Boiling performance on surfaces with capillary-length-spaced one- and two-dimensional laser-textured patterns

Abstract

This investigation used laser-processed 25-μm-thick stainless steel foils as heaters in pool boiling experiments under subcooled and saturated conditions at atmospheric pressure. Boling surfaces were modified by a nanosecond fiber laser. In most cases, laser-textured parts on boiling surfaces were spaced apart by a capillary length of water (2.5 mm) and had different shapes and arrangements. Multi-scale micro-cavities (with diameters ranging from 0.2 to 10 μm) on the laser-textured areas of the surfaces provided potential active nucleation sites. The highest heat flux measured before the burnout was observed on the fully treated sample; this heat flux was a factor of 3.7 greater than that of the untreated sample. The sample with hexagonally arranged textured circular shapes with a diameter of 2.0 mm provided a more than 4-fold higher heat transfer coefficient compared to the untreated sample. All of the laser-textured boiling surfaces showed enhanced pool boiling heat transfer performance in comparison to the untreated surface. The optimal spacing between the laser-textured regions was experimentally found to be equal to the capillary length of the working fluid. Our results demonstrate that laser texturing has strong potential for producing patterned surfaces for engineering applications of boiling heat transfer.

Hydrophilic and Hydrophobic Nanostructured Copper Surfaces for Efficient Pool Boiling Heat Transfer with Water, Water/Butanol Mixtures and Novec 649

“…Similarly, microcavity surfaces were previously shown to considerably enhance the boiling performance, especially the HTC [41,104,105]. Using patterned microcavity surfaces, Voglar et al [106] achieved an HTC of 54.6 kW m −2 K −1 on laser-textured stainless steel. Similarly, Može et al [107] produced microcavities in the size range of approx.…”

Experimental investigation of critical heat flux on SiO2 thin film deposited copper substrate in DI water at atmospheric pressure

“…The results indicated the enhancement observed due to rewetting characteristic performed on the modified surface. Voglar et al [7] showed that numerous active nucleation sites caused the significant improvement in peak heat flux. The nucleation sites are developed by creating cavities in microns by laser texturing on surfaces.…”

Laser Surface Engineering for Boiling Heat Transfer Applications

“…Here, the -cavities with diverse radii appear due to significant ejection of this remolten material. However, this strategy is not appropriate for processing thin foils (e.g., with a thickness of 25 m) that are required when measuring the transient temperature fields using an IR camera on the backside of the foil, as performed in several experimental studies [34,46,62,84,174], since very high fluences may lead to up to 100 m deep -channels (Fig. 12.13b).…”

“…This represents a tremendous capability to study the optimal distribution of active nucleation sites in the context of (i) achieving a uniform temperature field and high heat transfer rates at low superheats; and (ii) delaying the horizontal coalescence of bubbles that 58 prevents a generation of large vapor patches (i.e., to reach high CHF). Some studies [97,174,195] have shown that the optimal distance between the active nucleation sites (regions) that leads to the maximal enhancement of the HTC and CHF roughly corresponds to the capillary length of the working fluid. However, a possible deviations from this theory [84] might be attributed to the fact that the growth time, nucleation frequency and bubble size are not the same for all nucleation sites.…”