Abstract
This article presents an investigation for the secondary flow characteristics and associated pressure loss in fluid flow through helically coiled pipe. Computational fluid dynamics is employed to analyze the pipe flow with various geometries, and the accuracy of the numerical methodology is validated by conducting corresponding experiments. The analysis performs a detailed parametric study involving the pressure loss, the secondary vortex motion, and the secondary vortex intensity for a range of coil diameters ( D; ranging from 300 to 3000 mm) and pipe diameters ( d; ranging from 50 to 90 mm). The pipe flow develops to a stable state with increase in coil diameter, while an increase in pipe diameter delays this development. Then, the secondary flow characteristics are analyzed to explore the pressure loss mechanism. The distorted streamline of secondary vortices and the enlarged deflection angle of secondary vortices are both factors contributing to the enhanced pressure loss. Furthermore, the effects of pipe flow development on the following flow characteristics such as the turbulence dissipation rate and the secondary vortex intensity are revealed. These characteristics all distribute regularly and reach lower values when pipe flow begins to a stable state.
Highlights
Fluid flow through helically coiled pipe is a common occurrence in a vast range of agricultural and industrial applications, such as farm irrigation, wet dedusting, and heat exchangers
Two pressure gauges were mounted at the inlet of the water sprayer and before the entrance of the sprinkle nozzle to measure the pressure loss of the helical pipe
The vortex-deflection angle rises with the increase in pipe diameter, and the streamlines change from a smooth to a distorted pattern
Summary
Fluid flow through helically coiled pipe is a common occurrence in a vast range of agricultural and industrial applications, such as farm irrigation, wet dedusting, and heat exchangers. The secondary flow induced by the bend hinders the flow, goes smoothly along the main flow direction, and appears as a pair of counter-rotating vortices in the cross-section normal to the primary flow direction. The helically coiled pipe generates more pressure loss in overcoming the minor (secondary) flow. Many studies have reported on the influence of coil parameters on the pressure loss for helically coiled pipes. Liu et al.[2] conducted an experimental study to measure the pressure drop for laminar flow in helical pipes. A common method for calculating the pressure loss employs the friction factor.
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