Effect of Dead Volumes on Single Closed Loop Pulsating Heat Pipes

Pulsating Heat Pipes (PHPs) are novel promising two-phase passive heat transfer devices that seem to meet all present and possibly future thermal requirements. Although grouped as a sub-class of the heat pipes, the PHPs governing phenomena are quite unique and not fully understood yet. In particular, single closed loop PHPs, that might be considered as the basic constituents of multi turns PHPs, manifest a large number of drawbacks mostly related to the device thermal performance and reliability, i.e. the occurrence of multiple quasi-steady states during device operation. Many attempts have been made in literature in order to face the problem and promote the circulation of the working fluid in a preferential direction. In order to understand the effect of dead volumes on the PHP working regimes and on its stability, two slightly different versions of the single closed loop PHP showed in figure 1 (inner tube diameter of 2.0 mm, filled with ethanol 60 % vol.) are tested.