Fluid flow and heat transfer in an air-to-water double-pipe heat exchanger M. Sheikholeslami, M. Gorji-Bandpy and D. D. Ganji Eur. Phys. J. Plus, 130 11 (2015) 225 Published online: 05 November 2015 DOI: 10.1140/epjp/i2015-15225-y