The paper deals with entry-length conditions for transformer oil in vertical laminar flow through a uniformly heated duct allowing for changes in density, viscosity, and thermal conductivity. The calculation method uses a fundamental property of high Prandtl number fluids and assumes a series of truncated temperature profiles. Calculated wall mean temperature rises have been verified experimentally for a simple case. Local and mean Nusselt numbers have been derived and an empirical correlation relating mean and limiting Nusselt numbers applied. The analysis includes evaluation of the free-convective component of pressure head which causes flow and distinguishes this from free-convective effects within the duct.

This content is only available via PDF.
You do not currently have access to this content.