Heat Transfer Correlation Equation Research Articles

Correlation equations for free convection heat transfer in horizontal layers of air and water

New experimental measurements are reported on the natural convective heat transport through a horizontal layer of air, covering the Rayleigh number range from sub-critical to 4 × 10 6. When these data are combined with Goldstein and Chu's data for air, the full set of data points are demonstrated to bear a Nusselt number dependence which is asymptotic to a 1 3 power on the Rayleigh number as the Rayleigh number approaches infinity. The asymptotic coefficient of proportionality is consistent with that predicted by a simple “conduction layer model” which is described. Knowledge of the asymptote has permitted a simple but accurate correlation equation to be obtained, valid for the full range of Rayleigh number. By extension, a similar correlation equation is also obtained for water.

The influence of property variation on forced convection heat transfer to liquids

In this paper a new method of accounting for the influence of property variation on heat transfer by forced convection from heated surfaces to liquids is presented. The method is used in conjunction with new experimental data to develop a correlation equation for forced convection heat transfer from cylinders to liquids in crossflow. The method is also applied to heat transfer by forced convection to liquids from spheres and to turbulent flows of liquids in pipes.

A continuous correlation equation for heat transfer from cylinders to air in crossflow for reynolds numbers from 10 −2 to 2 × 10 5

A continuous correlation equation for heat transfer from cylinders to air in crossflow for reynolds numbers from 10 −2 to 2 × 10 5

Heat transfer from hydrocarbon-oxygen flames

Heat fluxes from premixed methane-oxygen and propane-oxygen flames of various equivalence ratios were measured, using a transient calorimetric method. The experimental results for heat transfer to the forward stagnation point of a hemispherical-nosed probe are compared with those calculated, assuming that ( a ) recombination reactions of dissociated species are frozen in the boundary layer and the surface is noncatalytic; ( b ) equilibrium is maintained thoughout the boundary layer, but the Lewis number of all atoms and radicals is unity; and ( c ) energy transfe, by diffusion and recombination of hydrogen atoms is more rapid than heat transfer by ordinary conduction, that is, there is a Lewis-number augmentation effect. These comparisons show that method ( a ) seriously underestimates the heat transfer and that the experimental values are intermediate between those calculated on the basis of assumptions ( b ) and ( c ). Since equilibrium is assumed, negligible concentrations of hydrogen atoms exist at temperatures below 1700°K, and the Lewis number is, therefore, calculated for the outer region of the boundary layer. The Lewis numbers of other species are not high enough to affect the heat flux to any significant extent. General methods of modifying low-temperature heat transfer correlation equations to allow for recombination and diffusion are presented.

Graphical interpretation of the local heat transfer correlation equation with combined free and forced convection

An account is given, illustrated by an example, of a graphical interpretation and of an examination of the correlation equation for local heat transfer with combined free and forced convection in a tube in which hydrodynamic flow stabilization occurs but thermal stabilization is absent.