Temperature measurements made in an annular, sodium filled enclosure heated at the inner wall or the roof boundary and cooled at the floor are reported. The dimensionless temperature profile of the bulk fluid in response to uniform wall heating is described by an empirical formula, which is the Fourier linear conduction equation with an additional simple function accounting for convection. The formula is subsequently shown to be a solution of the one-dimensional steady-state conduction equation involving energy generation in the medium. The analytical approach enables the convection and conduction heat transfer modes in the bulk fluid to be isolated and hence, the convection currents to be quantified.