Experimental investigation of frictional losses in a horizontal pipe flow at low reynolds numbers

Frictional losses in internal pipe flows play a decisive role in the design and performance of fluid transport systems, particularly under low Reynolds number conditions where laminar flow dominates. Accurate estimation of head loss in this regime is essential for applications such as microfluidic devices, laboratory-scale heat exchangers, biomedical flows, and low-velocity industrial pipelines. This study presents an experimental investigation of frictional losses in steady, incompressible flow through a horizontal circular pipe operating at low Reynolds numbers. Experiments were conducted using water as the working fluid, with Reynolds numbers maintained well below the laminar-turbulent transition threshold. Pressure drop measurements were obtained over a known pipe length using calibrated differential pressure instruments, allowing direct evaluation of friction factors. The experimental results were compared with classical theoretical predictions derived from the Hagen-Poiseuille equation and Darcy-Weisbach formulation. Observations indicate a strong linear relationship between pressure drop and mean flow velocity, confirming laminar flow behavior throughout the test range. Minor deviations from theoretical values were attributed to entrance effects, surface roughness, and measurement uncertainties. The study highlights the sensitivity of frictional losses to pipe diameter and flow rate under low Reynolds number conditions. Additionally, the experimental friction factors showed good agreement with analytical models, validating the applicability of conventional laminar flow correlations for practical engineering analysis. The findings reinforce the importance of precise experimental techniques in characterizing low-Reynolds-number flows and provide reliable benchmark data for validating numerical simulations. Overall, this investigation contributes to a clearer understanding of frictional behavior in laminar pipe flow and supports improved design accuracy for low-flow-rate piping systems where energy efficiency and pressure management are critical considerations in engineering practice.