To see the other types of publications on this topic, follow the link: Microchannel.
Dissertations / Theses on the topic 'Microchannel'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Microchannel.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Price, Gareth James. "Microchannel plates in astronomy." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/8638.
Full textAbstract:
This thesis describes both round-pore microchannel plates (MCPs) used in energetic pho¬ton and particle detectors and their square-pore offspring, micropore optics (MPOs), used to focus x-rays. A Monte Carlo electron raytracing software package is described that is used to predict the energy and angular distribution of electrons (EDOE and ADOE) in a microchannel electron multiplier's output charge cloud, including saturated operation. The model is shown to agree with experimental evidence. The addition of a micromachined electrostatic lens to the end of a microchannel is modelled and found to have no beneficial effects upon the EDOE and ADOE of the channel. The current state of the art planar and slumped 'lobster eye' square-packed MPOs are evaluated. The best focus (5' FWHM) from a large format (61mm x 56mm), small chan¬nel (10μm side length) planar MPO is reported, together with the observation of high energy (~50keV →65keV) x-ray focusing from large (500:1) aspect ratio channels. The alignment of many small lobster eye MPOs to create a large optic for the Lobster-ISS instrument is discussed and the alignment jig constructed for this purpose is used to measure the bias angles of a Lobster specification MPO. The bias angle is found to be 4 ± 1.5'. The concept of the microchannel conic approximation to the Wolter type I and II x- ray lenses is reviewed. A radially-packed twin MPO Wolter approximation is then tested, which while of poor quality, demonstrates true Wolter II imaging with a peak gain greater than unity. Currently proposed (UK) astronomical instruments that employ MPOs are then discussed in the light of the results from the current generation of MPOs.
2
Checketts, Gus Thomas. "Microchannel Radiator: an Investigation of Microchannel Technology with Applications in Automotive Radiator Heat Exchangers." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700005/.
Full textAbstract:
Microchannels have been used in electronics cooling and in air conditioning applications as condensers. Little study has been made in the application of microchannels in automotive heat exchangers, particularly the radiator. The presented research captures the need for the design improvement of radiator heat exchangers in heavy-duty vehicles in order to reduce aerodynamic drag and improve fuel economy. A method for analyzing an existing radiator is set forth including the needed parameters for effective comparisons of alternative designs. An investigation of microchannels was presented and it was determined that microchannels can improve the overall heat transfer of a radiator but this alone will not decrease the dimensions of the radiator. Investigations into improving the air-side heat transfer were considered and an improved fin design was found which allows a reduction in frontal area while maintaining heat transfer. The overall heat transfer of the design was improved from the original design by 7% well as 52% decrease in frontal area but at the cost of 300% increase in auxiliary power. The energy saved by a reduction in frontal area is not substantial enough to justify the increase of auxiliary power. The findings were verified through a computational fluid dynamic model to demonstrate the heat transfer and pressure drop of microchannel tubes. The results confirmed that heat transfer of microchannels does improve the thermal performance of the radiator but the pressure drop is such that the net benefit does not outweigh the operating cost. An additional CFD study of the new fin geometry and air-side heat transfer predictions was conducted. The results of the study confirmed the theoretical calculations for the fin geometry.
3
Benoit, Vincent. "Flow-through microchannel DNA chips." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368731.
Full text
4
Martin, Adrian Peter. "Exploitation of microchannel plate optics." Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30635.
Full textAbstract:
This thesis contains work on microchannel plate (MCP) optics as used for X-ray focusing, and can be split into two sections; research and applications.;Research into improving the reflectivity of MCPs is presented which includes results obtained at the Daresbury Synchrotron, and electron microscope analysis. Different treatments performed on Nova Scientific channel plates were shown only to make a improvement to reflectivity in the case of annealing. Evidence for a 300A layer of silica on the surfaces of the microchannels, a result of the acid etching process, was discovered.;The method of bending, or slumping MCPs to a spherical form by Photonis and Nova has been assessed, and X-ray images using slumped plates are presented. The accuracy and reproducibility of the process was not found to be excellent (within 10% of the target radius), but were acceptable for the plates slumped to date.;A comprehensive report is given of the application of channel plates as the imaging device in an Imaging X-ray Fluorescence Spectrometer, firstly at the Rutherford Appleton Laboratory and subsequently in the laboratory in Leicester. The spectrometer successfully imaged a multi-element target, resolving both elementally (down to Fluorine, Z=9) and spatially (to under 2mm) in a 34 hour integration. The concept of Bragg reflection imaging is examined as another use of the spectrometer.
5
Siu, Billy Chin Pang. "Condensation heat transfer in microchannel /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?MECH%202004%20SIU.
Full textAbstract:
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 43-46). Also available in electronic version. Access restricted to campus users.
6
Mehrotra, Rajat. "Monodispersed polygonal water droplets in microchannel." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2726.
Full text
7
Burg, Thomas P. (Thomas Peter). "Suspended microchannel resonators for biomolecular detection." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34471.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (leaves 115-124).
Microfabricated transducers enable the label-free detection of biological molecules in nanoliter sized samples. Integrating microfluidic detection and sample-preparation can greatly leverage experimental efforts in systems biology and pharmaceutical research by increasing analysis throughput while dramatically reducing reagent cost. Microfabricated resonant mass sensors are among the most sensitive devices for chemical detection, but degradation of the sensitivity in liquid has so far hindered their successful application in biology. This thesis introduces a type of resonant transducer that overcomes this limitation by a new device design: Adsorption of molecules to the inside walls of a suspended microfluidic channel is detected by measuring the change in mechanical resonance frequency of the channel. In contrast to resonant mass sensors submersed in water, the sensitivity and frequency resolution of the suspended microchannel resonator is not degraded by the presence of the fluid. Our device differs from a vibrating tube densitometer in that the channel is very thin, and only molecules that bind to the walls can build up enough mass to be detected; this provides a path to specificity via molecular recognition by immobilized receptors.
(cont.) Suspended silicon nitride channels have been fabricated through a sacrificial polysilicon process and bulk micromachining, and the packaging and microfluidic interfacing of the resonant sensors has been addressed. Device characterization at 30 mTorr ambient pressure reveals a quality factor of more than 10,000 for water filled resonators; this is two orders of magnitude higher than previously demonstrated Q-values of resonant mass sensors for biological measurements. Calculation of the noise and the sensitivity of suspended microchannel resonators indicate a physical limit for mass resolution of approximately 0.01 ng/cm2 (1 Hz bandwidth). A resolution of -0.1 ng/cm2 has been experimentally demonstrated in this work. This resolution constitutes a tenfold improvement over commercial quartz crystal microbalance based instruments. The ability to detect adsorbing biomolecules by resonance frequency has been validated through binding experiments with avidin and various biotinylated proteins.
by Thomas P. Burg.
Ph.D.
8
Parak, Muhammad. "Development of a microchannel reactor model." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11615.
Full textAbstract:
Includes abstract.Includes bibliographical references (p. 151-157).
The development and future wide-spread use of hydrogen fuel cells is inhibited by problems associated with hydrogen storage. A possible alternative is to store and then reform hydrocarbons to yield hydrogen in an on-board fuel processing system. Microchannel reactors have reduced mass and heat transfer limitations and are able to exploit fast intrinsic kinetics. Also, their high surface area to volume ratio reduces their size for a constant throughput, increasing their potential for miniaturised deployment. Current microchannel reactor models are either over simplified and neglect important subtleties, or too complex and are not usable for optimisation or sensitivity studies. The objective of this project is to develop a comprehensive model that obeys the phenomenological laws and is fast enough to be used for optimisation.
9
Fogg, David W. "Bubble dynamics in microchannel flow boiling /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
10
Dagle, Robert Alexander. "Fuel processing catalysis for microchannel applications." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Spring2005/r%5Fdagle%5F050305.pdf.
Full text
11
Pettersen, Jostein. "Flow vaporization of CO2 in Microchannel Tubes." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-87.
Full text
12
Lee, Hyun Ho. "A thin film transistor driven microchannel device." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1439.
Full textAbstract:
Novel electrophoresis devices for protein and DNA separation and identification
have been presented and studied. The new device utilizes a contact resistance change
detection method to identify protein and DNA in situ. The devices were prepared with a
microelectronic micromechanical system (MEMS) fabrication method. Three model
proteins and six DNA fragments were separated by polyacrylamide gel microchannel
electrophoresis and surface electrophoresis. The detection of the proteins or DNA
fragments was accomplished using the contact resistance increase of the detection
electrode due to adsorption of the separated biomolecules. Key factors for the success of
these devices were the optimization of fabrication process and the enhancement of
detection efficiency of the devices. Parameters, such as microchannel configuration, size
of electrode, and affinity of protein or polyacrylamide gel to the microchannel sidewall
and bottom surface were explored in detail. For DNA analysis, the affinity to the bottom
surface of the channel was critical. The surface modification method was used to
enhance the efficiency of the microchannel surface electrophoresis device. The
adsorption of channel separated protein and DNA on the detection electrode was
confirmed with the electron spectroscopy for chemical analysis (ESCA) method. The
electrical current (I) from the protein microchannel electrophoresis was usually noisy
and fluctuated at the early stage of the electrophoresis process. In order to remove the
current perturbation, an amorphous silicon (a-Si:H) thin film transistor (TFT) was
connected to the microchannel device. The self-aligned a-Si:H TFT was fabricated with
a two-photomask process. The result shows that the attachment of the TFT successfully
suppressed the current fluctuation of the microchannel electrophoresis process. In
summary, protein and DNA samples were effectively separated and detected with the
novel TFT-driven or surface microchannel electrophoresis device.
13
Gao, Yanfeng. "Inertial migration of particles in microchannel flows." Thesis, Toulouse, INSA, 2017. http://www.theses.fr/2017ISAT0010/document.
Full textAbstract:
Cette thèse a pour objectif de mieux comprendre les mécanismes physiques qui contrôlent les trajectoires de particules anisotropes dans des écoulements confinés, afin d’en améliorer la prédiction. Nous avons dans un premier temps développé des outils expérimentaux basés sur la microscopie et le traitement d’images afin d’analyser les positions de particules en écoulement confiné dans des microcanaux de section carrée. Ces outils ont ensuite permis l’obtention de résultats originaux sur la migration latérale de particules sphériques dans des écoulements faiblement inertiels. Nous avons montré en particulier que les particules migrent au centre du canal à faible nombre de Reynolds et à proximité du centre de chaque face à Reynolds plus élevé et que ces deux régimes co-existent pour des Reynolds intermédiaires. Parallèlement à leur migration latérale, les particules en écoulement confiné peuvent s’espacer régulièrement sous certaines conditions pour former des trains. Ce travail a donc consisté à mener une étude statistique pour quantifier et localiser la formation des trains. Il a été montré que la formation des trains était contrôlée par la configuration de l’écoulement dans le sillage des particules et que leurs caractéristiques, i.e., le pourcentage de particules en trains et la distance interparticulaire, étaient fonction du nombre de Reynolds particulaire. Enfin, des résultats préliminaires sur le cas d’écoulements bi-disperses ont été obtenus. Pour terminer, les perspectives et développements futurs de ce travail sont dégagésThis thesis aims to better understand the physical mechanism controlling the trajectories of particles in confined flows in order to improve predictive models. In the first step we have developed experimental tools based on microscopy and image analysis in order to identify the particles positions in confined flows in square section microchannels. These tools have then permitted to obtain original results on the lateral migration of spherical particles in flows at low inertia. In particular we have shown that neutrally buoyant particles in square channels are focused at channel center at low Reynolds number and at four channel faces at high Reynolds, and that there is a co-existence of the two regimes for intermediate Reynolds. In addition to their lateral migration, under certain conditions, particles can also align in the flow direction to form trains of evenly spaced particles. This work has thus been devoted to the statistical study on the quantification and localization of the train formation and configuration. It has been shown that the formation of trains is controlled by the flow configuration in the wake of the particles, and that the train characteristics, i.e., the fraction of particles in trains and the interparticle distance, are functions of the particle Reynolds number. Finally, preliminary results on flows of bidisperse suspensions have been obtained. To conclude, the perspectives and future developments of this work are presented
14
Carpenter, James David. "Microchannel plates in astronomy and planetary science." Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/7983.
Full textAbstract:
Since their declassification in the late 1960s microchannel plates (MCPs) have been used as detectors for X-ray and extreme ultraviolet (EUV) astronomy, offering a unique sensitivity in the EUV waveband. The post 1990 era, however, has seen a universal, and unexplained, reduction in EUV quantum efficiency (QE). An analysis of microchannel plate glass composition has recorded variations in along channel composition for the first time. These observations may provide insight into the lost QE problem and present a way forward for the development of future EUV missions. Although originally developed as photon detectors MCPs have more recently been applied as low mass X-ray optics for X-ray astronomy and planetary science, where fluorescent X-rays from planetary surfaces yield information on surface composition. The Mercury Imaging X-ray Spectrometer (MIXS), on the BepiColombo mission to Mercury, will have two instrument channels, both of which use MCP optical elements. The optimisation of the high spatial resolution imaging X-ray optics of MIXS-T is described and the novel MCP collimator geometry for the high throughput MIXS-C channel is introduced for the first time. The performance of both channels at Mercury is predicted. An in situ investigation into the effects of the International Space Station space environment on MCP optics has led to the serendipitous discovery of nanometre scale dust particles in near Earth space and the realisation of filmed MCPs as extremely sensitive cosmic dust detectors. Analysis of the exposed samples and evaluation of the discovery are presented and possibilities for future dedicated experiments are explored. Microchannel plates continue to be an important technology in astronomy and planetary science. This thesis describes developments in traditional MCP applications and the introduction of new ones, all of which will lead to unique measurement capabilities and significant scientific advancements.
15
Green, James Alexander. "Mixing in surface tension driven microchannel flows." Thesis, University of Hertfordshire, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440160.
Full text
16
Chen, Siyu S. M. Massachusetts Institute of Technology. "Bubble dynamics on structured surface in microchannel." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81595.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 69-70).
Surface enhancement is a potential way to improve the performance of flow boiling in microchannels, which is considered to be one of the most promising cooling methods to solve thermal management challenges faced by future semiconductor products. Considerable research has been done on examining the functions of engineered surfaces. However, the mechanism of how these surfaces improve the flow boiling performance is still unclear. In this thesis, bubble dynamics on micropillar array surfaces were studied. A surface energy based model is presented to predict the bubble morphology on pillar array surfaces. The results showed that bubbles tend to stay on top surfaces of pillars at solid fractions greater than 0.162, keeping liquid films underneath the bubbles. On the other hand, on surfaces at solid fraction less than 0.162, bubbles tend to propagate within the pillar unit cells. A flow loop with good degassing and a fluid temperature control system was designed and built for various flow boiling experiments. Five different types of silicon micropillar array surfaces were fabricated. Moreover a setup for observing bubble dynamics in microchannels under flow boiling conditions was developed. Experiments were performed to investigate the bubble dynamics on silicon micropillar array surfaces. Bubble departure modes were observed. The bubble departure size of direct departing mode was found to be independent with flow rate while departure size of sliding mode decreased with increasing of the flow rate. Three potential methods to create single nucleation sites for improved studies of bubble dynamics were also presented in this thesis. An experimental setup to investigate behavior of a single bubbles created by air injection on micropillar array was presented. Single 10-30 [mu]m injection holes were fabricated on micropillar array surfaces by laser cutter. The experimental results show that structured surfaces have higher bubble departure sizes than that for a plain surface. The surfaces with solid fractions greater than 0.162 had larger departure sizes than that of surfaces with solid fractions smaller than 0.162 at mass flow rates above 250 kg/m²s while departure sizes of the higher solid fraction surfaces become smaller than that of lower solid fraction surfaces when flow rates decreased below 200 kg/m²s. The similarity between the departure sizes obtained by air injection experiments and flow boiling experiments suggest that air injection experiments could provide useful information on understanding the vapor bubble departure behavior on micropillar array surfaces. Silicon micropillar array surfaces may have larger bubble departure sizes than plain surfaces, however, the surfaces with solid fractions greater than 0.162 are suggested for boiling due the a large amount of liquid thin films may create for higher heat transfer rates.
by Siyu Chen.
S.M.
17
Phillips, Richard J. "Forced-convection, liquid-cooled, microchannel heat sinks." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14921.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: v.2, leaves 286-291.
by Richard J. Phillips.
M.S.
18
Talebi, Mohammadmahdi [Verfasser]. "Local Sensing in Microchannel Boiling / Mohammadmahdi Talebi." München : Verlag Dr. Hut, 2021. http://d-nb.info/1240540027/34.
Full text
19
Kulkarni, Amit S. "Effects of surface roughness in microchannel flows." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0003400.
Full text
20
Kuravi, Sarada. "Numerical Study of Encapsulated Phase Change Material (EPCM) Slurry Flow in Microchannels." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4093.
Full textAbstract:
Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m width and 533 [micro]m height with water as base fluid and n-Octadecane as PCM to validate the key conclusions of the numerical model. Since the flow is not fully developed in case of microchannels (specifically manifold microchannels, which are the key focus of the present study), thermal performance is not as obtained in conventional channels where the length of the channel is large (compared to length of microchannels). It was found that the thermal conductivity of the base fluid plays an important role in determining the thermal performance of slurry. The effect of particle distribution can be neglected in the numerical model under some cases. The performance of slurry depends on the heat flux, purity of PCM, inlet temperature of the fluid, and base fluid thermal conductivity. Hence, there is an application dependent optimum condition of these parameters that is required to obtain the maximum thermal performance of PCM slurry flows in microchannels.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering PhD
21
Cetin, Murat. "Design And Experimental Investigation Of Microchannel Heat Exchanger." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611856/index.pdf.
Full textAbstract:
Due to the high performance of electronic components, the heat generation
is increasing dramatically. Heat dissipation becomes a significant issue in
efficiency promotion and stable operation. Microchannels are of current interest
for use in heat exchangers where very high heat transfer performance is desired.
Microchannels provide high heat transfer coefficients because of their small
hydraulic diameters. In this study, the design and experimental investigation of
fluid flow and heat transfer in a microchannel heat exchanger is conducted. Water
and air are used as the working fluids and flowed through microchannels. The heat
exchanger has been designed with 6 rows of microchannels for water flow and 7
rows of microchannels for forced flow of air. The heights of the microchannels are
4 mm and 10 mm respectively for water and air flows. Microchannels are brazed
to form the heat exchanger. For forced convection cooling with air, a military fan
is used. A constant heat source has been specifically designed for experiments.
Water flow and heat transfer experiments are conducted on the aluminum
microchannel heat exchanger. An experimental method of imposing a constant
heat flux to water prior to the entrance to the microchannel heat exchanger, to
adjust the inlet temperatures is used.
v
From the data obtained, the rate of heat transfer, effectiveness and various
other parameters have been computed and the results have been compared with
those from an available commercial heat exchanger. The results indicate that the
heat exchanger performs well and provides 681 W of cooling in a volume 677.6
cm3 while the commercial heat exchanger provides 702.5 W of cooling in a
volume 2507.5 cm3. In addition, air-side Colburn modulus has been obtained with
respect to Reynolds number.
22
Ellob, Mohamed. "Process intensification : hydrocarbon cracking using a microchannel reactor." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500964.
Full textAbstract:
Olefins (Ethylene and Propylene) are the most important products of the petrochemical industry, because of their wide range of applications. The global demand tor ethylene and propylene is expected to increase over tne next live years and production capacity must also increase to Keep up witti tins demand growth. There are several industrial processes for ethylene and propylene production; the most widely used process is the steam cracking process in which the hydrocarbon ieed is thermally-cracked to produce olefins. Coke is an undesirable by-product because it deposits on the internal walls of the reactor tubes, consequently reducing the heat transfer rate and increasing the pressure drop across the reactor. The reactor has to be shut down frequently for decoking. Several research studies have been conducted and new technologies developed to improve the performance of the steam cracking process.
23
Davies, Colin John Stephen. "MRI studies of complex fluids and microchannel flows." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598355.
Full textAbstract:
This thesis considers the use of NMR (Nuclear Magnetic Resonance) in investigating both the formulation, using microchannels, and characterisation of complex fluids using NMR techniques. Multiphase microchannel flows have many applications and understanding the hydrodynamics and mass transfer is essential for developing such systems. Time-averaged velocity images of the parallel flow of PDMS (polydimethylsiloxane) and water in a 500 μm x 250 μm microchannel were compared with an analytical solution and simulations. This was extended into imaging multiphase flows in a smaller (250 μm x 100 μm) microchannel. Poor signal-to-noise levels in this geometry led to the adoption of a spatially- and chemical-shift-resolved propagator acquisition. This was used to differentiate two different flow regimes: parallel flow and droplet production. RheoNMR is the use of NMR techniques in the study of rheology. Time-averaged velocity imaging was used to image a shear-banding micellar solution, cetylpyridinum chloride with sodium salicylate (CPyC1 / NaSal) in sodium chloride brine, in a variety of standard rheological geometries. The fast velocity measurement sequence GERVAIS was used to measure starting and stopping of flows of the CPyC1 / NaSal solution in a wide-gap Couette cell; these were compared to similar experiments performed using PDMS. The propagation of an elastic wave across the cell was seen during start-up and an unusual rebounding oscillation was evident in the stopped flow experiments in the CPyC1 sample. The fast diffusion measurement sequence, Difftrain, was modified to reduce the achievable incremental observation time (at the expense of slightly reduced chemical resolution). This was applied to two case studies: measuring the surface-to-volume ratio of a model porous medium and the droplet sizing of oil-in-water emulsions manufactured with fast-diffusing oils. Finally, NMR relaxometry and diffusometry were used to investigate a phase transition in the structure of a sample of a commercial face cream.
24
Lackritz, Neal M. "MERLIN : a multiprocessor design for a MicroChannel architecture." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14287.
Full text
25
Son, Sungmin. "Suspended microchannel resonators for ultralow volume universal detection." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44867.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaves 32-33).
Universal detectors that maintain high sensitivity as the detection volume is reduced to the sub-nanoliter scale can enhance the utility of miniaturized total analysis systems ([mu]-TAS). Here the unique scaling properties of the suspended microchannel resonator (SMR) are exploited to show universal detection in a 10 pL analysis volume with a density detection limit of ~1 ([mu]g/cm³ (10 Hz bandwidth) and a linear dynamic range of six decades. Analytes with low UV extinction coefficients such as polyethylene glycol (PEG) 8 KDa, glucose, and glycine are measured with molar detection limits of 0.66 ([mu]M, 13.5 ([mu]M, and 31.6 ([mu]M, respectively. To demonstrate the potential for real-time monitoring, gel filtration chromatography was used to separate different molecular weights of PEG as the SMR acquired a chromatogram by measuring the eluate density. This work suggests that the SMR could offer a simple and sensitive universal detector for various separation systems from liquid chromatography to capillary electrophoresis. Moreover, since the SMR is itself a microfluidic channel, it can be directly integrated into ([mu]-TAS without compromising overall performance.
by Sungmin Son.
S.M.
26
Chivengwa, Tapiwa. "Microchannel flow fields for polymer electrolyte fuel cells." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/13674.
Full textAbstract:
Fuel cell technology represents an efficient and relatively quiet way of generating electricity. Among the various types of fuel cells, the polymer electrolyte fuel cell (PEFC) is the leading candidate for portable, automotive and more recently stationary applications. One of the key challenges affecting both the performance and durability of low temperature PEFCs is water management. Various water management strategies in PEFCs have been employed to date ranging from manipulation of operating conditions, fuel cell component design and flow field design to name a few. The optimisation of the flow field design for water removal has primarily focused on the use of flow channels which are in the minichannel range. This study investigated the use of a microchannel flow field design (channel hydraulic diameters of less than or equal to 200 ìm) for a low temperature PEFC. Specifically it focused on the effect of using a microchannel design on overall fuel cell performance, pressure drop and the cell voltage behaviour over time. In addition the effect of different operating conditions was also investigated. The overall aim was to develop a more comprehensive understanding of the use of a microchannel based flow field system with specific focus on water management. Fuel cell testing of two different flow field designs, namely a microchannel design and a more conventional commercial minichannel design, was performed in a single cell set up. Two operating conditions, cathode flow rate and cell compression, were varied and the effect on overall fuel cell performance and limiting current was investigated. Several diagnostic measurements including polarization curve, high frequency resistance, electrochemical impedance spectroscopy, pressure drop co-efficient and cell voltage monitoring were conducted to understand the water management behaviour and trends in the two different aforementioned flow field designs.
27
Lee, Man. "Forced convection heat transfer in integrated microchannel heat sinks /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LEE.
Full text
28
Turkakar, Goker. "Numerical Simulation And Analytical Optimization Of Microchannel Heat Sinks." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612377/index.pdf.
Full textAbstract:
This study has two main objectives: The performance evaluation of existing microchannel heat sinks using a CFD model, and the dimensional optimization of various heat sinks by minimizing the total thermal resistance.
For the analyses, the geometric modeling is performed using the software GAMBIT while the thermal analysis is performed with FLUENT. The developed model compares very well with those available in the literature. Eight different metal-polymer microchannel heat sinks are analyzed using the model to find out how much heat could be provided to the systems while keeping the substrate temperatures below 85°C under a constant pumping power requirement. Taking the objective function as the total thermal resistance, the optimum geometries have been obtained for the mentioned metal-polymer heat sinks as well as more conventional silicon ones. The results of the optimization code agreed very well with available ones in the literature. In the optimization study, the Intel Core i7-900 Desktop Processor Extreme Edition Series is considered as a reference processor which is reported to dissipate 130 W of heat and to have chip core dimensions of 1.891 cm ×
1.44 cm. A dimensional optimization study has been performed for various copper and silicon microchannel heat sinks to cool down this processor. To the best of the author&rsquo
s knowledge, this study contributes to the literature in that, as opposed to the available analytical microchannel optimization studies considering constant thermophysical properties at the fluid inlet temperature, the properties are evaluated at the area weighted average of the fluid inlet and iteratively calculated outlet temperatures. Moreover, the effects of the thermal and hydrodynamic entrance regions on heat transfer and flow are also investigated.
29
Ulu, Ayse Gozde. "Experimental Investigation Of Uninterrupted And Interrupted Microchannel Heat Sinks." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614227/index.pdf.
Full textAbstract:
Experimental measurements are conducted on uninterrupted and interrupted aluminum microchannel heat sinks of 300, 500, 600 and 900 &mum channel widths. Two different versions of interrupted channels are tested
with single interruption and with 7 interruptions. Distilled water is used as the working fluid and tests are conducted at volumetric flow rates in a range of 0.5-1.1 lpm. Thermoelectric foils are used to supply uniformly distributed heat load to the heat sinks such that for all the tests the heat removed by water is kept constant at 40 W. Pressure drop and temperature increase are measured along the channels of different configurations for a number of different flow rates. For the interrupted channels thermal boundary layers re-initialize at the leading edge of each interrupted fin, which decreases the overall boundary layer thickness. Also the flow has been kept as developing, which results in better heat transfer performance. Due to the separation of the flow into branches, secondary flows appear which improves the mixing of the stream. Advanced mixing of the flow also enhances the thermal performance. In the experiments, it is observed that interruption of channels improved the thermal performance over the uninterrupted counterparts up to 20% in average Nusselt number, for 600 micron-wide channels. The improvement of average Nusselt number between the single interrupted and multi interrupted channels reached a maximum value of 56% for 500 micron-wide channels. This improvement did not cause a high pressure drop deviation between the uninterrupted and interrupted microchannels even for the maximum volumetric flow rate of 1.1 lpm. Highest pressure drop through the channels was measured as 0.07 bar, which did not require to change the pump. In the tests, maximum temperature difference between the inlet of the fluid and the base of the channel is observed as 32.8°
C, which is an acceptable value for electronic cooling applications.
30
Schindhelm, Eric R., J. C. Green, Oswald H. W. Siegmund, Camden Ertley, Brian T. Fleming, Kevin C. France, Walter M. Harris, Alex Harwit, Stephan R. McCandliss, and John V. Vallerga. "Microchannel plate detector technology potential for LUVOIR and HabEx." SPIE-INT SOC OPTICAL ENGINEERING, 2017. http://hdl.handle.net/10150/626502.
Full textAbstract:
Microchannel plate (MCP) detectors have been the detector of choice for ultraviolet (UV) instruments onboard many NASA missions. These detectors have many advantages, including high spatial resolution (<20 mu m), photon counting, radiation hardness, large formats (up to 20 cm), and ability for curved focal plane matching. Novel borosilicate glass MCPs with atomic layer deposition combine extremely low backgrounds, high strength, and tunable secondary electron yield. GaN and combinations of bialkali/alkali halide photocathodes show promise for broadband, higher quantum efficiency. Cross-strip anodes combined with compact ASIC readout electronics enable high spatial resolution over large formats with high dynamic range. The technology readiness levels of these technologies are each being advanced through research grants for laboratory testing and rocket flights. Combining these capabilities would be ideal for UV instruments onboard the Large UV/Optical/IR Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission (HABEX) concepts currently under study for NASA's Astrophysics Decadal Survey.
31
Bennett, Christopher James. "Solitary and transitional waves in two-layer microchannel flows." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5922/.
Full textAbstract:
The understanding of wave dynamics in interfacial microchannel flows is important for many technological applications in the micro-device industry. Here, a theoretical and numerical study is undertaken in order to understand the propagation of interfacial waves in a two-layer flow. The flow is considered to be driven by, in separate cases, the force of gravity and a pressure gradient. The results may provide steps towards more efficiently designed microfluidic products, and a better understanding of experimentally observed waves.
32
Stockslager, Max A. "Measuring single-cell density using serial suspended microchannel resonators." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111934.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 42-43).
Cells adjust their composition during important physiological processes, including cell cycle progression, apoptosis, and disease. Due to differences in the densities of water and the various macromolecules which compose cells, changes in cellular composition are reflected by changes in cell density. Previously, methods have been described for measuring density at the single-cell level using suspended microchannel resonators by weighing the same cell in fluids of different densities. Here we describe a high-throughput version of this approach, in which cells are weighed sequentially in three cantilevers containing fluids of different densities. The system design and operation are described, measurement uncertainty is characterized, and single-cell density measurements are compared to those obtained using existing techniques. As a demonstration, we use the system to characterize the biophysical response of CD8' T cells during activation. We find that single-cell density distinguishes between the phenotypically distinct human CD8' T cells of healthy vs. chronic lymphocytic leukemia donors, suggesting possible utility as a lymphocyte transformation assay. In summary, the system as described is capable of measuring single-cell density with improved throughput, and the approaches used here for on-chip fluid exchange are applicable to other SMR devices where it is desirable to weigh a cell in multiple fluids, e.g., to measure single-cell growth rate before and after drug or media perturbations..
by Max A. Stockslager.
S.M.
33
Von, Muhlen Marcio Goldani. "Label-free buoyant mass assays with suspended microchannel resonators." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62389.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 105-112).
Improved methods are needed for routine, inexpensive monitoring of biomarkers that could facilitate earlier detection and characterization of complex diseases like cancer. Development of new assay formats based on microfluidic, label-free platforms enable radical reductions in assay complexity and reagent requirements with the potential for such applications. Suspended microchannel resonators (SMRs) are highly sensitive, batch-fabricated microcantilevers with embedded microchannels that can measure mass with femtogram precision. Biomolecules such as proteins and nucleic acids are denser than water, and their presence can thus be quantified by their buoyant mass, or increase in mass relative to the solution they displace. This thesis presents two approaches to conducting label-free, buoyant-mass immunoassays with SMRs with potential for clinical applications. The sensor surface can be functionalized to bind targets directly, or individually weighed polystyrene beads can be used as mobile supports. As in other label-free detection methods, biomolecular measurements in complex media such as serum are challenging due to high background signals from non-specific binding. We demonstrate that carboxybetaine-derived polymers developed to adsorb directly onto SMR SiO2 surfaces act as ultra-low fouling and functionalizable surface coatings. Coupled with a reference microcantilever, this approach enables detection of activated leukocyte cell adhesion molecule (ALCAM), a model cancer biomarker, in undiluted serum with a limit of detection of 10 ng/mL. Decoupling the complexity of surface modifications from the sensor precludes the need for specialized reagents. Monodisperse, micron-scale polystyrene beads are widely available and can be used as mobile supports, with the mean mass of a bead population quantifying target binding onto bead surfaces. Inherent mass variability in the bead population is masked by matching solution density to bead density. We demonstrate that by weighing hundreds of beads in 30 min, mean mass can be estimated with a resolution of 100 attograms. A proof-of-principle assay is demonstrated that quantifies IgG binding onto functionalized beads at 5.20 femtograms per bead.
by Marcio Goldani von Muhlen.
Ph.D.
34
Alexander, Brentan R. "Design of a microbreather for two-phase microchannel devices." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44919.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 50-52).
Multiphase flows in microchannels are encountered in a variety of microfluidic applications. Two-phase microchannel heat sinks leverage the latent heat of vaporization to offer an efficient method of dissipating large heat fluxes in a compact device. In microscale methanol-based fuel cells, the chemical reactions produce a two-phase flow of methanol solution and carbon dioxide gas. Differences in the underlying physics between microscale and macroscale systems, however, provide a new set of challenges for multiphase microscale devices. In thermal management devices, large pressure fluctuations caused by the rapid expansion of vapor are prevalent in the flow channels. In fuel cells, the gaseous carbon dioxide blocks reaction sites. In both of these cases, dry-out is a problem that limits device performance. We propose a design for a microscale breather that uses surface chemistry and microstructures to separate gas from a liquid flow to improve two-phase microchannel performance. To better understand the physics and governing parameters of the proposed breather, we have designed and fabricated test devices that allow cross-sectional visualization of the breathing events. We have conducted various experiments to examine the effects of device channel hydraulic diameters ranging from 72 [mu]m to 340 [mu]m and liquid inlet flow rates ranging from 0.5 cm/s to 4 cm/s on the maximum gas removal rate. We demonstrated a maximum breather removal rate of 48.1 [mu]l/min through breather ports with a hydraulic diameter of 4.6 [mu]m connected to a microchannel with a hydraulic diameter of 72 [mu]m, and a liquid inlet flow velocity of 0.5 cm/s. A model was developed that accurately predicts the exponential dependence of the maximum gas removal rate on a non-dimensional ratio of the pressure across the breather ports compared to the pressure drop in the main channel caused by the venting bubble.
(cont.) These results serve as design guidelines to aid in the development of more efficient and sophisticated breathing devices. The successful implementation of a microchannel with an efficient breather will allow for new technologies with higher heat removal capacities or chemical reaction rates that can be effectively used by industry.
by Brentan R. Alexander.
S.M.
35
Zandi, Matthew A. "Single Position Focusing of Cells in a Microchannel System." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1428066046.
Full text
36
Truter, Lara. "Development of a zeolite washcoating technique for microchannel reactors." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10855.
Full textAbstract:
Microreactor technology is becoming an increasingly active research field in terms of chemical reaction engineering and process intensification. An important feature of microreactor technology is the requirement of a catalyst layer.
37
Skog, Torkel. "CuPGS Laminate Core for a Matrix Microchannel Heat Exchanger." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76914.
Full textAbstract:
Cryocooling is a continuously developing field of engineering, applied in the fieldsof aerospace, military, and medical sciences among others. There is a demand forsmaller and more efficient cryocoolers for spaceborne low-light observation missions,with many custom cooling systems having completed successful missions. The Stir-ling cycle is the most prevalent refrigeration technique used for space applications,with the pulse-tube, Joule-Thomson or reverse Brayton cycles being used in somespecial cases.A matrix heat exchanger is designed with 3D-printed 17-4 PH stainless steel end capsstreamlined for computer numerical control (CNC) production. The heat exchanger (HX) core consists of 1mm thick stainless steel spacers and 250μm thick copperchips that are tolerance-matched for photo etching, as well as pyrolytic graphitesheets (PGS) of 25μm, the thickest commercially available PGS without addedadhesive film material.The experiments of joining PGS and copper chips with Epo-Tek 301-2 epoxy tocreate a solid core structure for the heat exchanger did not result in a pressure-resistant laminate material. The graphite surface proved difficult to adhere to usingthis epoxy, creating voids, and easily delaminated into separate layers of PGS. Bond-ing the stack together using indium, testing epoxy with a higher ability to permeatethe PGS or diffusion-bonding through other means are presented as options forfurthering the HX development.Pressure testing of a copper-only laminated heat exchanger core showed that theend cap recess adhesion capability is a potential point of failure, as the designedstructure makes it impossible to inspect the results of the bond without curingthe epoxy and pressurising the system. The difficulty in establishing a tight seambetween the main counter-flow channels of the HX is also demonstrated here, asleakage between the channels occurred at pressures in the vicinity of 2
38
Shiao, Shin-Duan, and 蕭心端. "Experimental Study of Microchannel Geometry on the Microchannel Heat Sink Performance Enhancement." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/77817152086764854254.
Full textAbstract:
碩士國立中興大學
機械工程學系所
94
In this study，performances of two types of microscale heat sinks based on the modifications from the conventional parallel channel heat sink (PCHS) are studied experimentally。By referring the walls that separating the channels in PCHS as the plate fins，the first type of modified heat sinks involves placing obstacles alternatively on the plate fins. As a result，the original parallel channels in PCHS become winded。This type of heat sink is referred to as the obstructive channel heat sink (OCHS)。It is intended to enhance the heat transfer coefficient by the flow disruption in this heat sink design。In the second type of heat sink，the plate fins are cut into segments and arranged in staggered form。This results in the plate fins in the original parallel heat sink been modified to a staggered arranged pin fin array and the heat sink is referred as the pin fin heat sink (PFHS)。Since the transverse fluid flow in pin fin array is allowed，the PFHS is designed to have two inlets and two outlets to enhance heat transfer coefficient。The heat sink base plate temperature uniformity，thermal resistance，and pressure drop across the heat sink are the three parameters used to evaluate the performances of the heat sinks studied。For all these three parameters，the experimental results show that the PFHS can provide best temperature uniformity，lowest thermal resistance and lowest pressure drop among the three heat sink designs in this study。
39
Huang, Yu Hsiang, and 黃友相. "Laminar Heat Transfer in Microchannel." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/33228770672319143894.
Full text
40
Li, Chi-hung, and 李奇翃. "Biomolecular Adsorption in the Microchannel." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/63123549499748252059.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
102
The protein adsorption is a critical factor in influencing the performance of a biochip which is used for disease detection. In this study, numerical simulation was used to estimate the protein adsorption rate in terms of the flowing velocity, design of the inlet, the length of the microchannel. To validate the simulation results, the microfluidic devise was fabricated with a micromilling machine and the PDMS casting technique. Then the microchannel was sealed with another piece of glass with the surface plasma treatment and used for experiments. Multiple experiments were conducted either with a confocal microscope or a fluorescence microscope, but the results were not steady enough to compare or even conclude with the simulation result. Therefore modification of the experiments will be made to improve the quality of the experiments, then validate the simulation results.
41
Yen, Hung-Yu, and 顏鴻宇. "Capillary Phenomena in a Microchannel." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/76515072230750919342.
Full textAbstract:
碩士國立臺灣大學
化學工程學研究所
101
This work investigate capillary phenomenon in different types of microchannels. Capillary rise can be described by Jurin’s Law under specific scale and the results are consistent with Surface Evolver simulation. However, capillary rise can also be studied via the energy minimization method, thus the capillary rise in the stepped tube and in composite tube are examined to model the water transportation in trees. In the process of increasing the tube height, liquid level increases with the tube height. The highest liquid level is determined by the radius of the top opening which is consistent with the effective volume theory. According to this result, we propose that the height of water transportation in trees is determined by the radius of the stomas. The simulation results of the capillary rise in a composite tube also coincide the effective volume theory. And the results of capillary rise in composite tube indicate that the highest liquid level is restricted by the max radius on the top opening of the composite tube. The liquid drop captured at the capillary end, which is observed in capillary valve and pendant drop technique, is also investigated theoretically and experimentally in this thesis. Because of contact line pinning of the lower meniscus, the lower contact angle is able to rise from the intrinsic contact angle ( ) so that the external force acting on the drop can be balanced by the capillary force. In the absence of contact angle hysteresis (CAH), the upper contact angle remains at . However, in the presence of CAH, the upper contact angle can descend to provide more capillary force. The coupling between the lower and upper contact angles determines the equilibrium shape of the captured drop. In a capillary valve, the pinned contact line can move across the edge as the pressure difference exceeds the valving pressure, which depends on the geometrical characteristic and wetting property of the valve opening. When CAH is considered, the valving pressure is elevated because the capillary force is enhanced by the receding contact angle. For a pendant drop under gravity, the maximal capillary force is achieved as the lower contact angle reaches 180˚ in the absence of CAH. However, in the presence of CAH, four regimes can be identified by three critical drop volumes. The lower contact angle can exceed 180˚ and therefore the drop takes on the shape of a light bulb, which does not exist in the absence of CAH. The comparisons between Surface Evolver simulations and experiments are quite well.
42
Tu, Kuan-Hsu, and 凃冠旭. "Condensation Heat Transfer Enhancementin Microchannel." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61905943294136803719.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
101
The microchannel evaporator with two-phase heat transfer achieves a high heat transfer coefficient, and low working fluid demands; therefore, is considered to have high potential. Thus, the use of microchannel condenser that uses two-phase heat transfer is seen as a cooling component with very high potential. By making it a porous structure that creates a 3D porous network, resulting in advantages such as large evaporation area, high capillary force, and high permeability, the heat transfer performance of the microchannel condenser is expected to increase significantly. This study used copper to manufacture both the flat-plate microchannel condenser and porous microchannel condenser, with 30 microchannels of width and depth 500μm×155μm; Using water as working fluid, with mass flux range of 65~95 kg/m2 s, for heat transfer performance test. This study first investigates the effect of copper powder size and the structure’s base thickness of a porous microchannel condenser on heat transfer performance, then compares its heat transfer performance, pressure drop, and flow patterns to those of flat-plate microchannel condenser. Comparing experimental results for heat transfer performance to heat transfer correlation of the conventional channel showed that the MAE is still large. With regard to pressure drop, compare with the correlation of microchannel developed recently, it correlated with our result, indicating a certain degree of reliability. For flat-plate microchannel condenser, from flow visualizations of flows, 5 most common types of flow in condensation process can be seen clearly: droplet flow, annular flow, injection flow, slug flow, and bubbly flow. Heat transfer coefficient and pressure drop is positive correlative with increasing mass flux. When mass flux increases, the flow velocity increases, and the liquid-vapor interface shear stress increases, resulting in thinning of the liquid film, and the annular flow region increases; the heat transfer performance was thus enhanced accordingly. Heat transfer coefficient is 23~79kw/m2k. The overall pressure drop was also enhanced due to increased flow rate of the working fluid and elongation of the two-phase region. For porous microchannel condenser, manufacturing parameters such as the base thickness range of 150~300μm and copper powder diameter range of 1~150μm was investigated. Experimental results showed that highest heat transfer coefficient was achieve with base thickness of 150μm and powder diameter of 88μm; heat transfer coefficient is 43~161kw/m2k, on average, the heat transfer coefficient of porous microchannel condenser was increased by 110% compared to that of flat-plate microchannel condenser. The absorption of condensed water build up by a porous microchannel structure allows for the thinning of the condensed liquid film and the annular flow region is more extended, therefore its heat transfer performance is better than that of a regular flat-plate microchannel condenser. Concerning pressure drop, the overall pressure drop is greater than that for flat-plate microchannel condenser, with a greatest enhancement value of 15kpa. To summarize this study, porous microchannel effectively enhance the heat transfer performance of condenser, It is highly potential for the high-power thermal management application.
43
Chung, Kun-Zhi, and 鍾昆志. "Decomposition of hydrogen iodide in microchannel." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/16334133895192271472.
Full text
44
Lin, Hung-chun, and 林鴻鈞. "Electroosmotic Flows in a Square Microchannel." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/34202341015506051500.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
93
Experiments were performed using a microparticle image velocimetry (MPIV) for full field velocity distributions of electroosmotically driven flows in a 40 mm long microchannel with a square cross section of 200 µm × 200 µm. Electroosmotic flow bulk fluid velocity measurements were made in a range of streamwise electric field strengths from 5 to 25 kV/m. A series of seed particle calibration tests can be made in a 200 µm x 200 µm x 24000 µm untreated PDMS channel incorporating MPIV to determine the electrophoretic mobilities in aqueous buffer solutions of 1 TAE, 1 TBE, 10 mM NaCl, and 10 mM borate, respectively. A linear/nonlinear (due to Joule heating) flow rate increase with applied field was obtained and compared with those of previous studies. A parametric study, with extensive measurements was performed with different electric field strength and buffer solution concentration under a constant zeta potential at wall for each buffer. The characteristics of electroosmotic flow in square microchannels were thus investigated. Finally, a composite correlation of the relevant parameters was developed within accuracy for 99% of the experimental data.
45
Chen, Yu-Tang, and 陳育堂. "Fabrication and Analysis on Microchannel Structures." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/61864081139843190767.
Full textAbstract:
博士淡江大學
機械與機電工程學系
92
Micro shaping techniques have been realized for various applications. In this dissertation, polymer micro manufacturing techniques are proposed to fabricate different profile microchannel structures. Besides, air flow through microtubes with diameters of 0.287 and 0.409 mm was investigated experimentally. Polymethylmethacrylate (PMMA) was dipped into methyl for two hours to fully generate the physical-chemical change. The PMMA swelling appeared through the mass transfer effect. This polymer swelling process was implemented to form the 3D micro venturi tube into a curved nozzle with the throat size successfully reduced to 100m. This dissertation presents an economical fabrication process for micro venturi tubes for future analysis in micro technologies. Additionally, a novel technique for fabricating microchannels in SU-8 by inserting optical-fibers as sacrificial moulds is also proposed in this dissertation. The embedded circular microchannels, with inner diameters of 36, 80, and 125μm (i.e., the diameters of optical-fibers), have been made successfully using a low-temperature fabrication process; where the SU-8 transparent negative-bone photo-resist is selected as the structure layer built in multilayers. Preliminary results show that the microchannels fabricated with the proposed technique have an average surface roughness (Ra) of the inner wall less than 10nm and roundness deviation less than 8.5%. This new fabrication technique of microchannel manufacture provides a new approach in selecting SU-8 for the structure material containing microchannels. Moreover, the air flow through microtubes with diameters of 0.287 and 0.409 mm was investigated experimentally. The experimental results indicate that the friction factor obtained from the Fanno-line flow function shows good conformity with the Poiseuille (f = 64/Re) and Blasius equations (f = 0.316/Re0.25) in both laminar and turbulent flow. These results illustrate the continuity and coherence in the study. Therefore, Fanno-line flow analysis can predict the general trends of the experimental results, enabling approximate analysis for many engineering application. Furthermore, the maximum pressure loss coefficient of micro nozzle / diffuser without “separation”, and the designs for the optimum profile of micro nozzle / diffuser are numerically analyzed in this dissertation. The SU-8 negative bone photo-resist is then introduced for the molding structure of micro nozzle / diffuser, and Polydimethyl-siloxane (PDMS) is used for the structure of micro nozzle / diffuser by copy. A low-temperature bonding technique using glass to bounding is introduced in this dissertation. Through the measurement of the pressure and flow, the analysis and investigation of fluid dynamics characteristics are then achieved. This dissertation consists of numerous existing as well as future allocations, especially in the pumps without valves where the micro nozzle / diffuser is the major structure. In sum, the theoretical analysis and design basis can then be formulated for the reference and application need in the fabrication of micro nozzle / diffuser from this study.
46
Hwang, Chen-yu, and 黃振彧. "Computation of Gaseous Flows in Microchannel." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/98579110067504277835.
Full textAbstract:
碩士國立成功大學
航空太空工程學系碩博士班
95
In the last decade, the microelectromechanical system(MEMS) field has significant and impressive progress. For the microchannel flows, a lot of experimental and theoretical results have been presented, but it still exists some problems which are worthwhile to study. In this thesis, the numerical computations are performed to investigate the gaseous flow behaviors in the microchannels. First the unstructured tetrahedral and prismatic meshes are created in the flow domain, the four-step Runge-Kutta time integration scheme and finite volume upwind method are adopted to solve the unsteady three-dimensional Navier-Stokes equations in he Cartesian coordinate system. To efficiently treat the geometric problem, the CATIA software is introduced to generate geometric shape, surface triangular grids and prismatic meshes. Then the mesh generation technique presented by Liu and Hwange is utilized to finish the distribution of tetrahedrons. To investigate the low speed flows, the approach for solving the pressure, which was presented by Rossow, is adopted in this study. On the unstructured tetrahedral/prismatic meshes, the above approach is extended to solve the three-dimensional inviscid and laminar flow. To evaluate this numerical method, the inviscid flows around sphere and passing through the converging-diverging nozzle with circular crosssection are investigated first. For the different Mach number, the comparision between the computed pressure coefficient and velocity distributions on the surface of sphere and the results from the potential flow theory is performed. Also the history of convergence is studied. About the nozzle flow, the pressure and velocity distributions along the nozzle axis are compared with those from the isentropic flow. Secondly, the computation of pipe flow is processed. For the comparision between the present results and the analytical solution for the poiseuille flow (such as entrance length and poiseuille number), the accuracy of current numerical approach for solving the laminar flow is confirmed. Finally, the present solution procedure is applied to study the trapezoidal microchannel. For the different value of Knudsen number and Mach number, the distribution of Poiseuille number and pressure distribution are computed and compared with the related data in the other literature.
47
SU, BO-YU, and 蘇柏瑜. "Magnetohydrodynamic Effect in a Circular Microchannel." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/2aw584.
Full textAbstract:
碩士明志科技大學
化學工程系碩士班
107
The main purpose of this paper is to investigate the application of a magnetic field to control the flow rate of the solution in the annular microfluidic channel. The annular microchannel used in the experiment includes three slots. The first type consists of an ITO conductive film with 1.20 cm in inner diameter and a graphite carbon electrode with of 0.80 cm in inner diameter to form a channel with 0.20 cm in width. The other two trenches are made up of 0.10 cm and 0.20 cm wide channels made of white gold rings with outer diameters of 1.80 cm, 1.50 cm and 1.20 cm. The working fluid in the experiment is a mixed solution of potassium ferricyanide and potassium ferrocyanide at 0.5 M, 0.6 M, 0.7 M, and 0.8 M. Polystyrene microspheres are added to the solution to facilitate testing of the flow rate. This experiment used several magnets with various magnetic flux densities to change the magnetic field. The flow rate changes with various magnetic field strengths and concentrations were measured by cross-testing of different concentrations of working fluid.
48
Chen, Chia-Yung, and 陳家勇. "Thermal fluid analysis of compressible microchannel flow." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/29612527353265423501.
Full textAbstract:
碩士國立中央大學
機械工程研究所
90
This numerical study analyzed the thermal-flow characteristics of the compressible laminar flow over the microchannel (dh < 4μm). The channel wall is assumed as non-slip flow condition. Two flow regimes were considered: 1) Ma=0.07~0.21, Re=1~10; 2) Ma=(3~12)×10-4, Re=(1.2~8.9)×10-3. Numerical results show that the compressible laminar flow has abrupt velocity jump near the channel entrance, and the fully developed flow can never be achieved no matter how long the channel is. In addition, further increases inlet velocity, more significant increasing of velocity at the outlet is predicted. The predicted velocity of present non-slip flow has a flat profile, which is similar to the solution of the slip flow simulation, and the velocity distribution is flatter as the flow approaches the outlet. Near the inlet, velocity profiles have a concave shape due to the viscosity heating at wall. For the heating wall case, the Nusselt number is inversely proportional to the wall temperature. When the wall temperature is higher, the flow needs longer channel to reach a constant Nusselt number. Comparing with the incompressible flow, nonlinear pressure distribution is obtained due to the compressibility effect. Both pressure and velocity gradient reach the maximum value at the outlet. Furthermore, enforcing higher pressure ratio (inlet value to outlet value), more significant nonlinear level of pressure distribution is observed. Because of the channel size effect, even the inlet velocity is very low (Main~10-3), numerical results reveal that a slight velocity difference makes a huge dissimilar pressure distribution in microchannel.
49
Chiu, Yi-Shan, and 邱義善. "Investigation of Heat Transfer on Microchannel Evaporator." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/24616800940770022083.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
95
Microchannles provide a large heat transfer surface area per unit flow volume. Phase change in microchannel evaporator makes it desirable for three reasons：(1) high critical heat flux (2) high heat transfer coefficient (3) low coolant flow rate. Therefore, they are well suited for high heat flux removal and high temperature uniformity cooling applications. Present research successfully established a reliable microchannel evaporator experimental system to investigate heat transfer behavior in microchannels and enhance heat transfer performance by sintered porous structure. The working liquid used is refrigerant R-134a, operating pressure is 8 bar, and mass flux ranges from 222 to 464kg/m2s. The microchannel evaporator was fabricated from oxygen-free copper, and top platform was cut to form 62 parallel rectangular 225μm×660μm microchannels. The top platform of porous microchannel evaporator was sintered to form 62 parallel rectangular 210μm×660μm microchannels. The thickness of porous surface structure is 96μm, and the porosity is 54%. The average particle size is 30μm. The results reveal that flow boiling pressure drop is primarily affected by mass velocity and heat flux, which increases with increasing mass velocity and heat flux. The predictability of separated flow model is much better than homogeneous equilibrium model on flow boiling pressure drop in microchannel, and the lowest MAE is 10.6%. Flow boiling in microchannel can be classified either as boiling-dominated region or convection-dominated region. In boiling-dominated region, the heat transfer coefficient increases with increasing heat flux. In convection-dominated region, the heat transfer coefficient decreases with decreasing vapor quality. These two region are separated by the peak value of heat transfer coefficient, and this separation will change if mass velocity differs. The heat transfer data closely match with some previous correlations, and the lowest MAE is 13.6%. The critical heat flux is primarily affected by mass velocity, which increases with increasing mass velocity. The CHF data also closely match with some previous correlations, and the lowest MAE is 2.6%. As for heat transfer enhancement, in the same volume flow rate 167 ml/min, the heat transfer coefficient and CHF of porous microchannel evaporator is enhanced by 2-3.8 times and 19-23% respectively.
50
Chen, Hong-Ren, and 陳弘仁. "Design and Fabrication of the Microchannel System." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/58397027681977147649.
Full textAbstract:
博士國立成功大學
航空太空工程學系
89
The objective of this present work applied MEMS technology to fabricate a micro-channel for the study of inside flow and heat transfer process. Due to the complexity of the rarefied gas heat transfer, we would like to focus our attention in a simplified case where the size of the channel is close to the mean free path of the gas. By performing some experiments to this micro-channel we can study the heat transfer inside a channel with different gas flows at the slip or transition regime with the bottom wall of a channel heated uniformly. The entire fabrication of the micro-channel system was to employ MEMS techniques to integrate micro-channel, micro-sensors and micro-heaters together within the suspended insulation system of a 1cm x 1cm chip. The channels were designed with 4000μm in length, 40μm in width and 0.8μm in height. The chip can heat uniformly the bottom wall and provide measurements of the temperature and pressure distributions along the flow direction. The Kn number of the gas in this channel falls between 0.053 and 0.154 from the calculation. Therefore, one can study the rarefied gas flow heat transfer under both the slip-flow and the transition-flow regimes. All of the sensors and the heaters were made of polysilicon doped with different concentrations of boron or phosphorous, which results in different electric resistance. To achieve a better insulation, the channel was made of low thermal conductivity material, silicon oxide, to reduce the heat loss. The entire fabrication process was made with the equipments in NDL. Followings are summarized results of current achievements: 1) Develop a fabrication procedures that can be fitted to the requirements set by IC processing laboratory. 2) Develop a new planarization process for poly-Si sacrificial layer. 3) Develop wet etching process for poly-Si sacrificial layer removal. 4) Develop photolithography process on surface with large size and deep ditches. Through years of revisions and adjustments the design and fabrication in the current chip has been greatly simplified. Many problems encountered during fabrication such as thick film stress, wet-etching contamination or step coverage effects etc. have also been overcame. Therefore, one has achieved the goals to establish the primary techniques for heat transfer application in MEMS and to develop experimental methods for micro-scale flow and heat transfer study successfully.