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Heat transfer and friction factor in a tube with turbulator internally grooved and rib are studied using numerical simulation. Two different turbulator geometries, including only groove and both groove and rib, on the tube wall are investigated. The study is developed for different parameters of turbulator including pitch ratio (PR), groove and rib height (DR), and Reynolds number in the range of 10 000 to 38 000. The results revealed that the best Nusselt number is achieved for GR turbulator and for the tube wall with PR = 2 and DR = 1. Furthermore, for a specific turbulator parameter, Nusselt number is improved by 46% compared with the experimental result. The results show that the friction factor decreases by increase of both step and height ratios. For example, based on Reynolds number, 21% to 69% reduction in the friction factor was observed for PR = 7 and DR = 3. In addition, the correlations for Nusselt number and friction factor with acceptable deviation are presented for the studied turbulators.Finally, thermal performance enhancement factor is defined to be a good criterion for selection of the optimum turbulator and their parameters.correlation, friction factor, Nusselt number, thermal performance enhancement factor, turbulator

In this paper, thermo-hydraulic analysis of a diamond-shaped turbulator in a tube was investigated using the numerical simulation. Nusselt number and friction factor were evaluated by variation of Reynolds number in the range of 3500–16 500 and turbulator parameters including step ratio and rode diameter. Numerical validation was performed with experimental model and a good matching was observed. Then, closed form correlations for the Nusselt number and friction factor were presented with respect to Reynolds number. Numerical results revealed that a turbulator with a step ratio =1 and rod diameter = 3 mm provide the best Nusselt number. In addition, the results showed that the friction factor reduces by increment of both step ratio and rode diameter. Furthermore, by adjusting a turbulator with the new parameters, 40–56% improvement in the friction factor was noticed compared with the literature results. Then, by using definition of efficiency, the effect of both step ratio and rod diameter was investigated. The results revealed 4.60%–18.20% improvement in the efficiency for step ratio = 3 and rod diameter = 3 mm in comparison with the reported results in the literature. Finally, some correlations for Nusselt number and friction factor using the numerical results were presented with acceptable agreement.