Abstract: Provided are heat exchanging structures 12 for use in transferring heat energy between an exchange fluid 22 and a working fluid 14. An exemplary structure 12 has a face sheet 30, a back sheet 36 and first and a second interior sheets 32, 38. The first and second interior sheets 32, 38 are undulant and are bonded to one another at a plurality of interior joints 42. The first interior sheet 32 is bonded to the face sheet 30 at a face joint 34 and the second interior sheet 38 is bonded to the back sheet 36 at a back joint 40. A fluid passage 44 is formed between the first and second interior sheets 32, 38. The exchange fluid 22 circulates about the structure 12 and exchanges heat with the working fluid 14.