Application of the Reynolds analogy to the estimation of the limits of cooling by natural convection (electron equipment)

It is demonstrated that air flow for a required dissipation requires a predictable minimum pressure drop and that the dependency is a simple square-root relationship. The buoyancy of heated air as produced by the system electronics is the source to produce the available pressure difference. The maximum dissipation is shown to be proportional to the top area of the carrier of circuit packs. This result allows the estimation of the minimum size of a power unit as a function of its dissipation capacity and the available pressure drop, whether from the buoyancy of natural convection or from an external source such as a fan.<>