Abstract Mini channel solution is used in devices that require a high density of transmitted thermal power as a very large-scale integration design in computer systems and compact exchangers. Furthermore, the mini channels are extensively investigated in the literature for turbulent and laminar regimes. In this project, different configurations of mini channels have been studied to enhance heat transfer, using simulations with a commercial multi-physics code. Thanks to the results of the models, more promising configurations with 3D printing technique may be built. The project challenge is improving convective thermal power extracted by the exhaust gases of a mini-catalytic combustor. The combustor feeds six modules for thermoelectric power production (TEMs). As the first step, three different mini channel geometries have been chosen; the first one with 19 channels with rectangular cross-section, the second one with 6 channels with a convergent profile, and the latter with 2 channels with a fractal branching geometry. Simulations started from studying fluid dynamic to investigate the velocity field at the exit of the mini channels. The analysis has been extended by adding the conjugate heat exchange between fluid and combustor wall. The results show an increase in heat exchange compared to the base case for all configurations, with a maximum value for the 19 mini channels configuration.