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 (φ) 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 φ. 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 φ 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.
