Abstract Usual commercial thermoelectric modules are produced in the form of flat shapes. However, tube-bundle arrangement of tubular thermoelectric modules as an air cooler (proposed for the first time in this paper as shown in the graphical abstract) is very meaningful and straightforward compared to the coolers made by flat-shape thermoelectric modules. It is assumed that, the water fluid moves through the inside of the tube-bundle thermoelectric (to adjust the hot surface temperature of the thermoelectric) while the air fluid moves through the outer surface of the tubular thermoelectric (cold side) in cross-section direction. In order to clarify the applicability of the tubular thermoelectric for aforementioned aim, thermal behavior of the tubular thermoelectric legs (in terms of temperature distribution through the legs, heat transfer rate and COP of the cooling process) are comprehensively studied in this paper via a validated 3D numerical simulation by consideration of appropriate boundary conditions. Moreover, geometric characteristics of tubular thermoelectric as an air cooler are investigated and presented in this study which have not been reported before. The results showed that tubular thermoelectric can be appropriately employed for said aim if thermal and geometric parameters are selected in desired range.