This invention relates to the field of heat-driven cooling devices, heat pumps or thermal transformers, in particular to those devices, known as sorption devices, which employ an ad- or absorbent material as a chemical compressor to raise the pressure of a refrigerant gas. This invention is particularly concerned with a heat exchanger suitable for use as a generator in a sorption device. Embodiments of the invention provide a heat exchanger comprising: a plurality of stacked plate members each plate member being provided with at least one fluid channel therein, each plate member having a channel inlet and a channel outlet associated with each channel of the plate member; a plurality of chambers, the chambers being provided between opposed major faces of respective adjacent plate members, the chambers containing a sorbent material; a thermal fluid inlet in communication with a plurality of the channel inlets and a thermal fluid outlet in communication with a plurality of the channel outlets; and a sorbate inlet and a sorbate outlet in communication with each of the chambers, the fluid channels being provided in fluid isolation from the chambers.