Heat transfer enhancement by a multilobe vortex generator in internally finned tubes

A three-dimensional computational method is employed to study the flow and heat transfer in internally finned tubes with a multilobe vortex generator inserted. Governing equations are discretized using the finite volume metho d The irregular lobe geometry is treated using curvilinear nonstaggered gri ds. The linear interpolation method is adopted to calculate face velocities . The results show that secondary flows induced by the lobes are transforme d to become axial vortices downstream of the vortex generator. As a consequ ence of the transport by the vortex flow, the core flow is moved to the fin s and the tube wall, while the wall flow moves to the core. In this way, bo th heat transfer and flow mixing are enhanced. When the fin height is incre ased the axial vortex is more restricted in the centerline region, and the strength of the vortex flow, represented by circulation, is decreased. In t urn, the total pressure loss is also decreased However, the heat transfer i ncreases with fin height. Consequently, efficiency is greatly promoted.