Abstract

In this work, the validity of the length-to-inner diameter ratio (L/D) as a scaling tool in extra-long two-phase thermosyphons for geothermal applications has been experimentally studied. Two thermosyphons with different dimensions were studied,maintaining the L/D equal to 110. The results obtained show that the thermosyphon of smaller size and larger inner diameter operated at higher vapor temperatures (up to 20 ◦C) and lower thermal resistances (up to 50%), showing that the L/D ratio is not sufficient to scale thermosyphons without losing fundamental information on the operation of these devices. A characteristic length, given by D2/L, has been proposed, which allows reducing by 30% the differences between the thermal resistance of both thermosyphons.