Forced convective heat transfer, friction factor, enhancement efficiency and entropy generation characteristics past equilateral triangular tubes at rotational angles have been investigated experimentally. Utilizing air as an operating for
wide ranges of the Reynolds number (Re) (26×102≤ Re ≤10.32×103 ) and angle of rotational (0°≤  ≤ 90°). The experimental results show that a considerable increase in Nusslet Number (Nu) for circular tubes than equilateral triangular tubes at the vertex facing the flow ( = 0°), while the Nu for equilateral triangular tubes bundle increases than
a circular tube at rotational angles above ( = 0°). Also, results indicated that the best Nu and overall enhancement
efficiency is achieved for the flat surface facing the flow values of ( = 90°). The results obtained are correlated in the
form of Nu, friction factor and enhancement efficiency as a function of Re and angles of rotational.