Dissertations / Theses on the topic 'Boiling on porous surfaces'
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Pasek, Ari Darmawan. "Pool boiling on porous surfaces in cryogenic and refrigerant liquids." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315511.
Full textFurberg, Richard. "Enhanced Boiling Heat Transfer on a Dendritic and Micro-Porous Copper Structure." Doctoral thesis, KTH, Tillämpad termodynamik och kylteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-47538.
Full textQC 20111111
Carbonell, Ventura Montserrat. "Estudio experimental del proceso de calentamiento de medios porosos saturados hasta ebullición-"Dryout" de su fase líquida." Doctoral thesis, Universitat Politècnica de Catalunya, 2000. http://hdl.handle.net/10803/6743.
Full textLos objetivos planteados en la presente tesis se han orientado hacia un mejor conocimiento de la influencia de diversos parámetros estructurales del medio poroso, así como de las propiedades de las substancias que constituyen la matriz sólida y la fase fluida saturante, en las características de ebullición de un medio poroso inicialmente saturado, calentado por su frontera inferior y limitado por una capa superior del mismo líquido saturante.
A tal fin, se ha estudiado la influencia de la estructura del medio poroso (granular o fibrilar) y de la naturaleza de la sustancia que constituye la matriz sólida sobre la permeabilidad del medio poroso al agua y a una solución acuosa de tensioactivo, de baja concentración. Así mismo se ha estudiado la influencia respecto a la conductividad y difusividad térmicas efectivas en régimen no estacionario. Por último, utilizando la misma variedad de medios porosos saturados, se estudia el proceso de ebullición hasta que se alcanzan condiciones de "dryout", y se analizan las consecuencias que resultan de la variación de la estructura física del medio poroso, de la naturaleza de la sustancia que constituye su matriz sólida y de las propiedades del fluido saturante.
En lo referente a las características fluidodinámicas y térmicas de los medios porosos estudiados se ha podido concluir:
- La adición de un tensioactivo al agua saturante del medio poroso produce un comportamiento diferente según la naturaleza del sólido: en caso de inorgánica (arena) ocasiona un aumento de la permeabilidad intrínseca, mientras que en caso de orgánica (fibras de algodón) produce una reducción tanto mayor cuanto menor es la porosidad del medio poroso. Las causas de este diferente comportamiento, son las notables diferencias de absorción del tensioactivo según el tipo de sólido (orgánico o inorgánico) y la mejora substancial de la humectación de la superficie del sólido inorgánico por el fluido lo que activa la eficacia de desplazamiento de toda fase no acuosa adsorbida o retenida entre partículas.
- La difusividad térmica efectiva promediada espacialmente tiende al valor de la difusividad del componente del medio poroso de menor difusividad térmica a medida que transcurre el tiempo de calentamiento.
- La difusividad térmica efectiva de los medios porosos saturados en los que s / l < 1 se aproxima a la de la fase líquida; en los medios para los que s / l >> 1, dicha difusividad térmica efectiva es un grado de orden superior a la de la fase líquida.
- La adición de tensioactivo a la fase líquida saturante provoca la disminución de la conductividad térmica efectiva de medio poroso saturado en aquellos en que la fase sólida es granular e inorgánica.
En lo referente al proceso de calentamiento de un medio poroso saturado hasta ebullición-"dryout" de su fase líquida se ha descrito un modelo físico de comportamiento de los diferentes medios porosos que comporta las siguientes fases:
i) Calentamiento del medio hasta la temperatura de saturación de su fase líquida, con evidente aumento de volumen de las fases sólida y líquida por dilatación térmica.
ii) Proceso de evaporación con formación de una capa bifásica cuya frontera superior se desplaza a la velocidad del frente de vapor. Simultáneamente se produce una disminución de la presión fluidoestática en la frontera de la capa bifásica, lo que se traduce en una reducción del reflujo de líquido hacia la placa calefactora.
iii) Total desaturación de la entrefase medio poroso-placa calefactora al recibir por reflujo menos líquido del que es capaz de evaporar la placa calefactora. Aparición del "dryout" y elevación progresiva de la temperatura de la placa.
iv) Aparición, en algún caso, de un fenómeno de basculamiento de la fase líquida desde la capa subenfriada a la zona desaturada del medio poroso.
A large number of difficulties are found in the experimentation and later modelization of transport and transfer heat and mass process in saturated porous media, which basically derive from the heterogeneity of the medium, the methodology of structural and physic parameterization to assimilate it to a continuous medium.
The raised aims in this doctoral thesis have been directed towards a better knowledge of the influence of several structural parameters of the porous medium, as well as of the properties of the solid matrix and the saturating fluid phase, in the characteristics of boiling of an initially saturated porous medium, heated by its lower boundary and limited by an upper layer of the same saturating liquid.
For this, the influence of the structure of the porous medium (granular or fibrous) and the nature of the solid matrix on the permeability to water and to a surfactant solution of lower concentration have been studied. The influence in relation to effective thermal conductivity and diffusivity in unstationary regime has also been studied. Finally, the boiling process until to achieve dryout conditions has been studied, and the consequences result from the variation of the physical structure of the porous medium, the nature of the solid matrix and the properties of the saturating fluid have been analyzed.
About the fluid dynamic and thermal characteristics of the porous media studied, the thesis concludes that:
- The addition of a surfactant to the saturating water of the porous medium produces a different behaviour depending on the nature of the solid: in inorganic matrix (sand) occasions an increase in the intrinsic permeability, whereas in organic matrix (cotton fibres) produces a decrease as greater as smaller is the porosity of the porous medium. The reasons of this different behaviour are the notable differences of absorption of the surfactant depending on the sort of solid matrix (organic or inorganic) and the important increase of the wetting of the inorganic solid's surface by the fluid activating the displacement of all adsorbed or retained not watery phase between particles.
- The spatially averaged effective thermal diffusivity tends to the value of the diffusivity of the component of the porous medium with lower thermal diffusivity throughout the boiling process.
- The effective thermal diffusivity of the saturated porous media which have s / l < 1 approaches to of the liquid phase; in the media with s / l >> 1, the effective thermal diffusivity is a grade of upper order to the of liquid phase.
- The addition of surfactant to the saturating liquid phase gives rise to the decrease of the effective thermal conductivity of the saturated porous medium with granular and inorganic solid phase.
A physical model of behaviour of the different saturated porous media concerning heating process until to achieve dryout conditions has been described considering the next phases:
i) Heating of the medium until the saturation temperature of its liquid phase, with evident increase of volume of the solid and liquid phases by thermal dilatation.
ii) Evaporation process with creation of a biphasic layer whose upper boundary displaces to the velocity of the vapour front. Simultaneously a decrease of the fluid static pressure in the boundary of the biphasic layer is produced, what result in a reduction of the reflux of liquid towards the heating plate.
iii) Total unsaturation of the porous medium-heating plate interphase caused by to receive less liquid by reflux that the heating plate is capable of evaporating.
iv) Appearance, in some case, of a fast phenomenon of turn upside down of the liquid phase from subcooled layer to the unsaturated zone of the porous medium.
Witharana, Sanjeeva. "Boiling of refrigerants on enhanced surfaces and boiling of nanofluids." Licentiate thesis, KTH, Energy Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1589.
Full textSriraman, Sharan Ram. "Pool boiling on nano-finned surfaces." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2091.
Full textRoberts, Ian David. "Droplet evaporation from porous surfaces." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294978.
Full textWebb, Stephen David. "Jet impingement on porous surfaces." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/47117/.
Full textZhang, Ke. "Enhanced boiling heat transfer on micro/nano structured surfaces." Thesis, Boston University, 2013. https://hdl.handle.net/2144/21284.
Full textBoiling heat transfer is a critical process in large-scale industrial applications such as steam engines and heat exchangers in power plants, and in microscopic heat transfer devices such as heat pipes and microchannels for cooling electronic chips. Enhancing boiling heat transfer thus has great significance on lots of energy transportation and utilization systems. Recent studies has suggested that micro/nano structured surfaces can produce considerably different boiling heat transfer curves than normal plain surfaces, resulting in different values of the critical heat flux (CHF) and heat transfer coefficient (HTC). In this thesis, pool boiling on several new micro/nano structured surfaces was experimentally investigated to further understand the mechanism of boiling heat transfer and increase boiling performance. We first evaluated enhanced boiling heat transfer on three kinds of micro/nano structured super-hydrophilic surfaces: 1) nanowire coated super-hydrophilic surfaces, 2) hybrid microscale cavity and nanowire structured surfaces and 3) hybrid microscale pillar and nanowire structured surfaces. All three surfaces showed significant enhancement of CHF and HTC compared to plain silicon surfaces. Combined micro/nano structured surfaces presented better performance than nanowire coated surfaces suggesting that both active nucleation density and surface roughness significantly affect boiling heating transfer. Experimental investigations indicate an optimum design both in size (~ 20μ𝑚) and density (between 0 and 10000=cm^2) of cavities for microscale cavity/nanowire structured surfaces. The highest CHF and peak HTC values were obtained on microscale pillar/nanowire structured surfaces. Among the test surfaces, the largest enhancements of CHF and peak HTC were 228% and 298%, respectively, compared to plain silicon surfaces. For a better understanding of the boiling phenomena, pool boiling on super-hydrophobic surfaces was also studied. We found that, for super-hydrophobic surfaces, the major heat transfer mechanism at the initial boiling regime is natural convection of liquid water. In conclusion, micro/nano structured surfaces can greatly influence nucleate boiling heat transfer. The various physical attributes employed with the structured surfaces further revealed the profound influence of surface topography on enhancing boiling heat transfer.
2031-01-01
Kim, Dae Whan. "Convection and flow boiling in microgaps and porous foam coolers." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7446.
Full textThesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Kelley, Mitchell Joseph. "Experimental design for study of nucleate boiling in porous structures." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68530.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 48).
The superheat required to initiate nucleate boiling inside porous wicks is not well understood in practice. This thesis reports the design of an experimental setup for investigating the onset of vapor nucleation in sintered porous structures. Pressure sensing was evaluated as an effective means of detecting the onset of nucleation. Thermal studies were conducted with a custom finite difference script in conjunction with finite element analysis. Heat conduction through a three dimensional wick was reduced to one dimensional conduction via symmetry and design constraints. The wick was optimized to achieve a temperature drop of 30 *C at a common heat pipe operating temperature of 70 °C.
by Mitchell Joseph Kelley.
S.B.
Showkat, Ali Syamir Alihan. "Flow over and past porous surfaces." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/86527ebe-9574-425b-a1c4-6152f07cf4b4.
Full textMacIver, Alasdair. "The application of enhanced surfaces to boiling over tube bundles." Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1472.
Full textSathyamurthi, Vijaykumar. "Pool boiling studies on nanotextured surfaces under highly subcooled conditions." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1155.
Full textLi, Nanxi. "High-pressure pool boiling and physical insight of engineered surfaces." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35561.
Full textDepartment of Mechanical and Nuclear Engineering
Amy R. Betz
Boiling is a very effective way of heat transfer due to the latent heat of vaporization. Large amount of heat can be removed as bubbles form and leave the heated surface. Boiling heat transfer has lots of applications both in our daily lives and in the industry. The performance of boiling can be described with two important parameters, i.e. the heat transfer coefficient (HTC) and the critical heat flux (CHF). Enhancing the performance of boiling will greatly increase the efficiency of thermal systems, decrease the size of heat exchangers, and improve the safety of thermal facilities. Boiling heat transfer is an extremely complex process. After over a century of research, the mechanism for the HTC and CHF enhancement is still elusive. Previous research has demonstrated that fluid properties, system pressures, surface properties, and heater properties etc. have huge impact on the performance of boiling. Numerous methods, both active and passive, have been developed to enhance boiling heat transfer. In this work, the effect of pressure was investigated on a plain copper substrate from atmospheric pressure to 45 psig. Boiling heat transfer performance enhancement was then investigated on Teflon© coated copper surfaces, and graphene oxide coated copper surfaces under various system pressures. It was found that both HTC and CHF increases with the system pressure on all three types of surfaces. Enhancement of HTC on the Teflon© coated copper surface is contributed by the decrease in wettability. It is also hypothesized that the enhancement in both HTC and CHF on the graphene oxide coated surface is due to pinning from micro and nanostructures in the graphene oxide coating or non-homogeneous wettability. Condensation and freezing experiments were conducted on engineered surfaces in order to further characterize the pinning effect of non-homogeneous wettability and micro/nano structure of the surface.
Masondo, Phumlani Thulani. "Further development of Twinlay porous asphalt surfaces." Thesis, Peninsula Technikon, 2001. http://hdl.handle.net/20.500.11838/1031.
Full textRoad traffic noise (with tyre/road interaction being the predominating factor to the generation of noise production especially at vehicle speed above 50 km/h) is becoming an escalating problem that poses a threat to the environment. Ways and means of eradicating or at least retarding this problem have led to the development of Porous Asphalt surfaces which has excellent functionality. Porous asphalt has been used mainly for reducing aquaplaning subsequently reducing splash and spray thereby reducing accident rate during wet weather conditions, reducing road traffic noise and improves wet weather skid resistance Two layered construction so called "Twinlay" is a new development which was initiated in the Netherland with an intention of optimizing reduction to road traffic noise and also to solve the shortfalls (e.g. clogging) associated with the conventional single layer of porous asphalt. Twinlay is made up of a bottom layer of porous asphalt with a coarse single grained aggregate (11/16) and a thin top layer of fine porous asphalt (4/8). Twinlay has many advantages as opposed to the previous practises (single layer of porous asphalt) in South Africa, e.g the fine top layer acts as a sieve preventing sand or dirt from clogging the coarse bottom layer, and also, the fine surface texture of the top layer reduces tyre/road noise and many more. More research into road/traffic noise reveals that the acoustic properties of a conventional Twinlay porous asphalt surface can be further improved by introducing a thick double layer system (e.g. Superfine Twinlay) with a superfine top singlegrained aggregate mixture.
Furberg, Richard. "Enhanced boiling heat transfer from a novel nanodendritic micro-porous copper structure." Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4057.
Full textTow, Emily Winona. "Bubble behavior in subcooled flow boiling on surfaces of variable wettability." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75682.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 59).
Flow boiling is important in energy conversion and thermal management due to its potential for very high heat fluxes. By improving understanding of the conditions leading to bubble departure, surfaces can be designed that increase heat transfer coefficients in flow boiling. Bubbles were visualized during subcooled nucleate flow boiling of water on a surface of variable wettability. Images obtained from the videos were analyzed to find parameters influencing bubble size at departure. A model was developed relating the dimensions of the bubble at departure to its upstream and downstream contact angles based on a rigid-body force balance between momentum and surface tension and assuming a skewed truncated spherical bubble shape. Both experimental and theoretical results predict that bubble width and height decrease with increasing flow speed and that the width increases with the equilibrium contact angle. The model also predicts that the width and height increase with the amount of contact angle hysteresis and that the height increases with equilibrium contact angle, though neither of these trends were clearly demonstrated by the data. Several directions for future research are proposed, including modifications to the model to account for deviations of the bubbles from the assumed geometry and research into the parameters controlling contact angle hysteresis of bubbles in a flow. Additionally, observations support that surfaces with periodically-varying contact angle may prevent film formation and increase the heat transfer coefficients in both film and pool boiling.
by Emily W. Tow.
S.B.
Emerson, Preston Todd. "Thermal Atomization Due to Boiling During Droplet Impingement on Superhydrophobic Surfaces." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/7878.
Full textGreene, George W. IV. "Surface modification of sintered porous polyethylene membrane." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/20126.
Full textAlfama, Marco. "Theoretical and experimental investigation of the heat transfer and pressure drop optimisation on textured heat transfer surfaces." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/62792.
Full textDissertation (MEng)--University of Pretoria, 2017.
Mechanical and Aeronautical Engineering
MEng
Unrestricted
Bailey, Wendell O. S. "Applications of pool boiling heat transfer on modulated surfaces in organic liquids." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437112.
Full textSathyanarayana, Aravind. "Pool and flow boiling of novel heat transfer fluids from nanostructured surfaces." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50299.
Full textTarrad, Ali Hussain. "Pool boiling of pure fluids and mixtures on plain and enhanced surfaces." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/865.
Full textButterfield, David Jacob. "Jet Impingement Heat Transfer from Superheated, Superhydrophobic Surfaces." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/9167.
Full textZacharia, Renju. "Desorption of gases from graphitic and porous carbon surfaces." [S.l. : s.n.], 2004. http://www.diss.fu-berlin.de/2004/162/index.html.
Full textWal, Bouwe Pieter van der. "Static and dynamic wetting of porous Teflon® surfaces." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/297984551.
Full textHultstein, Eric. "Process Parameters for Creation of Porous Stainless Steel Surfaces." Thesis, KTH, Materialvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145121.
Full textThis work aim to investigate a novel process by means of process parameters for creationof porous austenitic stainless steels surfaces as well as investigate if they permit anyimprovements compared to reference materials. Porous surfaces were created by a two-step method; samples were initially oxidised in a wet argon atmosphere and subsequentlyreduced in a pure hydrogen. The materials used in this investigation are all stainless steelswith specications according to steel grades 1.4301 (304), 1.4404 (316L), 1.4435 (316L)and F-138 (316LVM). The oxidation process is performed above 630 ◦ C for 150 - 1200 s in aow of wet argon or dry air and reduction is performed with a ow hydrogen for 150 - 2400 s.In order to understand the heat treatment processes, samples were characterised by usinga scanning electron microscope together with an electron dispersive x-ray spectrometer.However, light optical microscopy, image analysis and heat transfer measurement werealso used. Results show that all materials can obtain porous structures even though itis evident some process parameters cannot support successful creation of porosity. Ingeneral, the porosity depends on the structure created upon oxidation. It has not beenpossible to identify any crystal structures but compositional analysis as well as previousliterature suggest presence of chromia, (Cr,Fe) spinels and iron oxides. It is concluded thatshort time oxidation frequently creates chromia layers and prolonged oxidation inducesiron oxides due to breakaway oxidation. An increased reduction time results in larger andfewer pores. Compositional analyses show that all porous morphologies are created withina very iron rich layer. It is suggested that wet oxidation promote chromium evaporation,which consequently reduces the amount of chromium in the surface and enables iron oxideto rapidly form. Furthermore, results show that the porous layer is very susceptible tocorrosion as almost no chromium is present after the heat treatment. Evaluation of the properties of porous surfaces reveals a signicant improvement in heattransfer due to natural convection. Heat exchange between uids is though not enhancedgreatly by porous surfaces, a small improvement can be seen for low ow rates but for largerows no improvement is found.
O'Hanley, Harrison Fagan. "Separate effects of surface roughness, wettability and porosity on boiling heat transfer and critical heat flux and optimization of boiling surfaces." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78208.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 157-161).
The separate effects of surface wettability, porosity, and roughness on critical heat flux (CHF) and heat transfer coefficient (HTC) were examined using carefully-engineered surfaces. All test surfaces were prepared on nanosmooth indium tin oxide - sapphire heaters and tested in a pool boiling facility in MIT's Reactor Thermal Hydraulics Laboratory. Roughness was controlled through fabrication of micro-posts of diameter 20[mu]m and height 15[mu]m; intrinsic wettability was controlled through deposition of thin compact coatings made of hydrophilic SiO₂ (typically, 20nm thick) and hydrophobic fluorosilane (monolayer thickness); porosity and pore size were controlled through deposition of layer-by-layer coatings made of SiO₂ nanoparticles. The ranges explored were: 0 - 15[mu] for roughness (Rz), 0 - 135 degrees for intrinsic wettability, and 0 - 50% and 50nm for porosity and pore size, respectively. During testing, the active heaters were imaged with an infrared camera to map the surface temperature profile and locate distinct nucleation sites. It was determined that wettability can play a large role on a porous surface, but has a limited effect on a smooth non-porous surface. Porosity had very pronounced effects on CHF. When coupled with hydrophilicity, a porous structure enhanced CHF by approximately 50% - 60%. However, when combined with a hydrophobic surface, porosity resulted in a reduction of CHF by 97% with respect to the reference surface. Surface roughness did not have an appreciable effect, regardless of the other surface parameters present. Hydrophilic porous surfaces realized a slight HTC enhancement, while the HTC of hydrophobic porous surfaces was greatly reduced. Roughness had little effect on HTC. A second investigation used spot patterning aimed at creating a surface with optimal characteristics for both CHF and HTC. Hydrophobic spots (meant to be preferential nucleation sites) were patterned on a porous hydrophilic surface. The spots indeed were activated as nucleation sites, as recognized via the IR signal. However, CHF and HTC were not enhanced by the spots. In some instances, CHF was actually decreased by the spots, when compared to a homogenous porous hydrophilic surface.
by Harrison Fagan O'Hanley.
S.B.
S.M.
Clavijo, Angeles Cristian Esteban. "Droplet Impingement on Superhydrophobic Surfaces." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6306.
Full textNgan, Mei Lun. "Photoluminescence excitation of porous silicon." HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/139.
Full textBashir, Imran. "Acoustical exploitation of rough, mixed impedance on porous surfaces outdoors." Thesis, Open University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606960.
Full textSearle, Matthew Clark. "Thermal Transport at Superhydrophobic Surfaces in Impinging Liquid Jets, Natural Convection, and Pool Boiling." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7065.
Full textKaradeniz, Hüseyin [Verfasser]. "Numerical Modeling of Stagnation Flows over Porous Catalytic Surfaces / Hüseyin Karadeniz." Karlsruhe : KIT Scientific Publishing, 2016. http://www.ksp.kit.edu.
Full textNeyland, Ryan P. "Colloid Detachment from Rough Surfaces in the Environment." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-050505-114151/.
Full textBockwoldt, Todd S. "Induced convective enhancement of the critical heat flux for partially heated surfaces in pool boiling." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/13094.
Full textBian, David (David Wei). "Enhanced flow boiling heat transfer in microchannels with structured surfaces at varied mass flow rates." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98956.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 39-40).
This thesis investigates the role of mass flux on flow boiling heat transfer in microchannels with surface micropillar arrays. The motivation for this investigation was to determine the general trends of the optimal micropillar array geometry in terms of its heat transfer capabilities. The experiment was conducted with three microchannels: a flat surface microchannel, a sample called the 5-15 (height h = 25 [mu]m, diameter d = 5 [mu]m, and pitch l = 15 [mu]m) and a sample called the 10-40 (height h = 25 [mu]m, diameter d = 10 [mu]m, and pitch l = 40 [mu]m). The structured surface microchannels, due to their capillary pressure-induced wicking capabilities, exhibited less temperature rise and pressure drop fluctuations at high heat fluxes. Furthermore, it was verified that the critical heat flux value of all microchannels increased with mass flux. In addition, it was concluded that at lower mass fluxes, the relative percentage heat transfer enhancement of the structured surface microchannels over the flat surface microchannel was greater. The trend observed suggests that denser samples are better at lower mass fluxes. However, if a sample is too dense, there may be too much viscous drag. Thus, an optimal balance between capillary force and viscous drag must be found in order to determine the optimum micropillar array geometry and density for maximizing the critical heat flux value. Finally, for a given mass flux, the pressure drop across every microchannel was approximately equal at all heat fluxes. This implies that no additional power consumption is required to pump a particular mass flux through a structured surface microchannel than a flat surface microchannel, though there is certainly additional power required to increase the mass flux. This work provides insights into the roles of both the micropillar array surface structures and the mass fluxes on the heat transfer performance of flow boiling in microchannels. The results and observations of this experiment may prove helpful in guiding future work in an attempt to optimize microchannels for heat transfer applications in electronics.
by David Bian.
S.B.
Sapin, Paul. "Etude expérimentale de l'ébullition en masse dans un milieu poreux modèle." Phd thesis, Toulouse, INPT, 2014. http://oatao.univ-toulouse.fr/12148/1/sapin_partie_1_sur_2.pdf.
Full textLiu, Yawen. "Research of Two Types of Slippery Surfaces: Slippery Polydimethylsiloxane Elastomers and Polyelectrolyte Multilayers Slippery Surfaces." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1530877456582558.
Full textEsawy, Mohamed [Verfasser], and Hans [Akademischer Betreuer] Müller-Steinhagen. "Fouling of structured surfaces during pool boiling of aqueous solutions / Mohamed Esawy. Betreuer: Hans Müller-Steinhagen." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2011. http://d-nb.info/1017079862/34.
Full textJoshua, Nihal E. "Direct Immersion Cooling Via Nucleate Boiling of HFE-7100 Dielectric Liquid on Hydrophobic and Hydrophilic Surfaces." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699916/.
Full textZhu, Geyunjian. "FABRICATION OF SLIPPERY LIQUID-INFUSED POROUS SURFACES USING LAYER-BY-LAYER ASSEMBLY: TOWARDS MULTIFUNCTIONAL SURFACES AND FACILE FABRICATION PROCESSES." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1518051453328934.
Full textСтрельцова, Юлія Валеріївна. "Характеристики металевих пористих матеріалів: вплив на теплообмін у теплових трубах хімічно-енергетичного призначення." Thesis, КПІ ім. Ігоря Сікорського, 2017. https://ela.kpi.ua/handle/123456789/20601.
Full textThe dissertation is devoted to the investigation of two types of metal porous materials, which can be used as capillary structures of heat pipes – monofibrous and composite fibrous-powder structures. The dependences for engineering calculations of frame thermal conductivity for monofibrous and composite materials were obtained after the experiments of heat conduction processes in metallic porous materials. Multi-factor dependence for calculations of temperature difference of the water boiling beginning on metallic porous surfaces was proposed on the basis of the experimental studies of boiling in free water flow. The obtained experimental data allowed to compare the real values of heat transfer coefficients α with the data obtained by the model of boiling on porous surfaces (the KPI model) specified in the dissertation. As a result of model elaboration, It became possible to bring the calculated values obtained by the experiments to the model calculated α values and to confirm the adequacy of the model. It was refined the method of internal thermal resistance determining in heat pipes with metal porous structures by the application of the KPI model. The cycle of experimental studies of heat pipes with monofibrous and composite capillary structures showed, that in horizontal position heat pipes with composite structures do not concede with the main characteristics (maximum heat transfer capacity and thermal resistance) to the heat pipes with monofibrous capillary structures. In addition, maximum heat transfer capacity of composite heat pipes has higher values, than the same one of mono-fibrous pipes, when working against the forces of gravity.
Диссертация посвящена исследованию двух типов металлических пористых материалов, которые могут быть использованы в качестве капиллярных структур тепловых труб – моноволокнистых и композиционных волокнисто-порошковых структур. В результате исследований процессов теплопроводности металлических пористых материалов получены зависимости для инженерных расчетов теплопроводности каркаса моноволокнистих и композиционных материлов. Многофакторные зависимости характеризуют взаимосвязь между теплопроводностью каркаса материалов и их структурными характеристиками. Однофакторные функции вида λ кс = f(П) позволили сравнить теплопроводность композиционных и моноволокнистих структур, в результате чего было установлено, что коэффициенты теплопроводности λ кс композиционных капиллярных структур несколько ниже, чем у моноволокнистых структур, для одинаковых диапазонов пористости. Однако это различие в значениях λ кс является незначительным. На основе экспериментальных исследований влияния характеристик металлических волокнистых материалов на процессы кипения в условиях свободного движения воды предложено формулу для инженерных расчетов температурных напоров начала кипения воды на металловолокнистых пористых поверхностях. Полученные в работе результаты удовлетворительно коррелируются с известными данными, однако существуют и определенные различия, которые влияют на уменьшение температурных напоров закипания при одинаковых значениях пористости капиллярных структур. Исследование температурного напора начала кипения на пористых поверхностях позволило определить, что для пористых медных образцов данный температурный напор составляет 0,5-2,0 ⁰С, в то время как температурный напор начала кипения на относительно «гладких» технических поверхностях – от 7 до 12 ⁰С. Экспериментальные данные позволили сравнить реальные значения коэффициентов теплоотдачи α с данными, полученными по уточненной в данной работе модели кипения на пористых поверхностях (модель КПИ). В результате уточнения удалось значительно приблизить рассчитаные по модели величины α к экспериментальным значениям и подтвердить адекватнисть модели. Анализ полученных экспериментальных данных кипения на металлических пористых поверхностях свидетельствует о том, что медные волокнистые структуры средней пористости (40-50 %) в диапазоне толщин от 0,5 до 1,0 мм позволяют обеспечить наибольшие значения коэффициентов теплоотдачи α, по сравнению с металлическими волокнистыми структурами других диапазонов пористостей и толщин, исследованными в данной работе. Также с применением модели кипения КПИ была уточнена методика определения внутреннего термического сопротивления тепловых труб с металлическими пористыми структурами. Выполненный цикл экспериментальных исследований тепловых труб с металло-волокнистыми и композиционными капиллярными структурами с использованием этанола в качестве теплоносителя показал, что в горизонтальном положении и в положении «режим термосифона» тепловые трубы с капиллярными структурами обоих типов обеспечивают стабильное функционирование в диапазоне тепловых потоков до 70 Вт. При этом термические сопротивления тепловых труб с «новым» типом капиллярных структур не превышают термические сопротивления труб, изготовленных на основе моноволокнистых структур. В положениях, когда зона нагрева трубы находится выше, чем зона охлаждения, композиционные капиллярные структуры нового типа обеспечивают стабильное функционирование для тепловых потоков до 25 Вт, что является более высоким показателем, чем у тепловых труб с моноволокнистыми структурами (10-15 Вт). Последний факт нужно учитывать при конструировании аппаратов и приборов с тепловыми трубами.
Mei, Fang. "COATING OF SILVER FILM ONTO THE INNER PORE SURFACES OF THE RETICULATED ALUMINA BY AN ELECTROLESS PLATING METHOD." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin971276657.
Full textDietl, Jochen [Verfasser], Peter [Akademischer Betreuer] Stephan, and Johannes [Akademischer Betreuer] Janicka. "Numerical Simulation of Pool Boiling from Reentrant Type Structured Surfaces / Jochen Dietl. Betreuer: Peter Stephan ; Johannes Janicka." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/1111910588/34.
Full textKaradeniz, Hüseyin [Verfasser], and U. [Akademischer Betreuer] Maas. "Numerical Modeling of Stagnation Flows over Porous Catalytic Surfaces / Hüseyin Karadeniz. Betreuer: U. Maas." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/107393991X/34.
Full textGolding, Randy Dale. "Synthesis and application of alkyl dihydrochlorosilanes: A new approach to the surface modification of porous silica." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184427.
Full textGershen, Lewis Elliot. "Performance characterization of pool boiling on innovative foams and micro structured surfaces - application to direct immersion cooling of electronics." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/159.
Full textThesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Piatt, Joseph John 1966. "Sorption and Biodegradation of Organic Solutes Undergoing Transport in Laboratory-scale and Field-scale Heterogeneous Porous Media." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/191215.
Full textKapetas, Leon. "Microbial controls on contaminant metal transport in porous media." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5769.
Full textChennell, Philip. "Préparation et caractérisation de surfaces poreuses ordonnées en polymères en vue d'applications médicales." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAS005/document.
Full textUreteral stents and nephrostomy catheters are made of silicone or thermoplastic polyurethane (TPU). A topographical modification creating an ordered porous surface could limit the infectious risks during their implantation, by reducing bacterial adhesion and creating a loading platform from which anti-infectious compounds could be released.In this work, a two-steps replication method was used to create ordered porous polymer surfaces (silicone or TPU) using porous anodic aluminium oxide (PAAO) as master template. The PAAO surfaces were prepared by double mild or double hard/mild anodization. Three intermediate mould materials were tested (acrylonitrile butadiene styrene, polystyrene, polyacrylate resin). The polymer material (silicone or TPU) was then moulded onto the intermediate mould surfaces that possessed freestanding pillar arrays, to imprint pores. The obtained surfaces were characterized by microscopic and spectroscopic methods. The initial PAAO surfaces prepared by double mild anodization possessed pores of about 50 nm diameter and 100 nm depth, whereas those prepared after development of the double hard/mild anodization method were bigger, of about 125 nm diameter and several hundred nanometers deep. The intermediate mould structure possessed freestanding arrays, but instabilities (lateral adhesion) were noted for certain conditions. The best pattern replication was observed for TPU. In conclusion, these novel porous polymeric surfaces could be optimized and tested for an anti-biofilm effect