Thermal performance of a compact two-phase thermosyphon: response to evaporator confinement and transient loads

摘要

The heat dissipation rates at the chip level are slated to reach the 100 W/cm~2 mark 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 confinement on the performance of an enhanced microstructure based thermosyphon,that has shown very high heat transfer rates (upto 100 W/cm~2).The top spacing between the microstructure and the cover of the evaporator was varied and the effect of this variation was stuided.The effect of sidewall spacing was studied next.The resuls show that the effect of confinement on the boiling performance of the microstructure is negligible.Total blockage does deteriorate the performance at very high heat fluxes (40-70 W/cm~2).However,a minute gap of the order of a few millimeters is sufficient to get to performance levels close to pool boiling.The response of the confined setup was then studied under suddenly applied loads.This is of particular importance to practical applications where a sudden temperature excursion could be detrimental to electronics.The results show a very smooth transition from startup to steady state.No incipience excursion was observed in any of the runs.