The present work aims at analyzing the heat transfer, pressure drop characteristics and determination of Nusselt number in a double pipe heat exchanger, who's inner surface is modified through the shot peening process. The effects of shot peening on the fluid flow and heat transfer in the annulus are studied in detail and the results are reported. First, the convective heat transfer coefficient (CHTC) and pressure drop of water flow in the heat exchanger with a modified/roughened surface was measured and compared with a smooth tube. Later, the study is extended to analyze the variations in CHTC, the pressure drop of the nanofluid multi-walled carbon nanotubes (MWCNT-Solar glycol). The experiments were carried out at different volume concentrations (0.2%, 0.4%, and 0.6%) of the nanofluids. Experimental results showed that shot peening in tube surfaces has an appreciable effect on the performance of flow behavior and heat transfer. The CHTC of the nanofluid containing 0.6% of MWCNT nanomaterials is improved to a maximum of ~115% at a mass flow rate of 0.04 kg/s. Enhancement in thermal conductivity up to 30.59% was achieved with the MWCNT volume concentration of 0.6% and a temperature range from 30 to 50 °C. Pressure drop increased with an increase in mass flow rate, and volume concentrations of MWCNT nanoparticles. The augmentation in pressure drop for 0.6% volume concentration of MWCNT– solar glycol nanofluid is 1.56 times for a mass flow rate of 0.08 kg/s. The experimental results show that the combination of shot peening and nanofluids in the heat exchanger increases its heat transfer rate as well as its thermo-hydraulic performance. © 2019 Elsevier B.V.