This paper presents a three dimensional numerical simulation to predict heat transfer and pressure drop of turbulent fluid flow inside internally star finned tubes. The effects of Reynolds number (Re = 5000–30,000), fin numbers (n= 5, 10), and fin geometry (smooth, straight wavy, curved wavy, regularly spaced) on Nusselt number (Nu), friction factor (f) and thermal performance factor (PEC) are investigated under uniform wall heat flux condition. The obtained results reveal that both heat transfer rate and friction factor of star finned tubes are significantly higher than those of plain tube. Maximum values of Nu and ffor case with wavy star fins are 510 and 779% higher than those for plain tube. Thermal performances of all investigated cases are higher than unity and it increases by rise of Reynolds number. Moreover, maximum obtained value of PEC is 2.96 and maximum obtained increase in Nu in comparison with plain tube is 521%.
