Adrian Bejan(Editor), Allan D. Kraus (Editor). Heat transfer Handbok (776115), страница 65
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— John Wiley & Sons / Page 430 / 2nd Proofs / Heat Transfer Handbook / Bejan10.42749pt PgVar(5.47)(5.48)[430], (36)SUMMARY OF FORCED CONVECTION RELATIONSHIPS123456789101112131415161718192021222324252627282930313233343536373839404142434445431• Staggered plates:DoptL −1/2−1/4ReL 5.4PrLb(5.50)for the range102 ≤ ReL ≤ 104Pr = 0.720.5 ≤Nb≤ 1.3L• Bundle of cylinders in cross flow:Sopt(H /D)0.52 1.59DP̃ 0.13 · Pr 0.24P̃ =∆PD 2µν(5.51)[431], (37)for the range0.72 ≤ Pr ≤ 50104 ≤ P̃ ≤ 10825 ≤H≤ 200DLines: 1478 to 1540———2.59857pt PgVarSopt(H /D)0.52 1.70 0.26DReD · Pr 0.24(5.52)TD − T∞4.50.90qD/kLWReD · Pr 0.64(5.53)———Short PagePgEnds: TEX[431], (37)withReD = U∞Dν140 ≤ ReD ≤ 14,000• Array of pin fins with impinging flow:Sopt 0.81Pr −0.25 · Re−0.32LL(5.54)for the range0.06 ≤HD≤ 0.140.28 ≤≤ 0.560.72 ≤ Pr ≤ 7LL10 ≤ ReD ≤ 70090 ≤ ReL ≤ 6000• Turbulent duct flow:Dopt /L−5/11· Be−1/114/11 = 0.071Pr1 + t/DoptBOOKCOMP, Inc.
— John Wiley & Sons / Page 431 / 2nd Proofs / Heat Transfer Handbook / Bejan(5.90)432123456789101112131415161718192021222324252627282930313233343536373839404142434445FORCED CONVECTION: INTERNAL FLOWSqmaxt −67/99k4/991+· Be47/99≤ 0.57 2 (Tmax − T0 ) PrHLWLDopt(5.91)withBe =∆PL2µαfor the range104 ≤ ReDh ≤ 106106 ≤ ReL ≤ 1081011 ≤ Be ≤ 1016• Turbulent flow and entrance lengths:[432], (38)XXT 10 DD(5.60)Lines: 1540 to 1609• Turbulent flow friction factor:−1/5f 0.046ReD———13.15723pt PgVar2 × 104 ≤ ReD ≤ 105(see Fig.
5.13)(5.68)———Normal Page* PgEnds: Eject(5.75)[432], (38)• Turbulent flow heat transfer:St · Pr 2/3 f2for Pr ≥ 0.5NuD =hD4/5= 0.023ReD · Pr 1/3k(5.76)for Pr ≥ 0.502 × 104 ≤ ReD ≤ 106NuD = 0.023ReD · Pr n4/5(5.77)where n = 0.4 for heating the fluid and n = 0.3 for cooling the fluid in the rangeL> 60D0.7 ≤ Pr ≤ 1202500 ≤ ReD ≤ 1.24 × 1054/5NuD = 0.027ReD · Pr 1/3in the rangeBOOKCOMP, Inc.
— John Wiley & Sons / Page 432 / 2nd Proofs / Heat Transfer Handbook / Bejanµµ00.14(5.78)SUMMARY OF FORCED CONVECTION RELATIONSHIPS1234567891011121314151617181920212223242526272829303132333435363738394041424344450.70 ≤ Pr ≥ 16,700433ReD ≥ 104Hereµ0 = µ(T0 )(T0 is the wall temperature)µ = µ(Tm )(Tm is the bulk temperature)NuD =(f/2)ReD · Pr(5.79a)1.07 + 900/ReD − 0.63/(1 + 10Pr) + 12.7(f/2)1/2 (Pr 2/3 − 1)NuD =(f/2)ReD · Pr1.07 + 12.7(f/2)1/2 (Pr 2/3 − 1)(5.79b)where[433], (39)0.5 ≤ Pr ≤ 104000 ≤ ReD ≤ 5 × 1066Lines: 1609 to 1688and f from Fig. 5.13.———(f/2)(ReD − 103 )PrNuD =1 + 12.7(f/2)1/2 (Pr 2/3 − 1)(5.80)where0.5 ≤ Pr ≤ 1062300 ≤ ReD ≤ 5 × 106(5.81a)where0.5 ≤ Pr ≤ 1.5104 ≤ ReD ≤ 5 × 106 0.4NuD = 0.012 Re0.87D − 280 Pr(5.81b)where1.5 ≤ Pr ≤ 500NuD =3 × 103 ≤ ReD ≤ 1060.936.3 + 0.0167Re0.85D · Prq0 = constant(5.82)4.8 +T0 = constant(5.83)0.0156Re0.85D· Pr0.93where for eqs. (5.82) and (5.83),0.004 ≤ Pr ≤ 0.1BOOKCOMP, Inc.
— John Wiley & Sons / Page 433 / 2nd Proofs / Heat Transfer Handbook / Bejan104 ≤ ReD ≤ 106———Normal PagePgEnds: TEX[433], (39)and f from Fig. 5.13. 0.4NuD = 0.0214 Re0.8D − 100 Pr0.55222pt PgVar434123456789101112131415161718192021222324252627282930313233343536373839404142434445FORCED CONVECTION: INTERNAL FLOWS• Total heat transfer rate:q = hAw ∆Tlm(5.85)• Isothermal wall:∆Tin − ∆Toutln(∆Tin /∆Tout )q = ṁcp ∆Tin 1 − e−hAw /ṁcp∆Tlm =(5.86)(5.87)• Uniform heat flux:∆Tlm = ∆Tin = ∆Tout(5.89)[434], (40)Lines: 1688 to 1776NOMENCLATURERoman Letter SymbolsAcross-sectional area, m2Awwall area, m2(a)pressure at point 1, PaBcross-section shape number, dimensionlessBeBejan number, dimensionlessblength, m(b)pressure at point 2, PaCcross-section shape factor, dimensionlesslocal skin friction coefficient, dimensionlessCf,xspecific heat at constant pressure, J/kg·KcpDspacing, diameter, mhydraulic diameter, mDhffriction factor, dimensionlessGraetz number, dimensionlessGzHheight, mhheat transfer coefficient, W/m2·Kspecific bulk enthalpy, J/kgkthermal conductivity, W/m·Ksize of sand grain, mksLflow length, mṁmass flow rate, kg/sNnumber of plate surfaces in one elemental channel,dimensionlessNuNusselt number, dimensionlesslocal Nusselt number, dimensionlessNuxBOOKCOMP, Inc.
— John Wiley & Sons / Page 434 / 2nd Proofs / Heat Transfer Handbook / Bejan———-3.56396pt PgVar———Normal PagePgEnds: TEX[434], (40)NOMENCLATURE123456789101112131415161718192021222324252627282930313233343536373839404142434445P∆PPrPr tpq rrhr0RaReDReDhReLSSttTTinToutTm∆Tavg∆Tlmuu∗UvWxx∗x+XXTyyVSLpressure, Papressure difference, dimensionlesspressure difference, PaPrandtl number, dimensionlessturbulent Prandtl number, dimensionlessperimeter of cross section, mheat flux, W/m2radial position, mhydraulic radius, mtube radius, mRayleigh number, dimensionlessReynolds number based on D, dimensionlessReynolds numbers based on Dh , dimensionlessReynolds number based on L, dimensionlessspacing between cylinders, mStanton number, dimensionlessplate thickness, mtemperature, Kinlet temperature, Koutlet temperature, Kmean temperature, Kaverage temperature difference, Klog-mean temperature difference, Klongitudinal velocity, m/sfriction velocity, m/smean velocity, m/stransversal velocity, m/swidth, mlongitudinal position, mlongitudinal position, dimensionlesslongitudinal position, dimensionlessflow entrance length, mthermal entrance length, mtransversal position, mviscous sublayer thickness, mGreek Letter Symbolsαthermal diffusivity, m2/sthermal eddy diffusivity, m2/sHmomentum eddy diffusivity, m2/sMbulk temperature, dimensionlessθ∗mµviscosity, kg/s-mνkinematic visocity, m2/sρdensity, kg/m3τappapparent sheer stress, PaBOOKCOMP, Inc.
— John Wiley & Sons / Page 435 / 2nd Proofs / Heat Transfer Handbook / Bejan435[435], (41)Lines: 1776 to 1794———0.20847pt PgVar———Normal PagePgEnds: TEX[435], (41)436123456789101112131415161718192021222324252627282930313233343536373839404142434445FORCED CONVECTION: INTERNAL FLOWSτavgτwφSubscriptsinmaxoptout00-x∞averaged wall shear stress, Pawall shear stress, Pafully developed temperature profile, dimensionlessinletmaximumoptimumoutletwallaveraged longitudinallyfree stream[436], (42)Superscripts−+time-averaged componentsfluctuating componentswall coordinatesLines: 1794 to 1847———3.39505pt PgVarREFERENCESAsako, Y., Nakamura, H., and Faghri, M.
(1988). Developing Laminar Flow and Heat Transferin the Entrance Region of Regular Polygonal Ducts, Int. J. Heat Mass Transfer, 31, 2590–2593.Bar-Cohen, A., and Rohsenow, W. M. (1984). Thermally Optimum Spacing of Vertical, NaturalConvection Cooled, Parallel Plates, J. Heat Transfer, 106, 116–123.Bejan, A.
(1984). Convection Heat Transfer. Wiley, New York, p. 157, prob. 11.Bejan, A. (1993). Heat Transfer, Wiley, New York, Chap. 9.Bejan, A. (1995). Convection Heat Transfer, 2nd ed., Wiley, New York.Bejan, A. (2000). Shape and Structure, from Engineering to Nature, Cambridge UniversityPress, Cambridge.Bejan, A., and Morega, A. M. (1994). The Optimal Spacing of a Stack of Plates Cooled byTurbulent Forced Convection, Int. J. Heat Mass Transfer, 37, 1045–1048.Bejan, A., and Sciubba, E.
(1992). The Optimal Spacing of Parallel Plates Cooled by ForcedConvection, Int. J. Heat Mass Transfer, 35, 3259–3264.Bhattacharjee, S., and Grosshandler, W. L. (1988). The Formation of a Wall Jet near a HighTemperature Wall under Microgravity Environment, ASME-HTD-96, ASME, New York,pp. 711–716.Campo, A. (1999). Bounds for the Optimal Conditions of Forced Convective Flows InsideMultiple Channels Whose Plates Are Heated by Uniform Flux, Int. Commun.
Heat MassTransfer, 26, 105–114.Campo, A., and Li, G. (1996). Optimum Separation of Asymmetrically Heated Sub-channelsForming a Bundle: Influence of Simultaneous Flow and Temperature, Heat Mass Transfer,32, 127–132.BOOKCOMP, Inc. — John Wiley & Sons / Page 436 / 2nd Proofs / Heat Transfer Handbook / Bejan———Short PagePgEnds: TEX[436], (42)REFERENCES123456789101112131415161718192021222324252627282930313233343536373839404142434445437Churchill, S.
W., and Ozoe, H. (1973). Correlations for Forced Convection with UniformHeating in Flow over a Plate and in Developing and Fully Developed Flow in a Tube, J.Heat Transfer, 95, 78–84.Colburn, A. P. (1933). A Method of Correlating Forced Convection Heat Transfer Data and aComparison with Fluid Friction, Trans.
Am. Inst. Chem. Eng., 29, 174–210.Dittus, F. W., and Boelter, L. M. K. (1930). Heat Transfer in Automobile Radiators of theTubular Type, Univ. Calif. Publ. Eng., 2(13), 443–461; Int. Commun. Heat Mass Transfer,12(1985), 3–22.Drew, T. B. (1931). Mathematical Attacks on Forced Convection Problems: A Review, Trans.Am. Inst. Chem. Eng., 26, 26–80.Fowler, A. J., Ledezma, G. A., and Bejan, A.
(1997). Optimal Geometric Arrangement ofStaggered Plates in Forced Convection, Int. J. Heat Mass Transfer, 40, 1795–1805.Gnielinski, V. (1976). New Equations for Heat and Mass Transfer in Turbulent Pipe andChannel Flow, Int. Chem. Eng., 16, 359–368.Graetz, L. (1883). Uber die Wärmeleitungfähigkeit von Flüssigkeiten (On the Thermal Conductivity of Liquids), Part 1, Ann. Phys. Chem., 18, 79–94; Part 2 (1885), Ann. Phys. Chem.,25, 337–357.Hagen, G. (1839). Uber die Bewegung des Wassers in engen zylindrischen Rühren, Pogg.
Ann.,46, 423.Hoffmann, E. (1937). Die Wärmeübertragung bei der Strömung im Rohr, Z. Gesamte KaelteInd., 44, 99–107.Hornbeck, R. W. (1965). An All-Numerical Method for Heat Transfer in the Inlet of a Tube,ASME-65-WA/HT-36, ASME, New York.Kays, W.M., and Perkins, H. C. (1973). Forced Convection, Internal Flow in Ducts, in Handbook of Heat Transfer, W. M. Rohsenow and J.
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