Heat exchanger

A two-start helical heat exchanger comprising:

• a helical baffle extending along a length of the heat exchanger and having first and second surfaces,
• a cylindrical core encircled by the helical baffle, and
• a casing within which the baffle is mounted;
• wherein the helical baffle is a hollow thread;
• wherein the first surface of the baffle is an interior surface of the baffle and is arranged to provide a first helical fluid flow path within the baffle for a first fluid;
• wherein the second surface of the baffle is an exterior surface of the baffle and is arranged to provide a second helical fluid flow path around the baffle for a second fluid, the second surface having a flat portion in direct thermal contact with an interior surface of the casing;
• wherein the cylindrical core is hollow at a first end to form a fluid inlet for the first fluid flow path, hollow at a second end to form a fluid outlet for the first fluid flow path, and solid between the two hollow ends;
• and
• wherein the baffle is arranged such that the first and second fluid flow paths are in thermal contact with each other through the baffle, the second fluid flow path is in direct thermal contact with the casing, and the first fluid flow path is in thermal contact with the casing through the baffle.