A Capillary Tube Pulsating Heat Pipe With Asymmetric Adiabatic Channels for Thermal Management

The two-phase flow passive thermal management device, an asymmetric (adiabatic channel) closed-loop pulsating heat pipe (aCLPHP), has been investigated experimentally. The thermo-hydrodynamic behavior of a pulsating heat pipe (PHP) strongly depends on various operating and geometric parameters. In this effort, asymmetry has been adopted to promote the unidirectional two-phase oscillatory motion of the working fluid. In the present study, simultaneous pressure and temperature variations under gradual and sudden heat loads are monitored to estimate thermal performance. The effects of inclination angles (IAs), heat loads, working fluids, and filling ratios (FRs) on thermal performance have been demonstrated using average thermal resistance. In a two-turn (four-channel) aCLPHP in bottom heating mode, acetone and water were used as working fluids within 50%-70% of FRs. The results show that the startup phenomena of two-phase flow and pseudo-steady-state temperature were achieved using acetone at a 60% FR up to 30° angle from a horizontal orientation. In the vertical orientation, the working fluid water at 60% FR performed well under a sudden heat load of 50 W. Adding asymmetric adiabatic channels to a PHP can be a simple and inexpensive way to improve its thermal performance.