Pengujian Karakteristik Perpindahan Panas Dan Faktor Gesekan Pada Penukar Kalor Pipa Konsentrik Saluran Annular Dengan Alternate Clockwise And Counter Clockwise Twisted Tape Insert

Abstract

Abstract : This research was conducted to examine the characteristics of heat transfer and friction factor in the annular channel concentric tube heat exchanger with the addition of alternate clockwise and counter clockwise (C-CC) twisted tape insert with the twist angle variation (θ) = 30o, 45o, and 60o. Test section was the single pass concentric tube heat exchanger with inner tube and outer tube made of aluminum. Flows in the inner tube and in annulus were counter flow. Working fluid in the inner tube was hot water which its inlet temperature was maintained at 60°C, whereas the working fluid in the annulus was cold water with its inlet temperature of ± 28oC. Classic twisted tape insert and CCC twisted tape inserts with twist angle (θ) = 30o, 45o and 60o installed in the inner tube of the concentric tube heat exchanger. For comparison, inner tube tested without twisted tape insert (plain tube) and with the addition of classic twisted tape insert. Classic twisted tape insert and C-CC twisted tape insert made of aluminum strip with a thickness of 0.7 mm, width 12.6 mm, which had a twist ratio of 4.0 and the pitch length of 50.3 mm. The research result has showed that the concentric tube heat exchanger with the addition of C-CC twisted tape insert with θ = 30o, 45o and 60o into its inner tube produce Nusselt number, pressure drop, friction factor and thermal performance greater than the classic twisted tape insert. C-CC twisted tape insert with θ = 60o has produced Nusselt numbers, pressure drop, friction factor and thermal performance higher than the C-CC twisted tape insert with θ = 30o and 45o. The addition of C-CC twisted tape insert has resulted in enhancement heat transfer better than the classic twisted tape insert. At the same Reynolds number, the addition of classic twisted tape insert, C-CC twisted tape insert with θ = 30o, 45o and 60o into the inner tube increase the average Nusselt numbers has been 45.82%, 51.34%, 60.23%, and 70.02% compared to the plain tube, respectively. At the same Reynolds number, the addition of classic twisted tape insert, C-CC twisted tape insert with θ = 30o, 45o and 60o into inner tube has produced an average friction factor of 3.020; 3.223; 3.473; and 3.737 times than the friction factor of plain tube, respectively. The addition of classic twisted tape insert, C-CC twisted tape insert with θ = 30o, 45o and 60o into the inner tube has produced an average thermal performance of 1.001; 1.011; 1.045; and 1.085, respectively.

Keywords : Nusselt number, Reynolds number, Friction factor, Alternate clockwise and,counter clockwise twisted, tape insert, Twist angle