Thermal management for the future generations of electronics faces challenges including total heat dissipations exceeding 100 W and local hotspots resulting from non-uniform heating. This work develops microchannel heat sinks with cross-linked channels to achieve a better chip temperature uniformity under non-uniform heating conditions. Stream-wise microchannels with a hydraulic diameter of 420 μm are subjected to pressure driven water flow. Channel cross-links with a hydraulic diameter of 150 μm, under non-uniform heating conditions, allow fluid lateral transport between the stream-wise channels in the region receiving the largest heat flux and those on the rest of the chip. As a result, a better chip temperature uniformity is achieved by utilizing the local pressure difference and capillary effect. Experimental results with a localized heating condition demonstrate an improvement of approximately 10% in the ratio of temperature of the heater to that of the rest of the chip. Analysis suggests that greater improvement can be achieved through optimization of the dimensions of the cross-links with respect to those of the stream-wise channels and through tailoring more cross-links within the hotspot region.
In the present study, self-sustained shear layer oscillations over shallow, open cavities beneath a low speed, subsonic, laminar boundary layer were studied experimentally in a wind tunnel. The cavities were rectangular in cross-section. The research concentrated upon determining the effects upon cavity resonance of rotating the leading edge of the cavity away from normal to the flow direction. Cavity resonance was identified through spectra of flow fluctuations sensed with hot wire anemometer probes. The resonance frequency was found to decrease gradually as the cavity leading edge was rotated up to 30 degrees from normal to the flow. Nomenclature D cavitydepth(m) L cavity length (m) L' U W effective stream wise cavity length, L/Cos a (m) .-./ St s t r o u~ number (W or ~L'/u) mean free stream velocity in direction x (ds) spanwise width of the cavity (m) f frequencyW) n x streamwise coordinate (m) y transverse ooordinate (m) a 0 h disturbance wave length (m) w angular frequency (radiands) mode of oscillation, n = 1,2, 3 . .angle of cavity rotation from normal (degrees) boundary layer momentum thickness at the cavity leading edge (m)
The improved rates of heat transfer in microchannel gas flows are promising for the design and development of microfluidic systems. This research focuses on the flow characteristics of air in rectangular micro/minichannels at moderate velocities (∼100 m/sec). The 50.8 mm long channels vary from approximately 266 μm to 1090 μm in hydraulic diameter, and the aspect ratio ranges from 0.1 to 0.75. The value of Re ranged from 250 to 4300, with the intention of studying the transition to turbulence. The friction factor is found to be higher than predicted values for Re < 1400 and lower when Re > 1400 suggesting earlier transition to turbulence.
Two-phase microchannel heat sinks are promising for the cooling of high power VLSI chips, in part because they can alleviate spatial temperature variations, or hotspots. Hotspots increase the maximum junction temperature for a given total chip power, thereby degrading electromigration reliability of interconnects and inducing strong variations in the signal delay on the chip. This work develops a modeling approach to determine the impact of conduction and convection on hotspot cooling for a VLSI chip attached to a microchannel heat sink. The calculation approach solves the steady-state two-dimensional heat conduction equations with boundary conditions of spatially varying heat transfer coefficient and water temperature profile. These boundary conditions are obtained from a one-dimensional homogeneous two-phase model developed in previous work, which has been experimentally verified through temperature distribution and total pressure drop measurements. The new simulation explores the effect of microchannels on hotspot alleviation for 20 mm × 20 mm silicon chips subjected to spatially varying heat generation totaling 150 W. The results indicate that a microchannel heat sink of thickness near 500 μm can yield far better temperature uniformity than a copper spreader of thickness 1.5 mm.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.