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Pulsed Boiling Immersion Cooling of Microelectronic Circuits

IP.com Disclosure Number: IPCOM000121302D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 111K

Publishing Venue

IBM

Related People

Anderson, TM: AUTHOR [+2]

Abstract

Heat can be dissipated from computer chips, heat sinks attached to computer chips, and other surfaces to known fluids by pool or convective boiling. In conventional boiling processes, vapor must be dissipated by condensation or flow away from the heated surface at the same rate at which it is generated. The upper limit for the rate of heat dissipation by conventional boiling processes is largely determined by the onset of film boiling, which is commonly referred to as burn-out.

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This is the abbreviated version, containing approximately 52% of the total text.

Pulsed Boiling Immersion Cooling of Microelectronic Circuits

      Heat can be dissipated from computer chips, heat sinks
attached to computer chips, and other surfaces to known fluids by
pool or convective boiling.  In conventional boiling processes, vapor
must be dissipated by condensation or flow away from the heated
surface at the same rate at which it is generated.  The upper limit
for the rate of heat dissipation by conventional boiling processes is
largely determined by the onset of film boiling, which is commonly
referred to as burn-out.

      Referring to Fig. 1, one or more computer chips or other heat
sources 100 are immersed in a conventional liquid coolant in a
suitable enclosure.  A periodic variation of the coolant saturation
temperature is imposed on the system by varying the pressure 101 in
the enclosure.  The amplitude of the pressure oscillations is
controlled so that the saturation temperature falls close to the
thermodynamic temperature (low subcooling) 102 for part of the cycle
and rises close to or above the heated surface temperature (high
subcooling) 103 at another time in the cycle.  Vigorous boiling and
boiling-induced mixing, with the associated high rate of heat
dissipation, ensues when the subcooling is low 104.  Vapor is
condensed when the liquid is subcooled 105, which reduces or
eliminates the net vapor generation. Large-scale mixing of the
coolant, which will further enhance heat transfer, is promoted by the
repeated growth and collapse of vapor bubbles near the heated
surface.  This mixing is in addition to the usual boiling-induced
mixing that results from steady boiling.  Pressure variations are
sine, square or customized waveforms where the relative time per
cycle of high and low subcooling are set to achieve the desired
cooling and net vapor generation rates.  A rapid transition between
the high and low system pressures (sub-cooling) will induce violent,
large-scale mixing, and further enhance cooling.  More gradual
pressure-induced variations of the saturation temperature will yield
less violent mixing when that is a design requirement.  Heat fluxes
in excess of what would cause burn-out in steady boiling can be
accommodated over a port...