Study of a Single, Straight Tube Pulsating Heat Pipe (Oscillation Behavior and Heat Transport Characteristics)

Abstract

Oscillation behavior and heat transport characteristics in a pulsating heat pipe consisting of a single and straight tube with an open end are investigated experimentally. Periodic oscillation of a vapor plug with a large stroke over two thirds of the heat transport tube length is excited for heating powers larger than 20 W at horizontal orientation and continues for a long period over 8,000 s without cease. Heat transport rate and the effective thermal conductivity increase with heating power up to approximately 75 W and 40 kW/(m·K), respectively. Heating section, which has an inner diameter little larger than that of the heat transport section, is maintained at almost the saturation temperature of the working liquid throughout the succession of oscillation. Liquid film beneath the vapor plug is partially pushed back to the heating section to spread on the wick each time the vapor plug shrinks. The small step at the tube connection between the heating section and the heat transport tube section and the wick inside the heating section are shown to be essential structures for realizing the stable oscillation leading to high heat transport characteristics.