Experimental Investigation into the Forced Convective Heat Transfer of Aqueous Fe₃O₄ Nanofluids under Transition Region

Abstract

The forced convective heat transfer (FCHT) properties of nanofluids, made of Fe 3 O 4 nanomaterials and deionized water, are firstly measured by a self-made forced convective heat transfer apparatus. The nanofluid flows through a horizontal copper tube in the transition region with Reynolds numbers in the range of 2500-5000. Some parameters including Reynolds number, axial distance, and mass concentration are also investigated. The preliminary results are firstly presented that the heat transfer coefficients of Fe 3 O 4 nanofluids systematically decrease with increasing concentration of nanoparticles under transition region which contradicts the initial expectation.

A review on laminar-to-turbulent transition of nanofluid flows

“…Although the heat transfer coefficient of the nanofluid was detected to enhance with the Reynolds number, it decreased with the increase of the concentration and was realized to be lower than the base fluid for all cases. The findings of the Ma et al [43] contradict the other studies in the literature. The possible reason might be the fact that the authors used empirical relation to determine the specific heat value of the nanofluid instead of measurements.…”

“…This was attributed to the chaotic movement of nanoparticles within the fluid. In addition to above studies, a group of researchers found that the ACCEPTED MANUSCRIPT / CLEAN COPY nanoparticles presented in the base liquid increase the thermal conductivity, delay and disturb the thermal boundary layer and accelerate the energy exchange process in the fluid due to the chaotic movement of the nanoparticles [17,8,43], Investigation on convective heat transfer and flow features of nanofluids, 2003). The increase in the thermal conductivity leads to an increase in heat for the MWCNT-water nanofluid at volume concentrations of 0.75% and 1.0%, and reduction in heat transfer coefficient for the MWCNT-water nanofluid at volume concentrations of 0.33%, can be explained by Fig.…”

“…Since the authors conducted experiments for single concentration value, it is hard to compare the friction factor values of the water and the Al 2 O 3 -water nanofluid. Ma et al [43] performed series of experiments to investigate the heat transfer characteristics of F e 3 O 4 -water nanofluid in a horizontal copper pipe in the transition region (2500 ≤ Re ≤ 5000). Although the heat transfer coefficient of the nanofluid was detected to enhance with the Reynolds number, it decreased with the increase of the concentration and was realized to be lower than the base fluid for all cases.…”