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Littérature scientifique sur le sujet « Microchannel absorber »

Auteur : Grafiati

Publié le 21 décembre 2024

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Articles de revues sur le sujet "Microchannel absorber"

Goel, Nitin, et 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^o 2 (26 mai 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^o 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 et Michael Leung. « Performance investigation and enhancement of membrane-contactor microchannel absorber towards compact absorption cooling ». International Journal of Heat and Mass Transfer 169 (avril 2021) : 120978. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2021.120978.

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

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

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

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Sui, Zengguang, Chong Zhai et Wei Wu. « Parametric and comparative study on enhanced microchannel membrane-based absorber structures for compact absorption refrigeration ». Renewable Energy 187 (mars 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 et Robert A. Taylor. « Experimental Testing of Hydrophobic Microchannels, with and without Nanofluids, for Solar PV/T Collectors ». Energies 12, n^o 15 (6 août 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 et Wei Wu. « Multi-objective optimization of a microchannel membrane-based absorber with inclined grooves based on CFD and machine learning ». Energy 240 (février 2022) : 122809. http://dx.doi.org/10.1016/j.energy.2021.122809.

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Wei, Xinghua, Rijing Zhao, Siyuan Wu, Shouzhen Wang et 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 (août 2023) : 124097. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2023.124097.

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Thèses sur le sujet "Microchannel absorber"

Cheng, Hao. « Etude d'absorption chimique du dioxyde de carbone : transfert de masse en écoulement diphasique dans un minicanal et conception d'un nouvel absorbeur multicanaux ». Electronic Thesis or Diss., Nantes Université, 2024. http://www.theses.fr/2024NANU4030.

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Les dispositifs à micro/mini-canaux suscitent un vif intérêt pour l'absorption chimique efficace du CO₂ dans le cadre du captage de CO2. Cette thèse de doctorat vise à caractériser et à étudier le processus de transfert de masse à travers l’écoulement diphasique accompagné de réactions chimiques dans les mini-canaux, ainsi qu'à concevoir et développer de nouveaux absorbeurs de CO₂ miniaturisés avec des structures optimisées vis-à-vis de leurs performances d'absorption. Tout d'abord, la dynamique des bulles dans un mini-canal droit en T a été observée par moyen optique, montrant que la réaction chimique supprime la fragmentation des bulles mais favorise leur rétrécissement. Ensuite, le champ de vitesse et le champ de concentration de CO₂ dans le liquide ont été déterminés respectivement par la PTV et la colorimétrie sensible au pH, permettant le développement d'un modèle de transfert de masse de cellule unitaire modifié, intégrant les effets de la recirculation du flux et de la réaction chimique. En outre, une structure de chicane en spirale a été intégrée dans le mini-canal, d’où une amélioration significative du transfert de masse avec une faible augmentation des pertes de charge. Enfin, sur la base de cette stratégie d'intensification, une conception innovante d'absorbeur de CO₂ multicanaux intégrés, caractérisée par des unités parallèles de minicanaux croisés en double hélice conjuguée (Codohec), a été proposée. Un module à l'échelle du laboratoire de cette conception a été réalisé et ses performances d'absorption ont été évaluées de manière exhaustive, mettant en évidence divers avantages tels qu'un coefficient de transfert de masse élevé, une consommation d'énergie acceptable, un taux d'élimination élevé et une grande capacité de traitement du CO₂. Les résultats de cette thèse pourraient fournir de nouvelles perspectives sur les mécanismes de transport sousjacents du transfert de masse gaz-liquide accompagné de réactions chimiques et contribuer à la conception et à l'optimisation d'absorbeurs de CO₂ miniaturisés hautement efficaces pour des applications industrielles
Micro/minichannel devices show great interests for their potential in efficient CO2 chemical absorption in the context of the carbon capture. This PhD these aims to characterize and investigate the transport mechanisms involved in chemical reactionaccompanied two-phase mass transfer in minichannel, and to design and develop novel miniaturized CO2 absorbers featuring intensified structures and optimized absorption performances. Firstly, bubble dynamics within a T-junction straight minichannel were optically observed, showing that the chemical reaction tends to suppress bubble breakup while promoting its shrinkage. Then, the velocity field and CO2 concentration field in the liquid slug were determined using PTV and pH-sensitive colorimetry, respectively, permitting the development of a modified unit-cell mass transfer model that incorporates the effects of flow recirculation and chemical reaction. Further enhancement was achieved by embedding a spiral distributed baffle structure into the minichannel, leading to a significant increase in mass transfer coefficient with only a minor rise in pressure drop. Finally, building on this intensification measure, a novel design for an integrated multichannel CO2 absorber was proposed, featuring paralleling units of conjugated double-helix cross minichannels (Codohec). A lab-scale module of this design was realized, and its absorption performance was comprehensively evaluated, highlighting various advantages including a high mass transfer coefficient, acceptable energy consumption, high remove rate, and large CO2 treatment capacity. These findings may provide new insights into the underlying transport mechanisms of chemical reaction-accompanied gas-liquid mass transfer and contribute to the design and optimization of highly efficient miniaturized CO2 absorbers for industry applications

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Ammari, Ali. « Experimental Investigation of two-phase flow in microchannels. Co-current Absorption of Ammonia in Water to Design an Innovative Bubble Plate Absorber ». Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-156190.

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For ammonia-water absorption refrigeration technology it is suggested to use bubble type absorbers because the higher contact surface area provides a higher mass transfer rate. Furthermore, dispersion of bubbles in the bulk of liquid phase also exhibits better heat transfer characteristics that facilitate the recovery of dissipated heat of the exothermic absorption. In this context, plate heat exchangers are believed to be an option to be employed as absorber in some applications. Commercial plate heat exchangers have only one inlet and outlet for a working fluid and as a result, gas and liquid should be mixed before supplied to a gap between the two adjacent plates. The consequence is the high risk of bubble mergence to form a bigger bubble and to follow the shortest flow paths in vertical direction so that not all the heat transfer surface can be effectively used. Furthermore this feature makes plate heat exchangers sensitive to the angle of plate relative to the vertical which would be worst when it is laid to its side on a horizontal plane. Austrian Institute of Technology (AIT) develops an efficient Bubble Plate Absorber for applications in high-pressure absorption systems and this work tries to investigate design possibility of this Bubble Plate Absorber based on a plate heat exchanger equipped with microchannels between plates. Two sets of seven parallel microchannels same in shape and dimension were tested. The first set had a continuous wall which means fluids could flow independently along the microchannels; whereas, the other set was benefiting from some linkages between channels that fluids could cross from one microchannel to another one. Ammonia vapour was injected via one and two-holed distributors. It was found that microchannels with continuous wall deliver higher concentration and less unabsorbed bubbles at the microchannels outlet. In visual analysis by high-speed camera, changing the vapour distributors from single-hole to double-hole had no significant effect on the bubble distribution quality in lower flowrates; however, double-hole vapour distributor showed better performance in higher vapours flowrates.

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Ammari, Ali. « Experimental Investigation ofTwo-phase Flow in Microchannels“Co-current Absorption of Ammonia in Water to Design an Innovative Bubble Plate Absorber” : “Co-current Absorption of Ammonia in Water to Design an Innovative Bubble Plate Absorber” ». Thesis, KTH, Tillämpad termodynamik och kylteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116779.

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For ammonia-water absorption refrigeration technology it is suggested to use bubble type absorbers because the higher contact surface area provides a higher mass transfer rate. Furthermore, dispersion of bubbles in the bulk of liquid phase also exhibits better heat transfer characteristics that facilitate the recovery of dissipated heat of the exothermic absorption.In this context, plate heat exchangers are believed to be an option to be employed as absorber in some applications. Commercial plate heat exchangers have only one inlet and outlet for a working fluid and as a result, gas and liquid should be mixed before supplied to a gap between the two adjacent plates. The consequence is the high risk of bubble mergence to form a bigger bubble and to follow the shortest flow paths in vertical direction so that not all the heat transfer surface can be effectively used. Furthermore this feature makes plate heat exchangers sensitive to the angle of plate relative to the vertical which would be worst when it is laid to its side on a horizontal plane.Austrian Institute of Technology (AIT) develops an efficient Bubble Plate Absorber for applications in high-pressure absorption systems and this work tries to investigate design possibility of this Bubble Plate Absorber based on a plate heat exchanger equipped with microchannels between plates.Two sets of seven parallel microchannels same in shape and dimension were tested. The first set had a continuous wall which means fluids could flow independently along the microchannels; whereas, the other set was benefiting from some linkages between channels that fluids could cross from one microchannel to another one. Ammonia vapour was injected via one and two-holed distributors.It was found that microchannels with continuous wall deliver higher concentration and less unabsorbed bubbles at the microchannels outlet. In visual analysis by high-speed camera, changing the vapour distributors from single-hole to double-hole had no significant effect on the bubble distribution quality in lower flowrates; however, double-hole vapour distributor showed better performance in higher vapours flowrates.

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Actes de conférences sur le sujet "Microchannel absorber"

Nagavarapu, Ananda Krishna, et Srinivas Garimella. « Falling-Film Absorption Around Microchannel Tube Banks ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63094.

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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 pre-cooler, 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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Liu, Yunshan, et Ebrahim Al Hajri. « Mass and Heat Transfer Characteristics of a Single-High Aspect Ratio Microchannel Absorber ». Dans ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89787.

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Recently, study on a microscale-based absorption refrigeration system has sprung up motivated by the need of efficient energy utilization. Heat-driven absorption systems offer a possibility of generating both power and cooling with environment friendly refrigerants, such as ammonia/water and LiBr/water. However, these systems are often large in size and low in COP especially in single stage absorption systems. These characteristics of absorptions systems make them unattractive in most cases. This work introduces the utilization of micro-channel enhanced surfaces as heat exchangers to enhance the component and system performance, to reduce the system size and to reduce the cost of the system as well. In this work, a new concept of enhancing heat and mass transfer processes is applied in the absorber part of the absorption cycle by using a single micro-channel. Due to its merit of high area to volume ratio, microchannel technology has been well theoretically validated to be a very effective and potential choice for enhancing heat transfer performance. But there is a lack of research work on the mass transfer performance in micro-channels. This work investigated simultaneous mass and heat transfer characteristics of a novel microchannel absorber that uses LiBr/water as the working fluid. A microchannel with hydraulic diameter of 0.7mm is employed in this characterization study. Velocity distribution, pressure drop, concentration and temperature profile inside the microchannel as well as effects of the inlet absorbent concentration, flow rate and temperature together with the refrigerant flow rate on the heat/mass transfer are predicted. Investigations on the optimum inlet angle design of a single channel absorber are also presented in the end of this work. Feasibility of this novel absorber design was proved via this numerical simulation as the mass transfer taking place inside the mixing channel was observed to achieve the identical performance but with a size reduction by 1/27 compared to a conventional falling film absorber. A 7 times enhancement of the heat transfer coefficient was also achieved with the comparison of a macro-scale based absorber configuration.

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de Vega, Mercedes, Néstor García-Hernando et María Venegas. « Experimental measurement of mass transfer resistances in a membrane based adiabatic microchannel absorber ». Dans The 4th World Congress on Momentum, Heat and Mass Transfer. Avestia Publishing, 2019. http://dx.doi.org/10.11159/icmfht19.104.

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Jenks, Jeromy, et Vinod Narayanan. « Effect of Channel Geometry Variations on the Performance of a Microscale Bubble Absorber ». Dans ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32445.

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The effect of microchannel geometry variations on heat transfer and absorption rate of an ammonia-water constrained thin film bubble absorber are presented. Experiments are performed at an absolute pressure of four bar and at a fixed inlet mass concentration of ammonia of 15 percent. The mass flow rate of the inlet weak solution are varied from 10 g/min to 30 g/min, and that of ammonia gas are varied from 1 g/min to 3 g/min. Five geometries, including two smooth-bottom-walled channels of differing depths, and three channels with structured bottom walls are considered. For identical rates of vapor absorption, the overall heat transfer coefficient for the 400 μm smooth microchannel is significantly larger than of the 150 μm smooth channel as well as that of the cross-ribbed and angled-cross-ribbed structured channel. The streamwise-finned channel exhibit high overall heat transfer coefficients for vapor flow rates of up to 2 g/min.

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Jenks, Jeromy, et Vinod Narayanan. « An Experimental Study of Ammonia-Water Bubble Absorption in a Large Aspect Ratio Microchannel ». Dans ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-14036.

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An experimental study of absorption of ammonia into a constrained thin film of ammonia-water solution is presented. A large aspect ratio microchannel with one of its walls formed by a porous material is used to constrain the thickness of the liquid film. An exit visualization section was used to confirm absorption of ammonia gas within the microchannel. Experiments were performed at a pressure of 1 bar and a fixed inlet temperature of the weak solution, for weak solution flow rates from 10 to 30 g/min, inlet mass concentrations from 0 to 15 percent, and gas flow rates between 1 and 3 g/min. Results indicate that the overall heat transfer coefficient changes little for lower inlet weak solution concentrations and for lower gas flow rates, but increases noticeably for a higher solution and gas flow rate. The solution side log-mean temperature distribution increases with an increase in inlet solution concentration. Absorber exit visualization revealed the presence of periodic ammonia bubbles, occurring in varying sizes and periods, indicating that improvements to the current design are necessary to ensure complete absorption within the microchannel.

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Chugh, Devesh, Rasool Nasr Isfahani, Kyle Gluesenkamp, Omar Abdelaziz et Saeed Moghaddam. « A Hybrid Absorption Cycle for Water Heating, Dehumidification, and Evaporative Cooling ». Dans ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ipack2015-48816.

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In this study, development of a novel system for combined water heating, dehumidification, and space cooling is discussed. The system absorbs water vapor from an air stream into an absorbent. The latent heat of absorption, released into the absorbent, is transferred into the process water that cools the absorbent. The solution is regenerated in the desorber, where it is heated by a heating fluid. The water vapor generated in the desorber is condensed and its heat of phase change is also transferred to the process water. The condensed water is then used in an evaporative cooling process to cool the dehumidified air exiting the absorber. Essentially, this open-absorption cycle collects space sensible heat and transfers it to hot water. Another novel feature of the cycle is recovery of the heat energy from the solution exiting the desorber by heat exchange with process water rather than with the solution exiting the absorber. This approach has enabled heating the process water from an inlet temperature of 15°C to 57°C (conforming to the required DOE building hot water standard) and compact fabrication of the absorber, solution heat exchanger, and desorber in plate and frame configuration. The system under development currently has a water heating capacity of 1.5 kW and a thermal coefficient of performance (COP) of 1.45.

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Cardenas, Ruander, et Vinod Narayanan. « A Numerical Study of Ammonia-Water Absorption Into a Constrained Microscale Film ». Dans ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67021.

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A one-dimensional, steady state, semi-empirical model of an ammonia-water microscale bubble absorber is presented. The geometry consists of a microchannel through which a solution of ammonia-water flows. Ammonia vapor is injected through one of the walls of the channel. A counter flowing coolant solution removes the heat generated due to absorption from the opposite wall. The 1-D, steady state species and energy transport equations are solved to yield, along the length of the channel, concentration and temperature profiles of the solution stream and the temperature profile of the coolant fluid stream. Values for the overall heat transfer coefficient from experimental results are used in this model. A parametric study of fluid and geometrical parameters based on the model is presented. The varied fluidic parameters include the mass flow rates of the weak solution, coolant, and vapor, the inlet coolant temperature, and the weak solution concentration. Two variations of the vapor distribution that resulted from a geometrical variation of the porous plate are considered: (a) variation in length of the non-porous section, and (b) variation in the number of intermittent sections in which there was no injection of vapor. Trends of the parametric study were consistent with those of experiments. A salient result of the parametric study indicates that incomplete absorption occurs with an increase in weak solution flow rate due to the decrease in residence time within the microchannel for absorption. At a specific fixed flow condition, a single porous section followed by a non-porous section provides the optimal vapor distribution for absorption within the channel. The length of this non-porous section for optimal absorption within the channel is also determined using the model.

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Kim, Yoon Jo, Yogendra K. Joshi et Andrei G. Fedorov. « Design of an Absorption Based Miniature Heat Pump System for Cooling of High Power Microprocessors ». Dans ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ipack2007-33245.

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An absorption based miniature heat pump system, which can be driven by the low quality waste heat, is designed for chip cooling applications. Miniaturization is achieved, as the chemically-driven absorption/desorption process permits pressurization of the working fluid in liquid phase, requiring much smaller displacement volume than in vapor compression systems. The goal of this work is to design a system that keeps the chip junction temperature near room temperature, while removing 100 W of heat load. Water/LiBr pair is used as a working fluid. A dual micro-channel array evaporator is used to reduce both the mass flux through each micro-channel and the channel length, thus minimizing the pressure drop. Microchannel arrays for the desorber and condenser are placed in intimate communication with each other using a hydrophobic membrane, which provides a common chemically-selective interface between the desorber and condenser to separate the water vapor from LiBr solution. The separated water vapor is immediately cooled and converted into a liquid phase at the condenser side. For direct air cooling of the condenser and absorber, offset strip fin arrays are used. The performance of the components and the entire system is numerically evaluated and discussed.

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Nasr Isfahani, Rasool, et Saeed Moghaddam. « Absorption Characteristics of Thin Lithium Bromide (LiBr) Solution Film Constrained by a Porous Hydrophobic Membrane ». Dans ASME 2013 11th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icnmm2013-73158.

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An experimental study on absorption characteristics of water vapor into a thin lithium-bromide (LiBr) solution flow is presented. The LiBr solution flow is constrained between a superhydrophobic vapor-permeable wall and a solid surface that removes the heat of absorption. As opposed to conventional falling film absorbers, in this configuration, the solution film thickness and velocity can be controlled independently to enhance the absorption rate. The effects of water vapor pressure and cooling surface temperature on the absorption rate are studied. An absorption rate of approximately 0.005 kg/m2s was measured at a LiBr solution channel thickness and flow velocity of 160 μm and 4 mm/s, respectively. The absorption rate increased linearly with the water vapor driving potential at the tested solution channel thickness. The high absorption rate and the inherently compact form of the proposed absorber promise compact small-scale waste heat or solar-thermal driven cooling systems.

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Kelkar, Kanchan M., Suhas V. Patankar et Sukhvinder Kang. « Computational Method for Characterization of a Microchannel Heat Sink Involving Two-Phase Flow ». Dans ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73119.

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Microchannel heat sinks are being increasingly considered for the cooling of electronic equipment because of their ability to absorb high heat fluxes directly from the heat-dissipating components in a compact manner with a low thermal resistance. In this study, a computational method is presented for the analysis of conjugate heat transfer and two-phase flow in a heat sink containing a single microchannel. It involves a two-domain solution of the three-dimensional conduction within the solid region and the one-dimensional two-phase momentum and energy transfer within a microchannel. The nonlinear coupling between the two domains that occurs through the heat exchange at the walls of the microchannels is handled using an iterative calculation. Analysis of the flow and heat transfer in the microchannel is based on the homogenous flow assumption that is deemed to be accurate for the flow of low surface tension coolants such as methanol, isobutane, and HFC’s. Representative single and two-phase correlations are used for the calculation of the friction factor and the heat transfer coefficient. The computational model is applied for the prediction of the performance of a microchannel heat sink over a range of mass flow rates. The results of the analysis show the important physical effects that govern the performance of the microchannel heat sink involving two-phase flow. These include the acceleration of the flow in the microchannel in the two-phase region that influences the pressure drop through it and the two-phase enhancement of heat transfer that determines the temperature field within the solid region. This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

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