Abstract
Swirling flow has been shown to increase heat transfer in heat exchangers. However, producing swirl while not presenting a severe pressure drop can be a challenge. In this paper, a desired shape of guidance blades for laminar swirl flow is determined by numerical simulation in OpenFOAM. Emphasis is on the mesh technique, where a predefined blade shape is formed by mesh twisting, or morphing. The validity of numerical simulations on a twisted mesh is shown by comparing it to the theoretical solution of laminar flow in a pipe without swirl and guidance blades. A sensitivity study shows that a cell size ratio of 0.025 of diameter is sufficient and affects the solution minimally. To determine the desired shape of guidance blades previously found optimal swirl decay and velocity profile for laminar swirling flow are utilized. Three blade shapes are explored: (I) with a twist angle that varies with axial location only; (II) having a deviation angle matching the theoretical deviation angle for laminar swirling flow; (III) same as II but with a hollow center. Simulations are performed for Re = 100 and swirl number S = 0.2 . Case II is able to sustain swirl longest while maintaining a low pressure drop and is therefore a desired swirler shape profile as predicted theoretically.
Highlights
Swirling flow can by found in many applications: heat exchangers, combustion chambers of jet engines, mixing tanks and more
Instead of manually adjusting the mesh to conform to the irregular shaped guidance blades and possibly causing the largest errors where the most accuracy is needed, a high quality mesh was constructed with blades conforming to the x, y, z-axes and the mesh twisted until the desired shape of the guidance blades was reached
When deciding on a desired shape of the guidance blades, the deviation angle based on the theoretical optimal velocity profile was used
Summary
Swirling flow can by found in many applications: heat exchangers, combustion chambers of jet engines, mixing tanks and more. Swirling flow in pipes can be produced by active methods (rotating cylinders [2] or rotating propellers [3]) or passive methods (like tangential inlet (e.g., [4,5]), radial/axial swirl blades at the inlet (e.g., [6,7]) or guided swirlers further downstream (more on passive swirl methods in [8,9]). The most common guided swirlers are twisted tape (generally covering the full length of the pipe e.g., [4,12,13], which leads to greater pressure drop), either fixed [14] or free to move with the flow, [15] propeller-type or other types of fixed vanes [16]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
