Browsing by Author "Jafari, M"

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    Thermo-hydraulic performance and entropy generation of biologically synthesized silver/water-ethylene glycol nano-fluid flow inside a rifled tube using two-phase mixture model
    Shahsavar, A; Jafari, M; Askari, IB; Selimefendigil, F
    In this paper, the two-phase mixture model is used to determine the influence of the number of ribs on the first-law and second-law performance features of the laminar forced convection flow of a biologically prepared silver/water-ethylene glycol nano-fluid (NF) in a rifled tube. The influence of the Reynolds number (Re), nanoparticle concentrations (phi) on the outcomes are also evaluated. Two parameters of Performance Evaluation Criterion (PEC) and Figure of Merit (FOM) are defined to analyze the merit of using rifled tube and NF over the plain tube and water-ethylene glycol mixture (50:50 by volume) for the same Re and phi. The results showed that the increase in the number of ribs is desirable from the first-law viewpoint and undesirable from the second-law viewpoint. It was found that for all the examined cases, the hydrothermal performance of the rifled tube is always better than the plain tube, and boosting the Re and decreasing the phi leads to an increase in FOM. Moreover, it was observed that the PEC for the six-head and eight-head rifled tubes is always greater than unity and for the two-head rifled tube is always less than unity.
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    Two-phase mixture modeling of turbulent forced convective flow of water-silver nanofluid inside a rifled tube: hydrothermal characteristics and irreversibility behavior
    Shahsavar, A; Jafari, M; Selimefendigil, F
    This work aims to present a numerical evaluation of the turbulent forced convective flow of water-silver nanofluid (NF) inside a horizontal internally spiral-ribbed heat exchanger tube using the two-phase mixture model. The considered NF is prepared using an environmentally friendly method. The influences of the volume concentration of silver nanoadditives (phi), Reynolds number (Re), rib width (W), rib height (H) and rib pitch (P) on the convection coefficient, pressure loss, irreversibility in fluid friction ((S) over dot(g,f)) and heat transfer ((S) over dot(g,f)) and total irreversibility ((S) over dot(g,f)) are assessed. The outcomes disclosed that the hydrodynamic characteristics and irreversibility behavior of NF flow in the ribbed tube are better than that of the water flow in the plain tube. In addition, it was found that the best first-law performance belongs to the case phi = 1%, Re = 5000, W = 2 mm, H = 2 mm, P = 4 mm, while the best second-law performance occurs at phi = 0%, Re = 20,000, W = 2 mm, H = 1 mm, P = 5 mm.