The pressure drop across 90deg sharp-angled miter elbows connecting straight circular pipes is studied in a bespoke experimental facility by using water and air as working fluids flowing in the range of bulk Reynolds number 500<Re<60,000. To the best of our knowledge, the dependence on the Reynolds number of the pressure drop across the miter elbow scaled by the dynamic pressure, i.e., the pressure-loss coefficient K, is reported herein for the first time. The coefficient is shown to decrease sharply with the Reynolds number up to about Re=20,000 and, at higher Reynolds numbers, to approach mildly a constant K=0.9, which is about 20% lower than the currently reported value in the literature. We quantify this relation and the dependence between K and the straight-pipe friction factor at the same Reynolds number through two new empirical correlations, which will be useful for the design of piping systems fitted with these sharp elbows. The pressure drop is also expressed in terms of the scaled equivalent length, i.e., the length of a straight pipe that would produce the same pressure drop as the elbow at the same Reynolds number.

Air-water flow in a 90° sharp elbow (mitre bend) is studied in a new purpose-built experimental facility at the University of Sheffield. For the first time, the two-phase flow is investigated in a mitre bend for water-based Reynolds numbers Re w = 5600-12800 and water-to-air mass flow rate ratios  mm wa / =10-3800. Four different flow patterns are observed in the upstream pipe (plug, slug, slug-annular and annular) by using a high-speed high-resolution camera. The results show that the perturbation length upstream and downstream of the elbow and the pressure drop are significantly affected by the flow patterns. Two new values of the Lockhart-Martinelli parameter C are found for the pressure drop across the elbow.

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Pressure drop of turbulent flow across 90[Formula: see text] round bends with 10mm inside diameter investigated by employing the shear stress transport [Formula: see text] turbulent model for numerous curvature ratios and flow conditions. A total of 10 flow velocities varied from 1 to 10 m/s and 17 curvature radii between 5 and 300  mm were examined. Velocity profiles were evaluated at eight locations to examine the entrance effect. The simulation results were verified by comparing the evaluated Darcy friction factor with a well-known published correlation. The obtained results of bend pressure drop demonstrate the domination of the curvature ratio effect on the pressure drop over the influence of other factors. The computed pressure loss across the bend in terms of pressure loss coefficient [Formula: see text] and equivalent length to diameter ratio [Formula: see text] shows a good agreement with various published data in the literature with [Formula: see text] maximum average error. The coincidence between the results and the published data verifies the accuracy of the employed model to evaluate the pressure drop of turbulent flow throughout 90[Formula: see text] bends for the applied boundary conditions.