[en] An experimental study has been conducted on the steady-state heat transfer and the transient thermal response in an internally heated fluid layer bounded from below by a segment of a sphere. The layer is bounded from above by a rigid, isothermal horizontal surface and from below by a rigid, zero heat-flux surface. The spherical segment has a total polar angle of 60⁰, and experimental data have been obtained for layer geometries that range from nearly a spherical segment to a spherical segment with a superposed horizontal layer. Volumetric energy sources within the fluid are produced by Joule heating with alternating current passing between the upper and lower surfaces of the layer