Heat exchanger (20) for plants for drying bulk agricultural products; the heat exchanger (20) comprising a combustion chamber (23) with a first end (24) suitable to be engaged by a fuel burner (18), wherein the combustion of fuel substantially occurs inside the combustion chamber (23); the heat exchanger (20) including at least one hollow tubular element (40) arranged outside the combustion chamber (23), wherein the heat exchanger (20) comprises a first collector (21) applied to the second end (25) of the combustion chamber (23) opposite to the first end (24), and wherein the collector (21) comprises deviation means that can be alternatively switched between a first position and a second position, so as to convey the hot flue gases, resulting from the combustion of the fuel, from the inside of the combustion chamber (23) to the at least one hollow tubular element (40) and from the combustion chamber (23) to the outside of the heat exchanger (20), respectively.
