Dissertations / Theses on the topic 'Horizontal convection'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Horizontal convection.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
Chiu-Webster, Sunny. "Horizontal convection and glass furnaces." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611923.
Full textKerr, O. S. "Horizontal effects in double-diffusive convection." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380229.
Full textJansen, Adrian J. "Natural convection above a horizontal heat source." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from the National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA267212.
Full textHort, Matthew C. "Transient natural convection within horizontal cylindrical enclosures." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313250.
Full textGrine, K. "Free convection problems from a semi-infinite horizontal plate." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383889.
Full textAli, Hafiz-Muhummad. "Free-convection condensation on single horizontal pin-fin tubes." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/2322.
Full textDyko, Mark P. "Three-dimensional buoyancy-driven convection in horizontal cylindrical annuli /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486402288261566.
Full textStraneo, Fiammetta. "Dynamics of rotating convection including a horizontal stratification and wind /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10996.
Full textLagana, Anthony. "Mixed convection heat transfer in vertical, horizontal, and inclined pipes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq29607.pdf.
Full textLagana, Anthony. "Mixed convection heat transfer in vertical, horizontal, and inclined pipes." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27234.
Full textAn innovative design allows, for the first time, flow visualization over the entire heated portion of the test section. The key element of this design is a thin, electrically conductive gold-film heater suitably attached to the outside surface of a plexiglas pipe: the gold film is approximately 80% transparent to electromagnetic radiation in the visible wavelength band. This test section was mounted inside a transparent vacuum chamber to insulate it from the environment. A dye injection technique was used to visualize the mixed-convection flow patterns. The apparatus was also designed and instrumented to allow the measurement of both circumferential and axial temperature variations over the heated tube.
The flow-visualization results revealed the following: (i) a steady recirculating flow pattern, followed by laminar flow instability in vertical tubes; (ii) steady spiralling flow patterns in inclined and horizontal tubes, that confirmed earlier numerical predictions. The temperature results agreed qualitatively with earlier published experimental and numerical data. Local and overall Nusselt numbers can be calculated using the data presented, but this is not within the scope of this thesis.
Blasick, Ann Marie. "Onset of flow instability in heated horizontal annuli." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19538.
Full textMURRAY, BRUCE THOMAS. "EXPERIMENTAL AND NUMERICAL INVESTIGATION OF DOUBLE-DIFFUSIVE CONVECTION IN A HORIZONTAL LAYER OF POROUS MEDIUM." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183899.
Full textStone, Rebecca E. "Entrainment, detrainment, and large-scale horizontal gradients in oceanic deep convection." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA367100.
Full text"June 1999". Dissertation supervisor(s): Roland W. Garwood. Includes bibliographical references (p. 63-67). Also available online.
Barozzi, Giovanni Sebastiano. "Combined convection and other effects in heat transfer in horizontal flows." Thesis, City, University of London, 1993. http://openaccess.city.ac.uk/16971/.
Full textBorjini, Mohamed Naceur. "Etude numérique du couplage rayonnement-convection naturelle d'un espace annulaire d'axe horizontal." Perpignan, 1998. http://www.theses.fr/1998PERP0316.
Full textWang, Chong-Sheng. "Laminar natural convection heat transfer from isothermal horizontal cylinders with annular fins." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0011/NQ30657.pdf.
Full textBentley, Jonathan Foy. "Evolution of natural convection in a horizontal cylinder with different end temperatures." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/18184.
Full textTsitsopoulos, Vasileios. "Modelling of buoyant flows associated with large area fires and indirect free convection." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/modelling-of-buoyant-flows-associated-with-large-area-fires-and-indirect-free-convection(7e849d5b-6b95-4534-b387-63387f5ff26f).html.
Full textAbid-David, Chérifa. "La convection mixte dans un conduit horizontal : instabilités thermiques dans la transition "laminaire-turbulent"." Aix-Marseille 1, 1993. http://www.theses.fr/1993AIX11007.
Full textSteffen, Elizabeth Laird. "Observations of vertical and horizontal aspects of deep convection in the Labrador Sea by fully Lagrangian floats /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/11028.
Full textBarbosa, Saldana Juan Gabriel. "Numerical simualtion of mixed convection over a three-dimensional horizontal backward-facing step." Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/2353.
Full textKuo, Hai-perng. "Stability and finite amplitude natural convection in a shallow cavity with horizontal heating /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487265143146491.
Full textKukrer, Cenk Evren. "Direct Numerical Simulation Of Liquid Flow In A Horizontal Microchannel." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606495/index.pdf.
Full textChaengbamrung, Apichart. "Turbulent plumes generated by a horizontal area source of buoyancy." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060227.102144/index.html.
Full textWangdhamkoom, Panitan. "Characteristics of multimode heat transfer in a differentially-heated horizontal rectangular duct." Thesis, Curtin University, 2007. http://hdl.handle.net/20.500.11937/1007.
Full textHickey, Christopher N. "Natural convection from a horizontal heater in response to steady and pulsatile input powers." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23977.
Full textU-Cheul, Shin. "Etude théorique de la convection naturelle thermique à l'interieur d'une calotte cylindrique d'axe horizontal." Perpignan, 1993. http://www.theses.fr/1993PERP0144.
Full textVaux, Samuel. "Etude numérique des instabilités hydrodynamiques dans un cylindre soumis à un gradient horizontal de température." Ecully, Ecole centrale de Lyon, 2004. http://www.theses.fr/2004ECDL0029.
Full textDuring crystal growth processes, the control of the hydrodynamic instabilities in the melt is primordial in order to obtain good quality crystals. In this thesis, we study by direct numerical simulation (D. N. S. ) natural convection in a laterally heated horizontal cylinder. We consider different low Prandtl number liquid metals and different aspect ratio cylinders. We then study the appearance of the oscillatory instability determining its threshold, nature, the characteristics of its structure and its origin by energetic analysis. The use of Proper Orthogonal Decompostion (P. O. D. ) allows the extraction of the principal modes of the flow and important features of the dynamic of the system
Varrall, Kevin. "Etude expérimentale de l'écoulement de convection mixte à travers un orifice horizontal reliant deux compartiments." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4314/document.
Full textTo answer to building issues and fire safety challenges, this thesis deals with the mixed convection flow through a horizontal orifice linking two compartments. The aim is to improve the understanding and modeling of the exchange of variable density gas through the opening. A small scale experimental study and a theoretical approach are proposed.The study is first focussed on the impact of the geometrical ratio L/D of the opening on the exchanged flow rate variation for free convection regime. Non-intrusive measurements of these flow rates, via the tracking of the interface between two non miscible liquids in an isothermal approach, and thanks to the SPIV in a thermal approach, permit to describe the bidirectional exchange process and to consolidate existing correlations.Experiments in mixed convection regime aim to study the impact of mechanical ventilation (in blowing and extracting mode) on the exchanged flow rates. The comparison between existing correlations and experimental data shows large differences. A change making the coorelation of Cooper 89 more accurate is proposed. A theoretical approach from the simplified Navier Stokes equations and with the Boussinesq approximation permits to discuss the construction of existing correlations. From this theory, a model more accurate than those available in the literature is proposed thanks to an adjustment of discharge coefficients from experimental data
Yu, Youmin. "The Effects of Gravity Modulation on The Instability of Double-Diffusive Convection in a Horizontal Tank." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195265.
Full textStoddard, Ryan Manse. "Onset of flow instability and critical heat flux in horizontal, thin, uniformly-heated annuli." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17135.
Full textFritzgerald, Claire Louise. "Forced-convection condensation heat-transfer on horizontal integral-fin tubes including effects of liquid retention." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/2353.
Full textHung, Ming-Cheng. "Transitions in convection of a low Prandtl number fluid driven by a horizontal temperature gradient /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487668215807295.
Full textWangdhamkoom, Panitan. "Characteristics of multimode heat transfer in a differentially-heated horizontal rectangular duct." Curtin University of Technology, Department of Mechanical Engineering, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17353.
Full textMouhtadi, Driss. "Etude numérique de la convection naturelle thermique engendrée par des blocs générant de la chaleur dans un canal horizontal et dans une géométrie cubique." Thesis, Cergy-Pontoise, 2012. http://www.theses.fr/2012CERG0564/document.
Full textThe object of this work is to study the details of the flow and heat transfer induced by natural convection in a channel (2D simulation) and in a cubic cavity (3D simulation) containing heating blocks. The heat released by the blocks results from a uniform volumetric heat generation, a constant hot temperature or a uniform surface flux. Air (Pr=0.72) is used as working fluid. The parameters of the study are the thermal conductivities ratio of solid blocks and fluid (0.1≤k*≤200), the Rayleigh number (〖10〗^4≤Ra≤〖10〗^7) and the relative height of the blocks (1/8≤B≤1/2). Among the main objects of this work is the determination of the conditions of validity of the model with isothermal blocks and the model with blocks releasing a uniform surface flux, as functions of the thermal conductivities ratio and the other parameters of the problem. The results obtained show that the flow and heat transfer and the conditions of validity of the models mentioned are strongly affected by the control parameters and the multiplicity of solutions found in the convective regime
Begum, Latifa. "Natural and mixed convection in a horizontal cylindrical annulus with and without fins on inner cylinder." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112556.
Full textOzdemir, Mehmet Ozan. "Optimum Design Of Parallel, Horizontal And Laminar Forced Convection Air-cooled Rectangular Channels With Insulated Lateral Surfaces." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610710/index.pdf.
Full textDoder, Dejan. "Experimental analysis of the pressure characteristic curve of a forced convection boiling flow in single horizontal channel." Thesis, Norges Teknisk-Naturvitenskaplige Universitet, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20917.
Full textMemory, Stephen B., Vance Hiro Adams, and P. J. Marto. "Theoretical study of laminar film condensation on horizontal elliptical tubes under conditions of free and forced convection." Thesis, Monterey, California: Naval Postgraduate School, 1993. http://hdl.handle.net/10945/24236.
Full textPetrone, Giuseppe. "Etude numérique des écoulements de convection naturelle et mixte dans un espace annulaire horizontal : approche par analyse de stabilité linéaire." Marne-la-Vallée, 2004. http://www.theses.fr/2004MARN0225.
Full text"Experimental studies of Rayleigh-Bénard convection and horizontal convection." 2013. http://library.cuhk.edu.hk/record=b6115868.
Full text論文的第二部分對另外一種重要的熱對流系統,水平對流,進行了實驗研究。在加熱和冷卻位于系統上邊界同一高度的條件下,我們觀測到了一個貫穿整個對流槽的大尺度環流。通過染料示蹤表明,流場中的迴流并不一定需要損耗能量來跨越溫度邊界層,因此可以更有效地維持其流動強度。對於熱傳輸效率以及溫度邊界層厚度隨瑞利數的變化關係,實驗觀測到了一個0.3的標度律,不同于經常被報道的理論值(0.2),這可能是因為在高瑞利數下流動狀態發生了轉變。本研究的结果表明,表面温度梯度不仅可以驱动大尺度环流,而且其強度也比人们普遍认为的要强。
This thesis consists of two self-contained parts, both related to the topic of thermal convection.
In the first part, two sets of studies on turbulent Rayleigh-Bénard convection are presented.
The first study addresses the confinement effects on the heat transport and flow dynamics in quasi-2D geometry. The experiments were conducted in five rectangular cells with the same height and length, while the width being varied to produce a lateral aspect ratio Γ ranging from 0.6 to 0.1. As expected, with decreasing Γ, i.e. increasing the level of confinement, the overall flow slows down and more plumes travel through the bulk region, thus resulting in a large-scale circulation with more frequent reversals. Surprisingly, despite a slower flow, the global heat transport efficiency enhances significantly. Detailed examinations from experiment and simulation show that this enhancement is brought about by the changes in the dynamics and morphology of the thermal plumes in the boundary layers: the confined geometry produces more coherent and energetic plume clusters that in turn result in more uniform and thinner thermal boundary layers. This study demonstrates how changes in turbulent bulk flow can influence the boundary layer dynamics and shows that the quasi-2D geometry is very different from the true 2D and also the 3D systems.
The second study investigates the influence of thermal boundary conditions. Two experimentally achievable configurations are examined; one is fixed-flux at the bottom boundary and fixed-temperature at the top (HC cell), while the other is fixed-temperature at both boundaries (CC cell). It is found that, rather surprisingly, the Rayleigh number dependence of the thermal boundary layer thickness follows a 1/3 power law approximately under the condition of constant temperature, in contrast to the behavior in the case of constant flux (close to a 2/7 scaling). It is further found that the flow strength is on average ∼ 9% larger in the CC cell, and its flow reversal frequency is ∼ 1.5 faster than that for the HC case, which may be understood as changes in the plume emission dynamics.
The second part deals with horizontal convection. The experiment was conducted with a long apparatus (∼ 2.4 m) with the heating and cooling imposed over the top boundary. Flow visualization studies revealed a full penetrating circulation and suggest that the returning flow does not necessarily overcome the stratification to penetrate the entire thermal BL, in such a way that it can “save its kinematic energy thus supports the motion more efficiently. Both the heat transport efficiency and thermal BL thicknesses are found to follow a 0.3 power law, in contrast to the often-reported value of 0.2. This is likely caused by a flow-regime transition in the high Ra number range. This study demonstrates experimentally that a surface temperature gradient is capable of driving a large-scale circulation and its strength is much stronger than what is generally believed by the oceanography community.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Huang, Shidi = 瑞利-伯納德對流及水平對流的實驗研究 / 黃仕迪.
Thesis (Ph.D.) Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 97-110).
Abstracts also in Chinese.
Huang, Shidi = Ruili-Bonade dui liu ji shui ping dui liu de shi yan yan jiu / Huang Shidi.
Narambhatla, Sambamurthy *. "Conjugate Natural Convection In Horizontal Annuli." Thesis, 2004. http://etd.iisc.ernet.in/handle/2005/1236.
Full textSHI, CHONG-GUANG, and 施重光. "Mixed convection and thermophoresis in a horizontal circular tube." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/24958376569282124710.
Full text國立成功大學
航空太空工程研究所
80
MCVD製程是目前製造光纖的方法中最廣為採用的方法,其製造成本與反應氣體反應後 所產生之粒子的堆積效率有關,如何提高粒子堆積效率是本文探討的課題所在。 本文以雷射光束加熱-旋轉圓管,改變雷射強度及電射光束寬度,以及電射的中心位 置,並考慮流場高溫時所不能忽略的熱輻射效應。在沒有電射加熱時,探討圓管轉速 、入口速度、入口溫度對流場、溫度場和粒子濃度場之影響,尋求一較佳的粒子堆積 效的狀況。 對圓管旋轉時,在θ方向引入強制對流,使得浮力效應對二次流的影響較小,當轉速 為60rpm 和120rpm時溫度場變化不大。當轉速提高為300rpm時,溫度場趨向對稱,使 得管壁附近的溫度梯度減小,故粒子堆積效率較低。 以雷射光束加熱流場時,雷射強度越大,流場溫度越高,有助於提高粒子堆積效率, 並且存在一最佳的雷射光束分佈,而獲得最高的粒子堆積效率。當雷射光束分佈不是 十分集中時,雷射中心在管中央時有較高的粒子堆積效率;當雷射光束分佈十分集中 時,雷射中心位於圓管底端時粒子堆積效率較高。考慮熱輻射時,流場的溫度分佈較 為平緩,粒子堆積效率也會降低。
Chen, Li-Sun, and 陳立山. "Experimental Investigation of Natural Convection Over a Horizontal Plate." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/53151605671856037485.
Full textLee, Wei Yi, and 李唯溢. "Parametric Study on Natural Convection from Horizontal Finned Tubes." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/72974438074859140720.
Full text林志傑. "Three-Dimensional Mixed Convection betwen Two Horizontal Eccentric Cylinders." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/84203473063407501113.
Full text國立成功大學
航空太空工程學系
87
Placing the power cable underground is an engineering tendency in the present days, especially in city areas and industrial zones. The constant heat flux is generated from the electrical resistance of the power cable which lies on the bottom of the conduit, while the concrete wall is adiabatic. This configuration does not permit of steady-state solution of a two-dimensional case. Many theoretical and experimental studies on natural convection in horizontal, eccentric annuli have been carried out. In most of these studies, a two-dimensional model was used in which the annuli were assumed to be coupled with thermal boundary conditions on the cylinder surfaces specified as either with two constant wall temperatures or one with constant wall temperature while the other with constant wall heat flux (including adiabatic surface). A comprehensive literature survey revealed that published work is largely nonexistent on the three-dimensional eccentric annuli between two horizontal cylinders, where their geometric configurations possess an open end. The existed three-dimensional studies on natural convection were limited to the cavity flow problem. The boundary conditions for this problem are as follows. The adiabatic condition is given on the outer cylinder (concrete conduit) surface, while a constant heat flux which is specified with the heat dissipated from the power cable is given on the inner cylinder (power cable). Due to the symmetric natural convection of the flow field with respect to the two free ends and to a vertical plane crossing the center of the cylinders, zero-gradient conditions are given there. Thus, the free end consists of inflow (fresh air) and outflow (heated air) at the same plane. This flow configuration leads to that there is no thermal fully developed field at the open end. Instead, the computational domain has to be extended into the outside environment so that the proper boundary condition can be specified. The "zonal grid" method is used to tread numerically this two-zone approach. In addition to natural convection, mixed convection is studied in this work. In mixed convection, the fluid enters the annuli at one free open end and the other one becomes the outlet plane. For a long enough axial distance in the flow field, the "fully developed" boundary conditions can be reasonably specified at the outlet plane. It is economic to use the "fully developed" boundary conditions at outlet plane as compared to the two-zone approach. The present work investigates that under what conditions (in terms of Gr/Re2 which represents the ratio of buoyant force to inertia force), the fully-developed outlet boundary conditions cab be properly used in the modeling. Effects of the eccentricity on the surface temperature distribution of the inner cylinder are also investigated in this work.
Wu, Sheng Ju, and 吳聖儒. "Wave instability and thermal convection between horizontal parallel plates." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/06748381884902768668.
Full text國立清華大學
動力機械工程學系
85
The physical mechanism of Tollmien-Schlichting wave and heat transfercharacteristic in the fully developed region between horizontal parallelplates are analysed theoretically by a direct numerical simulation. In thisinvestigation, a direct numerical scheme is developed to study the temporalamplification of a two-dimensional disturbance in plane Poiseuille flow.Transient non-linear equations are applied in a region of a wavelengthmoving with the wave propagation speed. The complex amplitude involved inthe perturbation functions is considered as the initial input of thenon-linear stability equations. The growth and decay of disturbance withtime are presented, and the neutral stability curves is in good agreementwith the existing solutions. In the subcritical regime usingfinite-amplitude approach, the neutral stability curves shift toward lowerReynolds number, and the critical conditions as a function of the initialmagnitude A0 of the disturbance is presented. The friction factor increaseswith the increase in the Reynolds number in the supercritical regime. This thesis also investigates numerically the effect of asymmetricheating on wave instability and thermal convection in a horizontal parallelplate channel. The lower plate and upper plate are at two differenttemperature levels. By the linear stability theory, the critical Reynoldsnumber decreases due to the heating of the lower plate and increases due tothe heating of the upper plate. The result of linear theory shows thevariation of critical Rec with the varying Grashof number for Pr = 0.7 and7. By using a direct numerical simulation on the amplification of a 2-Ddisturbance, the thesis also studies the flow and heat transfercharacteristics in the post-critical regime with the effect of asymmetricheating. The numerical results show the non-linear and time-periodicbehavior of the streamlines, vorticities, velocity vectors, and isotherms. Subsequently, one attempt is to explore the effect of nonlinear basictemperature distribution due to the constant wall heat flux on the wavestability. The modified Grashof number Gr* characterizes the effect ofconstant wall heat flux. Gr* > 0 indicates the heating and Gr* < 0 standsfor the cooling of the channel. The governing parameters are Gr*, Pr and Re.By the linear stability theory, the critical Reynolds number alwaysincreases with the increase in the magnitude of Gr* for both heating andcooling. The boundary condition of the wall heat flux tends to stabilize theflow. For a fixed Gr*, the effect of axial temperature gradient becomessignificant for a small Pr. The T-S wave moves upward due to expandedreverse flow near the lower plate as Gr* > 0 and moves downward due toexpanded reverse flow close to the upper plate as Gr* < 0. This means thatthe axial temperature gradient can enlarge the effect of adverse temperaturegradient in the gravitational direction. The effect of axial temperaturegradient decreases with the increase in the Reynolds number because thebuoyancy force is suppressed by the inertia force. The friction factors andthe Nusselt numbers at the upper plate and the lower plate in thepost-critical regime are exhibited.
Lir, Jihn-Tsair, and 黎進財. "Vortex Structures of Air Flow in Near Critical Natural Convection in a Horizontal Shallow Cavity and Mixed Convecton in a Horizontal Flat Duct." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/62394036230457662062.
Full text國立交通大學
機械工程系
89
The present study includes two parts. In the first part flow visualization is conducted to study the vortex flow patterns associated with the Rayleigh-Bénard convection in a horizontal shallow cavity of air. The cavity is a rectangular enclosure characterized by the aspect ratios Ax = 16 and Az = 20. Attention is focused on the convection rolls driven at slightly supercritical and subcritical buoyancies. The results show that at slightly subcritical Ra the induced vortex flow is in the form of rectangular rolls along the cavity sides and short straight parallel rolls in the cavity core. At slightly higher Ra near Rac ( = 1,708) more rectangular rolls appear and the short straight rolls in the cavity core merge together to form a serpentine roll. At slightly supercritical buoyancy with 2000 £ Ra £ 3,000 the entire cavity is filled with the straight rolls all parallel to the short sides of the cavity. At an even higher Ra of 4,000 the vortex rolls become irregular and time dependent. Moreover, the processes through which various vortex flow structures evolve during the transient stage are shown to be rather complicate and the vortex flow patterns during the flow formation are significantly affected by the heating rate in raising the buoyancy force. Furthermore, the wavenumber reduction at higher Ra for the parallel vortex roll pattern was noted to mainly result from the splitting of some rectangular rolls into cells and the subsequent merging of the cells into bigger rolls at the intermediate stage of the flow formation. In the second part of the study, combined experimental flow visualization and temperature measurement are carried out to investigate the spatial and temporal structure of the buoyancy driven vortex flow in a mixed convective air flow through a bottom heated horizontal flat duct. Particular attention is paid to the flow at a very low Reynolds number for 1.0 £ Re £ 5.0 and low Rayleigh number for 1,200 £ Ra £ 4,000. Here the possible presence of any vortex flow at subcritical Rayleigh number is also studied. The experiment is conducted in an open loop mixed convection apparatus by choosing a high aspect ratio rectangular duct ( A = 16 ) as the test section. The results from the flow visualization have revealed four new vortex flow patterns in addition to the oftenly seen patterns — longitudinal rolls (L rolls), moving transverse rolls (T rolls), and mixed longitudinal and transverse rolls (M rolls). The newly observed vortex flow patterns include stable longitudinal rolls along with nonperiodic traversing transverse waves, mixed longitudinal and transverse rolls as well as irregular cells, stable stationary transverse rolls in the duct entry and stable longitudinal rolls in the downstream, and U-rolls. The later two vortex patterns are only noted at Re = 1.0. Moreover, steady longitudinal rolls, nonperiodic traversing transverse waves and stationary inlet transverse rolls are induced even at subcritical Rayleigh number. The temporal and spatial characteristics of the new vortex flows are inspected in detail. The buoyancy driven flow formation processes resulting in various vortex flow structures are also investigated here. Many complicate processes during the vortex flow formation are noted, such as the generation of the L and T rolls, merging of L and T rolls to form U-rolls, splitting of rolls into cells and the reverse process of cell integration into rolls, aside from the moving of T rolls, roll bending and degeneration of T rolls. Moreover, the flow formation processes leading to the two new vortex flow structures are also examined carefully. Furthermore, a correlation is given to estimate the local onset locations of the longitudinal rolls. Meanwhile, the oscillation frequency and convection speeds of the transverse rolls are correlated from the present data. Finally, a flow regime map is provided to delineate various vortex flow structures observed in this study at the slightly supercritical and subcritical buoyancies.
Shaija, A. "Laminar Conjugate Natural Convection And Surface Radiation In Horizontal Annuli." Thesis, 2008. http://hdl.handle.net/2005/796.
Full textJeng, Ying-Chou, and 鄭英周. "Mixed Convection in Horizontal Rectangular Channel Heated from the Sid." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/37465435084606477793.
Full text國立成功大學
航空太空工程學系
86
Experimental studies of mixed convection flow and heat transfer in horizontal rectangular channel heated from a side have been carried out. The channel is made of two vertical parallel plates with one of the plate heated uniformly and the opposite plate well insulated. The gap between the parallel plates is small and the height to the gap ratio of the channel cross section is 6.67. Both flow visualization and the heat transfer along the heated wall are measured. The Reynolds number ranges from 316 to 1500, the buoyancy parameter, from 0 to 20000 and Pr of the airflow is 0.7. Flow structure inside the channel is visualized by injecting smoke at the inletflowing along the heated side wall. The heated buoyant flow accumulates in the upper region of the channel, which grows in size as the buoyancy parameter increases. The accumulated flow is thermally stable and has a slower motion, which can reduce the heat transfer enhancement by the buoyancy force. The effect of the Reynolds number and the buoyancy par ameter on the heat transfer is presented and discussed. The normalized Nusselt numbers are in proportion to the Buoyancy parameter. This suggests that correlations of both the local and the averaged Nusselt number in terms of the buoyancy parameter can be successful, and thus obtained.