دراسة عملية لتأثير تثقيب الزعانف على الأداء الحراري للأنابيب المزعنفة حلزونيا

الملخص EN

The present research includes an experimental study for the effect of fins perforation on the performance of helically finned tubes.

The experiments were made on five models of (18 mm) diameter tubes finned spirally with (12 mm) 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 & 3 mm) respectively.

Each tube was tests horizontally by forcing air with (1.5-7.5 m / s) maximum velocity and Reynolds number range (21.15 × 103-105.7 × 103) on the tube.

The effect of number and diameter of holes were studied.

The experimental results showed that the fins perforation increase the overall heat transfer coefficient for all perforated fins tubes, but the percentage increase differs from tube to another.

From the comparison of overall heat transfer coefficient for perforated finned tube ((3 hole / fin), (3 mm) hole diameter) with unperforated finned tube found that it is increased to (12.3 %) at air velocity (4.5 m / s), this percentage continue with increasing until to reach (36 %) at (7.5 m / s).

It is found that for two tubes with same fins dimensions and same number of holes (3 hole / fin), the tube with smaller hole (2 mm) is better than that of the larger hole (3 mm) by (28 %) at (7.5 m / s) maximum air velocity, the increase of the number of holes from (2) to (3) for constant hole diameter (3 mm) improves the overall heat transfer coefficient by (7.8 %) at (7.5 m / s) maximum air velocity .So the increasing of holes number increase the overall heat transfer coefficient more than the increasing of holes diameter for constant fins surface area (for research case).