Effects of Surface Roughness and Inclination Angle on Nucleate Boiling of PF-5060 Dielectric Liquid on Copper

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, h_NB, increases with increasing surface roughness and with decreasing inclination angle. The measured enhancements in h_NB with increased surface roughness are in excess of 36%. In the upward facing orientation, the experimental values of h_NB are correlated in terms of the surface heat flux in the experiments, q, as: h_NB = A q^B. 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.