Surface structures with a well-defined shape and dimension in a staggered arrangement were evaluated in terms of their capability to improve the single-phase convective heat transfer in channels with small dimensions. Two evaluation criteria were used: (i) the thermal efficiency index, defined by the ratio of heat transfer enhancement and pressure drop increase, and (ii) the irreversible entropy generation which is determined by the entropy production rates through heat conduction and dissipation. Beside experimental measurements, parametric studies were performed using computational fluid dynamics to establish the entropy generation rates within the heated flow channel.