functional single-effect absorption chiller, including a desorber, rectifier, condenser, evaporator, solution heat exchanger, and refrigerant precooler, to obtain realistic operating conditions at the absorber and to account for the influence of the other components in the system. Unlike studies in the literature on bench-top, single-component, single-pressure test stands, here the experiments were conducted on the absorber at vapor, solution, and coupling fluid conditions representative of space-conditioning systems in the heating and cooling modes. Absorption measurements were taken over a wide range of solution flow rates, concentrations, and coupling fluid temperatures, which simulated operation of thermally activated absorption systems at different cooling capacities and ambient conditions. These measurements are used to interpret the effects of solution and vapor flow rates, concentrations, and coupling fluid conditions on the respective heat and mass transfer coefficients.

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35

Chaurasia, Harsh, e Kalvala Srinivas Reddy. "Integrated Model for Comprehensive Performance Investigation of Solar Concentrated Photovoltaic‐Thermal System Embedded with Microchannel Heat Sinks". Energy Technology, 9 aprile 2024. http://dx.doi.org/10.1002/ente.202400005.

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Concentrated photovoltaic (CPV) is a well‐established renewable energy technology. A significant challenge in CPV systems is their low efficiency, majorly due to localized heating yielded from concentration, often requiring the use of cooling systems. The accurate performance analysis and cooling system design for CPV systems require a multiphysics model. Herein, an integrated optical–thermal–electrical model is proposed for the performance evaluation of CPV systems incorporated with different configurations of microchannel heat sinks. The heat sink configuration includes 116 parallel and counter microchannels (Configuration A and B), a single wide microchannel (Configuration C), and single wide minichannel (Configuration D) heat sinks. This study involves 3D Monte‐Carlo ray tracing, finite volume method, and cell‐based electrical modeling. The results indicate that the flux profile over the absorber is highly nonuniform in nature. Furthermore, the CPV system with a Configuration C heat sink achieves a better uniformity in temperature, providing an optimized thermal performance of 64.63%. Moreover, the integrated model considers the impact of PV cell current mismatch that becomes prominent at increasing incidence angles. A maximum deviation of 6.9% in electrical power is obtained while comparing predicted numerical results against experimental results available in literature.

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36

Chandrasekaran, Sriram, Matthew Hughes, Girish Kini e Srinivas Garimella. "A microchannel shell-and-tube absorber for ammonia-water absorption". Applied Thermal Engineering, novembre 2020, 116321. http://dx.doi.org/10.1016/j.applthermaleng.2020.116321.

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37

Wang, Xueqing, Haifeng Wu, Yusen Ma, Suilin Wang e Rongji Xu. "Homogenization Function of Microchannel on Heat Absorber with Compound Parabolic Concentrator". Journal of Thermal Science, 17 ottobre 2022. http://dx.doi.org/10.1007/s11630-022-1609-6.

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38

Jenks, Jeromy, e Vinod Narayanan. "Effect of Channel Geometry Variations on the Performance of a Constrained Microscale-Film Ammonia-Water Bubble Absorber". Journal of Heat Transfer 130, n. 11 (5 settembre 2008). http://dx.doi.org/10.1115/1.2970065.

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An experimental study of the absorption of ammonia vapor in a constrained thin film of ammonia-water solution is presented. A large aspect ratio microchannel with one of its walls formed of a porous material is used to constrain the thickness of the liquid film. Experiments are performed at a pressure of 2.5 bar absolute and 4 bar absolute and at a fixed weak solution inlet temperature. Weak solution flow rates are varied from 10 g/min to 30 g/min (corresponding to the weak solution Reynolds number, Re, from 15 to 45), inlet mass concentrations are varied from 0% to 15%, and gas flow rates are varied between 1 g/min and 3 g/min (corresponding to the vapor Re from 160 to 520). Six geometries, including three smooth-bottom-walled channels of differing depths and three channels with structured bottom walls, are considered. Results indicate that, for identical rates of vapor absorption, the overall heat transfer coefficient of the 400 μm absorber is in most cases significantly larger than that of other absorbers. For the 150 μm and 400 μm absorbers, a trade-off between the high overall heat and mass transfer coefficients is achieved for the highest vapor to solution flow rate ratio.

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39

Wälchli, R., T. Brunschwiler, B. Michel e D. Poulikakos. "Self-Contained, Oscillating Flow Liquid Cooling System for Thin Form Factor High Performance Electronics". Journal of Heat Transfer 132, n. 5 (8 marzo 2010). http://dx.doi.org/10.1115/1.4000456.

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A self-contained, small-volume liquid cooling system for thin form-factor electronic equipment (e.g., blade server modules) is demonstrated experimentally in this paper. A reciprocating water flow loop absorbs heat using mesh-type microchannel cold plates and spreads it periodically to a larger area. From there, the thermal energy is interchanged via large area, low pressure drop cold plates with a secondary heat transfer loop (air or liquid). Four phase-shifted piston pumps create either a linearly or radially oscillating fluid flow in the frequency range of 0.5–3 Hz. The tidal displacement of the pumps covers 42–120% of the fluid volume, and, therefore, an average flow rate range of 100–800 ml/min is tested. Three different absorber mesh designs are tested. Thermal and fluidic characteristics are presented in a time-resolved and a time-averaged manner. For a fluid pump power of 1 W, a waste heat flux of 180 W/cm2(ΔT=67 K) could be dissipated from a 3.5 cm2 chip. A linear oscillation flow pattern is advantageous over a radial one because of the more efficient heat removal from the chip and lower hydraulic losses. The optimum microchannel mesh density is determined as a combination of low pump losses and high heat transfer rates.

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40

Sui, Zengguang, Yunren Sui e Wei Wu. "Multi-Objective Optimization of a Microchannel Membrane-Based Absorber with Inclined Grooves Based on CFD and Machine Learning". SSRN Electronic Journal, 2021. http://dx.doi.org/10.2139/ssrn.3892177.

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41

Liu, Yang, Yu-Tong Xiong, Shu-Zhou Qu, Yu-Xin Liao, Hao-Sen Kang, Liang Ma, Jing-Wen Zou, Tao-Yuan Du, Hui-Hui Yang e Si-Jing Ding. "Dual‐Plasmonic Ti₃C₂T_x/CuSe 2D/2D Solar Absorber and A Hydrophilic Device for Efficient Solar‐Driven Water Collection". Solar RRL, 18 dicembre 2023. http://dx.doi.org/10.1002/solr.202300935.

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Solar water evaporation is an emerging technology for drinkable water generation, while it remains a challenge to develop materials and device for efficient water evaporation and collection. Herein, dual‐plasmonic Ti3C2Tx/CuSe two‐dimensional (2D)/2D hybrids are prepared for high‐efficiency solar water evaporation and a hydrophilic device is designed for efficient water collection. The Ti3C2Tx/CuSe hybrids, which monocrystalline CuSe ultrathin nanosheets are chemically bonded with Ti3C2Tx nanosheets, show efficient photothermal conversion owing to the plasmon‐coupling‐induced strong light absorption and fast charge transfer in the 2D/2D interface. By transferring the hybrids on a cotton piece, the Ti3C2Tx/CuSe membrane displays over 95% of solar light absorption, a stable evaporation rate of 1.893 kg m‐2 h‐1, and solar‐to‐vapor efficiency of 99.13% under one‐sun irradiation. The membrane can also treat water with more than 20 wt% salinity due to the rich microchannel for ion diffusion. Furthermore, a water evaporation device, which the cambered roof is painted with hydrophilic SiO2, is designed for efficient water collection. The treated roof can efficiently reduce the optical loss and transfer the vapor condensation, leading to a high average freshwater generation of 16.4 kg/m2 in a daily (10 h) natural light irradiation, much higher than other reported devices.This article is protected by copyright. All rights reserved.

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42

Hoysall, Dhruv C., Khoudor Keniar e Srinivas Garimella. "Visualization of Two-Phase Flow in Serpentine Heat Exchanger Passages With Microscale Pin Fins". Journal of Heat Transfer 140, n. 1 (23 agosto 2017). http://dx.doi.org/10.1115/1.4037342.

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Microchannel heat exchangers offer the potential for high heat transfer coefficients; however, implementation challenges must be addressed to realize this potential. Maldistribution of phases among the microchannels and the changing phase velocities associated with phase change present design challenges. Flow maldistribution and oscillatory instabilities can affect transfer rates and pressure drops. In condensers, evaporators, absorbers, and desorbers, changing phase velocities can change prevailing flow regimes from favorable to unfavorable. Geometries with serpentine passages containing pin fins can be configured to maintain favorable flow regimes throughout the component for phase-change heat and mass transfer applications. Due to the possibility of continuous redistribution of the flow across the pin fins along the flow direction, maldistribution can also be reduced. These features enable high heat transfer coefficients, thereby achieving considerable compactness. The characteristics of two-phase flow through a serpentine passage with micro-pin fin arrays with diameter 350 μm and height 406 μm are investigated. An air–water mixture is used to represent two-phase flow through the serpentine test section, and flow features are investigated using high-speed photography. Improved flow distribution is observed in the serpentine geometry. Distinct flow regimes, different from those observed in microchannels, are also established. Void fraction and interfacial area along the length of the serpentine passages are compared with the corresponding values for microchannels. A model developed for the two-phase frictional pressure drops across this serpentine micro-pin fin geometry predicts experimental values with a mean absolute error (MAE) of 7.16%.

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43

Uddin, Rony Rajib, e Gladen Adam. "Numerical Modeling of a Photovoltaic/Microchannel Direct-Expansion Evaporator for a CO2 Heat Pump". Journal of Thermal Science and Engineering Applications 13, n. 2 (7 agosto 2020). http://dx.doi.org/10.1115/1.4047819.

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Abstract A numerical model of a PV/microchannel direct-expansion evaporator for a CO2 heat pump is developed and validated with experimental data from the literature. The effects of degree of superheating, CO2 mass flux, and evaporation temperature on the amount of heat absorbed, pressure drop in the microchannel evaporator, PV temperature, and electrical efficiency are analyzed. The analysis shows that increasing the degree of superheating decreases the amount of heat absorbed, has minimal effect on the PV temperature (for superheating <15 °C), but reduces the pressure drop. The variation of CO2 mass flux has a minimal effect on the amount of heat absorbed and the PV temperature, but the pressure drop increases with increasing CO2 mass flux. Increasing the evaporation temperature decreases the amount of heat absorbed, reduces the pressure drop, and increases the PV temperature. For average ambient conditions for Fargo, North Dakota, a 5–10 °C of superheating at the evaporator outlet, an evaporator temperature between −5 and +5 °C, and a CO2 mass flux of 330–550 kg · m−2 · s−1 balance maximizing the heat absorption while minimizing the pressure drop. To maximize the PV efficiency, lower evaporation temperatures should be used. At an evaporation temperature of 0 °C and an insolation level of 1000 W · m−2, the CO2 microchannel evaporator causes a 23 °C reduction in PV panel temperature which corresponds to a 1.44% absolute increase in PV efficiency.

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44

Park, Jeongeun, Beomseok Cha, Furkan Ginaz Almus, Mehmet Akif Sahin, Hyochan Kang, Yeseul Kang, Ghulam Destgeer e Jinsoo Park. "Acoustic Waves Coupling with Polydimethylsiloxane in Reconfigurable Acoustofluidic Platform". Advanced Science, 30 ottobre 2024. http://dx.doi.org/10.1002/advs.202407293.

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AbstractAcoustofluidics is a promising technology that leverages acoustic waves for precise manipulation of micro/nano‐scale flows and suspended objects within microchannels. Despite many advantages, the practical applicability of conventional acoustofluidic platforms is limited by irreversible bonding between the piezoelectric actuator and the microfluidic chip. Recently, reconfigurable acoustofluidic platforms are enabled by reversible bonding between the reusable actuator and the replaceable polydimethylsiloxane (PDMS) microfluidic chip by incorporating a PDMS membrane for sealing the microchannel and coupling the acoustic waves with the fluid inside. However, a quantitative guideline for selecting a suitable PDMS membrane for various acoustofluidic applications is still missing. Here, a design rule for reconfigurable acoustofluidic platforms is explored based on a thorough investigation of the PDMS thickness effect on acoustofluidic phenomena: acousto–thermal heating (ATH), acoustic radiation force (ARF), and acoustic streaming flow (ASF). These findings suggest that the relative thickness of the PDMS membrane (t) for acoustic wavelength (λPDMS) determines the wave attenuation in the PDMS and the acoustofluidic phenomena. For t/λPDMS ≈ O(1), the transmission of acoustic waves through the membrane leads to the ARF and ASF phenomena, whereas, for t/λPDMS ≈ O(10), the acoustic waves are entirely absorbed within the membrane, resulting in the ATH phenomenon.

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45

Pereira, Ana Teresa, Virginia Chu, Duarte M. F. Prazeres e Joao P. Conde. "Miniaturization of Immunoassays Using Optical Detection with Integrated Amorphous Silicon Photodiodes". MRS Proceedings 1191 (2009). http://dx.doi.org/10.1557/proc-1191-oo08-04.

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AbstractImmunoassays are currently the main analytical technique for quantification of a wide range of analytes of clinical, medical, biotechnological, and environmental significance with high sensitivity and specificity. Miniaturization of immunoassays is achieved using microfluidics coupled with integrated optical detection of the antibody-antigen molecular recognition reaction using thin-film amorphous silicon (a-Si:H) photodiodes. The detection system used consists of an a-Si:H photodiode aligned with a polydimethylsiloxane (PDMS) microchannel. An enzymatic reaction taking place in the microchannel yields a product which is a light-absorbent molecule and hence can be optically detected by the integrated photodiode. Specific antigen-antibody reaction was detected and distinguished from the non-specific reaction.

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46

Heffner, Herman, Marcos Soldera e Andrés Fabián Lasagni. "Optoelectronic performance of indium tin oxide thin films structured by sub-picosecond direct laser interference patterning". Scientific Reports 13, n. 1 (16 giugno 2023). http://dx.doi.org/10.1038/s41598-023-37042-y.

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AbstractA route to increase the efficiency of thin film solar cells is improving the light-trapping capacity by texturing the top Transparent Conductive Oxide (TCO) so that the sunlight reaching the solar absorber scatters into multiple directions. In this study, Indium Tin Oxide (ITO) thin films are treated by infrared sub-picosecond Direct Laser Interference Patterning (DLIP) to modify the surface topography. Surface analysis by scanning electron microscopy and confocal microscopy reveals the presence of periodic microchannels with a spatial period of 5 µm and an average height between 15 and 450 nm decorated with Laser-Induced Periodic Surface Structures (LIPSS) in the direction parallel to the microchannels. A relative increase in the average total and diffuse optical transmittances up to 10.7% and 1900%, respectively, was obtained in the 400–1000 nm spectral range as an outcome of the interaction of white light with the generated micro- and nanostructures. The estimation of Haacke’s figure of merit suggests that the surface modification of ITO with fluence levels near the ablation threshold might enhance the performance of solar cells that employ ITO as a front electrode.

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47

Choi, Jihun, Hansol Lee, Bokyeong Sohn, Minjae Song e Sangmin Jeon. "Highly efficient evaporative cooling by all-day water evaporation using hierarchically porous biomass". Scientific Reports 11, n. 1 (19 agosto 2021). http://dx.doi.org/10.1038/s41598-021-96303-w.

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AbstractWe developed a 3D solar steam generator with the highest evaporation rate reported so far using a carbonized luffa sponge (CLS). The luffa sponge consisted of entangled fibers with a hierarchically porous structure; macropores between fibers, micro-sized pores in the fiber-thickness direction, and microchannels in the fiber-length direction. This structure remained after carbonization and played an important role in water transport. When the CLS was placed in the water, the microchannels in the fiber-length direction transported water to the top surface of the CLS by capillary action, and the micro-sized pores in the fiber-thickness direction delivered water to the entire fiber surface. The water evaporation rate under 1-sun illumination was 3.7 kg/m2/h, which increased to 14.5 kg/m2/h under 2 m/s wind that corresponded to the highest evaporation rate ever reported under the same condition. The high evaporation performance of the CLS was attributed to its hierarchically porous structure. In addition, it was found that the air temperature dropped by 3.6 °C when the wind passed through the CLS because of the absorption of the latent heat of vaporization. The heat absorbed by the CLS during water evaporation was calculated to be 9.7 kW/m2 under 1-sun illumination and 2 m/s wind, which was 10 times higher than the solar energy irradiated on the same area (1 kW/m2).

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48

Cataldo, Filippo, e Yuri Carmelo Crea. "Experimental Analysis and Modeling of a Novel Thermosyphon System for Electronics Cooling". Journal of Electronic Packaging 143, n. 4 (5 novembre 2021). http://dx.doi.org/10.1115/1.4052670.

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Abstract In an era of ever-growing digitalization, the absorbed power of processing units is becoming an actual challenge for cooling systems. The effectiveness is imperative, but compactness and passiveness are driving factors in the design as well. The goal of this paper is twofold: (1) to present a detailed experimental campaign on a thermosyphon system for high-heat-load electronics and (2) to propose a model of the thermosyphon system using a Machine Learning approach. The thermosyphon system is composed of a microchannel evaporator plate directly attached to the heat-generating device and an air-cooled multiport condenser. The height between the evaporator and condenser inlets is 12 cm. The condenser is also proposed in two solutions: the first one has a footprint heat exchange area of 180 × 120 mm2, which allows a single fan's placement; the second one has a footprint area of 240 × 120 mm2, allowing the placement of two fans. The working fluid used in the system is R1234ze(E) with different charges. The experimental results show that the single-fan condenser reached a maximum heat rejection of 330 W, corresponding to a heat flux of 21.9 W/cm2. The double-fan condenser bore a maximum heat rejection of 570 W (37.7 W/cm2). The model, constructed purely via a machine learning tool, shows a satisfactory agreement between experimental and predicted data.

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Zhao, Xiaomeng, Heng Zhang, Kit-Ying Chan, Xinyue Huang, Yunfei Yang e Xi Shen. "Tree-Inspired Structurally Graded Aerogel with Synergistic Water, Salt, and Thermal Transport for High-Salinity Solar-Powered Evaporation". Nano-Micro Letters 16, n. 1 (17 giugno 2024). http://dx.doi.org/10.1007/s40820-024-01448-8.

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Abstract Solar-powered interfacial evaporation is an energy-efficient solution for water scarcity. It requires solar absorbers to facilitate upward water transport and limit the heat to the surface for efficient evaporation. Furthermore, downward salt ion transport is also desired to prevent salt accumulation. However, achieving simultaneously fast water uptake, downward salt transport, and heat localization is challenging due to highly coupled water, mass, and thermal transport. Here, we develop a structurally graded aerogel inspired by tree transport systems to collectively optimize water, salt, and thermal transport. The arched aerogel features root-like, fan-shaped microchannels for rapid water uptake and downward salt diffusion, and horizontally aligned pores near the surface for heat localization through maximizing solar absorption and minimizing conductive heat loss. These structural characteristics gave rise to consistent evaporation rates of 2.09 kg m−2 h−1 under one-sun illumination in a 3.5 wt% NaCl solution for 7 days without degradation. Even in a high-salinity solution of 20 wt% NaCl, the evaporation rates maintained stable at 1.94 kg m−2 h−1 for 8 h without salt crystal formation. This work offers a novel microstructural design to address the complex interplay of water, salt, and thermal transport.

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