A pool boiling phenomenon referred to as secondary effects is discussed. Based on the experimental trends, a mechanism proposed that identifies parameters lead this phenomenon. Secondary refer distinct decrease in wall superheat temperature near critical heat flux due significant increase transfer coefficient. Recent experiments using femtosecond laser processed Inconel, stainless steel, and copper multiscale surfaces consistently displayed effects, which were found be result of both drop...

Pool boiling heat transfer with the use of femtosecond laser surface processing (FLSP) on copper surfaces has been studied. FLSP creates a self-organized micro/nanostructured surface. In previous pool studies stainless steel surfaces, enhancements in critical flux (CHF) and coefficients (HTCs) were observed compared to polished reference However, this study shows that exhibit reductions both CHF HTCs consistently. This reduction performance is result an oxide layer covers microstructures...

We present friction drag reduction in minichannel laminar flow past superhydrophobic metallic surfaces. Femtosecond laser surface processing (FLSP), a one-step scalable method, was used to create permanent microscale and nanoscale structures on 316 stainless steel plates. The resulting superhydrophilic plates were covered by tall (215 μm) or short (27 structures. FLSP then transitioned evaporative deposition of fluorinated silane, low energy coating. Using purified water, the factor obtained...

Abstract It is very challenging to achieve near perfect absorption or emission that both broadband and omnidirectional while utilizing a scalable fabrication process. Femtosecond laser surface processing an emerging low-cost large-scale manufacturing technique used directly permanently modify the properties of material. The versatility this produce tailored has resulted in rapidly growing number applications. Here, we demonstrate perfect, broadband, emissivity from aluminum surfaces by...

In this paper, the authors report on use of femtosecond laser surface processing (FLSP) to enhance anti-icing properties a commonly used aircraft alloy, Al 7075-O Clad. By changing morphology through FLSP and chemistry siloxane vapor deposition, wettability Clad was altered. Tall mound short functionalized surfaces were created two sets parameters. Condensation subsequent freezing condensates studied. Both structure height shown play role in delay freezing. Freezing occurred superhydrophilic...

Femtosecond laser surface processing (FLSP) is an emerging technique for creating functionalized surfaces with specialized properties, such as broadband optical absorption or superhydrophobicity/superhydrophilicity. It has been demonstrated in the past that FLSP can be used to form two distinct classes of mound-like, self-organized micro/nanostructures on various metals. Here, formation mechanisms below growth (BSG) and above (ASG) mounds polycrystalline Ni60Nb40 are studied. Cross-sectional...

In this paper, experimental results of pool boiling inversion and hysteresis on functionalized 304 stainless steel using distilled water at atmospheric pressure are presented. The surface was modified femtosecond laser processing to create hierarchical micro/nanostructures. Boiling curves were generated once steady-state reached, with defined as having a temperature slope less than 0.25 degrees Celsius per minute. criterion examined by allowing the have extended times specified heat fluxes....

The use of self-organized micro/nanostructured surfaces formed using femtosecond laser surface processing (FLSP) techniques has become a promising area research for enhancing properties metals, with many applications including heat transfer. In this work, we demonstrate advantages the dual-pulse versus single-pulse FLSP to produce micro/nanostructures on copper. With technique, pulses out (spaced 1 ms apart) are split into pulse pairs spaced < ns apart and focused collinear sample surface....

Femtosecond laser surface processing (FLSP) is a unique material technique that can produce self-organized micro/nanostructures on most materials including metals, semiconductors, and dielectrics. These structures have demonstrated the enhancement of properties such as heat transfer broadband light absorption. The chemical composition morphology FLSP highly dependent parameters background gas composition, pressure, fluence, number pulses. When carried out in open atmosphere, thick oxide...

In this study, a vapor chamber - thermal diode apparatus is fabricated and tested. The system's components are laser-functionalized, wickless, wettability-patterned copper plates. This the first management component that completely wick-free operates due to surface modification wettability patterning instead of utilizing wicks or any kind wicking structures. Our approach takes advantage phase-changing property water in closed loop composed two initially identical plates, one acting as an...

The capability to produce femtosecond laser pulses with wavelengths in the atmospheric absorption window requires a new understanding of pulse propagation effects. In this work, we characterize changes temporal middle infrared by cross-correlation frequency resolved optical gating (XFROG). temporally distorted are cross-correlated 800 nm four-wave mixing process air. For first time, investigate these effects through gas molecules that not present atmosphere. Each molecule is shown have...

Femtosecond laser surface processing (FLSP) is a material technique used to produce self-organized micro/nanostructures on metals. The hierarchal structures can improve the properties of materials when applied specific applications such as enhancing heat transfer. In this paper, we demonstrate recently developed termed multi-material, multi-layer FLSP (3ML-FLSP). With 3ML-FLSP, micro/nanoscale features be produced that are composed multiple by surfaces using traditional techniques layered...

A pool boiling phenomenon referred to as secondary effects is discussed. Based on experimental trends and numerical simulations, a mechanism proposed that identifies the parameters lead this phenomenon. Secondary refer distinct decrease in wall superheat temperature near critical heat flux due significant increase transfer coefficient. Recent experiments femtosecond laser processed Inconel stainless steel multiscale surfaces consistently displayed effects. Through studies, it was determined...

Femtosecond lasers can be used to create self-organized micro/nanostructures on the surface of most materials. However, copper, these structures do not form uniformly and require higher laser fluence when compared other metals. We report a method copper by clamping foil stainless steel prior processing. All samples reported are processed using peak 2.71 J/cm2, which is below threshold for micro/nanostructure formation copper. When layered created that consist both at pulse counts 998 1,197....