plenum 130 can be incorporated into any of the previously discussed embodiments fig1 shows a longitudinal cross section of another embodiment of the present invention very similar to that disclosed in fig3 this embodiment however is based on a simplified housing structure in this embodiment the catalytic reactor 200 comprises a housing 202 having an exit and defining at least one aperture 207 at least two conduits 210 made from a heat conducting material and adapted for conducting a fluid are positioned within the housing 202 the conduits have an entrance 216 an exit 217 with an exit periphery 213 an interior surface 212 and an exterior surface 211 the conduits 210 are positioned within the housing 202 such that the conduits 210 penetrate the housing thereby having the conduit exits within the housing 202 and the conduit entrances 216 opening to an area outside the housing 202 a first fluid 220 entering conduits 210 enters housing 202 if at all by exiting conduits 210 the conduit exit periphery 213 positions the conduits 210 relative to each other and the housing interior surface 214 fig1 depicts an unpartitioned flow path this embodiment however has all the flexibility of the first embodiment as with the first embodiment a plenum could also be incorporated for application in a gas turbine the catalytic reactor must be integrated into the gas turbine combustion system for gas turbine engines using a combustor shell to contain the high pressure gases within the combustion section and to provide a sealed flow path from compressor exit to turbine inlet.