In this paper, the design and thermo-hydraulic performance of a double pipe heat exchanger with helical baffles in the annulus side, are investigated numerically. Three-dimensional computational fluid dynamics (CFD) model, using the software FLUENT, have been performed to investigate the annulus side fluid flow, heat transfer coefficient and pressure drop for different configurations. A numerical analysis is conducted for different values of Reynolds number and baffle spacing (0.025-0.1 m). The numerical model was first validated for a simple double pipe heat exchanger by comparison with empirical correlations. The model was then used to investigate the helical baffles effects. The results obtained for a helically baffled annulus side provide enhanced heat transfer performance and high-pressure drop compared to the simple double-pipe exchangers. Thermal performance and high-pressure drop is an increasing function of baffle spacing and Re. In addition, empirical correlations expressing the results were developed based on curve fitting. (C) 2016 Elsevier Ltd. All rights reserved.