A microscale combustor recuperator and oil heat exchanger – design and thermofluidic characterization

A two-dimensional numerical model of an integrated microscale hydrogen–air catalytic combustor, recuperator, and oil heat exchanger is presented. Catalytic combustion occurs on the walls of the microchannel in the presence of a platinum catalyst. The performance of the combustor is documented using validated CFD simulations for variations in geometric and fluidic parameters. Varied geometric parameters include the length and location of the catalyst bed, length of the device, and the height of the combustion channel. Varied fluidic parameters include the oil inlet temperature, flow rates of oil and reactants, and the equivalence ratio of the reactants. Performance is characterized using a global efficiency, heat transfer effectiveness and hydrogen conversion. The parametric variations are captured non-dimensionally as variations in Damkohler and Peclet numbers, which are in turn used to describe the changes in hydrogen conversion and efficiency. Performance maps for hydrogen conversion and pressure drop in the combustion channel are presented based on values of the Damkohler and Peclet numbers and regions of desired operability of the combustor are identified.