Effect of geometric asymmetry on thermal performance in non-coaxial L-shape oscillating heat pipe

Abstract

The paper investigates the performance of a novel oscillating heat pipe with a unique L-shaped geometry, where the evaporator is oriented at a 90° angle to the condenser. The experiment explores the influence of gravitational acceleration by adjusting the inclination angle of the system across a full range from 0° to 180°, using acetone as the working fluid. The capillary tube has an inner diameter of 1.5 mm, allowing the formation of liquid plugs and vapor bubbles. Three filling ratios were evaluated: 50 %, 70 %, and 80 %, with a maximum applied heat flux of 43 kW m⁻². Under optimal conditions, the thermal resistance was found to be 0.48 K W⁻¹. The findings indicate that the geometric design and orientation relative to the gravitational field of Earth have a significant impact on the thermal performance of the oscillating heat pipe. Although the device has relatively few bends, it achieved efficient horizontal heat transfer under certain conditions. In particular, these results, particularly for high filling ratios, have not been reported in previous studies. In addition, the research improves the analysis of oscillating heat pipes, with thermal resistance trends providing valuable insights into start-up behavior, overheating risk, and different operating modes.