The invention relates to a heat exchanger comprising a first free space (7) for a first fluid (3), a thermally conductive wall (11) which, at least locally, delimits said first free space (7), in such a way that an exchange of heat can occur between the first fluid and the thermally conductive wall (11) which is hollow and encloses a material (13) for storing thermal energy by accumulation of latent heat, by heat exchange with at least the first fluid. The first free space (7) is divided into at least two separated channels (7a, 7b) in which two streams of the first fluid (3) can circulate at the same time but separately, the thermally conductive wall (11) which encloses the thermal energy storage material (13) being interposed between the two channels (7a, 7b).