Determination of the coefficient of convective heat transfer in a transient pipe flow at high Grashof numbers

Abstract

An equation for determining the coefficient of convective heat transfer in a pipe with a transient flow in which the effect of natural convection is taken into account is proposed. It is shown that the upper limit of applicability of the Nusselt equation (that is, the upper limit at which the flow in a pipe still remains laminar at high Grashof numbers) is lower than the conventionally accepted value. An equation for determining the critical Reynolds number as a function of the Grashof number is proposed.