Comparison of pool boiling heat transfer for different tunnel-pore surfaces

Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were performed. Experimental data were discussed for three kinds of enhanced surfaces: tunnel structures (TS), narrow tunnel structures (NTS) and mini-fins with the copper wire net (NTS-L). The experiments were carried out with water, ethanol, R-123 and FC-72 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 and 10 mm high rectangular main fins and horizontal inter-fin surface. The NTS-L surfaces were formed by mini-fins of 0.5 and 1 mm height uniformly spaced on the base surface. The wire mesh with an aperture of 0.32, 0.4 and 0.5 mm sintered with the fin tips formed a system of connected perpendicular horizontal tunnels. The tunnel width was 0.6 – 1.0 – 1.5 mm and the depth was 0.5 or 1.0 mm. The effects of the Bond number and dimensionless parameters for three kinds of enhanced structures on heat transfer ratio at nucleate pool boiling were examined