Heat Sink & Heat Exchanger Design

Though microchannel heat sinks are highly effective cooling devices for electronic components, significant temperature variations across the chip still persist since the heat transfer performance deteriorates in the flow direction in microchannels as the boundary layers thicken and the coolant heats up. The temperature non-uniformities are compounded by the fact that different integrated circuit (IC) components can generate significantly different amounts of heat. These temperature gradients across the chip and so-called localized “hot spots” can compromise the reliability of ICs and result in early failures. Therefore, it is desirable to further enhance the heat transfer performance of a microchannel heat sink, both globally and locally. One of the proposed strategies involves the creation of recess(es) in the lid of a microchannel heat sink for modulating the flow resulting in heat transfer enhancement.

A conventional microchannel heat sink involves fluid flowing straight through from the entrance to the exit of the channel. When a recess is introduced into the lid, the fluid relaxes into this expansion. For a given fixed pressure drop across the heat sink, the presence of the recess
induces more flow into the system due to its lower flow resistance, leading to a higher heat transfer rate (without the penalty of increased pressure head). In addition, when the flow re-enters the microchannels from the recess, re-initialization of the boundary layer causes significant increases in the local heat transfer coefficients. Such strategies can be exploited to mitigate the
critical issue of hot spots.

Thermal management is a must in many applications.

• Cooling of computer chips
• Cooling of batteries
• Heat dissipation of power plants

Air is still a coolant of preference.

• Simple & affordable equipment
• Easy maintenance
• Reliable & safe with electronics
• Available in the atmosphere

The conventional heat sink & heat exchanger designs cannot maintain safe operating temperatures for electronics or cope with the heat dissipation loads. The newly designedCross-connected alternating converging-diverging channel can :

• Reinitializes the boundary layers repeatedly
• Induces fluid mixing and more uniform temperature build up
• Induces chaotic advection
• Improves wall temperature significantly compared to the straight channel heat sink at negligible pressure drop penalty