In industrial heat management, the design of baffles within heat exchangers is crucial. They guide fluid flow and enhance turbulence, optimizing heat transfer. Yet, their configuration must be carefully considered to balance thermal efficiency with energy expenditure and pressure management. This research conducts practical tests on the hydrothermal attributes of a counter-flow double-pipe heat exchanger. It evaluates two baffle layouts: segmental and flower, considering baffle cut-off ratio (16.7%≤δ≤50%), pitch ratio (8.3%≤≤22.2%), flower-design relative angle (30≤≤90), and operating conditions of annulus-side (2660≤Rean≤13110, 5.21≤Pran≤7.48). The findings assure that installing the baffles results in notable increases in both ¯Nu_an and f_an. Besides, lowering baffle cut-off and pitch ratios, and increasing the relative angle of flower baffles lead to additional increases. Moreover, raising the annulus-fluid temperature reduces ¯Nu_an with a negligible effect on f_an. Increasing 〖Re〗_an leads to a reduced f_an and greater ¯Nu_an. Compared with no baffles, the maximum recorded increases in the ¯Nu_an and f_an are 147.4% and 60.2%, respectively, realized by incorporating flower layout. On average, the flower baffles boost the ¯Nu_an by 20.8% more than those using conventional baffles, with an average increase of 4.3% in the f_an. To judge the benefit of utilizing baffles, the Hydrothermal Performance Index (HTPI) is calculated, and its highest value is recorded as 2.23, attained by running the annular pipe at the lowest flow rate and temperature, with inserting flower baffles (δ=16.7%, λ=8.3%, =90°). Finally, correlations for ¯Nu_an, HTPI, and f_an prediction are suggested.