The apparatus comprises a fuel cell unit (2) with a plurality of fuel cells defining a longitudinal axis and a main flow direction (100) coaxial to the longitudinal axis. Fuel cell inlets and fuel cell outlets are arranged at opposite ends of the fuel cell unit (2) and in line with the main flow direction (100). The apparatus further comprises a component (1,3) comprising first fluid conduits arranged parallel to the main flow direction, the first fluid conduits comprising first fluid inlets and first fluid outlets arranged at opposite ends of the component and in line with the main flow direction. The component (1,3) is arranged adjacent the fuel cell unit (2) such that at least one of the first fluid inlets and the first fluid outlets of the component are arranged adjacent at least one of the fuel cell outlets and the fuel cell inlets such that a fluid flow may flow substantially parallel to the longitudinal axis of the apparatus in the first fluid conduits of the component (1,3) and in the fuel cell unit (2) and when passing from the component to the fuel cell unit or vice versa.