Evaluation of different numerical models for prediction of pressure drop in laminar nanofluid flows

Pressure drop and increase of pumping power is a major issue associated with the applications of nanofluids in thermal systems. Accordingly, the accurate prediction of the pressure drop is important for the optimization of these systems. In this paper, predictions of three numerical models (the discrete phase model (DPM), two-phase mixture model, and the effective single-phase model) for the pressure drop of the alumina-water nanofluid flow through a tube were compared. The volume fraction of nanoparticles, phi, was varied from 0.1% to 6%. The nanofluid flows with the Re numbers of 450 and 900 were considered in the performed simulations. The results were compared with the available experimental data. Accordingly, it was concluded that the DPM provides more accurate results for phi>1%, while the mixture and single-phase models have better predictions for phi<1%. At phi = 1%, DPM provided more accurate predictions for the nanoparticle sizes smaller than or equal to 40 nm. However, the other two models led to better predictions for the nanoparticle sizes greater than or equal to 50 nm. Moreover, a sharp reduction in the nanofluid pressure drop was observed when the nanoparticle diameter rose from 40 nm to 50 nm at phi=1%.