Experimental investigation of pool boiling heat transfer coefficients and critical heat flux of a ternary hybrid nanofluid

Abstract

This study aims to examine the heat transfer mechanisms of ternary hybrid nanofluids during pool boiling. The experimental investigation focused on the effects of various nanoparticles, including aluminum oxide (Al2O3), silicon dioxide (SiO2), and multi-walled carbon nanotubes (MWCNTs), in combination with surfactants, on the boiling heat transfer coefficient (HTC) and critical heat flux (CHF) of refrigerant R141b. Ternary hybrid nano-fluids exhibited similar effects on the HTC and CHF as those containing only MWCNTs. Adding Al2O3 and SiO2 to the MWCNT nanofluid did not significantly influence the pool-boiling HTC and CHF. None of the tested nano-fluids outperformed pure refrigerant R141b in terms of pool-boiling HTC until the heat flux reached the CHF of pure R141b. At higher heat fluxes, the MWCNT nanofluids yielded nearly the highest HTC values whereas base refrigerant, R141b, exhibited burnout due to exceeding its own CHF. MWCNT nanoparticles were observed to deposit on the heat transfer surface during boiling. This deposition reduced the volume fraction of MWCNTs in nanofluids, thereby affecting performance. The study highlights the importance of considering the surfactant's effect on the CHF. Adding a sodium dodecyl benzene sulfonate surfactant increased the CHF of R141b by 16 % at 1 atm.