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Heat Transfer Handbook part 100

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986 HEAT TRANSFER IN ELECTRONIC EQUIPMENT. WL (13.54). where W and L are the width and length of the printed circuit board, respectively.. The factor κ n simply represents the fraction of the conduction area missing due to the cutouts.. W (13.55). The thermal resistance of each of the layers making up the printed circuit board in the normal direction...

Heat Transfer Handbook part 101

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plate or nozzle array, and the freedom to tailor the jet flow to the local cooling requirements, have made impingement cooling one of the most promising alternatives forthe cooling of high-heat-flux components.. The axis of the impinging jet may be perpendicular or inclined to the surface of the component. Moreover, in the application of liquid jets, a distinction can be...

Heat Transfer Handbook part 102

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oriented base with vertical fins and channels, yielded the highest heat transfer coef- ficients most often. However, in a relatively large number of situations, the thermal performance of the vertical–vertical arrays was indistinguishable from that attained by a vertical base plate with fins rotated 30° from the axis, a horizontal base plate, and a base plate inclined 60° from the...

Heat Transfer Handbook part 103

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1016 HEAT TRANSFER IN ELECTRONIC EQUIPMENT. to obtain engineering estimates of the thermal performance, Bar-Cohen et al. 13.8 THERMOELECTRIC COOLERS. 13.34. Solution of the governing equations for a thermoelectric couple yields a relation for the maximum temperature differential obtainable with such a device, as. 2 KR (13.93). L b (13.94). A b (13.95). It may thus be observed that the...

Heat Transfer Handbook part 104

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1026 HEAT TRANSFER IN ELECTRONIC EQUIPMENT. U., Krotzsch, P., and Hennecke, F. Sergent, J., and Krum, A. W., Nakayama, W., and Oktay, S. Heat Transfer in Elec- tronic Packages, in Microelectronics Packaging Handbook, 2nd ed. Sitharamayya, S., and Raju, K. Heat Transfer between an Axisymmetric Jet and a Plate Hold Normal to the Flow, Can. Song, S., Lee, S., and...

Heat Transfer Handbook part 105

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Normal Page PgEnds: TEX It may be noted that objectives 1, 2, and 4 yield savings in operating (or energy). These ob- jective functions and constraints have been described by many different performance evaluation criteria (PEC) in the literature (Bergles et al., 1974a,b. The heat exchanger performance is represented by two dependent variables: heat transfer rate Q and pressure drop...

Heat Transfer Handbook part 106

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there are limited data which indicate that the tube bundle performance in a ther- mosyphon reboiler may be different from that of a single tube (Yilmaz et al., 1981).. A laterstudy (Jensen et al., 1992), however, suggests that single-tube results may be used to predict tube bundle behavior.. Several attempts have been made to model the nucleate boiling mechanisms on...

Heat Transfer Handbook part 107

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Normal Page PgEnds: TEX on the basis of equal pumping power, it was shown that CHFs for the rough tubes. In another study (Gomelauri and Magrakvelidze, 1978) with two-dimensional structured roughness, CHF is found to be dependent on the degree of subcooling. Swenson et al. (1962) and Watson et al. Three more recent studies (Celata et al., 1994. Kabata et...

Heat Transfer Handbook part 108

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14.20. Wang et al.. 14.21 show a strong influence of the wall waviness on the enhanced performance represented by the area goodness factor ( j/f. Subsequent work on three-dimensional wavy plate fin channels (finite fin height) shows trends that are similar, albeit different in magnitude (Muley et al., 2002. Zhang et al., 2002).. 14.4.2 Boiling. 14.22. As pointed out by...

Heat Transfer Handbook part 109

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14.30a, makes them particularly useful in fouling situations, where frequent tube-side cleaning may be required.. 14.30b, include the 180° twist pitch H , tape thickness δ, and tape width w (which is usu- ally about the same as the tube inside diameter d in snug- to tight-fitting tapes). When placed inside a circular tube, the flow field gets altered in...

Heat Transfer Handbook part 110

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In-tube condensation of both steam and refrigerant vapor in the presence of twisted- tape inserts have been considered in the literature (Manglik and Bergles, 2002a). For describing condensing heat transfer with and without twisted-tape inserts, Fig. 14.34 for a once-through flow system is once again relevant, but with the sequence of event reversed. That is, entering from the right of...

Heat Transfer Handbook part 111

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Contrarily, with the addition of a surfactant to seawater, the overall heat transfer coefficient was found to be doubled in vertical upflow boiling in a desalination application.. For stirring and surface scraping devices, Uhl (1970) and Hagge and Junkhan (1974) provide early reviews and the applications include both single-phase and boiling heat transfer. Vidyanidhi et al., 1977). In most recent...

Heat Transfer Handbook part 112

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Two-Phase Flowand Heat Transfer in the Power and Process Industries, Hemisphere Publishing, Washington, DC.. Enhanced Heat Transfer . Heat Transfer in a Pulsed Fluidized Bed, Trans.. C., Sr., and Blomgren, O. Heat Transfer of Evaporating Freon with Inner-Fin Tubing, Refrig. Pool Boiling Heat Transfer from Scored Surfaces, Chem. Briggs, A., and Rose, J. Cooling Air in Turbulent Flow with Internally...

Heat Transfer Handbook part 113

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Kulenovic, R., Mertz, R., and Groll, M. Enhanced Heat Transfer . Lan, J., Disimile, P., and Weisman, J. Effect of Sound on Heat Transfer from a Horizontal CircularCylinderat Large Wavelength, J. A Theory of Heat-Transfer by Dropwise Condensation, Proc. 3rd International Heat Transfer Conference, Vol. Lemlich, R., and Rao, M. Acoustical Effects on Free Convective Heat Transfer from a Horizontal...

Heat Transfer Handbook part 114

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15.0pt PgVar. Use of Internally Grooved Rough Surfaces and Twisted Tapes, Heat Transfer Jpn. Pool Boiling Heat Transfer from Teflon-Coated Stainless Steel, J. Heat Transfer . LaminarFlow Heat Transferin Internally Finned Tubes with Twisted-Tape Inserts, in Heat Transfer 1978, Vol. Heat Transfer to Boiling Binary Liquid Mixtures, Br. Heat Transfer to Boiling Binary Liquid Mixtures, Chem. An Analysis of Steady...

Heat Transfer Handbook part 115

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150(1 − φ) 2 (15.15). φ 3 d (15.16). K∇ 2 v (15.17). µ∇ 2 v (15.18). (15.17) without the body force term and multiplied by K/µ.. (15.17) and (15.18), two viscous terms are evident. (15.18).. (15.13) and the Brinkman model ofeq. (15.17), were used simultane- ously by Vafai and Tien (1981) in a study of forced-convection boundary layer heat...

Heat Transfer Handbook part 116

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L ∼ Be −n L (15.58). where L is the dimension ofthe given volume in the flow direction, and Be L is a new dimensionless group (the Bejan number) that serves as the forced-convection analog ofthe Rayleigh number ofnatural convection (Bhattacharjee and Grosshandler, 1988;. µ f α f (15.59). (15.58) is equal to 1 4 in the case oflami- nar...

Heat Transfer Handbook part 117

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Figure 15.5 Natural convection heat transfer in confined porous media heated from the side: (a) rectangular enclosure. Figure 15.6 Four heat transfer regimes for natural convection in an enclosed porous layer heated from the side. (Bejan, 1984), that is, four ways to calculate the overall heat transfer rate q = H. In this regime, the heat transfer rate scales as...

Heat Transfer Handbook part 118

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Figure 15.10 Asymptotes ofthe function Nu (Ra H , Pr p ) for convection in a porous layer heated from below. 15.10). In this formulation the Darcy flow result of eq. (15.115) becomes. (15.118) The experimental data for convection in the entire regime spanned by the asymptotes given by eqs. (15.116) and (15.118) are correlated by. (15.119). Normal Page PgEnds:...

Heat Transfer Handbook part 119

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Bejan, A., and Morega, A. Heat Transfer . Bejan, A., and Poulikakos, D. The Non-Darcy Regime for Vertical Boundary Layer Natural Convection in a Porous Medium, Int. Bejan, A., and Sciubba, E. Bejan, A., and Tien, C. Natural Convection in a Horizontal Porous Medium Sub- jected to End-to-End Temperature Difference, J. Natural Convection in Horizontal Space Bounded by Two Concentric...