Single chamber compact thermosyphons with micro-fabricated components

This study presents the thermal performance evaluation of a compact single-chamber thermosyphon. The thermosyphon set-up has a central evaporator section with integrated fins for cooling along the edges. The evaporator employs a microfabricated three-dimensional copper structure for enhancing boiling heat transfer. The thermal performance of the system was characterized at various power levels and condenser cooling conditions. The size of the boiling enhancement structure and effects of liquid fill volumes on performance were also investigated. Incorporation of the enhancement structure resulted in an improvement in the thermosyphon performance by decreasing the wall temperature at the evaporator by 8/spl deg/C, for a power dissipation of 36 W/cm/sup 2/ at an air speed of 1 m/s. The maximum heat flux obtained based on a maximum evaporator temperature of 75/spl deg/C for an air speed of 1 m/s was 42.5 W/cm/sup 2/. Variation in the liquid fill volume showed negligible effect on the maximum temperature at the evaporator, as long as the enhanced structure was fully flooded. Increasing the footprint size of the enhancement structure showed marginal improvement in boiling heat transfer performance. This increased the number of pores in the enhancement structures and did not result in a corresponding increase in the performance.