This paper explores the heat transfer mechanisms involved in a high-pressure carbon monoxide (HiPCO) chemical reactor, which is used to produce single-wall carbon nanotubes (SWCNTs). The efficiency of catalyst usage, and of the reaction itself, depends upon the thermal conditions in the mixing region. This is directly linked to the costs associated with producing SWCNTs, as well as the ability to scale the manufacturing of SWCNTs to increase the material availability for nanotechnology development. Simple models are used to study several user-configurable contributions (gas flow rates, gas temperatures, reactor geometry, and reactor orientation) to the energy balance within the reactor mixing region. Results of these models are used to identify means of improving reaction efficiency. All contributions are then combined into a computational fluid dynamics model to confirm the findings of the simpler models. The results identify the design features that lead to a maximally efficient HiPCO reactor.