Authors:

Fredrick G Mungai

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About Paper:

Two-phase loop thermosyphons are a promising technology with the potential to passively cool high heat flux electronics using only buoyancy forces to pump a coolant. The coolant undergoes a large density difference that causes flow circulation due to evaporation, when it adsorbs heat from a source, and condensation, when the heat is released to the environment. Modeling thermosyphons remains challenging due to the complex coupling of flow and heat transfer resulting from natural circulation of the flow. Therefore, this research seeks to develop a predictive mathematical model, with complementary experiments, to characterize the operation of small-scale loop thermosyphons. A model has been developed to predict the steady state operation of the thermosyphon. Experiments with an in-house loop thermosyphon facility that is 0.88 meters tall and constructed using 1.27 centimeter diameter tubing, are used to verify the model and identify opportunities to improve its predictive capabilities. Startup instabilities observed when subcooled liquid enters the evaporator causing dynamic pressure, flow and temperature oscillations. This motivates extending to a transient two- phase flow model, to capture the observed mechanism, enabling better understanding of the occurrence of the instabilities and methods of mitigation. This research will address the lack of predictive capabilities for two- phase flow instabilities during closed-loop natural circulation, which is one of the main barriers to the adoption of this technology in industry. Future work involves running the experimental facility for a comprehensive set of operating parameters to capture all the thermosyphon's operating regimes, providing a database for validation of the transient model. Keywords: [no keywords provided]

Source:

Purdue University / 2024

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Co-authors:

Fredrick G Mungai