Improving flat heat pipe performance with lattice Boltzmann method: Evaluating flow and heat transfer in typical porous wick structures

Flat heat pipes are essential for cooling electronic devices, with performance largely dependent on the wick structure. Reliable models for microgroove, sintered powder, and mesh wick structures were developed and validated to investigate their operational differences. The flow field was simulated using the pseudo-potential multiple relaxation time Lattice Boltzmann Method, while the gas-liquid phase change temperature field was solved using the finite difference method. Gas-liquid distribution and heat flux variations were studied under different superheating levels and evaporation surface wettability conditions. Results showed that the microgroove wick was more effective at triggering nucleate boiling and preventing film boiling, with its maximum heat flux density 1.7 times higher than the sintered powder wick and 1.9 times higher than the mesh wick. Enhancing surface hydrophilicity increased the maximum heat flux density by 9.6%. Under no-gravity conditions, heat transfer performance deteriorated significantly, with the condensation heat transfer coefficient under normal gravity at least five times higher than under no-gravity. Improvements such as optimizing wick spacing, enhancing hydrophilicity, and promoting gas-liquid flow to prevent heat transfer deterioration, particularly film boiling, were recommended. This work provides methods for comparing different heat pipe wick structures and offers insights for enhancing heat transfer capabilities in various scenarios.