Abstract— This paper focuses on two-phase flow boiling of
refrigerant R134a inside a copper multi-microchannel heat sink
for microelectronic central processing unit cooling applications.
The heat sink is composed of 100 parallel microchannels, 100 µm
wide, 680 µm high, and 15 mm long, with 72-µm-thick fins
separating the channels. The base heat flux was varied from
2.57 to 189 W/cm2 and the mass flux from 205 to 1000 kg/m2s,
at a nominal saturation temperature of 63 °C. Over 40 000
local heat transfer coefficients were measured at 35 locations
using local heaters and temperature sensors, for which different
heat transfer trends were identified. The main ones were that
the heat transfer coefficient increased with heat flux and was
independent of mass flow rate. Heat transfer coefficients as high
as 270 000 W/m2K (relative to the base area) were reached,
keeping the chip under 85 °C with a maximum of 94 kPa of
pressure drop, for no inlet subcooling and a coolant flow rate of
1000 kg/m2s.