Synergistic effect of helically-finned directional tracks and lubricant viscosity on droplet dynamics and condensation heat transfer of bioinspired slippery surfaces

Abstract

Slippery lubricant-infused porous surfaces (SLIPSs) have been presented herein, developed on helically-fined grooves of copper tubes (HF-SLIPSs). The high viscosity lubricant (GPL 107) has been employed which is firmly locked by the nano-pores of oxidized layer fabricated on helically-finned grooves. The influences of synergistic cooperation of helically-finned grooves and infused lubricant on the condensed droplet dynamics and heat transfer are systematically investigated. Findings demonstrate that HF-SLIPSs not only improve the droplet mobility but also expand the condensing area and provide directional transport tracks where small-sized droplets quickly coalesce on fin surface and slide orderly along the helical grooves, resulting in short renewal time period of 2.99 s. Moreover, the condensation heat transfer on HF-SLIPSs(GPL 107) is better than other test tubes, and condensation heat transfer coefficients are 35.8% and 55.9% higher than that of smooth SLIPSs tubes impregnated with GPL 103 and GPL 107, respectively, and 98.1% and 204.4% higher comparing with smooth hydrophilic and helically-finned hydrophilic tubes, respectively. This indicates that the synergistic cooperation of high viscosity lubricant and helically-finned grooves plays a great role by providing certain directional and stable SLIPSs tracks where droplets are guided and transported faster which ensure the enhanced condensation heat transfer.