Staggered cross flow heat exchangers are commonly employed as air coolers and steam generators. This study aims to boost their thermal performance by proposing a modification to the tube geometry; semicircular tube (SCT) instead of complete circular tube (CCT). Through the runs, numerous gaps between SCTs-bases with different pitches in both longitudinal/transversal directions are tested. The runs are performed with moving cooling water through the tubes while heating air flows across the tube bundles. The results state that the SCT can be used as a passive approach for augmenting the heat exchange rates. As geometry, increasing the gap between their bases increases both the heat exchange rate and fluid pressure loss at the same time. Additionally, reducing the longitudinal and/or transversal pitch ratios leads to enlarging these increases. In addition, the thermal performance index (TPI) is slightly augmented by extending the distance between the SCTs’ bases or reducing the transversal and/or longitudinal spacings. Also, an increase in the TPI is resulted by raising the airflow rate. Moreover, the extreme determined TPI is 1.98.