Super Micro-Cool: Forced Boiling in a Micro-channel Pumped Fluid Loop

Two-phase heat rejection offers vast potential in reducing the thermal control footprint of vehicles and equipment in terms of mass, volume, and parasitic power loss. This potential follows from the latent heat associated with phase change: in order to remove the same heat as a single phase water loop having a 20C temperature rise, a two-phase loop needs only 5% the flow rate, and consequently 3 orders of magnitude lesser pumping power, while simultaneously providing a constant heat rejection temperature. A key issue in consideration of two-phase, however, is predicting behavior in partial and micro-gravity environments. Recent research indicates that the performance of forced boiling in constrained channels, e.g. micro-channels or micro- heat exchangers, is not affected by the presence or lack of gravity. This is a consequence of a characteristic length scale small enough that surface tension forces dominate flow behavior rather than buoyancy forces which dominate at conventional scales. This project proposes to demonstrate a pumped two-phase cooling loop, e.g. one that collects heat from heat sources through forced micro-channel boiling, mitigating unknowns of microgravity boiling, and does not employ a compressed vapor phase.

Two-phase pumped loops have many strong benefits in cooling applications outside of NASA, particularly in modern cloud computing server farms and rack cooling where the low flow rate and parallel placement of a vast number of two-phase micro coldplates can be leveraged for considerable cooling power reductions.

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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