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

► Air-filled closed parallelogrammic cavities are treated in this work. ► Transient natural convection is generated by isothermal hot wall. ► Correlations of the type Nusselt-Rayleigh-Fourier are proposed in transient regime. ► Numerical results based on the finite volume method are validated by measurements. ► This study covers a wide range of the Rayleigh number and various angles of inclination.