A reformer assembly includes a vortex tube receiving heated fuel mixed with steam. A catalyst coats the inner wall of the main tube of the vortex tube and a hydrogen-permeable tube is positioned in the middle of the main tube coaxially with the main tube. With this structure the vortex tube outputs primarily Hydrogen from one end and Carbon-based constituents from the other end. In some embodiments a second vortex tube receives the Carbon output of the first vortex tube to establish a water gas shift reactor, producing Hydrogen from the Carbon output of the first vortex tube.