Experimental study on the thermal performance of a novel two-phase loop thermosyphon under low-heat-flux conditions

Abstract

Two-phase loop thermosyphons are efficient heat transfer components that do not require extra power and can effectively transfer heat over long distances. In this study, two kinds of novel ethanol loop thermosyphons with and without wicks inside their evaporators were fabricated to experimentally investigate the start-up characteristics and thermal performance of the systems under low-heat-flux conditions and with different filling ratios; in addition, there was no height difference between the evaporator outlet and condenser inlet. As a result, temperature overshoot and geyser boiling were evidenced as start-up phenomena specific situations. Both systems failed to transfer heat when the filling ratio was below 30 % because some temperature measurement points were higher than 100 °C, at which point the limits of the experiment were reached. When the heat input was higher than 10 W, the loop thermosyphon with a wick structure could run and stay stable, while the regular loop thermosyphon system stabilized when the heat input was higher than 25 W. The increase in the filling ratio worsened the uniformity of the temperature distribution in the evaporator. The thermal resistance of the system was at its minimum when the filling ratio was 70 %. Both systems had good heat transfer performance when the heat input was high enough.