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1
Vestlund, Johan. "Gas-filled, flat plate solar collectors." Doctoral thesis, Högskolan Dalarna, Energi och miljöteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:du-6182.
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This work treats the thermal and mechanical performances of gas-filled, flat plate solar collectors in order to achieve a better performance than that of air filled collectors. The gases examined are argon, krypton and xenon which all have lower thermal conductivity than air. The absorber is formed as a tray connected to the glass. The pressure of the gas inside is near to the ambient and since the gas volume will vary as the temperature changes, there are potential risks for fatigue in the material. One heat transfer model and one mechanical model were built. The mechanical model gave stresses and information on the movements. The factors of safety were calculated from the stresses, and the movements were used as input for the heat transfer model where the thermal performance was calculated. It is shown that gas-filled, flat plate solar collectors can be designed to achieve good thermal performance at a competitive cost. The best yield is achieved with a xenon gas filling together with a normal thick absorber, where normal thick means a 0.25 mm copper absorber. However, a great deal of energy is needed to produce the xenon gas, and if this aspect is taken into account, the krypton filling is better. Good thermal performance can also be achieved using less material; a collector with a 0.1 mm thick copper absorber and the third best gas, which is argon, still gives a better operating performance than a common, commercially produced, air filled collector with a 0.25 mm absorber. When manufacturing gas-filled flat plate solar collectors, one way of decreasing the total material costs significantly, is by changing absorber material from copper to aluminium. Best yield per monetary outlay is given by a thin (0.3 mm) alu-minium absorber with an argon filling. A high factor of safety is achieved with thin absorbers, large absorber areas, rectangular constructions with long tubes and short distances between glass and absorber. The latter will also give a thin layer of gas which gives good thermal performance. The only doubtii ful construction is an argon filled collector with a normal thick (> 0.50 mm) aluminium absorber. In general, an assessment of the stresses for the proposed construction together with appropriate tests are recommended before manufacturing, since it is hard to predict the factor of safety; if one part is reinforced, some other parts can experience more stress and the factor of safety actually drops.
2
Reiter, Christoph Nikolaus. "Polymeric solar-thermal flat-plate collectors." Thesis, De Montfort University, 2014. http://hdl.handle.net/2086/10755.
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State-of-the-art solar-thermal flat-plate collectors suffer from a limited potential to decrease production costs for the necessary higher economic benefit of so-lar-thermal systems. Costly metallic materials and corresponding manufactur-ing processes prevent further cost reductions. For that issues, plastic materials can offer a promising approach. The main hurdle for the use of cost-effective plastics lies in the high thermal loads on the collector components — absorber and insulation — which were identified in a field-testing. The necessary overheating protection approaches to lower these thermal loads were investigated in a literature review. A large number of relevant concepts was evaluated related to achievable temperature reduction, influence on solar yield, additional costs and intrinsic safety. There-fore, a mathematical model was developed to determine the solar-thermal col-lector´s behaviour in a solar-thermal system for hot water and space heating. This way, the most promising overheating concepts were simulated and ana-lysed with regard to component temperatures and system performance. Omitting the selective absorber coating and reducing the backside insulation was found to be the most suitable solution for component materials with limited temperature resistance like polypropylene. In the second part of the research, collector design concepts were developed on the basis of the characteristics of plastic material processing. The identified unit costs showed savings of more than 50 % in comparison to stateof- the-art collectors. The analysis regarding temperature loads and annual solar yield by simulation proved the performance of the concepts. The collector costs and the simulation results were used to define the total costs of the solar-thermal sys-tems and to evaluate the economic benefits by means of the collector con-cepts. The benefits were similar to state-of-the-art set-ups. Thus, further adjustments at system level are necessary to lower the total costs. Therefore, the system set-up has to be harmonised with the collector requirements and investigated in detail.
3
Grooth, Pieter Jan. "Wave reflection by a flat plate cascade." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/42459.
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Olsson, Jörgen. "Localized disturbances in a flat plate boundary layer." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/47351.
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Wedow, Jaret M. "A Flat Plate Skin Friction Correlation Including Transition." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2299.
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Many existing boundary layer models treat transition as a rapid switch from laminar to turbulent flow, with correlations defining properties in each respective region. Natural transition, however, is not always a very spanwise uniform process, with the onset of transition varying somewhat between different streamwise paths of fluid flow. Thus, a spanwise average of natural transition can result in a more gradual, extended transition region than many existing models predict. Modern applications, such as aircraft wings and fuselages, are extremely streamlined and smooth, allowing for natural transition to occur rather than flow tripping to turbulent near the leading edge. Under these conditions, a skin friction model that takes this extended transition region into account provides a more accurate model compared to those which incorporate a rapid transition from laminar to turbulent flow. Lienhard’s recent publication 1 presents a new rationale for modeling the extent of the transition region on a smooth flat plate developed from re-analysis of existing heat transfer data. This correlation accounts for the extended natural transition region corresponding to a spanwise average of values. The primary objective of this thesis was to reinterpret Lienhard’s heat transfer correlation to solve for skin friction coefficient, then compare this correlation to available experimental data and higher order boundary layer models. After reinterpreting Lienhard’s correlation using the Reynolds analogy, it produced a gradual, extended transition region for skin friction coefficient. The reinterpreted correlation had excellent agreement with experimental data corresponding to a spanwise average of flow with natural transition. Tripped transitional values and data taken along a streamwise path of fluid resulted in a more rapid transition from laminar to turbulent flow. Both an integral boundary layer model and a Reynolds-averaged Navier-Stokes boundary layer model were used to validate the reinterpreted Lienhard correlation. Both of these models produced transition curves steeper than the reinterpreted Lienhard curve. These existing boundary layer models do not take into account the gradual transition region that natural transition may produce when looking at a spanwise average of values. With a focus on spanwise averaged values, such as overall drag over a streamlined surface, existing sophisticated boundary layer models may not accurately predict the behavior produced. The reinterpreted Lienhard correlation provides a new representation of skin friction coefficient throughout the boundary layer that takes into account the extended transition region that may occur when it is desired to model a spanwise average of fluid flow.
1Lienhard, J. Heat transfer in flat-plate boundary layers: A correlation for laminar, transitional, and turbulent flow. ASME Journal of Heat Transfer, 142, 2020.
6
Pfautsch, Emily. "Forced convection in nanofluids over a flat plate." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5745.
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Thesis (M.S.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 14, 2009) Includes bibliographical references.
7
Subaschandar, N. "Turbulent Near Wake Behind An Infinitely Yawed Flat Plate." Thesis, Indian Institute of Science, 1995. https://etd.iisc.ac.in/handle/2005/146.
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Near wake is the region of wake flow just behind the trailing edge of the body where the flow is strongly influenced by the upstream flow conditions and also perhaps by the characteristics of the body. The present work is concerned with the study of the development of turbulent near wake behind an infinitely yawed flat plate. The turbulent near wake behind an infinitely yawed flat plate is the simplest of the three-dimensional turbulent near wake flows. The present study aims at providing a set of data on the turbulent near wake behind an infinitely yawed flat plate and also at understanding the development and structure of the near wake. Detailed measurements of mean and turbulent quantities have been made using 3-hole probe, X-wire and 3-wire hotwire probes.
Further an asymptotic analysis of the two-dimensional turbulent near wake flow has been formulated for the near wake behind an infinitely yawed flat plate. The feature that the near wake which is dominated by mixing of the oncoming turbulent boundary layer retains, to a large extent, the memory of the turbulent structure of the boundary layer, has been exploited to develop this analysis. The analysis leads to three regions of the wake flow (the inner near wake, the outer near wake and the far wake) for which the governing equations are derived. The matching conditions among these regions lead to logarithmic variations in both normal and longitudinal directions in the overlapping regions surrounding the inner wake. These features are validated by the present results.
A computational study involving seven well known turbulence models was also undertaken in order to assess the performance of the existing turbulence models in the prediction of the turbulent near wake behind an infinitely yawed flat plate. In this study all the seven models are implemented into a common flow solver code, thus eliminating the influence of grid size, initial conditions and different numerical schemes while making the comparison. This study shows that the K - e model performs better than other models in predicting the near wake behind an infinitely yawed flat plate.
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Subaschandar, N. "Turbulent Near Wake Behind An Infinitely Yawed Flat Plate." Thesis, Indian Institute of Science, 1995. http://hdl.handle.net/2005/146.
Full textAbstract:
Near wake is the region of wake flow just behind the trailing edge of the body where the flow is strongly influenced by the upstream flow conditions and also perhaps by the characteristics of the body. The present work is concerned with the study of the development of turbulent near wake behind an infinitely yawed flat plate. The turbulent near wake behind an infinitely yawed flat plate is the simplest of the three-dimensional turbulent near wake flows. The present study aims at providing a set of data on the turbulent near wake behind an infinitely yawed flat plate and also at understanding the development and structure of the near wake. Detailed measurements of mean and turbulent quantities have been made using 3-hole probe, X-wire and 3-wire hotwire probes.
Further an asymptotic analysis of the two-dimensional turbulent near wake flow has been formulated for the near wake behind an infinitely yawed flat plate. The feature that the near wake which is dominated by mixing of the oncoming turbulent boundary layer retains, to a large extent, the memory of the turbulent structure of the boundary layer, has been exploited to develop this analysis. The analysis leads to three regions of the wake flow (the inner near wake, the outer near wake and the far wake) for which the governing equations are derived. The matching conditions among these regions lead to logarithmic variations in both normal and longitudinal directions in the overlapping regions surrounding the inner wake. These features are validated by the present results.
A computational study involving seven well known turbulence models was also undertaken in order to assess the performance of the existing turbulence models in the prediction of the turbulent near wake behind an infinitely yawed flat plate. In this study all the seven models are implemented into a common flow solver code, thus eliminating the influence of grid size, initial conditions and different numerical schemes while making the comparison. This study shows that the K - e model performs better than other models in predicting the near wake behind an infinitely yawed flat plate.
9
Afhami, Shahab. "Strip model for capacity of flat plate-column connections." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22943.pdf.
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10
Redl, Erin. "Post-punching response of flat plate slab-column connections." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40840.
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The post-punching failure response of reinforced concrete flat plate slab-column connections is investigated. The first part of this thesis discusses previous research on the tensile membrane action of reinforced concrete slabs and the use of structural integrity reinforcement to prevent progressive collapse after punching failure of slab-column connections. The second part of this thesis describes the design of a flat plate slab system that is the basis for slab-column connection test specimens. Two specimens were constructed and tested to determine punching failure resistance and post-punching failure resistance. The parameter investigated was the detailing of structural integrity reinforcement. Observations from testing contributed to the understanding of the post-punching resisting mechanism that developed. Three failure modes observed during testing were the yielding of reinforcing steel, concrete failure similar to the breakout of embedments, and pullout bond failure. The test results were compared to the predicted resistance of structural integrity reinforcement by CSA A23.3-04 (2004). The test specimens achieved 98% and 104% of the predicted resistance. Test results were also used to evaluate the equation proposed by Melo and Regan (1998) for concrete failure similar to the breakout of embedments, and the equation was found to underestimate the post-punching resistance of flat plate slab-column connections.La réponse après-poinçonnement d’assemblages dalle-poteau de béton armé a été étudiée. Cette thèse constitue de deux parties dont la première discute les recherches précédentes sur l’effet des membranes en traction en plus de l’utilisation d’armature d’intégrité structurale de façon à éviter l’effondrement progressif après avoir subit un poinçonnement en cisaillement d’assemblage dalle-poteau. La deuxième partie décrit la conception d’un système formant d’une dalle plate qui sera la base des modèles d’assemblage dalle-poteau de cette recherche. Deux modèles ont été construits et testés à déterminer la résistance de poinçonnement en cisaillement et la résistance après-poinçonnement pour étudier le paramètre d’armature d’intégrité structurale.Les résultats expérimentaux obtenus ont contribués aux connaissances du mécanisme de résistance après-poinçonnement et trois modes de rupture ont été observés : le fluage de l’acier, la rupture du béton similaire aux brisures des ancrages, et l’échec du lien de retirement. Les résultats ont été comparés aux prédictions de la résistance d’armature intégrité structurale du CSA A23.3-04 (2004) et les modèles conçus ont obtenus 98% et 104% de la résistance prévue. De plus, ses résultats ont été utilisés pour évaluer l’équation proposée par Melo et Regan (1998) pour la rupture du béton similaire aux brisures des ancrages et cette équation a été déterminée à sous-estimer la résistance après-poinçonnement des assemblages dalle-poteau.
11
Burgoyne, Andrea. "Improving flux in flat plate modules for membrane distillation." Thesis, University of Sheffield, 1998. http://etheses.whiterose.ac.uk/6014/.
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This work is concerned with a study of membrane distillation, through modelling and experimental work, in order to determine factors which enhance the permeate flux in this process. The driving force in membrane distillation is a temperature induced vapour pressure difference caused by having a hot feed and a cold permeate. Three theoretical models were developed in order to analyse the process of membrane distillation in a flat plate module. The first was a flow distribution model utilising the relationship between flow rate and pressure drop in rectangular channels. It was found that increasing the flow rate increased the pressure drop over the module. The second model used mass and heat transfer to predict the permeate flux for PTFE, PVDF and Versapor membranes. The flux was found to increase with increasing mean membrane temperature, temperature difference, and decreasing channel height. It was concluded that the Versapor membrane was unsuitable for membrane distillation. The final model utilised boundary layer theory to predict the development of the thermal boundary layers in a flat plate module. Increasing the region where the boundary layer was still growing, reduced the drop in the temperature difference driving force over the module. For a specific velocity, there was an optimum channel height which produced the maximum possible flux. An experimental program was carried out in order to investigate membrane distillation, to characterise the performance of the flat plate module used and to provide corroborating data for the theoretical models described. A new module design was developed incorporating boiling and condensing heat transfer to overcome the decline in temperature driving force along a module channel. The heat transfer through the channel walls was found to stop the decline in driving force and introduce equilibrium.
12
Xue, Huizhong. "Progressive Collapse Resistance of Reinforced Concrete Flat Plate Structures." Thesis, Griffith University, 2019. http://hdl.handle.net/10072/388147.
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Progressive collapse of structures caused by extreme or accidental loads may lead to
significant loss of life and property. Considerable research efforts have been made to date
to mitigate the probability of progressive collapse and its consequences. However, a vast
amount of the existing knowledge is pertinent to the reinforced concrete (RC) frame
structures whilst the understanding of progressive collapse mechanisms of RC flat plate
structures is still limited.
RC flat plate structures represent one of the most common construction systems used in
residential buildings and car parks in Australia and internationally. The absence of beams,
column capitals and drop panels which can help to redistribute the concentrated loads,
makes flat plate structures susceptible to punching shear failure at their slab-column
connections and subsequent damage propagation, potentially leading to a catastrophic
progressive collapse. The post-punching shear behaviour of the slab-column connections
and the load redistribution in the slabs are of particular interests, which essentially
dominate the load-carrying capacities after punching shear failure.
To investigate the progressive collapse mechanisms and resistance of RC flat plates,
experimental tests were performed on two 1/3-scaled 2 2-bay RC flat plate substructures
specimens under an interior column removal scenario. In addition to the uniformly
distributed load (UDL) imposed on the slab, an incremental downward displacement was
applied to the interior slab-column connection to simulate the column loss and subsequent
collapse. Custom-built column load cells were designed and carefully calibrated to ensure
an accurate measurement of the reaction forces and moments at column bases. The overall
load-displacement responses, crack propagations, failure modes and strain developments, were recorded and analysed. The complete collapse-resistant behaviour and load
redistribution pattern of the specimens were examined, from which three load-carrying
mechanism phases, in the form of flexural, tensile membrane and a combination of oneway
catenary and dowel actions were distinguished in resisting the applied concentrated
load.
To study the punching and post-punching shear behaviours of RC slab-column
connections being isolated from their parent flat plate structures, a set of numerical
modelling techniques was established and verified against the experimental results of
eight slab-column connections. In this modelling strategy, the concrete was simulated
using solid elements with calibrated Continuous Surface Cap material model (CSCM)
and failure criterion for punching shear. The reinforcing bars were explicitly created using
beam elements with material properties obtained from the uniaxial tensile tests as well as
calibrated failure criterion for rebar rupture. As a result, a competent 3D nonlinear
numerical model of RC slab-column connections without shear reinforcement was
created, with which, the punching shear failure featuring a critical punching shear surface
and an abrupt drop of the applied force in the load-displacement response was able to be
accurately reproduced. The post-punching shear behaviour, taking the form of an
increased load-carrying capacity which was ceased by rebar fracture in the suspension
stage, was also well captured. Using the proposed numerical model, typical punching and
post-punching shear failure mechanisms were studied in some detail, finally leading to a
simple yet effective analytical solution to accurately and reliably predict the postpunching
shear response of RC slab-column connections.
To investigate the influences of critical slab design parameters on the progressive collapse
resistance of RC flat plate structures subjected to an interior column loss, the already established numerical modelling strategy for RC slab-column connections was employed
to simulate our own experiment of the 2 2-bay flat plate substructure under a
concentrated load and a similar test under a UDL in the literature for model validation. In
addition to the modelling techniques developed for RC slab-column connections, the
modelling of bond-slip behaviour at the interface between concrete and reinforcing bars
was also highlighted, which was found to have a significant impact on the structural
performance of flat plate substructures in progressive collapse. The key structural
behaviours of the substructures under large deformations including the tensile membrane
and suspension actions were able to be replicated. Further, the validated numerical model
being subjected to a concentrated load was used to conduct a series of parametric studies
in which the influences of concrete strength, slab thickness and reinforcement ratio on the
progressive collapse performance were examined. The outcomes of the parametric studies
indicated that the concrete strength and the slab thickness only affected the flexural
capacity to different degrees with no impact on the post-failure capacity, whereas the
load-carrying capacity due to the tensile membrane action was primarily governed by the
amount of slab reinforcement.
This research, covering experimental, numerical and analytical studies of RC slab-column
connections and flat plate substructures with a missing interior column, offers a further
understanding of their punching and post-punching shear behaviours as well as collapseresistant
mechanisms. The numerical modelling techniques developed for the
substructures with an interior column loss can be readily used to simulate other column
loss scenarios (edge column, corner column and multiple columns). Further detailed
analyses of the 3D numerical models will help to establish a simplified numerical model
to facilitate collapse simulations of entire flat plate structures induced by any potential
column removal scenarios.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Gerber, Adam Reynold. "Timber-concrete composite connectors in flat-plate engineered wood products." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57860.
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Timber-Concrete Composite (TCC) systems are comprised of a timber element connected to a concrete slab through a mechanical shear connection. When TCC are used as flexural elements, the concrete and timber are located in compression and tension zones, respectively. A large number of precedents for T-beam configurations exist; however, the growing availability of flat plate engineered wood products (EWPs) in North America in combination with a concrete topping has offered designers and engineers greater versatility in terms of architectural expression and structural and building physics performance. The focus of this investigation was to experimentally determine the properties for a range of proprietary, open source, and novel TCC systems in several Canadian EWPs. Strength and stiffness properties were determined for 45 different TCC configurations based on over 300 small-scale shear tests. Nine connector configurations were selected for implementation in full-scale bending and vibration tests. Eighteen floor panels were tested for elastic stiffness under a quasi-static loading protocol and measurements of the dynamic properties were obtained prior to loading to failure. The tests confirmed that both hand calculations according to the γ-method and more detailed FEM models can predict the basic stiffness and dynamic properties of TCC floors within a reasonable degree of accuracy; floor capacities were more difficult to predict, however, failure did usually not occur until loading reached 10 times serviceability requirements. The research demonstrated that all selected connector configurations produced efficient timber-concrete-composite systems.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Kallage, Mahmoud Rezai. "Punching shear strength of continuous post-tensioned concrete flat plate." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6605.
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A two bay by two bay continuous, unbonded post-tensioned flat plate was constructed and loaded to failure. The slab was designed in accordance with the provisions of ACI 319-89 except that no supplementary bonded reinforcing steel was provided. The prestressing tendons were uniformly distributed in one direction and banded in span/6 column strips in the other direction. In both directions the average prestress on the concrete was 3.5 MPa. The dimensions of each bay were 2.75 m, the slab thickness was 89 mm, mean concrete cylinder strength was 44 MPa. The load was applied monotonically until punching shear occurred at an edge column on the side parallel to banded tendons. The failed column was shored and the slab reloaded until punching shear occurred at the interior column. The lack of supplementary bonded reinforcing steel in regions of moment transfer had no apparent detrimental effects so it must be concluded that the prestress was effective right to the edge of the concrete. The use of 100% banded tendons in one direction and uniform distribution in the other direction had no adverse effects on either the flexural or punching shear behaviour. The literature was reviewed to locate experimental results of punching shear tests for isolated prestressed concrete flat plates, continuous prestressed flat plate systems and tests of flat plate column connections under shear and moment transfer. The strength capacities calculated using the provisions of ACI 318-89, CSA A23.3-84M, BS8110-85 and the CEB Model Code 1990 were compared to the test results and those from the literature review.
15
Dris, Antonis. "Boundary layer transition on a flat plate and concave surfaces." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399183.
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Kansara, Kaushalkumar. "Development of Membrane, Plate and Flat Shell Elements in Java." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9936.
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The development of triangular and quadrilateral membrane, plate and shell elements in Java using the object oriented programming technique is presented. The membrane elements developed are the constant strain triangle (CST) element and the four node isoparametric quadrilateral membrane element. The plate bending elements developed are the discrete Kirchoff triangular (DKT) element and discrete Kirchoff quadrilateral (DKQ) element. The flat shell elements are developed by super imposing the stiffness of the membrane element and plate bending element. A finite element analysis program is also developed to check the accuracy of the developed elements. The program is developed using the object oriented programming approach as an alternative to traditional procedural programming. Several test structures are analyzed using the developed program for each developed element and the results are compared with those obtained from the commercial finite element analysis program SAP 2000. The results indicate that all elements give accurate displacements. However, there were significant differences in stresses for the shell elements, which can be attributable to the approximate approach in these elements to model the drilling degree of freedom.Master of Science
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Linde, Daniel. "Evaluation of a Flat-Plate Photovoltaic Thermal (PVT) Collector prototype." Thesis, Högskolan Dalarna, Energiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:du-24061.
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This Master thesis, in collaboration with Morgonsol Väst AB, was completed as a part of the Solar Energy engineering program at Dalarna University. It analyses the electrical and thermal performance of a prototype PVT collector developed by Morgonsol Väst AB. By following the standards EN 12975 and EN ISO 9806 as guides, the thermal tests of the collector were completed at the facility in Borlänge. The electrical performance of the PVT collector was evaluated by comparing it to a reference PV panel fitted next to it. The result from the tests shows an improved electrical performance of the PVT collector caused by the cooling and a thermal performance described by the linear efficiency curve ηth=0.53-21.6(Tm-Ta/G). The experimental work in this thesis is an initial study of the prototype PVT collector that will supply Morgonsol Väst with important data for future development and research of the product.
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Kimura, Kichiro. "Flat plate buffeting in yawed wind with possible applications to bridges." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7792.
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The wind resistant design of bridges becomes more realistic if the directionality of wind is incorporated into the analysis. However, the necessary information about the bridge response under wind with yaw angle, namely, under a wind not perpendicular to the bridge longitudinal axis, has not been obtained to this date. This thesis is concerned with the buffeting response of cantilever models under yawed turbulent wind. The employed cantilever models can be thought as a simple version of a cable-stayed bridge under construction which is known to be extremely vulnerable to the wind action. It has been also indicated that these structures reveal relatively large response under yawed wind. Models with various cross-sections were tested under different flow conditions and the buffeting response was measured taking the yaw angle as a parameter. The response was mostly in the first vertical bending mode. For the flat plate cross-section models, the effect of the model width was found to be most significant. The wider the model was, the larger the response was found to be under the wind from the free end direction. Even the largest response was sometimes observed under the wind parallel to the model axis from free end direction. A simple response prediction by taking the cosine component of the wind velocity, which has been used from time to time, was found to give generally smaller values than the actual model response. The conventional buffeting analysis was modified so that the response of the cantilever structure under yawed wind can be predicted. Wind velocity components normal to the side and the end of the model were taken as the effective wind velocities, and the response was calculated separately corresponding to each effective wind velocity. The modified buffeting analysis was applied to the flat plate cross-section models. The analytical results generally explained the experimental findings regarding the effect of the wind yaw angle.
19
Qian, Ping. "A numerical study of viscous flows around stalled flat plate wings." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/12059.
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Heinrich, Roland Adolf Eberhard. "Flat-plate leading edge receptivity to various free-stream disturbance structures." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184860.
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The receptivity process by which two-dimensional, time-harmonic freestream disturbances generate instability waves in the incompressible Blasius boundary layer is investigated analytically. The importance of the leading edge region and the linear nature of the receptivity process are discussed, and Goldstein's (1983a, 1983b) theoretical framework for the leading edge receptivity problem is reviewed. His approach utilizes asymptotic matching of a region close to the leading edge, which is governed by the linearized unsteady boundary layer equation, with a region further downstream, which is described by an Orr-Sommerfeld type equation. The linearized unsteady boundary layer equation is solved numerically, using the slip velocity and pressure gradient obtained from the inviscid interaction of the freestream disturbance with the semi-infinite plate. A new method is developed to extract the receptivity coefficient from this numerical solution. The receptivity coefficient determines the amplitude of the instability wave--a quantity not available from classical stability theory. The freestream disturbances investigated are oblique plane acoustic waves, vortical gusts of various orientations convected downstream with freestream speed U(∞), and a Karman vortex street passing above the plate surface with speed U(p). In addition, the case of a semi-infinite plate in a channel of finite width subject to an upstream traveling acoustic wave on the upper plate surface is considered. For oblique acoustic waves, the dominant receptivity mechanism is related to scattering of the waves by the leading edge. In contrast, for vortical gusts the receptivity produced by leading edge scattering is very small. The boundary layer receptivity to a Karman vortex street is found to be a strong function of the speed ratio U(p)/U(∞). A pronounced influence of channel walls, which is related to the alternate cut-on of higher modes in the upstream and downstream channel halves, is found. A comparison of the present results with available experiments shows good qualitative and quantitative agreement.
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Rahman, Aevelina. "Characterization of Heat Transfer Enhancement for an Oscillating Flat Plate-Fin." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/98919.
Full textAbstract:
Heat transfer augmentation is of paramount importance in energy transfer and storage systems and the idea of using the inherent vibrations in a system to enhance heat transfer needs to be thoroughly researched upon. The current study numerically investigates an infinitesimally thin plate-fin undergoing forced oscillations over a range of amplitudes and frequencies in the presence of an approach flow. Reduced frequencies of 0.25 ≤ k ≤16 and plunge amplitudes of 0.03125 ≤ h ≤ 8 are investigated at Re=100 and Pr = 0.71. It is shown that the combined effect of frequency and amplitude on heat transfer enhancement can be accounted for as a single parameter “plunge velocity” (0.25 ≤ kh ≤ 4) instead of the individual frequency and amplitude values. For kh > 0.5 a significant increase in Nusselt number ( is observed compared to a stationary plate. With increasing kh or more vigorous oscillations, the increase in becomes more prominent and similar trends and comparable magnitudes were observed for a constant value. Unlike the hydrodynamic counterpart of the study, both Leading Edge Vortices (LEVs) and Trailing Edge Vortices (TEVs) are found to act positively to induce enhanced heat transfer on the plate. Finally, the dependence of heat transfer augmentation on the frequency and amplitude of vibration is quantified with a simple parameterization for a plate-fin in a fluid medium.M.S.
Heat transfer enhancement is of paramount importance in energy transfer and storage systems. The idea of using the inherent mechanical vibrations in a heat producing system to enhance transfer of unwanted heat from that system needs to be thoroughly researched upon. To investigate this idea, we numerically study an infinitesimally thin plate-fin undergoing forced oscillations over a range of amplitudes and frequencies in the presence of an incoming air flow. It is shown that the combined effect of frequency and amplitude on heat transfer enhancement can be accounted for as a single parameter called “plunge velocity” instead of the individual frequency and amplitude values. For a significant plunge velocity, a significant increase in Nusselt number ( is observed compared to a stationary plate representing an increase in the extent of heat transferred. With more vigorous oscillations, the increase in becomes more prominent and similar trends and comparable magnitudes were observed for a constant value. Finally, the dependence of heat transfer augmentation on the frequency and amplitude of vibration is quantified with a simple parameterization for a plate-fin in a fluid medium.
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Larssen, Jon Vegard. "Large Scale Homogeneous Turbulence and Interactions with a Flat-Plate Cascade." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/26540.
Full textAbstract:
The turbulent flow through a marine propulsor was experimentally modeled using a large cascade configuration with six 33 cm chord flat plates spanning the entire height of the test section in the Virginia Tech Stability Wind Tunnel. Three-component hot-wire velocity measurements were obtained ahead, throughout and behind both an unstaggered and a 35º staggered cascade configuration with blade spacing and onset turbulence integral scales on the order of the chord. This provided a much needed data-set of much larger Taylor Reynolds number than previous related studies and allowed a thorough investigation of the blade-blocking effects of the cascade on the incident turbulent field.
In order to generate the large scale turbulence needed for this study, a mechanically rotating â activeâ grid design was adopted and placed in the contraction of the wind tunnel at a streamwise location sufficient to cancel out the relatively large inherent low frequency anisotropy associated with this type of grid. The resulting turbulent flow is one of the largest Reynolds number (Reλ 1000) homogeneous near-isotropic turbulent flows ever created in a wind tunnel, and provided the opportunity to investigate Reynolds number effects on turbulence parameters, especially relating to inertial range dynamics. Key findings include 1) that the extent of local isotropy is solely determined by the turbulence generator and the size of the wind-tunnel that houses it; and 2) that the turbulence generator operating conditions affect the shape of the equilibrium range at fixed Taylor Reynolds number. The latter finding suggests that grid turbulence is not necessarily self-similar at a given Reynolds number independent of how it was generated.
The experimental blade-blocking data was compared to linear cascade theory and showed good qualitative agreement, especially for wavenumbers above the region of influence of the wind tunnel and turbulence generator effects. As predicted, the turbulence is permanently modified by the presence of the cascade after which it remains invariant for a significant downstream distance outside the thin viscous regions. The obtained results support the claim that Rapid Distortion Theory (RDT) is capable of providing reasonable estimates of the flow behind the cascade even though the experimental conditions lie far outside the predicted region of validity.Ph. D.
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Parkhe, Vineet. "A Parametric Study on Flow Over a Flat Plate with Microblowing." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1258390482.
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Kral, Linda Dee. "Numerical investigation of transition control of a flat plate boundary layer." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184621.
Full textAbstract:
A numerical model has been developed for investigating boundary layer transition control for a three-dimensional flat plate boundary layer. Control of a periodically forced boundary layer in an incompressible fluid is studied using surface heating techniques. The spatially evolving boundary layer is simulated. The Navier-Stokes and energy equations are integrated using a fully implicit finite difference/spectral method. The Navier-Stokes equations are in vorticity-velocity form and are coupled with the energy equation through the viscosity dependence on temperature. Both passive and active methods of control by surface heating are investigated. In passive methods of control, wall heating is employed to alter the stability characteristics of the mean flow. Both uniform and nonuniform surface temperature distributions are studied. In the active control investigations, temperature perturbations are introduced locally along finite heater strips to directly attenuate the instability waves in the flow. A feedback control loop is employed in which a downstream sensor is used to monitor wall shear stress fluctuations. Passive control of small amplitude two-dimensional Tollmien-Schlichting waves and three-dimensional oblique waves are numerically simulated with both uniform and nonuniform passive heating applied. Strong reductions in both amplitude levels and amplification rates are achieved. Active control of small amplitude two-dimensional and three-dimensional disturbances is also numerically simulated. With proper phase control, in phase reinforcement and out of phase attenuation is demonstrated. A receptivity study is performed to study how localized temperature perturbations are generated into Tollmien-Schlichting waves. It is shown that narrow heater strips are more receptive in that they maximize the amplitude level of the disturbances in the flow. It is also found that the local temperature fluctuations cause mainly a strong normal gradient in spanwise vorticity. Control of the early stages of the nonlinear breakdown process is also investigated. Uniform passive control is applied to both the fundamental and sub-harmonic routes to turbulence. A strong reduction in amplitude levels and growth rates results. In particular, the three-dimensional growth rates are significantly reduced below the uncontrolled levels. Active control of the fundamental breakdown process is also numerically simulated. Control is achieved using either a two-dimensional or three-dimensional control input.
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Dratler, David Ira. "Numerical investigation of laminar-turbulent transition in a flat-plate wake." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/184965.
Full textAbstract:
Laminar-turbulent transition of high-deficit flat plate wakes is investigated by direct numerical simulations using the complete Naver-Stokes equations. The simulations are based on a spatial model so that both the base flow and the disturbance flow can develop in the downstream direction. The Navier-Stokes equations are used in a vorticity-velocity form and are solved using a combination of finite-difference and spectral approximations. Fourier series are used in the spanwise direction. Second-order finite-differences are used to approximate the spatial derivatives in the streamwise and transverse directions. For the temporal discretization, a combination of ADI, Crank-Nicolson, and Adams-Bashforth methods is employed. The discretized velocity equations are solved using fast Helmholtz solvers. Code validation is accomplished by comparison of the numerical results to both linear stability theory and to experiments. Calculations of two- and/or three-dimensional sinuous mode disturbances in the wake of a flat plate are undertaken. For calculations of two-dimensional disturbances, the wake is forced at an amplitude level so that nonlinear disturbance development may be observed. In addition, the forcing amplitude is varied in order to determine its effect on the disturbance behavior. To investigate the onset of three-dimensionality, the wake is forced with a small-amplitude three-dimensional disturbance and a larger amplitude two-dimensional disturbance. The two-dimensional forcing amplitude is varied in order to determine its influence on the three-dimensional flow field. Two-dimensional disturbances are observed to grow exponentially at small amplitude levels. At higher amplitude levels, nonlinear effects become important and the disturbances saturate. The saturation of the fundamental disturbance appears to be related to the stability characteristics of the mean flow. Larger forcing amplitudes result in the earlier onset of nonlinear effects and saturation. At large amplitude levels, a Karman vortex street pattern develops. When the wake is forced with both two- and three-dimensional disturbances, strong interactions between these disturbances is observed. The saturation of the two-dimensional disturbance causes the three-dimensional disturbance to saturate. However, this is followed by a resumption of strong three-dimensional growth that may be due to a secondary instability mechanism. Larger two-dimensional forcing amplitudes accelerate the saturation of the two-dimensional and three-dimensional disturbances as well as accelerate the resumption of strong three-dimensional growth. These interactions also result in complicated distributions of vorticity and in a significant increase in the wake width.
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Meitz, Hubert Lorenz 1964. "Numerical investigation of suction in a transitional flat-plate boundary layer." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282209.
Full textAbstract:
Direct Numerical Simulations (DMS) of the incompressible Navier-Stokes equations are used to investigate the effect of wall suction on transition in a flat-plate boundary layer. The Navier-Stokes equations are cast in vorticity-velocity formulation. The streamwise and wall-normal derivatives are discretized with compact differences, with a pseudospectral treatment of the spanwise derivatives. Two different methods are used for the time integration. In most calculations, an explicit four-stage Runge Kutta method is used. In some cases, a semi-implicit combination of a three-stage Runge-Kutta- and a Crank-Nicolson method is used. Several case studies are performed. The first case treats the effect of a single row of suction holes, aligned in the spanwise direction, on the evolution of a Tollmien-Schlichting wave. It is found that suction through small holes leads to noticeable nonlinear effects on disturbances with large spanwise wavenumbers. The effect of suction on secondary instability with regards to a large-amplitude Tollmien-Schlichting wave is investigated in the second case study. The suction configurations here are a permeable wall, spanwise slots, and streamwise slots. It is found that sufficiently strong suction suppresses the secondary instability. The different suction configurations are equally effective. The role of the Klebanoff-mode in boundary layer transition is the subject of the third case study. A numerical model of the Klebanoff-mode is presented that agrees well with experimental observations. It is shown how the interaction between the Klebanoff-mode and a Tollmien-Schlichting wave can cause transition. Wall suction is found to be an effective means to prevent transition and maintain laminar flow even in the presence of high-amplitude Klebanoff-mode fluctuations. In the last case study, the limit of very strong suction through holes is investigated. It is shown how the suction holes generate streamwise vortices that can become unstable and lead to bypass transition.
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Munich, Chad Thomas. "Modeling of the Thermal Output of a Flat Plate Solar Collector." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/293541.
Full textAbstract:
Traditionally, energy capture by non-concentrating solar collectors is calculated using the Hottel-Whillier Equation (HW): Q(u)=A(c)*F(r)*S-A(c)*F(r)*U(l)*(T(fi)-Tₐ), or its derivative: Q(u)=A(c)*F(r)*S-A(c)*F(r)*U(l)*((T(fi)-T(fo))/2-Tₐ). In these models, the rate of energy capture is based on the collector's aperture area (A(c)), collector heat removal factor (F(r)), absorbed solar radiation (S), collector overall heat loss coefficient (U(l)), inlet fluid temperature (T(fi)) and ambient air temperature (Tₐ). However real-world testing showed that these equations could potentially show significant errors during non-ideal solar and environmental conditions. It also predicts that when T(fi)-Tₐ equals zero, the energy lost convectively is zero. An improved model was tested: Q(u)=A(c)F(r)S-A(c)U(l)((T(fo)-T(fi))/(ln(T(fo)/T(fi)))-Tₐ) where T(fo) is the exit fluid temperature. Individual variables and coefficients were analyzed for all versions of the equation using linear analysis methods, statistical stepwise linear regression, F-Test, and Variance analysis, to determine their importance in the equation, as well as identify alternate methods of calculated collector coefficient modeling.
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Grassie, Tom. "Optimisation of fluid-flow in a flat plate solar water heater." Thesis, Edinburgh Napier University, 2001. http://researchrepository.napier.ac.uk/Output/3862.
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Featherston, Carol. "Buckling of flat plates and cylindrical panels under complex load cases." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390476.
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Nalis, Amrizal. "Quasi-Dynamic Characterization of Hybrid Photovoltaic/Thermal (PV/T) Flat-Plate Collectors." Doctoral thesis, Universitat de Lleida, 2012. http://hdl.handle.net/10803/84100.
Full textAbstract:
Un model híbrid transitòria fotovoltaic / tèrmic ha estat desenvolupat i validat experimentalment. La metodologia s'estén el model tèrmic quasi-dinàmica s'indica a la norma EN 12975 per involucrar el rendiment elèctric i estudiar el comportament dinàmic minimitzar les limitacions de l'hora de caracteritzar el col • lector. Una es mou cap enrere procediment mitjà de filtrat s'ha aplicat per millorar la resposta del model de condicions de treball variables. Quant a la part elèctrica, el model inclou les dependències tèrmiques i la radiació en les seves variables. Els resultats van revelar que els paràmetres característics inclosos en el model raonablement d'acord amb els valors experimentals obtinguts de la norma d'estat estacionari i els mesuraments de la corba característica IV. Després d'un procés de calibració del model proposat és una eina adequada per predir el comportament tèrmic i elèctric d'un col • lector solar híbrida, per un temps determinat conjunt de dades.A hybrid photovoltaic/thermal transient model has been developed and validated experimentally. The methodology extends the quasi-dynamic thermal model stated in the EN 12975 to involve the electrical performance and to consider the dynamic behaviour minimising constraints when characterising the collector. A backward moving average filtering procedure has been applied to improve the model response for variable working conditions. Concerning the electrical part, the model includes the thermal and radiation dependences in its variables. The results revealed that the characteristic parameters included in the model reasonably agree with the experimental values obtained from standard steady-state and IV characteristic curve measurements. After a calibration process the proposed model is a suitable tool to predict the thermal and electrical performance of a hybrid solar collector, for a specific weather data set
Se ha desarrollado un modelo dinámico para caracterizar colectores solares híbridos térmofotovoltaicos. La metodología extiende el modelo térmico estipulado en la norma EN 12975 involucrando la aportación eléctrica y estudiando el comportamiento dinámico para minimizar las restricciones a la hora de caracterizar el módulo. Se han implementado procedimientos de filtrado que mejoran la respuesta del modelo bajo condiciones variables. En cuanto a la parte eléctrica, el modelo incluye las dependencias térmicas y la radiación en sus variables. Los resultados obtenidos a partir de caracterización dinámica del colector híbrido PV/T revelaron que los parámetros característicos incluidos en el modelo concuerdan razonablemente bien con los valores experimentales obtenidos siguiendo el estándar de caracterización estacionaria, la capacidad calorífica efectiva y las mediciones de la curva característica IV. Después de un proceso de calibración, el modelo es una herramienta adecuada para predecir el comportamiento de un colector solar híbrido, para unas condiciones externas determinadas.
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Johansson, Helena. "Nocturnal cooling : Study of heat transfer from a flat-plate solar collector." Thesis, Karlstad University, Faculty of Technology and Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1523.
Full textAbstract:
This thesis investigates the possibility of using an unglazed flat-plate solar collector as a cooling radiator. The solar collector will be connected to the condenser of a heat pump and used as cooler during nighttime. Daytime the solar collector will be connected to the evaporator of the heat pump and used as heat source. The two widely differing fields of application make special demands on the solar collector. The task is given by the heat pump manufacturer Thermia and the main objective is to find out whether a solar collector should be used as a cooler or not. The performance of the solar collector under varying environmental conditions is investigated using COMSOL Multiphysics 3.3. Only the cooling properties are investigated here. The performance of the solar collector as a heat exchanger is estimated using the effectiveness-NTU method, and the solar collector is found to be a good heat exchanger at low wind speeds. The heat transfer coefficients of the convection and radiation are determined for varying temperature and wind speeds. The convective heat transfer coefficient is lowered by tubes above the absorber plate and for a high convective heat transfer rate the solar collector surface should be smooth. For a high radiative heat transfer rate the surface needs to have a high emissivity. The cooling rate is higher from a warm surface than from a cold and since no temperature change of the heat carrier is necessary the solar collector should be kept at a high temperature. To increase the cooling rate alterations need to be made to the solar collector that makes its heating performance deteriorate. A solar collector that can be used for cooling is not an efficient solar collector.
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Mehta, Sean. "Investigation of capacity fade in flat-plate rechargeable alkaline MnO₂/Zn cells." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/56584.
Full textAbstract:
The rechargeable alkaline manganese dioxide-zinc (RAM™) battery system has been difficult to commercially develop in the past due to irreversible phase formation and progressive and cumulative capacity fade. This system has many advantages however, such as low cost and environmentally sustainable materials, long shelf life, moderate energy density, and safety. A flat-plate architecture was developed and investigated in half and full-cell apparatuses with the goal of understanding and improving cumulative capacity fade in the electrolytic manganese dioxide (EMD) cathode. Two types of cathode current collectors (CCs) were developed, a thin film foil CC and an expanded metal mesh CC and used to assess the effect of various additives over 30+ cycles under various operating conditions. Conductive carbon black (Super C65) and graphite (KS44) additives were shown to improve cell performance at 15 wt. % KS44 graphite providing an electrically conductive network between adjacent EMD particles. In addition, other chemical additives (BaSO₄, Sr(OH)₂•8H₂O, Ca(OH)₂, and Bi₂O₃) were investigated at 5 wt. % with Bi₂O₃ providing a reproducible improvement over a control recipe. Mechanical stability of the cathode electrode and pressure application were significant causes of cell failure. Slow rates of discharge, and shallow depth of discharge (DOD) charge/discharge protocols reduced capacity fade by limiting electrochemically irreversible phase formation such as Mn₂O₃, Mn₃O₄, Zn₂MnO₄, and Mn(OH)₂. Analytical characterization techniques including Scanning Electron Microscopy/ Energy Dispersive X-Ray Spectroscopy (SEM/EDS), X-Ray Photoelectron Spectroscopy (XPS), Powder X-Ray Diffraction (XRD), and Potentiostatic Electrochemical Impedance Spectroscopy (PEIS) were used to provide supporting evidence indicating that the main causes of capacity fade are linked to the cathode electrode’s mechanical properties, increased cell resistance, and progressive and irreversible phase formation.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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AD, Thirumuruga, and Paramita Das. "CFD Modelling of a flat plate." Thesis, 2010. http://ethesis.nitrkl.ac.in/1901/1/thiru_proj.pdf.
Full textAbstract:
Performance of an aircraft wing depends on the smoothness of the air flow over it. Any accumulation of frost, snow or ice on the wings or other horizontal surfaces will substantially alter the lifting characteristics of the airfoil and also changes the values of aerodynamic forces exerted on the airfoil. So any small change in flow parameters could affect its performance in a larger scale. This can sometimes be disastrous too. The wings of the airplane are also susceptible to corrosion also due to the excess humidity level. When it comes to large airfoils like aircraft wings, these parameters have to be maintained perfect so that the probability of failure is minimized. The basic test surface for investigating the effects of various parameters to the underlying boundary layer is the universal flat plate. Therefore a flat plate is used for this study.
The present paper concentrates on analyzing various flow parameters of cold air while it flows over a flat plate. Modeling and analysis of the flow were performed using FLUENT, version 6.3. The results obtained are purely the simulation software based calculations.
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Wang, Pei-Kang, and 王培綱. "Flat Plate Pulsating Heat Pipe Heat Spreader." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/78471415576473642443.
Full textAbstract:
碩士國立中央大學
能源工程研究所
95
This article is trying to develop a new kind heat spreader, which were used the theory of pulsating heat pipes. Channels were manufactured on copper plate, to finish the flat plate pulsating heat pipes. When heat input, fluid makes phase changes, produce the vapor pressure difference between the evaporation area and condensation area, the major heat transfer mechanism in a pulsating heat pipe is the sensible heat of liquid. Channels arrangement designed to two types, which were single loop and double side loop. In order to understand the influence by the wide of channel, there are two kinds of channel size, which wide were 0.5 mm and 1 mm. In this article, also experiment three fill rate, which were 20 %、50 % and 80 %. The heat transfer characteristics of flat plat pulsating heat pipes were investigated experimentally. The experimental results at the same input heat and same fill rate, the single loop design which heat transfer performance better than the double side loop. When fix the fill rate as 50 %, the minimum heating power is 15 W at 1 mm wide channel, 20 W at 0.5 mm wide channel. In the experiment of different fill rate, when fill rate 20 %, pulsation only occurs at heating power 15 W, as the heating power increase, pulsation stop. Also found that the optimal fill rate is around 50 % and 80 %. The drag force which caused by the channel walls will decrease the liquidity, also decrease the range of pulsation. In order to decrease the spreading resistance, we should make the design of channel better.
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Liu, Houn-Ta, and 劉宏達. "Examination of Contact Position of Flat Plate." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/93654630296388817019.
Full textAbstract:
碩士正修科技大學
機電工程研究所
98
In recent years, the use of touch panels becomes more and more popular. To fit the needs of the different products, the touch technology developed different types of touch screens. The touch screen monitors in the market either produce resistance, capacitance effect or block sensor signals through the touch of the fingers or the touch pen and the touch panels in the market is not suitable in a vicious environment. This study attempts to design a panel that can identify the location through the theory of vibration. This study applied the PVDF piezoelectric thin film to manufacture strain sensors and the PVDF piezoelectric thin film was glued on the four corners of the glass plate which was divided into 25 cells and with a length of 50 cm, width of 50 cm and thickness of 0.5 cm. The vibration signal is received by impacting the panel and the oscilloscope is then connected to the computer. After the oscilloscope received the data, the data were directly saved in the computer through the operation of the computer. Last, the computation and analysis derived using Visual C++ is used to differentiate the impact location. The result of this experiment showed that the algorithm used in this study can accurately detect the impact location using the glass plate that is divided into 25 cells.
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Juh, Lin Three, and 林燦柱. "A Study on Metal Plate Flat Rolling." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/90625688826081896199.
Full textAbstract:
碩士大葉大學
機械工程研究所
87
ABSTRACT This paper discussed the stress distribution of contact arc between roller and strip when the cold rolling is forming. After discussing, analyzing and comparing the existing research paper, the authors try to find a more reasonable math formula. In addition to the deformation of roller and the characteristic of plasticity stiffness body's work hardening, the authors discuss further about the influence that the tension stress of strip has on the stress S distribution of rolling. The numerical analysis methods that are used to solve the distribution of normal rolling force S in this paper are fourth-order Runge-Kutta integral, Simpson's integral and Trapez integral. According to the result of research, in the coordinate of the normal stress of roller and contact arc, the neutral point of the curve will become small and move to exit when the roller takes the behind pulling force. Because of the pulling force, there is enough energy for the plasticity deformation of the strip. It can mitigate the force on the roller. If the roller takes froward pulling force, the neutral point of the curve will become small and move to the entrance. Therefore, the neutral point will move more forward and the system will be more stable. Then, there will be better product of strip work. If there are both forward and behind pulling forces, the neutral point of the curve will decrease a lot. It means that the stress of the roller will decrease. This is the best condition. The tenure of use of the roller can lengthen and save the energy for the deformation of plasticity. Besides, the neutral point of the curve will move to the entrance of roller contact arc in the process of work hardening. So the roller strip will be more even and smooth and it is closer to the experimental data. Therefore, the consideration of work hardening is also very important. From the distribution of shear stress, we can know that the maximum of the shear stress will be on the neutral point of the curve. Furthermore, the authors will compare the result of this research with the data researched by Momati and Mcelwain, and the experimental data researched by Firband and Lancaster. This can prove that the analysis of the data matches the experimental data.
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ZHENG, MING-HE, and 鄭明和. "A vertically oscillating plate immersed in a flat-plate turbulent boundary layer." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/32614910233497174524.
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Grizzle, Joshua Peter Fletcher. "Film cooling on a flat plate: investigating density." 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2770.
Full textAbstract:
This study is an investigation of two specific effects on turbine blade film cooling. The
effect of coolant to mainstream density ratio and upstream steps was studied. The
studies were conducted on two flat plates with 4mm cylindrical film cooling holes, one
with simple angle and the other with compound angle, in a low-speed suction type wind
tunnel.
Density effect was studied at ratios of 0.93 and 1.47 by using air and CO2 as coolant. An
IR camera was used to record the temperature on the plate and T-type thermocouples
were used to record the coolant and mainstream temperatures. During the study the
nature of the conduction effect from the heated coolant was studied and found to be most
prevalent along the plate surface not through the plate from the plenum. A methodology
was presented by which conduction error free results were obtained. The results showed
an increased effectiveness at higher density ratios, particularly near the holes and for the
simple angle plate.
Upstream step effect was studied using pressure sensitive paint and a coupled strobe
light and camera. Steps of 0.5, 1 and 1.5mm were placed at the upstream edge of the
holes. The steps were found to increase effectiveness significantly more than previous
studies have shown when placing the step slightly upstream of the holes.
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Su, J. H., and 蘇瑞翔. "Impingement Cooling over a Flat Plate under Vibration." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/83943737518862233600.
Full textAbstract:
碩士國立成功大學
航空太空工程學系
88
Experiments are performed to study the effect of convectived heat transfer when the steady flow impinge on a uniform heated surface which is constant heat flux of the flat plate model. It is static or vibrating parallel to the fluid with variable excition of frequency and amplitude. Experimentally, linking with source of electric current to thin metal Ti stripes, and they are covered over the plate surface. The oscillation of the plate model is provided by the electric motor and the cam. The range of needed frequency is from 0 to 15 Hz, amplitude is 0.5, 1 and 1.5mm. The range of Reynolds number for the cross uniform flow is from 1000 to 2750 by small low-speed wind tunnel. The distribution of wall temperatures are measured by the K-Type thermocouples. According to the local and average Nusselt numbers the effect of vibrative frequency and amplitude on heat transfer from flat plate model could be analysis. Conclude the results, the more higher vibrative frequency the plate model has, the more better heat transfer efficiency on the plate surface it gets, in addition to the stagnation and the near wake region. And the more greater vibrative amplitude the plate model has, the more better heat transfer efficiency on the plate surface it gets, also in addition to the stagnation and the near wake region. In this experiments, if the proportion of distance to model''s surface is more than z/b=8，the convectived heat transfer will be no appreciable change. However, when the z/b=2, the average and stagnation point Nusselt number will be maximum. And there is more better heat transfer efficiency on the surface of plate, when the vibrative amplitude is greater to greater.
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Jung-ShunChen and 陳榮舜. "Heat transfer characteristics of flat plate heat pipe." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/sbs775.
Full textAbstract:
博士國立成功大學
工程科學系
103
The purpose of this study was to explore the heat transfer characteristics of flat plate heat pipes (FPHPs). The four parameters examined in this study were the liquid filling ratios, length, bending angles, and tilting; their effects on the heat transfer characteristics were examined experimentally. All the FPHPs were made of Al 6061 FPHPs which were filled with acetone (99.87% pure). The results showed that optimum liquid filling ratios Fr exhibited by the effective thermal resistance Rth(min) were 20.1%, 24.8%, 31.4%, and 35.1% for the length of 80 mm, 150 mm, 200 mm, and 300 mm, respectively. The effective thermal resistance Rth(min) ratios normalized by that of 80 mm FPHP were 2.4, 6.0, and 17.9 for lengths of 150 mm, 200 mm, and 300 mm, respectively. The maximum heat transport capability Qmax decreased greatly from 109.5 W to 49.6 W when length was increased from 80mm to 150 mm and then slowly decreased further to the minimum value of 35 W when the length was 300 mm. For the bending angle β from 0° to 90°, the maximum effective thermal conductivity Keff(max) increased from 1933W/mK to 6365W/mK, and the maximum heat transport capability Qmax increased from 45 W to 85 W. For the tilting angle θ from 0° to 90°, Keff(max) increased from 4561 W/mK to 5530 W/mK; whereas Rth(min) reduced from 0.22 W/K to 0.182 W/K. And the maximum heat transport capability Qmax increased from 39.7 W to 130 W. On the other hand, by tilting from 0° to -30°, the maximum heat transport capability Qmax reduced drastically to 3 W. That is, by the proper liquid filling ratio, length, bending angle and tilting angle, cooling enhancement of the FPHPs could be greatly achieved.
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Huang, Chih-Chien, and 黃之健. "A Study on Flat Plate Evacuated Solar Collector." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/72421370390178170722.
Full textAbstract:
碩士大葉大學
機械與自動化工程學系
97
When the storage of fossil fuels become less and less, the application of solar energy gets more and more important. However, the solar thermal heating systems on the market are currently costly, heavy, and bulky. This thesis introduces the design of a novel solar collector, which unites the advantages of a flat plate collector and an evacuated tube collector to form a “flat plate evacuated solar collector”. The research studies the feasibility of this kind of solar collector; the study methods include the numerical simulations of fluid flow associated with heat transfers and the experiments on a real flat plate evacuated solar collector. The results show that the efficiency of the flat plate evacuated solar collector lies between the evacuated tube collector and flat plate collector and this novel solar collector is worth further study.
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pei-sung, Tsai, and 蔡霈松. "Development of Wet-Type Flat-Plate Heat Transmitter." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/93022928113410878686.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
91
Abstract A flat-plate heat transmitter was developed to meet the requirements of high energy-dissipation rate and narrow space adaptation of modern CPU which was used in the notebook computers and other applications. A new working fluid (which was called TF-1) with differential thermodynamic properties at low and elevated temperatures was formulated to replace traditional mechanical-type capillary structure for enhancement of condensed-liquid recirculation. The geometry of the heat transmitter was appropriate for direct attaching to the square surface of the CPU and for spreading of heat to wider or off-set space so that the traditional fin-type air coolers or other liquid-cooling devices can be employed subsequently for heat removing. In order to perform this study, the vacuum system, heat-transmitter, test rig, cooling system, angle adjustment stand, test device of working fluid properties, etc., were assembled and/or manufactured in house. The experimental results showed that the benefits of using currently developed heat transmitter with the TF-1 working fluid were multiple folds. For example, the heat-transfer surface was extended so that more heat removing was possible, the temperature distribution on the base of heat-transfer surface was more uniform compared with that using the solid metal so that efficiency of subsequent heat-removing could be increased, the operation temperature at the evaporation section is low because the heat resistance was significantly decreased by about one order of magnitude at large heat dissipation rates, the critical heat dissipation rate subject to the dry-out limit was drastically extended to higher than 280W because the working fluid TF-1 never dried out under the present experimental conditions, and the capital cost was low because no mechanical capillary device was needed.
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Hsieh, Min-Jie, and 謝明婕. "Analysis of Dialysis through Flat-Plate Membrane Modules." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/32156398085560010746.
Full textAbstract:
碩士淡江大學
化學工程學系
90
A study on membrane dialysis in rectangular mass exchangers has been carried out under concurrent-flow, countercurrent-flow and cross-flow operations. It was found that mass transfer of dialysis in rectangular mass exchangers of microporous membrane can be analogous to heat transfer in rectangular heat exchangers. The separation efficiency increases with the flow rate of the retentate phase, or with the flow rate of dialysate phase, or with the ratio of the flow rate of the dialysate phase to that of the retentate phase. Under comparable conditions most solute is dialyzed in countercurrent-flow arrangement, the least in concurrent flow. However, the separation efficiencies of three flow-type devices approach one when the flow rate in the retentate phase or in the dialysate phase becomes very large. Theoretical prediction of solute concentration for the system of dialysis coupled with ultrafiltration in cross-flow membrane modules was obtained by an approximate solution and thus separation efficiencies could be calculated for various operating and design conditions. The overall mass transfer coefficient was assumed to be constant and the concentration polarization and pressure drop on both compartment were neglected in solving this problem. It was found that increasing the flow rate in retentate phase is more beneficial to the mass transfer than increasing in dialysate phase. The performance of dialysis can be improved significantly by the effect of ultrafiltration.
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Peng, Hsien-Kai, and 彭賢凱. "The Visualization of Flat Plate Pulsating Heat Pipe." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/07735348152154965157.
Full textAbstract:
碩士國立中央大學
機械工程研究所
98
This article is trying to etching manufactured pulsating heat pipes on copper plate, and design two kind of loop type channel, In this article, experiment three filling ratio 50 %, and different incline, which were 0°、30°、60° and 90°, also record vapor motion in the channel by high speed camera，and want to know different operate conditions effect to flat plate pulsating heat pipes by visualization observe. By visualization observe and thermal resistance analysis, it is found out that, with a filling ratio 50 % and incline angle 90° have optimal performance yields a thermal resistance, and the phenomenon of oscillating can observe from30°~90°, when heating rate at 45W, thermal resistance decrease 44% than heating rate at 15W. In the double loop pulsating heat pipes, thermal resistance change is unobvious with heat input. In this article we found that the flow oscillating can enhance heat transfer, but there is a critical in low incline angle.
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Chow, Kai Lee, and 周嘉莉. "The Flow Interference between Cylinder and Flat Plate." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/68090066580364723008.
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Ding, Yun. "Effective stiffness and punching failure of flat-plate structures." Thesis, 1990. http://hdl.handle.net/1911/13428.
Full textAbstract:
The existing equivalent frame methods for lateral displacement analysis of flat-plate structures are one-value stiffness models which do not reflect the realistic response of structures. Based on the experimental data, the procedure for predicting the drift response of flat-plate structures is reviewed and an approach is proposed which accounts for the changes in the stiffness during the loading history. The application of the suggested procedure is demonstrated through examples.
Punching failure in a flat-plate structure greatly changes the overall stiffness and results in moment redistribution between various members of the structure. This effect needs to be considered in the nonlinear analysis of flat-plate structures subjected to earthquake loading. A numerical procedure to account for the localized punching failure in calculating the response of flat-plate structures is developed. Furthermore, a hysteresis model suitable for slab-column connections is proposed on the basis of test results and implemented in a nonlinear dynamic analysis program.
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Wu, Tzong-Chian, and 吳宗謙. "Fabrication and Visualization of a Flat Plate Heat Pipe." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/85654078190185045565.
Full textAbstract:
碩士淡江大學
機械與機電工程學系碩士班
98
This study aims to design and fabricate a visualization flat plat heat pipe, with 0.4mm, 0.7mm and 1.0mm thick sintered copper wick structure. Three different sintering thicknesses of wicks with a series of filling ratio of deionized water were tested at heat input of 20W, 40W and 60W. Through a high-speed camera, the experiment was conducted to observe the boiling phenomenon of the evaporator in heat pipe. Evaporation resistance was evaluated from the measured temperature to analyze the parameters impact on performance. The experimental results showed that the flat plate heat pipe at the different heat input, with the different thicknesses of wicks and filling ratio, which would affect thermal performance of the module, such as temperature of heat source and evaporation resistance. At input power of 60W, the 0.4mm thick wick structure with 5% filling ratio has the lowest resistance of 0.119℃/W. Through visual observation, the liquid surface would descend when the heat flux increased, and the evaporation resistance could reach a minimum by increasing heat flux before drying out. We also found that the main reason for affecting the heat transfer mechanism is the height of working fluid inside the heat pipe. When the liquid surface is above the top of wicks, the mainly boiling mechanism is pool boiling with higher evaporation resistance, and a thin film boiling occurred with a lower resistance, when the surface is below the top of wicks.
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Lo, Chin-Chung, and 羅志忠. "Thermal Stress for Including Crack Flat Plate Characteristic Analysis." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/48188512548855936565.
Full textAbstract:
碩士國立交通大學
工學院碩士在職專班精密與自動化工程學程
93
To follow 21 century consumer market require，technology product more and more are stressing light、thin、short、small、high precision，however mobile phone、notebook、blue-tooth、digital camera、wireless module etc，have to combine every functional all in one。So can achieve high precision laser process become indispensable technology。 However heat always to cause PCB (Printer Circuit Board) and electrical component to lose efficacy main reason。This is different electronic component internal temperature not accord and package internal heat source to produce thermal stress，these thermal stress could cause substrate to emerge crack and cause destroy。 This paper purpose is use COSMOS analysis software to research thermal stress influence crack growth characteristic and analysis material crack growth forecast model。In package or system internal，integration thermal stress、thermal strain、and crack influence parameter and then analysis。As well to protect product in package process because to heat influence many problem，promote product yield and reliability。
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Chang, Yu-Hao, and 張育豪. "A Study on Dialysis in Flat-Plate Membrane Modules." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/73050755987985016860.
Full textAbstract:
碩士淡江大學
化學工程與材料工程學系
92
The mass transfer for membrane dialysis through a flat-plate module has been studied theoretically for single-pass and double-pass operations, analogous to heat transfer in a flat-plate heat exchanger. Experiments were carried out with the membrane sheet made of cellulose ester as a permeable barrier to dialyze urea from aqueous solution in a single-pass device. Theoretical predictions are in good agreement with the experimental results. Contrast a single-pass parallel-plate membrane channel, the improvement in mass transfer is obtainable if dialysis is operated in a double-pass device of same size which provides the increase of fluid velocity, resulting in reduced the mass-transfer resistance.
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Chang, Tsai Meng, and 蔡孟昌. "Flat Plate Heat Pipe for Cooling of Notebook Computer." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/33804823773703198678.
Full textAbstract:
碩士淡江大學
機械與機電工程學系
92
IC industry is one of Taiwan industries gaining strong global competitiveness. With increasing functions of electrical manufactures, we need advanced cooling systems to solve the high temperature problems resulted from interior concentrative power consumption of electric device. The available fan-heat sink mechanism will be certainly not satisfying with the cooling requirement of prospective electric devices. So we bring up the study of Flat Plate Loop Heat Pipe (FPLHP) utilizing the phase change phenomenon to enhance cooling ability. In this study, FPLHP consisting of an evaporator, vapor line, air condenser, and liquid line was fabricated and characterized. Evaporator with comb grooves and copper mesh is a novel design to increase capillary pumping capacity. FPLHP were realized by bonding a glass onto copper substrate, resulting in a transparent cover for observation. Methanol, Water, and Freon (HCFC 141b) were used as the working fluid in the experiment. Preliminary result showed that FPLHP filled with methanol could dissipate heat more than 68W. Under air cooling the total thermal resistance of such a system is 1.3 °C/W and depends strongly on the cooling conditions and the radiator efficiency. Research work is continuing for the heat transfer limitation, different fluid charge rate and optimization of the FPLHP size design in an effort to improve the cooling performance of the notebook computer.