NOVELTY - The system has a heated reaction chamber (46) reacting a mixture to create hot reactant gases. A looped gas flow path (59) has an exothermic heat exchange section (52) thermally exposed to the mixture, and an endothermic exchange section (56) is exposed to a hydrogen gas stream. A pump (62) pumps a gas medium (60) through the path at a predetermined mass flow rate, where the medium absorbs heat energy in the endothermic section and releases the energy in the exothermic section. A heat exchanger (57) absorbs the energy from a waste gas stream and the hydrogen gas stream to preheat the mixture.    USE - System for converting mixture of hydrocarbon fuel and water into hydrogen gas i.e. optimal gas medium, utilized to power a fuel cell.    ADVANTAGE - The system recovers latent heat of vaporization including a heated environment that adds heat to liquid material and converts a liquid material into gaseous material, so that the latent heat of vaporization is transferred to preheated water, thus increasing an overall efficiency of the system. The heat exchangers transfer heat from exhaust gases to a source material used to produce the exhaust gases, thus preheating the source material, effectively transferring the heat energy between a vapor and a liquid and maintaining a temperature difference in the heat exchanger using a non-condensing gas such as hydrogen, helium and nitrogen as a heat transfer medium. The heat exchanger uses the heat energy to preheat incoming water and the heat energy can be recycled, so that a steam engine can be able to run more efficiently.    DETAILED DESCRIPTION - The endothermic exchange section is a heat-absorbing exchange section, and the exothermic heat exchange section is heat-releasing exchange section. The heat exchanger is secondary dynamic active gas flow heat exchanger.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit block diagram of an active gas flow heat exchanger arrangement using hydrogen gas as a transfer medium between exhaust gases/liquids and an income liquid supply.    Heated reaction chamber (46)    Exothermic heat exchange section (52)    Endothermic exchange section (56)    Heat exchanger (57)    Looped gas flow path (59)    Gas medium (60)    Pump (62)