Patent ID: 7048043

Claim:
Grooved metal tubes ( 1 ), of thickness T f at the bottom of the groove, outer diameter De, intended for the manufacture of heat exchangers operating in evaporation or condensation or in reversible mode and using a phase transition coolant, said tubes being grooved internally with N helical ribs ( 2 ) of an apex angle α, height H, base width L N and helical angle β, two consecutive ribs being separated by a typically flat-bottomed groove ( 3 ) of width L R , with a pitch P equal to L R +L N , and wherein said tubes show a Cavallini factor at least equal to 3.1, the tubes further comprising an axial grooving creating in said ribbing notches with a triangular profile with a rounded top, said top showing an angle y ranging from 25 to 65°, said top is at a distance h from the bottom of said grooves ranging from 0 to 0.2 mm, characterised in that, a) the outer diameter De is between 4 and 20 mm, b) the number N of ribs ranges from 46 to 98, particularly as a function of the diameter De, c) the rib height H ranges from 0.18 mm to 0.40 mm, particularly as a function of the diameter De, d) the apex angle α ranges from 15° to 30°, e) the helical angle β ranges from 18° to 35°, so as to obtain simultaneously a high heat exchange coefficient both in evaporation and condensation, a low pressure loss and the lightest possible tube.