Correlations for transient natural convection in parallelogrammic enclosures with isothermal hot wall

Correlations of the type Nusselt–Rayleigh–Fourier are proposed to determine the convective exchanges that occur in transient regime in closed cavities of parallelogrammic section. They complement the correlations obtained in a previous work for steady state. The active vertical walls of these cavities are vertical, maintained isothermal and differentially heated, while the closing channel is adiabatic. This work covers a wide range of the Rayleigh number 1.84 × 105 ≤ Ra ≤ 1.70 × 109 and different angles of inclination ranging from −60° to 60°, enabling applications in several fields of engineering such as building, solar energy or power electronics. Correlations are obtained from numerical results based on the finite volume method and are validated by measurements.