Effect of concentration and period on the transient pool boiling heat transfer of Fe3O4-based aqueous nanofluids

Abstract

The high conductivity of metal nanoparticles and the flowability of the base fluid led to significant changes in heat transfer rates when ferrofluids are used in the boiling process. Pool boiling tests were conducted in this study using Fe₃O₄/water ferrofluid at concentrations of 0.01 %, 0.05 %, and 0.1 % under transient conditions lasting from 1 s to 5000 s. In the present study, the ferrofluid was prepared through a two-step process. A horizontal nickel-chrome wire served as the heater and the heat flux was assessed as a quadratic polynomial function for each period, with a linear increase in applied voltage. Results showed that increasing nanoparticle concentration accelerates the onset of nucleate boiling (ONB) and raises critical heat flux (CHF) by up to 137 %. However, longer periods lead to delayed ONB, increased superheat temperature, a maximum 25 % reduction in CHF, and a maximum 96 % reduction in heat transfer coefficient at the CHF point in any given nanoparticle concentration. at concentrations of 0.01 %, 0.05 %, and 0.1 %, the heat transfer coefficient at the CHF point experiences a decline of 96.5 %, 95.15 %, and 89.7 %, respectively, with an increased period compared to the baseline period of t = 1 s.