Abstract: A heat exchanger is disclosed having a first chamber, a second chamber positioned inside the first chamber, and a third chamber positioned inside the second chamber. The first, second, and third chambers are in coaxial alignment. A first portion of a first helical tube is positioned inside the second chamber and a second portion of the first helical tube is positioned inside the third chamber and a second helical tube is positioned inside the first chamber. The heat exchanger heats a cryogenic liquid to a gas phase using at least three different heat transfer fluids in one contained unit without mixing any of the fluids in the exchanger.