Cylinder combined convection

To illustrate the form of results obtained, consider assisting and opposing combined convective flow over a square cylinder at low Reynolds numbers (Fig. 9.13). A computer program, MIXSQCYL, that finds this solution can be obtained in the way discussed in the Preface. The program assumes that the flow over the cylinder is symmetrical about the vertical center-line of the cylinder. 

Typical streamline patterns for combined convective flow over a square cylinder at a Reynolds number of 50 and a Prandtl number of 0.7. 

Oosthuizen, P.H. and Leung, R.K., Combined Convective Heat Transfer from Vertical Cylinders in a Horizontal Air-Stream , Trans. CSME, Vol. 5. No. 2. pp. 115-117,1978. 

Oosthuizen, P.H. and Barnes, G.B., Experimental Study of Combined Convective Heat Transfer from Oblong Cylinders to Air , ASME Paper 76-HT-40, ASME-AIChE Heat Trans. Conf., St. Louis, MO, Aug. 1976. 

Oosthuizen, PH and Madan, S., Combined Convective Heat Transfer from Horizontal Cylinders in Air , J. Heat Transfer, Vol. 92, 1970, pp. 194-196,1970. 

Oosthuizen, P.H. and Madan.S.. The Effect of Flow Direction on Combined Convective Heat Transfer from Cylinders to Air , J. Heat transfer. May. pp. 240-242. 1971. 

Oosthuizen, P.H., Laminar Combined Convection from an Isothermal Circular Cylinder to Air , Trans. Inst, of Chem. Engs., Vol. 48, Nos. 7-10, pp. T227-T231, 1970. 

Combined thermal and diffusional free convection at a horizontal cylinder was investigated by Weder (W3a). He used a Grashof number of the type of Eq. (37), but corrected for the higher than 0.25 exponent of Gr found in... 

The problem to be solved in this paragraph is to determine the rate of spread of the chromatogram under the following conditions. The gas and liquid phases flow in the annular space between two coaxial cylinders of radii ro and r2, the interface being a cylinder with the same axis and radius rx (0 r0 < r < r2). Both phases may be in motion with linear velocity a function of radial distance from the axis, r, and the solute diffuses in both phases with a diffusion coefficient which may also be a function of r. At equilibrium the concentration of solute in the liquid, c2, is a constant multiple of that in the gas, ci(c2 = acj) and at any instant the rate of transfer across the interface is proportional to the distance from equilibrium there, i.e. the value of (c2 - aci). The dispersion of the solute is due to three processes (i) the combined effect of diffusion and convection in the gas phase, (ii) the finite rate of transfer at the interface, (iii) the combined effect of diffusion and convection in the liquid phase. In what follows the equations will often be in sets of five, labelled (a),..., (e) the differential equations expression the three processes (i), (ii) (iii) above are always (b), (c) and (d), respectively equations (a) and (e) represent the condition that there is no flow over the boundaries at r = r0 and r = r2. 

Oosthuizen, P.H., Combined Forced and Free Convective Heat Transfer from a Horizontal Cylinder in an Axiai Stream , Proc. 3rd Int. Conf. Num. Methods in Thermal Problems, Vol. 3, Pineridge Press, Swansea, U.K., pp. 529-539. 1983. 

Fand, R.M. and Keswani, K.K., Combined Natural and Forced Convection Heat Transfer from Horizontal Cylinders to Water , Int. J. Heat Mass Transfer, Vol. 16, p. 175, 1973. 

Mass How Rate ttirougn ttie Space beLV, een Plates 519 9-5 Natural Convection Inside Enclosures 521 effective Thermal Conductivity 522 Horizontal Rectangular Enclosures 523 Inclined Rectangular Enclosures 523 Vertical Rectangular Enclosures 524 Concentric Cylinders 524 Concentric Spheres 525 Combined Natural Convection and Radiation 525... 

Coefficients of heat transfer by natural convection from bodies of various shapes, chiefly plates and cylinders, are correlated in terms of Grashof, Prandtl, and Nusselt numbers. Table 8.9 covers the most usual situations, of which heat losses to ambient air are the most common process. Simplified equations are shown for air. Transfer of heat by radiation is appreciable even at modest temperatures such data are presented in combination with convective coefficients in item 16 of this table. 

A more precise and widely employed method makes use of a cylinder cut of the material to be tested which is revolved for a certain period of time in the melt. The reduction of its diameter is then measured. The test is usually carried out for several tens of hours at various speeds and the cylinder may also be kept stationary. In the latter arrangement, an idea is obtained of the intensity and direction of free convection if the cylinder acquires a wedge-like shape, possibly combined with an extensive corrosive effect at the flux-line. 

A. P. Hatton, D. D. James, and H. W. Swire, Combined Forced and Natural Convection With Low-Speed Air Flow Over Horizontal Cylinders, J. Fluid Mech. (42) 17-31,1970. 

The types of dryers used in the paper industry can be classified by the basic means of transferring heat to the paper. For conventional steam-heated cylinders, the predominant mechanism of heat transfer is conduction convection is for air dryers, such as impingement and through-dryers radiation is used for infrared dryers and dielectric heating is used for microwave and radio frequency (RF) dryers. On the other hand, some of the dryers use more than one means of heat transfer, for example, Yankee dryers are a combination of cylinder and impingement dryers. 

The individual resistances to the heat transfer on a steam-heated cylinder are shown in Figure 39.5. In practice, the overall heat-transfer coefficient, which is the combination of all conductive and convective resistances in the system, is used for calculation of the heat flux. The overall heat-transfer coefficient for the system illustrated in Figure 39.5 is... 

Figure 8-1 depicts a combined conduction-convection system. Basically, the inner cylinder could be a pipe and the outer cylinder a layer of insulation. One fluid flows inside the pipe and another is outside the insulation. The temperature profiles in the solid objects and between the fluids and solid surfaces are shown,... 

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