Abstract: The invention relates to a method for achieving an optimal energy exchange in regenerative heat exchange between the combustion air and precooled, wet flue gases from a cooling device. By letting the moisture in said flue gases be condensed on the heat transfer surfaces the moisture will be transferred over to the air side where it is vaporized, resulting in some advantages, e.g. an increased energy exchange. According to the invention it has turned out to be possible to achieve a further increase of the energy exchange in a simple way by ensuring that the heat transfer surfaces of the flue gas side become really water-soaked when on the flue gas side, e.g. by letting the condensed water from the precooling device (15) drip or flow down onto the heat transfert surfaces such that said surfaces will remain wet during the entire passage through the combustion air side (10).