Experimental Study of a Novel Helix-Shaped Oscillating Heat Pipe and Design Parameters for Flow Stabilization

Abstract A novel helix-shaped oscillating heat pipe (OHP) designed for enhanced heat transfer in thermal management and heat recovery was studied experimentally. Two orientations were explored: side-heated, the intended orientation in which improved fluid circulation is expected, and bottom-heated, a control resembling traditional bottom-heated OHPs. Results showed stronger circulation, reduced temperature differences, and lower start-up thresholds in most side-heated cases. This orientation achieved higher maximum heat loads at a fill ratio of 0.5, although the maximum heat load decreased at a fill ratio of 0.7. Notably, the experimental OHP attained an effective thermal conductivity over 9,000 W m-K-1 in multiple tests and a maximum heat transport of 676 W. Additional parameters were explored including heat load, fill ratio, condenser temperature, and the presence of noncondensable gases (NCGs). NCGs increased the temperature drop as expected, but also raised the maximum heat transport, indicating potential benefits in certain applications. Elevated condenser temperatures decreased temperature drops, but also reduced maximum heat transport. A previously developed OHP performance model was expanded to evaluate the novel helix-shaped OHP. The model reasonably predicted temperature drops during degassed experiments under moderate heat loads. However, most data points fell outside the model's scope, emphasizing the need to extend it to handle condenser bubble collapse. The expanded analytical models for side-heated helix OHPs highlighted restrictions on circulation that differed from traditional, bottom-heated OHPs, which explains the superior performance of the novel design.