An empirical correlation for electrohydrodynamic enhancement of natural convection

A correlation for predicting the extent of electrohydrodynamic enhancement of natural convection from heated horizontal cylinders is presented. This correlation is supported with results from two different experiments; the first involves natural convection from a thin platinum wire immersed in R-123 with a uniform electric field, while the second involves natural convection from a flooded tube immersed in R-123 in a non-uniform electric field. The Nusselt number enhancement is correlated in terms of a “corrected electrical Rayleigh number”, RaEl, to account for the effect of a non-uniform electric field on natural convection. The correlation is valid for the range 4.0×103≤RaEl≤8.0×108.