A coaxial heat transfer tube (100), comprising a first inner heat transfer tube (110) having straight parts (111, 113, 115, 117) and curved parts (112, 114, 116), a first outer heat transfer tube (120) having straight parts (121, 123, 125, 127) and curved parts (122, 124, 126). The first outer heat transfer tube (120) radially surrounds the first inner heat transfer tube (110) at least within the first primary straight part (121) and the first primary curved part (122). Thermally insulating material (530) has been provided in between a curved part (122) of the first outer heat transfer tube (120) and a curved part (112) of the first inner heat transfer tube (110). Neither straight part (121) nor a curved part (122) of the first outer heat transfer tube (120) comprises a longitudinal seam. A method for making a coaxial heat transfer tube (100).