Effects of Nanoparticle Deposition on the Flow Boiling Characteristics of a MWCNT Nanofluid

Abstract

In this study, highly conductive nanoparticles, known for their superior heat transfer enhancement in bulk domains, were incorporated into three-dimensional nanofluids containing multiwalled carbon nanotubes (MWCNTs). This study measures the thermal conductivity of deionized (DI) water and MWCNT-water nanofluids, revealing a significant improvement with the nanofluid. At the start of the process, a magnetic stirrer is employed to disperse the nanoparticles in DI water. Although various factors influencing the boiling performance of nanofluids were extensively examined, the combined effects of CNT concentration and sonication time remain relatively unexplored. To address this gap, the influence of coatings formed by different carbon nanotubes (CNTs) on boiling heat transfer was studied. Experiments analyzed boiled surface properties, including contact angle, scanning electron microscopic (SEM) morphology, and surface roughness. Flow patterns were recorded with a high-speed, high-resolution camera. The findings suggest that the heat transfer characteristics of MWCNT nanofluids and the surfaces coated with MWCNT deposits are superior to those of bare surfaces. The MWCNT-water nanofluid demonstrated enhanced thermal conductivity, leading to improved boiling performance. The boiling performance of deionized water on MWCNT-deposited nanocoated surfaces demonstrated improved characteristics comparable to the boiling performance of equivalent nanofluids on bare surfaces. In addition to enhancing the thermophysical properties of nanofluids, higher concentrations of MWCNT nanofluids increased the effective heat transfer area and surface roughness of the coated surfaces. These advancements led to improved bubble behavior and a more efficient heat transfer performance in the two-phase boiling regime.