# Pool Boiling Heat Transfer Characteristics of Hydrophobically Modified TiO2@Carbon Nanotube Composite Nanofluids

## TL;DR

This study improves boiling heat transfer using a composite nanofluid made of hydrophobic TiO2 and carbon nanotubes, achieving better efficiency and stability.

## Contribution

The novel hydrophobic TiO2@MWCNT composite nanofluid achieves simultaneous enhancement of heat transfer coefficient and critical heat flux.

## Key findings

- At a 2:1 mass ratio, the composite nanofluid increased heat transfer coefficient by 31.6% and critical heat flux by 46.5%.
- Hydrophobic nanoparticles reduce bubble nucleation energy barriers and mitigate initial boiling superheat.
- The synergistic effect of TiO2 and MWCNTs improves thermal conductivity and mechanical properties.

## Abstract

To tackle challenges including excessive initial boiling superheat and low heat transfer coefficients inherent in conventional working fluids, hydrophobic-modified TiO2@carbon nanotube (MWCNT) composite nanofluids were fabricated. Subsequently, the boiling heat transfer mechanisms were systematically investigated and visually verified. Hydrophobic TiO2 nanofluids exhibit enhanced stability, whereas hydrophobic TiO2@MWCNTs composite nanofluids demonstrate improved thermal conductivity. At a mass ratio of hydrophobic-modified TiO2 to MWCNTs of 2:1, the optimal heat transfer performance was attained, with a 31.6% increase in heat transfer coefficient (HTC) and a 46.5% increase in critical heat flux (CHF) density relative to hydrophobic-modified TiO2 nanofluids. Composite nanofluids exert effective regulation over bubble kinetic parameters: hydrophobic nanoparticles increase vaporization core density, reduce bubble nucleation energy barriers, and mitigate initial boiling superheat. Benefiting from the superior thermal conductivity and mechanical properties, MWCNTs remarkably promote heat transfer efficiency. The synergistic effect between the two components enables the concurrent enhancement of HTC and CHF, thus highlighting the promising application potential of hydrophobic-modified TiO2@MWCNTs composite nanofluids in intensifying pool boiling heat transfer.