EFFECT THE FORM OF PERFORATION ON THE HEAT TRANSFER IN THE PERFORATED FINS

Extended surface heat exchangers are easy in construction and extensively use in many of the industries. Continuous research is going on to improve its effectiveness by reducing the thermal boundary layer thickness and increasing the heat transfer surface area. Perforations in the fins one way that used to improve its effectiveness. An experimental study submitted to investigate the heat transfer by natural convection in a rectangular perforated fin plates. Five fins used in this work first fin non-perforated and others fins perforated by different shapes these fins perforation by different shapes (circle, square, triangle, and hexagon) but these perforations have the same cross section area(113 mm2. These perforations distributed on 3 columns and 6 rows. Experiments produced through in an experimental facility that was specifically design and constructed for this purpose. The results show that the drop in the temperature of the non-perforated fin from 72 to 57 oC while the temperature drop in perforated fins, at the same power supplied (126 W) was (72-52 oC), (72-51.5 oC), (72-50 oC) and (72 -48 oC) for shapes (hexagonal, square, circular and triangular) respectively Figure(9). The largest value of RAF at triangular perforation and the smaller value occurred in circular perforation. Also, triangular perforation gives best values of heat transfer coefficient and then the circular, square, hexagonal, and non-perforation respectively.