Adrian Bejan(Editor), Allan D. Kraus (Editor). Heat transfer Handbok (776115), страница 66
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P. Hartnett, eds., McGraw-Hill, New York,Sec. 7.Kim, S. J., and Lee, S. W., eds. (1996). Air Cooling Technology for Electronic Equipment, CRCPress, Boca Raton, FL, Chap. 1.Langhaar, H. L. (1942). Steady Flow in the Transition Length of a Straight Tube, J.
Appl.Mech., 9, A55–A58.Ledezma, G., Morega, A. M., and Bejan, A. (1996). Optimal Spacing between Pin Fins withImpinging Flow, J. Heat Transfer, 118, 570–577.Lévèque, M. A. (1928). Les lois de la transmission de chaleur par convection, Ann. MinesMem. Ser., 12, 13, 201–299, 305–362, 381–415.Matos, R.
S., Vargas, J. V. C., Laursen, T. A., and Saboya, F. E. M. (2001). OptimizationStudy and Heat Transfer Comparison of Staggered Circular and Elliptic Tubes in ForcedConvection, Int. J. Heat Mass Transfer, 44, 3953–3961.Mereu, S., Sciubba, E., and Bejan, A. (1993). The Optimal Cooling of a Stack of Heat Generating Boards with Fixed Pressure Drop, Flow Rate or Pumping Power, Int. J. Heat MassTransfer, 36, 3677–3686.Moody, L. F. (1944). Friction Factors for Pipe Flow, Trans.
ASME, 66, 671–684.Nikuradse, J. (1933). Strömungsgesetze in rauhen Röhren, VDI-Forschungsh., 361, 1–22.Notter, R. H., and Sleicher, C. A. (1972). A Solution to the Turbulent Graetz Problem, III:Fully Developed and Entry Region Heat Transfer Rates, Chem. Eng. Sci., 27, 2073–2093.BOOKCOMP, Inc. — John Wiley & Sons / Page 437 / 2nd Proofs / Heat Transfer Handbook / Bejan[437], (43)Lines: 1847 to 1887———5.0pt PgVar———Short PagePgEnds: TEX[437], (43)438123456789101112131415161718192021222324252627282930313233343536373839404142434445FORCED CONVECTION: INTERNAL FLOWSPetrescu, S.
(1994). Comments on the Optimal Spacing of Parallel Plates Cooled by ForcedConvection, Int. J. Heat Mass Transfer, 37, 1283.Petukhov, B. S. (1970). Heat Transfer and Friction in Turbulent Pipe Flow with VariablePhysical Properties, Adv. Heat Transfer, 6, 503–564.Petukhov, B. S., and Kirilov, V. V. (1958). The Problem of Heat Exchange in the TurbulentFlow of Liquids in Tubes, Teploenergetika, 4(4), 63–68.Petukhov, B. S., and Popov, V. N. (1963). Theoretical Calculation of Heat Exchange in Turbulent Flow in Tubes of an Incompressible Fluid with Variable Physical Properties, HighTemp., 1(1), 69–83.Poiseuille, J.
(1840). Recherches expérimentales sur le mouvement des liquides dans les tubesde très petit diamètres, Comptes Rendus, 11, 961, 1041.Prandtl, L. (1969). Essentials of Fluid Dynamics, Blackie and Son, London, p. 117.Reichardt, H. (1951). Die Grundlagen des turbulenten Wärmeüberganges, Arch. GesamteWaermetech., 2, 129–142.Rocha, L. A. O., and Bejan, A. (2001). Geometric Optimization of Periodic Flow and HeatTransfer in a Volume Cooled by Parallel Tubes, J. Heat Transfer, 123, 233–239.Schlichting, H. (1960). Boundary Layer Theory, 4th ed., McGraw-Hill, New York, pp. 169,489.Shah, R. K., and Bhatti, M.
S. (1987). Laminar Convective Heat Transfer in Ducts, in Handbookof Single-Phase Convective Heat Transfer, S. Kakaç, R. K. Shah, and W. Aung, Wiley, NewYork, Chap. 3.Shah, R. K., and London, A. L. (1978). Laminar Flow Forced Convection in Ducts, Suppl. 1to Advances in Heat Transfer, Academic Press, New York.Sieder, E. N., and Tate, G. E. (1936). Heat Transfer and Pressure Drop of Liquids in Tubes,Ind. Eng.
Chem., 28, 1429–1436.Sparrow, E. M. (1955). Analysis of Laminar Forced Convection Heat Transfer in the EntranceRegion of Flat Rectangular Ducts, NACA-TN-3331.Stanescu, G., Fowler, A. J., and Bejan, A. (1996). The Optimal Spacing of Cylinders in FreeStream Cross-Flow Forced Convection, Int. J. Heat Mass Transfer, 39, 311–317.Stephan, K. (1959). Wärmeübertragang und Druckabfall beinichtausgebildeter Laminarströmung in Röhren und in ebenen Spalten, Chem. Ing.
Tech., 31, 773–778.BOOKCOMP, Inc. — John Wiley & Sons / Page 438 / 2nd Proofs / Heat Transfer Handbook / Bejan[Last Page][438], (44)Lines: 1887 to 1919———168.04701pt PgVar———Normal PagePgEnds: TEX[438], (44)123456789101112131415161718192021222324252627282930313233343536373839404142434445CHAPTER 6Forced Convection: External FlowsYOGENDRA JOSHIGeorge W. Woodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlanta, GeorgiaWATARU NAKAYAMA[First Page]Therm Tech InternationalKanagawa, Japan6.16.26.36.4[439], (1)IntroductionMorphology of external flow heat transferAnalysis of external flow heat transferHeat transfer from single objects in uniform flow6.4.1 High Reynolds number flow over a wedge6.4.2 Similarity transformation technique for laminar boundary layer flow6.4.3 Similarity solutions for the flat plate at uniform temperature6.4.4 Similarity solutions for a wedgeWedge flow limits6.4.5 Prandtl number effect6.4.6 Incompressible flow past a flat plate with viscous dissipation6.4.7 Integral solutions for a flat plate boundary layer with unheated starting lengthArbitrarily varying surface temperature6.4.8 Two-dimensional nonsimilar flows6.4.9 Smith–Spalding integral method6.4.10 Axisymmetric nonsimilar flows6.4.11 Heat transfer in a turbulent boundary layerAxisymmetric flowsAnalogy solutions6.4.12 Algebraic turbulence models6.4.13 Near-wall region in turbulent flow6.4.14 Analogy solutions for boundary layer flowMixed boundary conditionsThree-layer model for a “physical situation”Flat plate with an unheated starting length in turbulent flowArbitrarily varying heat fluxTurbulent Prandtl number6.4.15 Surface roughness effect6.4.16 Some empirical transport correlationsCylinder in crossflowFlow over an isothermal sphere439BOOKCOMP, Inc.
— John Wiley & Sons / Page 439 / 2nd Proofs / Heat Transfer Handbook / BejanLines: 0 to 99———2.76408pt PgVar———Normal PagePgEnds: TEX[439], (1)440123456789101112131415161718192021222324252627282930313233343536373839404142434445FORCED CONVECTION: EXTERNAL FLOWS6.5Heat transfer from arrays of objects6.5.1 Crossflow across tube banks6.5.2 Flat platesStack of parallel platesOffset strips6.6 Heat transfer from objects on a substrate6.6.1 Flush-mounted heat sources6.6.2 Two-dimensional block array6.6.3 Isolated blocks6.6.4 Block arrays6.6.5 Plate fin heat sinks6.6.6 Pin fin heat sinks6.7 Turbulent jets6.7.1 Thermal transport in jet impingement6.7.2 Submerged jetsAverage Nusselt number for single jetsAverage Nusselt number for an array of jetsFree surface jets6.8 Summary of heat transfer correlationsNomenclatureReferences6.1INTRODUCTIONThis chapter is concerned with the characterization of heat transfer and flow underforced convection, where the fluid movement past a heated object is induced by an external agent such as a fan, blower, or pump.
The set of governing equations presentedin Chapter 1 is nonlinear in general, due to the momentum advection terms, variable thermophysical properties (e.g., with temperature) and nonuniform volumetricheat generation. Solution methodologies for the governing equations are based on thenondimensional groups discussed in Section 6.3. Solutions can be obtained throughanalytical means only for a limited number of cases. Otherwise, experimental or numerical solution procedures must be employed.6.2MORPHOLOGY OF EXTERNAL FLOW HEAT TRANSFERVarious cases arise from the geometry of a heated object and the constraint imposedon the fluid flow. Figure 6.1 shows the general configuration in which it is assumedthat the body is being cooled by the flow. The heated object is an arbitrary shapeenclosed in a rectangular envelope.
The dimensions of the envelope are L, the lengthin the streamwise direction, W , the length in the cross-stream direction (the width),and H , the height. Generally, the fluid flow is constrained by the presence of boundingBOOKCOMP, Inc. — John Wiley & Sons / Page 440 / 2nd Proofs / Heat Transfer Handbook / Bejan[440], (2)Lines: 99 to 154———-2.0pt PgVar———Normal PagePgEnds: TEX[440], (2)MORPHOLOGY OF EXTERNAL FLOW HEAT TRANSFER123456789101112131415161718192021222324252627282930313233343536373839404142434445441Figure 6.1 Heated object in a flow over a bounding surface.[441], (3)Lines: 154 to 167surfaces.
The bounding surface may be a solid wall or an interface with a fluid of adifferent kind, for instance, a liquid–vapor interface.The distance sx signifies the extent of the bounding surface in the streamwisedirection, and sz is the distance to the bounding surface. When sz H or L andsz sx , the flow around the object is uniform and free of the effect of the boundingsurface. Otherwise, the object is within a boundary layer developing on a largerobject. In laboratory experiments and many types of industrial equipment, one oftenfinds a situation where the object is placed in a duct.
When the duct cross section hasdimensions comparable to the object size, the flow has a velocity distribution definedby the duct walls and the object. Hence, the foregoing relations between H, L, sx , andsz can be put into more precise forms involving the velocity and viscosity of the fluidas well. In an extreme case, the object is in contact with the bounding surface; that is,sz = 0. In such cases the flow and temperature fields are generally defined by both thebounding surface and the object.
Only in cases where the object dimensions are muchsmaller than those of the bounding surface is the external flow defined primarily bythe bounding surface.Several external flow configurations are illustrated in Fig. 6.2. The symbols usedto define the dimensions are conventionally related to the flow direction.
For the flatplate in Fig. 6.2a, is the plate length in the streamwise direction, w is the length(width) in the cross-stream direction, and t is the plate thickness. The cylinder in Fig.6.2b has length and diameter d. For the rectangular block of Fig. 6.2c, is oriented inthe streamwise direction, h is the height, and w is the width.
Sometimes, these letterscan be used as subscripts to a common symbol for the block. The sphere (Fig. 6.2d) isdefined by only one dimension, that is, the diameter d. Although an infinite numberof configurations can be conceived from the combination of external flow and objectgeometry, only a limited number of cases have been the subject of theoretical studiesas well as practical applications.
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