An ejector device (400, 500) comprising: a housing (410A, 410B, 410C, 510A, 510B, 510C) having a motive fluid inlet (411, 511) to receive motive fluid, a suction fluid inlet (412, 512) to receive suction fluid and a fluid outlet (413, 513) to output the motive fluid and the suction fluid a plurality of nozzle and diffuser assemblies (450, 550) configured to fit within the housing wherein each of the nozzle and diffuser assemblies comprises: a nozzle; a diffuser a connecting structure connecting the nozzle to the diffuser, the connecting structure configured to permit fluid flow between the nozzle and the diffuser, the connecting structure having apertures (182, 482, 582) configured to allow fluid to be drawn into the fluid flow between the nozzle and the diffuser; wherein the housing comprises a first supporting wall (421, 521) and a second supporting wall (422, 522), wherein each of the first supporting wall and the second supporting wall extends radially across an interior of the housing, the first supporting wall and the second supporting wall axially spaced apart along the housing, each of the first supporting wall and the second supporting wall having a plurality of bores to receive the plurality of the nozzle and diffuser assemblies, wherein the nozzle and diffuser assemblies are individually removable from a downstream end of the housing, characterized in that an upstream end of each of the plurality of nozzle and diffuser assemblies is axially spaced from a constraining radial surface of the first supporting wall (421, 521) of the housing to allow for thermal expansion of the nozzle and diffuser assemblies. a housing (410A, 410B, 410C, 510A, 510B, 510C) having a motive fluid inlet (411, 511) to receive motive fluid, a suction fluid inlet (412, 512) to receive suction fluid and a fluid outlet (413, 513) to output the motive fluid and the suction fluid a plurality of nozzle and diffuser assemblies (450, 550) configured to fit within the housing wherein each of the nozzle and diffuser assemblies comprises: a nozzle; a diffuser a connecting structure connecting the nozzle to the diffuser, the connecting structure configured to permit fluid flow between the nozzle and the diffuser, the connecting structure having apertures (182, 482, 582) configured to allow fluid to be drawn into the fluid flow between the nozzle and the diffuser; a nozzle; a diffuser a connecting structure connecting the nozzle to the diffuser, the connecting structure configured to permit fluid flow between the nozzle and the diffuser, the connecting structure having apertures (182, 482, 582) configured to allow fluid to be drawn into the fluid flow between the nozzle and the diffuser; wherein the housing comprises a first supporting wall (421, 521) and a second supporting wall (422, 522), wherein each of the first supporting wall and the second supporting wall extends radially across an interior of the housing, the first supporting wall and the second supporting wall axially spaced apart along the housing, each of the first supporting wall and the second supporting wall having a plurality of bores to receive the plurality of the nozzle and diffuser assemblies, wherein the nozzle and diffuser assemblies are individually removable from a downstream end of the housing, characterized in that an upstream end of each of the plurality of nozzle and diffuser assemblies is axially spaced from a constraining radial surface of the first supporting wall (421, 521) of the housing to allow for thermal expansion of the nozzle and diffuser assemblies.