Improving Heat Flux Performance of Flat Surface in Spray-Cooling Systems

A method has been developed for improving heat flux performance relative to flat surfaces in spray-cooling systems. Similar enhancement techniques have been used for convective heat transfer, but, to the best knowledge at the time of this reporting, never spray cooling of foam. Previous studies have shown that spray-cooling heat flux enhancements may be attained using enhanced surfaces. However, most enhanced surface spray-cooling studies have been limited to extended and/or embedded surface structures. This study investigates the effect of foam on spraycooling heat flux.

The foam used was graphite Poco Foam. The foam piece was attached to a copper block with a cross-sectional area of 2 cm2 using high-thermal-conductivity epoxy as the thermal interface material. Measurements were also obtained on a heater block with a flat surface for purposes of baseline comparison. A 2×2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed conditions, with a chamber pressure of 41.4 kPa.

Results show that the highest heat flux attained was 113 W/cm2 using the graphite Poco Foam. The use of the foam does not require a significant amount of time dedicated to machining the heat exchange surface, and thus is a time-efficient enhancement technique. In addition, with foam, the thermally controlled surface does not experience abrupt catastrophic failure.

This work was done by Eric A. Silk of Goddard Space Flight Center. For further information, contact the Goddard Innovative Partnerships Office at (301) 286-5810. GSC-15553-1

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