Correlating equations for laminar and turbulent free convection from a horizontal cylinder

Publisher Summary Accurate knowledge of the overall convective heat transfer from circular cylinders is of importance in a number of fields, such as boiler design, hotwire anemometry, and the rating of electrical conductors. The wide dispersion in the published experimental data for the heat transfer from smooth circular cylinders by natural and forced convection is attributed to various factors associated with the experiments. The error due to heat conduction to the supports is particularly important with natural convection, especially where the heat loss and the temperature rise of the cylinder are calculated from the voltage drop across it. A common cause of error is the use of too small a space ratio, so that the temperature and velocity fields are distorted. To reduce this error to less than l%, the space ratio D c /D for natural convection or D T /D for forced convection should exceed 100. The error caused by blockage with wind tunnel measurements can be calculated depending on the type of tunnel. One of the greatest sources of error with forced convection is the failure to allow for the effect of stream turbulence.

The Overall Convective Heat Transfer from Smooth Circular Cylinders

The nature of vertical natural convection flows resulting from the combined buoyancy effects of thermal and mass diffusion

Numerical solution to the Navier-Stokes equations for laminar natural convection about a horizontal isothermal circular cylinder

Correlating equations for natural convection heat transfer between horizontal circular cylinders

In this article the problem of describing free convection near either horizontal cylinders or vertical axisymmetric bodies with fairly arbitrary body contours is studied. The solutions of two, coupled, partial differential equations, for the temperature and stream functions, are represented by series which are universal with respect to body contours within a specified class of body shapes (e.g. round-nosed cylinders). The series appear to converge rapidly so that a minimum of computational effort is required, even for classes of body shapes which do not admit the usual similarity transformations. For either horizontal, circular cylinders or spheres the series converge faster than expansions of the Blasius type and one-term approximations compare favourably with some of the existing experimental data.

S. W. Churchill

Papers

Laminar free convection in boundary layers near horizontal cylinders and vertical axisymmetric bodies