Experimental and Numerical Investigation of Drag Reduction and Heat-Transfer Characteristics of Xanthan Gum Solutions at Different Concentrations in Turbulent Pipe Flow Under Varying Temperature Conditions

This study presents a combined experimental and numerical investigation of xanthan gum solutions at 100 and 300 ppm in turbulent smooth pipe flow under temperatures of 30–50 °C and Reynolds numbers of 8000–12,000. Water was used as the Newtonian reference fluid, while xanthan gum was modelled using temperature- and concentration-dependent shear-thinning properties. Experimental pressure-drop data were used to evaluate drag-reduction behaviour, whereas numerical simulations were employed to analyse the associated flow and heat-transfer responses. The results show that XG 100 ppm produced a relatively stable drag-reduction response of approximately 31–39%, while XG 300 ppm showed a wider and more condition-dependent range of about 25–45%. Water exhibited higher Nusselt numbers of approximately 68–106. In contrast, XG 100 ppm produced Nusselt numbers of approximately 45–69, while XG 300 ppm showed lower values of about 35–61. The corresponding heat-transfer reduction ranged from approximately 26–48% for XG 100 ppm and 23–46% for XG 300 ppm. These findings confirm a clear hydraulic–thermal trade-off, indicating that the xanthan gum concentration should be optimised according to both pressure-loss reduction and heat-transfer requirements.