Free Convection from Horizontal Cylinders

The values of the constants C and m are given in Table 7-1 according to Refs. 4 and 76. The predictions of Morgan (Ref. 76 in Table 7-1) are the most reliable for Gr Pr of approximately 10 5. A more complicated expression for use over a wider range of Gr Pr is given by Churchill and Chu [70]  

A simpler equation is available from Ref. 70, but is restricted to the laminar range of 10-6 Gr Pr 109  

Heat transfer from horizontal cylinders to liquid metals may be calculated from Ref. 46  

0-cm-diameter horizontal heater is maintained at a surface temperature of 38°C and submerged in water at 27°C. Calculate the free-convection heat loss per unit length of the heater. 

A fine wire having a diameter of 0.02 mm is maintained at a constant temperature of 54°C by an electric current. The wire is exposed to air at I atm and 0°C. Calculate the electric power necessary to maintain the wire temperature if the length is 50 cm. 

---

G. D. Raithby and K. G. T. Hollands, Laminar and Turbulent Free Convection From Elliptic Cylinders, With a Vertical Plate and Horizontal Circular Cylinder as Special Cases, J. Heat Transfer (98) 72-80,1976. 

An empirical equation proposed by Heilman for the coefficient of heat transfer in free convection from a long horizontal cylinder to air is... 

Assume that one-half of the heat transfer by free convection from a horizontal cylinder occurs on each side of the cylinder because of symmetry considerations. Going by this assumption, compare the heat transfer on each side of the cylinder with that from a vertical flat plate having a height equal to thd circumferential distance from the bottom stagnation point to the top stagnation point on the cylinder. Discuss this comparison. 

Churchill. S. W., and H. H. S. Chu Correlating Equations for Laminar and Turbulent Free Convection from a Horizontal Cylinder, Int. J. Heat Mass Transfer, vol. 18, p. 1049, 1975. 

Churchill, S.W. Chu, H.H.S. Correlating equations for laminar and turbulent free convection from a horizontal cylinder. Int. J. Heat Mass Transfer 18 (1975) 1049-1053... 

H. Nakamura and Y. Asako, Laminar Free Convection From a Horizontal Cylinder With Uniform Cross-Section of Arbitrary Shape, Bull. JSME (21/153) 471-478,1978. 

R. C. Martinelli and L. M. K. Boelter, The Effect of Vibration on Heat Transfer by Free Convection From a Horizontal Cylinder, Heat. Pip. Air Cond. (11) 525-527,1939. 

R. M. Fand and J. Kaye, The Influence of Vertical Vibrations on Heat Transfer by Free Convection From a Horizontal Cylinder, in International Developments in Heat Transfer, pp. 490-498, ASME, New York, 1961. 

R. M. Fand and E. M. Peebles, A Comparison of the Influence of Mechanical and Acoustical Vibrations on Free Convection from a Horizontal Cylinder, J. Heat Transfer (84) 268-270,1962. 

Figure 6 5. Nusselt numbers for free convection from long horizontal cylinders. (Reproduced with permission from reference 23. Copyright 1960, John Wiley Sons.)...

Solution. Heat transfer may occur by both free convection transverse to the filament surface and by forced convection as the strand moves through the water. We first estimate h for free convection from a horizontal cylinder using Eq. 5.130. The properties of water are needed at >, but 7> changes along the length of the strand. We calculate Num at the beginning and end of the bath. At the beginning... 

When free convection occurs from a horizontal cylinder and Gr Pr > 10 ... 

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. 

Fig. 7-8 Free-convection heat-transfer correlation for heat transfer from heated horizontal cylinders, according to Ref 4.

For the heated vertical plate and horizontal cylinder, the flow results from natural convection. The stagnation configuration is a forced flow. In each case the flow is of the boimdai7 Kiyer type. Simple analytical solutions can be obtained when the thickness of the du.st-free space is much smaller than that of the boundary layer. In this case the gas velocity distribution can be approximated by the first term in an expansion in the distance norroal to the surface. Expressions for the thickness of the dust-free space for a heated vertical surface and a plane stagnation flow are derived below. 

P. H. Oosthuizen and J. T. Paul, An Experimental Study of the Free-Convective Heat Transfer From Horizontal Non-Circular Cylinders, Fundamentals of Natural Convection/Electronic Equipment, ASME HTD (32) 91-97,1984. 

A. L. Sprott, J. P. Holman, and F. L. Durand, An Experimental Study of the Effects of Strong Progressive Sound Fields on Free-Convection Heat Transfer From a Horizontal Cylinder, ASME Paper 60-HT-19, ASME, New York, 1960. 

---