Experimental and numerical investigation on bubble behaviors and pool boiling heat transfer of semi-modified copper square pillar arrays

Abstract

Abstract In the present study, bubble growth on the boiling surfaces and pool boiling heat transfer characteristics of semi-modified pillar arrays are experimentally investigated at atmospheric pressure, while the bubble behaviors inside pillar gaps are numerically revealed in different contact angles by lattice Boltzmann method based on the pseudopotential LB model. The hybrid and hierarchical pillars are fabricated by semi-silver-deposition and wire-electrode-cutting respectively. The effects of wettability, surface morphology and surfactant concentration are considered. Deionized water, aqueous isopropanol and n-heptanol solutions with concentrations of 100\xa0ppm, 200\xa0ppm, and 800\xa0ppm are used as the working liquids. The experimental results show that contact angles of isopropanol and n-heptanol solutions on copper plate are changed considerably by silver-deposition. Semi-silver-deposition and additions of isopropanol and n-heptanol considerably affect pool boiling heat transfer and bubble behaviors of straight and hierarchical copper square pillars. The numerical results show that vapor films generate at most gap bottoms at the contact angle of 131.8° which impede liquid supplement process toward the gaps compared with the contact angle of 98.7° on the straight pillar array surface.