Critical heat flux from a simulated chip to a confined rectangular impinging jet of dielectric liquid

Abstract

Experiments are performed to investigate boiling heat transfer from a smooth 12.7 mm × 12.7 mm heat source to a jet of dielectric Fluorinert FC-72 liquid issued from a thin rectangular orifice into a channel confined between the surfaces of the heat source and the nozzle. General boiling and critical heat flux (CHF) trends are examined with respect to variations in nozzle exit velocity, U = 1−13 m s −1, nozzle width, W = 0.127−0.508 mm, confinement channel height above the heated surface, H = 0.508−5.08 mm, and subcooling, Δ T sub = 0−40° C. Two regimes of CHF, medium and high velocity, are discovered, and an empirical correlation is developed for the medium velocity regime. The primary difference between the two regimes is a weak dependence of CHF on channel height for medium velocities compared to a stronger dependence for high velocities. It is found that operating in the high velocity regime, especially for the smallest channel height, can result in decreasing CHF with increasing jet velocity due to a stream-wise reduction of liquid subcooling within the channel. A self-contained cooling module consisting of a 3 × 3 array of heat sources confirms the uniformity and predictability of cooling for each of the nine heat sources, proving that the confined jet geometry is well suited for cooling large arrays of high-power-density heat sources such as electronic chips dissipating heat fluxes as high as 250 W cm −2.