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Experiments are performed to investigate saturation boiling of degassed PF-5060 dielectric liquid on microporous copper dendrite surface layers deposited on 10×10 mm2 Cu substrates. The electrochemically deposited surface layers are of different thicknesses (145.6 μm, 46.3 μm, and 33.1 μm). The thickest layer gives the best results: the saturation CHF of 25.27 W/cm2 occurs at a surface superheat of only 2.9 K and the maximum nucleate boiling heat transfer coefficient, hMNB, near the end of the fully developed nucleate boiling region, is 8.76 W/cm2 K. In addition, nucleate boiling ensues at a surface temperature slightly above saturation (<0.5 K), with no temperature excursion. The temperature excursions before initiating boiling on the 46.3 μm and 33.1 μm thick Cu nanodendrite surface layers are small (3.7 K and 6 K), corresponding to surface temperatures of ∼55.1°C and 57.4°C, respectively. These temperatures are much lower than recommended (85°C) for reliable operation of most silicon electronics and central processor units.

Saturation pool boiling experiments of PF-5060 dielectric liquid are performed using eleven different Cu surfaces with average roughness, Ra = 0.21 to 1.79 μm, at inclination angle, θ, from 0° (upward facing) to 180° (downward facing). Nucleate boiling heat transfer coefficient, hNB, increases with increasing surface roughness and with decreasing inclination angle. The measured enhancements in hNB with increased surface roughness are in excess of 36%. In the upward facing orientation, the experimental values of hNB are correlated in terms of the surface heat flux in the experiments, q, as: hNB = A qB. The coefficient “A” increases from ∼0.14 to 0.23, while the exponent “B” decreases from 0.76 to 0.69 as Ra increases from 0.21 to 1.79 μm.

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