Comparison between miniature periodic two-phase thermosyphons and miniature LHP applied to electronic cooling equipment

Several tests have been carried out with two miniature periodic two-phase thermosyphons (PTPTs), which have been developed for thermal control applications. A PTPT is a wickless device which can operates even against gravity. The two PTPTs have the same condenser and accumulator and different evaporators: the evaporator Type A, which can contain a large amount of liquid (20 × 10−6 m3) and which can be tilted up to 90°, and the evaporator Type B, which has an internal volume of 5 × 10−6 m3 and can operate just in horizontal orientation. Their unsteady and their periodic steady state performances have been studied and compared with those of several miniature loop heat pipes quoted in the references. The paper shows that the PTPT thermal resistances are similar to those of miniature LHPs, even those of PTPTs are less influenced by the arrangement of the condenser and the evaporator with respect to the gravity. The thermal resistance, as the PTPT steadily operates, is about 0.55 K/W with a heat load of 110 W. The main experimental observation on the PTPT unsteady behaviour is that their start-ups are rather smooth in the most cases. However the start-up performances does not depend on any configuration and orientation of the loop element.