A numerical method to compute time-dependent flows in helically coiled pipes with circular cross-section and constant curvature K and torsion r is presented. The incompressible Navier-Stokes equations, explicitly derived in an orthogonal helical co-ordinate system, are integrated numerically. The results show for example, the influence of curvature and torsion on the axial velocity profile. The numerical simulations also allow a detailed study of the secondary motion in the cross-section of the pipe by considering vector plots and contour lines of the streamfunction. Furthermore, the formation of a pressure distribution perpendicular to the pipe axis is shown. Besides the Reynolds number, other characteristic flow parameters, like the Dean numer De, and the Germano number Gn, are used to compare the flow through different pipe configurations