Dissipative Particle Dynamics has been used effectively as a modelling technique to perform Computational Fluid Dynamics. DPD preserves some molecular detail whereas in classical CFD this is lost. The technique has been tested in two cases of macromolecules in flow simulations. First, the behaviour of a polymer within a square capillary has been studied, which is the basis of hydrodynamic chromatography. Secondly, the effect of polymers on the melting in shear flow has been simulated.