Cooling tubes within a membrane reactor can help to maintain favorable operating conditions; however, the addition of cooling tubes significantly increases the complexity and number of alternatives for the internal layout. A method is proposed to configure a reactor with both membrane and cooling multitubes based on the results of a simplified asymmetric unit. This simplified triangular unit is used to preoptimize the operating conditions as well as provide guidelines for the relative dimensions of the packed bed, membrane, and cooling chambers. Cooling tubes with smaller diameters were placed next to the exterior wall to reduce the impact of having to break the central pattern. Furthermore, for this hexagonal multitube pattern, an external hexagonal wall significantly improved the reactor performance by keeping favorable temperature profiles throughout the cross section of the reacting chamber not just those regions near the center of the reactor.