Performance of a compact two-chamber twophase thermosyphon: effect of evaporator inclination, liquid fill volume and contact resistance

摘要

The heat dissipation rates at the chip level are projected to reach 50-100 W/cm~2 for some future high performance electronic systems. Liquid cooling has been demonstrated to be a very efficient technique for the thermal management of such high heat dissipation rates. Past work on liquid immersion cooling using fluorocarbons has shown the advantage of using enhanced surfaces to reduce boiling incipience excursion and raise the critical heat flux (CHF). Thermosyphons are an alternative to liquid immersion and are suitable for point cooling applications, where very compact evaporators are needed. This study investigates the effect of evaporator inclination (from 0 deg to 90 deg) ont he performance of an enhanced microstructure based thermosyphon that has shown very high heat transfer rates (up to 100 W/cm~2 for fluorocarbons with a wall superheat excursion of 27.8 deg C). The results show a slight improvement in the boiling performance for a vertical orientation. The response of the setup was then studied for varying liquid fill volumes. This is of particular importance to practical applications where the liquid volume reduces corresponding to a reduction in the evaporator size. The results show negligible effect of variation in liquid volume, as long as the boiling surface is submerged. The performance deteriorates for partially submerged surfaces. Finally, the effect of different bonding techniques in the fabrication of the enhanced structure was investigated and the results show that a tip soldered structure has a large contact resistance and results in poor performance compared to a diffusion bonded structure.