Thermal performance of two-phase thermosyphon loop in rotating thin pad

Abstract

Thermal performances of a sub-atmospheric Rotating Two-Phase Loop Thermosyphon Pad (RTPLTP) of 1 mm channel height were experimentally studied. Flow structures of vapor-liquid circulations, boiling/condensation heat transfer rates and thermal resistances (Rth) for the RTPLTP were detected at rotor speeds of 0, 100, 300 and 500 rev/min. With each rotor speed tested, experiments were performed at four ascending boiling numbers (Bo) with four descending non-dimensional condenser thermal resistances (Rth,con) at each Bo. Parametric test conditions specified by Bo, Rth,con and relative centrifugal acceleration (Ω) were 0.16–0.82, 0.07–0.3 and 0–28.2, respectively. Acting by the rotational force effects, the churn flow boiling structures in present thin static TPLTP initially transited into intermittent boiling flow structures with the temporal drifts of vapor bubbles along the vortical flow pathways in the rotating pad at Ω = 1.1. Further increasing Ω, the boiling flow structure yielded to the swaying and then the stable continuous tiny-bubble streams centered at the nucleate sites on the rotating boiling surface. Both averaged Nusselt numbers over evaporator (Nueva) and condenser (Nucon) of present RTPLTP increased as Ω increased. While Nucon kept increasing as Bo increased at all Ω tested, increases of Bo initially reduced Nueva at low Ω but turned to elevate Nueva at high Ω due to the Ω-induced variations in boiling flow structures. With the combined Bo and Ω effects on Nueva and Nucon, the total thermal resistances (Rth) of present thin RTPLTP decreased as Bo and/or Ω increased; but were increased by raising Rth,con. Empirical correlations evaluating Nueva, Nucon and Rth with Bo, Ω and Rth,con as the determining variables were devised to assist the relevant applications.