A coaxial heat transfer tube , comprising - a first inner heat transfer tube having a first primary straight part and a first primary curved part , - a first outer heat transfer tube having a first primary straight part , wherein - the first primary straight part of the first outer heat transfer tube radially surrounds at least a part of the first primary straight part of the first inner heat transfer tube , and - the first primary straight part of the first outer heat transfer tube does not comprise a longitudinal seam, characterized in that - the first outer heat transfer tube also has a first primary curved part , - the first primary curved part of the first outer heat transfer tube radially surrounds the first primary curved part of the first inner heat transfer tube , and - the first primary curved part of the first outer heat transfer tube does not comprise a longitudinal seam; and in that the coaxial heat transfer tube comprises - thermally insulating material in between the first primary curved part of the first outer heat transfer tube and the first primary curved part of the first inner heat transfer tube and - a first spacer arrangement comprising at least one spacer element , the first spacer arrangement configured to define a distance (d) between an inner surface of the first outer heat transfer tube and an outer surface of the first inner heat transfer tube , wherein - a thermal conductivity of the thermally insulating material is from 1 W/mK to 10 W/mK at a temperature of 20 °C and - the first spacer arrangement is arranged in between a first end of the first outer heat transfer tube and a second end of the first outer heat transfer tube in a direction of extension (de 120 ) of the first outer heat transfer tube . - a first inner heat transfer tube having a first primary straight part and a first primary curved part , - a first outer heat transfer tube having a first primary straight part , wherein - the first primary straight part of the first outer heat transfer tube radially surrounds at least a part of the first primary straight part of the first inner heat transfer tube , and - the first primary straight part of the first outer heat transfer tube does not comprise a longitudinal seam, characterized in that - the first outer heat transfer tube also has a first primary curved part , - the first primary curved part of the first outer heat transfer tube radially surrounds the first primary curved part of the first inner heat transfer tube , and - the first primary curved part of the first outer heat transfer tube does not comprise a longitudinal seam; and in that the coaxial heat transfer tube comprises - thermally insulating material in between the first primary curved part of the first outer heat transfer tube and the first primary curved part of the first inner heat transfer tube and - a first spacer arrangement comprising at least one spacer element , the first spacer arrangement configured to define a distance (d) between an inner surface of the first outer heat transfer tube and an outer surface of the first inner heat transfer tube , wherein - a thermal conductivity of the thermally insulating material is from 1 W/mK to 10 W/mK at a temperature of 20 °C and - the first spacer arrangement is arranged in between a first end of the first outer heat transfer tube and a second end of the first outer heat transfer tube in a direction of extension (de 120 ) of the first outer heat transfer tube . <EOS>