Mixed convection in a vertical helical annular pipe

Mixed convection in a vertical helical annular pipe is studied numerically using a second order finite difference method based on the projection algorithm. To do so, the governing equations are written in the helical orthogonal coordinate system and discretized on a uniform three-dimensional grid. Considering developing flow and the Boussinesq approximation for the buoyancy term in the momentum equation, mixed convection inside a helical annular pipe is investigated by applying a constant heat flux on the inner pipe wall while keeping the outer pipe wall insulated. The effects of governing non-dimensional parameters such as torsion, curvature, Reynolds number, Prandtl number, and Richardson number on the flow and temperature field patterns and consequently on the friction factor and heat transfer rate are studied in detail.