Experimental investigations of effect of sound waves on oscillation and startup characteristics of oscillating heat pipe at different orientations

This research deals with the effects of working fluid and use of sound waves on the startup and heat transfer characteristics in terms of thermal resistance of a closed loop oscillating heat pipe. The performance of the oscillating heat pipe is checked for different orientations as 90? (vertical position), 60?, and 30?. Initially water is used as working fluid and performance of the oscillating heat pipe is checked with and without sound waves. Then 0.1 wt.% Al2O3-water nanofluid is utilized as working fluid in oscillating heat pipe and its performance is analyzed with and without sound waves. In this work, sound waves of 1 kHz frequency are passed through the evaporator section of closed-loop oscillation heat pipe. Application of sound waves improved the oscillation characteristics of the CLOHP with reduced startup time and enhanced thermal performance at all orientations. In comparison between working fluids, 0.1 wt.% Al2O3-water nanofluid showed better oscillation characteristics at all orientations of CLOHP except at 90? where use of sound waves leads to dry-out condition.