Pressure Losses in Multiple-Elbow Paths and in V-Bends of Hydraulic Manifolds

[...]the connection of inclined channels that will be named in the following V-bend, has been considered; often the designer of hydraulic manifold for fluid power applications has to consider the use of this kind of connection to meet the requirements of minimum space and weight. Since data on the pressure losses for this geometry are not available in our field, a CFD analysis has been performed to study the influence of the main geometrical parameters and operating parameters (flow rate and fluid viscosity). [...]in Figure 23 the velocity intensity map are shown for a contraction ratio of 2 and still a reference fluid velocity of 6.4 m/s (flow rate 30 L/min); the velocity is non-dimensioned with respect to this reference value. In this last case, the total pressure loss value is near twice the loss on a single elbow. [...]the designer has to keep in mind that the best configuration for pressure loss reducing in the manifold is not to keep a great distance between the elbows, but instead to maintain a reciprocal distance less than 5 times the diameter and introducing a U shape or, if a U shape is not possible, to avoid geometries in which the twisting angle θ between the pipe channels is between 90° and 180°. [...]the pressure losses on the V-bend have been analysed also considering an expansion/contraction ratio between the diameters of the channels; the analysis confirms that, as for the 90° bend studied in [2], the expansion helps to lower the pressure losses; the contraction shows a much more slight decrease of the losses.