Determination of the head loss coefficient of closely spaced pipe bends

The head loss coefficient (HLC) of closely spaced pipe bends is presented in this study. The objective of this study was to develop an accurate but simple empirical correlation for computing an HLC of two 90⁰ smooth pipe bends that are separated by a short pipe. ANSYS Fluent 19.0, a commercial Computational Fluid Dynamic (CFD) package, was used to provide flow visualization and the magnitude of the HLC. The computational model was validated by comparing the HLC of a single bend and was found to be sound. The computational results for closely spaced pipe bends were compared to experiments that were conducted on smooth pipes and bends. The experiments showed HLC trends similar to those of the CFD simulations and of published data. The HLC is expressed as a single value for the two bends. The study found that this value increases as the spacer length between the two bends increases. The HLC depends on two geometric parameters, viz., spacing ratio and curvature ratio. When the spacer length exceeds 10D the HLC converges to the value of the sum of two conventional single bends HLCs.