A packed bed reactor made up of two hemispheres separated by an orifice plate can be operated as an adiabatic reverse flow reactor with nearly spherical symmetry. The reactor requires little or no insulation with external temperatures limited to the adiabatic temperature rise, but much higher internal temperatures. The operational characteristics of this type of reactor have been studied using a dynamic model and the steady state model obtained for fast switching of the flow direction. Due to the large cooling region, higher conversions than the conventional reverse flow reactor are predicted for reversible exothermic reactions.