A heat exchanger, comprising: a top enclosure comprising a finger plate or end cap (102c, 302a); a bottom enclosure comprising a finger plate or end cap; and a corrugated sheet between the top and bottom enclosure; wherein the heat exchanger is configured such that a first fluid flows on one side of the corrugated sheet and a second fluid flows on an opposite side of the corrugated sheet; wherein A) the heat exchanger comprises an anode cooler heat exchanger suitable for a solid oxide fuel cell system; characterized in that the top enclosure comprises a top finger plate; the bottom enclosure comprises a bottom finger plate; the corrugated sheet comprises a cylindrical metal sheet; the top finger plate comprises a hollow ring shaped plate having finger shaped extensions which extend into the inner portion of the ring; the bottom finger plate comprises a hollow ring shaped plate having finger shaped extensions which extend into the inner portion of the ring; and the top and bottom finger plates are offset from each other by one corrugation, such that fingers of the top finger plate cover every one either inward or outward facing recesses in the corrugated sheet, and fingers of the bottom finger plate cover every other one of the inward or outward facing recesses in the corrugated sheet; or B) the heat exchanger comprises a cathode recuperator single-shell heat exchanger comprising a monolithic assembly, the corrugated sheet comprises a single cylindrical corrugated fin plate, and further comprising a steam generator located above the cathode recuperator single-shell, wherein the steam generator comprises a steam generator coil, the steam generator coil is in fluid communication with a cathode exhaust outlet of the cathode recuperator to allow conversion of water to steam in the coil using heat of a stack cathode exhaust stream exiting the outlet of the cathode recuperator, and characterized in that the steam generator coil is supported by a baffle plate. a top enclosure comprising a finger plate or end cap (102c, 302a); a bottom enclosure comprising a finger plate or end cap; and a corrugated sheet between the top and bottom enclosure; wherein the heat exchanger is configured such that a first fluid flows on one side of the corrugated sheet and a second fluid flows on an opposite side of the corrugated sheet; wherein A) the heat exchanger comprises an anode cooler heat exchanger suitable for a solid oxide fuel cell system; characterized in that A) the heat exchanger comprises an anode cooler heat exchanger suitable for a solid oxide fuel cell system; characterized in that the top enclosure comprises a top finger plate; the bottom enclosure comprises a bottom finger plate; the corrugated sheet comprises a cylindrical metal sheet; the top finger plate comprises a hollow ring shaped plate having finger shaped extensions which extend into the inner portion of the ring; the bottom finger plate comprises a hollow ring shaped plate having finger shaped extensions which extend into the inner portion of the ring; and the top and bottom finger plates are offset from each other by one corrugation, such that fingers of the top finger plate cover every one either inward or outward facing recesses in the corrugated sheet, and fingers of the bottom finger plate cover every other one of the inward or outward facing recesses in the corrugated sheet; or B) the heat exchanger comprises a cathode recuperator single-shell heat exchanger comprising a monolithic assembly, B) the heat exchanger comprises a cathode recuperator single-shell heat exchanger comprising a monolithic assembly, the corrugated sheet comprises a single cylindrical corrugated fin plate, and further comprising a steam generator located above the cathode recuperator single-shell, wherein the steam generator comprises a steam generator coil, the steam generator coil is in fluid communication with a cathode exhaust outlet of the cathode recuperator to allow conversion of water to steam in the coil using heat of a stack cathode exhaust stream exiting the outlet of the cathode recuperator, and characterized in that the steam generator coil is supported by a baffle plate.