This study aims to improve the performance characteristics of a shell-tube heat exchanger in counterflow configuration. It considers the effect of using baffles and semicircular tubes as heat transfer surfaces. Twenty-nine heat exchangers are designed and constructed, consisting of tubes of circular or semicircular tubes (SCTs) with base spacing ratios () ranging from 23.6% to 55.1%. The examined baffles have a pitch ratio () of 1.47 to 2.36, a total cut ratio () of 16.5% to 25% and have two cutting configurations: edge cutting with a cutting ratio () of 0% to 16.5% and internal cutting baffles with a cutting ratio () of 0% to 16.5%. The experiments are done for Reynolds (3550≤Re_sh≤14580) and Prandtl numbers (4.47≤Pr_sh≤7.28). The results show that using baffles and/or SCTs increases the heat transfer rate and pressure loss, and when the SCT spacing ratio increases and baffles cut and pitch ratios decrease, these performance metrics significantly rise. However, baffles with edge cutting are better than those with internal cutting. The hydrothermal performance index is evaluated using the Stanton number of the shell side and fsh ratios, with a maximum value of 2.54 achieved by utilizing baffles of  =  = 16.5%,  = 0,  = 1.47, and SCTs of  = 55.1%, and lowest shell-side flow rate and inlet temperature. Finally, correlations are introduced to predict ¯Nush and fsh, besides the performance index of the tested heat exchangers.