ABSTRACTHeat transfer enhancement can be achieved by surface modification of fins using different notches. Fin arrays find wide applications in heat transfer studies and other fluid flow processes. The key factor is the fin geometry, which is much significant in the fin arrays. An experimental investigation of mixed convection heat transfer on rectangular fins with triangular notch, circular notch and without notch in a horizontal rectangular channel for a wide range of modified Rayleigh numbers and different flow rates has been carried out. From this investigation, it has been found that circular notch plays efficiently in heat transfer rate.