Abstract: The invention relates to a thermochemical reactor (1) for a cooling and/or heating apparatus, comprising at least one reagent unit (2) which, by means of chemical combination, can absorb, a gas stream originating from a tank and which, by means of the reverse chemical reaction, cab desorb said gas stream due to a rise in temperature. The reagent unit (2) is disposed in a container (3) comprising walls, of which at least some are equipped with diffuser means (7) for distributing the gas stream. In addition, the reagent unit (2) is of the type that can expand during absorption of the gas stream and retract during desorption of the gas stream, said unit being connected to heating means. Moreover, at least some of the above-mentioned walls consist of mobile walls, which can accompany the longitudinal movement performed by the reagent unit (2), such as to enable successive deformation phenomena.