NOVELTY - A flow arrangement comprises fuel cell stacks connected in parallel by their anode and cathode parts so that inlet of anode and cathode parts of each fuel cell stack group are connected to inlet manifolds and that exhaust of anode and cathode parts of each group are in connection with exhaust manifolds.    USE - For fuel cell stacks.    ADVANTAGE - The structure is both flow and heat efficient and compact in size, and provides a good total efficiency of the process.    DETAILED DESCRIPTION - A flow arrangement (1) comprises fuel cell stacks comprising fuel cell units (2), in which each fuel cell unit and fuel cell stack comprises an anode part (2.1) and a cathode part (2.2), the flow arrangement comprising an anode flow channel system (3) and a fuel source (8) being in connection by inlet part (3.1) of the anode flow channel system with the inlet (5) of the anode part of each fuel cell stack and in which the exhaust (5') of the anode part is in connection with the exhaust part (3.2) of anode flow channel system for directing exhaust gas away from each anode part of the fuel cell stack, a cathode flow channel system (4) comprising an inlet part (4.1) forming a flow connection for the cathode gas to the inlet (6) of the cathode part of each fuel cell stack and an exhaust part (4.2) of the cathode flow channel system being in connection with the exhausts (6') of the cathode parts for directing exhaust gas away from the fuel cell stacks, and a first heat exchanger (9) arranged into the first part of the cathode flow channel system. The fuel cell stacks are connected into fuel cell stack groups, in which a number of fuel cell stacks are connected in parallel by their anode and cathode parts so that the inlet of the anode part of each fuel cell stack group is connected to an anode part inlet manifold (11) common to these and that the exhaust of each anode part of each group is in connection with an anode part exhaust manifold (11') common to these, and so that the inlet of each cathode part of each group is in connection to a cathode part manifold (12) common to these and that the exhaust of the cathode part of each group is in connection to a cathode part manifold (12') common to these and that the cathode side flows of said fuel cell stack groups are connected in series and that the arrangement comprises a by-pass feed channel system via which at least one cathode part manifold subsequent to fuel cell stack group is in flow connection with the first part of the cathode flow channel system, in a place located before the first heat exchanger in the flow direction of the gas.    DESCRIPTION OF DRAWING(S) - The figure is an illustration of a flow arrangement of flow cell stacks.    Flow arrangement (1)    Fuel cell units (2)    Anode part (2.1)    Cathode part (2.2)    Anode flow channel system (3)    Inlet part (3.1)    Exhaust part (3.2)    Cathode flow channel system (4)    Inlet part (4.1)    Exhaust part (4.2)    Inlet (5)    Exhaust (5')    Inlet (6)    Exhausts (6')    Fuel source (8)    First heat exchanger (9)    Anode part inlet manifold (11)    Anode part exhaust manifold (11')    Cathode part manifold (12)    Cathode part manifold (12')