In this paper a system combining a diesel reformer using catalytic partial oxidation (CPOX) with the Solid Oxide Fuel Cell (SOFC) for Auxiliary Power Unit (APU) applications is modeled with respect to the cooling effect provided by internal reforming of methane in anode gas channel. A model mixture consisting of 80% n-hexadecane and 20% 1-methylnaphthalin is used to simulate the commercial diesel. The modelling consists of several steps. First

equilibrium gas composition at the exit of CPOX reformer is modelled in terms oxygen to carbon (O/C) ratio

fuel utilization ratio and anode gas recirculation. Second

product composition

especially methane content

is determined for the methanation process at the operating temperatures ranging from 500 ℃ to 520 ℃. Finally

the cooling power provided by internal reforming of methane in SOFC fuel channel is calculated for two concepts to increase the methane content of the diesel reformate. The results show that the first concept

operating the diesel reformer at low O/C ratio and/or recirculation ratio

is not realizable due to high probability of coke formation

whereas the second concept

combining a methanation process with CPOX

can provide a significant cooling effect in addition to the conventional cooling concept which needs higher levels of excess air.