EXPERIMENTAL STUDY OF FINS PERFORATION EFFECT ON THERMAL PERFORMANCE OF HELICALLY FINNED TUBES

Abstract

The present research includes an experimental study for the effect of fins perforation onthe performance of helically finned tubes. The experiments were made on five models of (18mm) diameter tubes finned spirally with (12mm) high fins perforated with a circular holes ,the number of holes was (3-3-6&2 hole /fin) and their diameters were (3,4,2&3mm)respectively .Each tube was tests horizontally by forcing air with(1.5-7.5 m/s) maximumvelocity and Reynolds number range (3105.7 10 321.1510  ) on the tube .The effect ofnumber and diameter of holes were studied.The experimental results showed that the finsperforation increase the overall heat transfer coefficient for all perforated fins tubes, but thepercentage increase differs from tube to another. From the comparison of overall heat transfercoefficient for perforated finned tube ((3 hole/fin), (3mm) hole diameter) with unperforatedfinned tube found that it is increased to (12.3%) at air velocity (4.5m/s), this percentagecontinue with increasing until to reach (36%) at (7.5 m/s). It is found that for two tubeswith same fins dimensions and same number of holes (3 hole/fin), the tube with smaller hole(2mm) is better than that of the larger hole (3mm) by (28%) at (7.5 m/s) maximum airvelocity, the increase of the number of holes from (2) to (3) for constant hole diameter (3mm)improves the overall heat transfer coefficient by (7.8%) at (7.5 m/s) maximum air velocity .Sothe increasing of holes number increase the overall heat transfer coefficient more than theincreasing of holes diameter for constant fins surface area (for research case).