Heat exchanger with plates, which is configured for a cross flow heat exchange between a hot fluid flowing in a hot pass and a cold fluid flowing in a cold pass, the fluids flowing between closing plates, comprising: - at least one core band arranged to form edges of the exchanger and to ensure sealing-tightness between the hot pass and the cold pass, - a plurality of closing bars disposed between each closing plate and defining, with the closing plates , flow channels for fluids passing through the exchanger, characterized in that the core band arranged at an inlet of the cold pass and an inlet of the hot pass comprises an inlet for supplying hot air, and a plurality of orifices disposed opposite at least one closing bar of the hot pass adjoining said core band , and in that at least one closing bar arranged in the lengthwise direction of the inlet of the cold pass comprises an inlet for said hot air opposite one of the orifices of the core band, and a circuit for the flow of said hot air connected to said hot air inlet, said flow circuit being U-shaped and comprising: - a first section and a second section each extending over the whole length of the closing bar , - a hot air outlet arranged at one end of the second section and configured to expel the hot air in the hot pass at the inlet of the hot pass, and - an intermediate section forming the base of the U and connecting the first section to the second section by their end respectively opposite to the hot air inlet and to the hot air outlet . - at least one core band arranged to form edges of the exchanger and to ensure sealing-tightness between the hot pass and the cold pass, - a plurality of closing bars disposed between each closing plate and defining, with the closing plates , flow channels for fluids passing through the exchanger, characterized in that the core band arranged at an inlet of the cold pass and an inlet of the hot pass comprises an inlet for supplying hot air, and a plurality of orifices disposed opposite at least one closing bar of the hot pass adjoining said core band , and in that at least one closing bar arranged in the lengthwise direction of the inlet of the cold pass comprises an inlet for said hot air opposite one of the orifices of the core band, and a circuit for the flow of said hot air connected to said hot air inlet, said flow circuit being U-shaped and comprising: - a first section and a second section each extending over the whole length of the closing bar , - a hot air outlet arranged at one end of the second section and configured to expel the hot air in the hot pass at the inlet of the hot pass, and - an intermediate section forming the base of the U and connecting the first section to the second section by their end respectively opposite to the hot air inlet and to the hot air outlet . - a first section and a second section each extending over the whole length of the closing bar , - a hot air outlet arranged at one end of the second section and configured to expel the hot air in the hot pass at the inlet of the hot pass, and - an intermediate section forming the base of the U and connecting the first section to the second section by their end respectively opposite to the hot air inlet and to the hot air outlet . <EOS>