Experimental Investigation of Pressure Drop in Pipe Flow with Standard Fittings at Varying Reynolds Numbers

Pipe fittings elbows, tee junctions, gate valves, and sudden expansions account for a significant fraction of total pressure loss in industrial piping systems, often exceeding the friction losses in straight pipe sections for compact installations. This experimental study measures the pressure drop and loss coefficient across five standard pipe fittings in a 25 mm internal diameter PVC pipe system over a Reynolds number range of 8,000 to 48,000 (turbulent flow). An open-circuit water flow loop equipped with a calibrated electromagnetic flow meter, differential pressure transducers, and thermocouples provided controlled test conditions. Loss coefficients (K-values) were determined experimentally and compared with published Crane Technical Paper 410 values. A 90-degree elbow showed the highest K value of 1.8 among the fittings tested, while a fully open gate valve gave the lowest at 0.18. The experimental K values agreed with published data within 7.4 percent mean absolute error across all fittings and flow rates. A simple correlation between K and Reynolds number is proposed for the tested fittings, valid for Re between 10,000 and 48,000.