This invention focuses on a technique to stabilize the flow boiling process within the micro/mini channels and achieve a better heat transfer performance, by modifying the geometry. The stepped fin microchannels are formed by reducing the fin height, in steps, at certain lengths, in a conventional straight microchannel. Depending on the heat transfer and stabilization requirements, the number of steps, the step height and the length of cut can all be varied. This geometry allows room for the vapor to expand span wise and hence flow downstream without appreciable flow reversal, acting like a diffuser.
Stepped fin microchannel design:
Thermal management of electronic devices involving high heat flux dissipation, such as
With heat flux dissipation levels from small form factor devices skyrocketing, conventional cooling methods like air flow over extended surfaces etc. have been unable to keep pace with the cooling demands.
Cooling by single phase flow through microchannels have gained tremendous popularity as a promising alternative and is being commercialized rapidly. However, significant temperature variations across the heat sink persist since the heat transfer performance deteriorates in the flow direction in microchannels as the boundary layers thicken and the coolant heats up by sensible heat gain.
Hence, for very high heat flux dissipation from narrow spaces, flow boiling through microchannels is evolving as a preferred cooling solution.
Two-phase flow instabilities may arise when boiling occurs in conventional size channels and more so in a parallel array of multiple micro/mini-channels. These undesired effects must be controlled or mitigated because they can induce mechanical vibrations in the system, degrade the heat transfer performances (premature dryout, CHF limitation) etc and lead to unreliable operation. Also, two-phase pressure drop is very high and increases the pumping power requirements significantly which affects the pump sizing. To enable and implement miniature cooling solutions, low pumping power is a key requirement. This behooves the invention of a technique to achieve all round improvement.