In this study, we simulate kettle reboilers by analyzing a two-dimensional slice with Eulerian multiphase CFD. We believe that by varying tube layout and tube cross-section as a function of elevation, we can affect recirculation and vapor escape from the bundle and thus improve the vapor generation rate. Our simulations show that both elliptical tubes and vapor escape lanes elevate the kettle exit vapor fraction, even when accounting for heat transfer area changes. Whether formed by the gaps between uniformly oriented elliptical tubes or by omitting tubes, these lanes appear to expedite the removal of vapor from the bundle. Our study shows that further investigation of the effects of these techniques in larger bundles of commercial interest is warranted.