Grooved metal tubes (1), of outer diameter De, the tubes being grooved
internally with N helical ribs (2) of an apex angle , height H, base
width LN and helical angle , two consecutive ribs being separated
by a flat-bottomed groove (3) of width LR, with a pitch P equal
to LR+LN. These tubes are characterised in that,
- a) De is between 4 and 20 mm,
- b) the number N of ribs ranges from 46 to 98,
- c) the rib height H ranges from 0.18 mm to 0.40 mm,
- d) the apex angle ranges from 15 to 30,
- e) the helical angle ranges from 18 to 35. These
tubes make it possible to simultaneously obtain a high heat exchange coefficient
in evaporation and condensation and a low pressure loss.
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