Thermal and Friction Characteristics of Laminar Flow through Square and Rectangular Ducts with Transverse Ribs and Twisted Tapes with and without Oblique Teeth

2010 ◽  
Vol 17 (1) ◽  
pp. 1-21 ◽  
Author(s):  
P. K. Pal ◽  
Sujoy Kumar Saha
Keyword(s):  
Laminar Flow ◽  
Friction Characteristics ◽  
Twisted Tapes ◽  
Flow Through

Heat Transfer Enhancement of Laminar Flow Through a Circular Tube Having Wire Coil Inserts and Fitted With Center-Cleared Twisted Tape

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Sujoy Kumar Saha ◽  
Bikash Kumar Barman ◽  
Soumitra Banerjee
Keyword(s):  
Nusselt Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Twisted Tape ◽  
Circular Duct ◽  
Twisted Tapes ◽  
Wire Coil ◽  
Flow Through ◽  
The Individual ◽  
Better Than

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having wire coil inserts and fitted with center-cleared twisted tape have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are the center-cleared twisted tapes in combination with wire coil inserts perform better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain amount of center-clearance.

Laminar Flow Through a Circular Tube Having Transverse Ribs and Twisted Tapes

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Manvendra Tiwari ◽  
Sujoy Kumar Saha
Keyword(s):  
Nusselt Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Circular Tube ◽  
Circular Duct ◽  
Viscous Oil ◽  
Twisted Tapes ◽  
Flow Through ◽  
The Individual ◽  
Better Than

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral transverse rib roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral transverse rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Thermohydraulics of Laminar Flow Through Rectangular and Square Ducts With Transverse Ribs and Twisted Tapes

2006 ◽  
Vol 128 (10) ◽  
pp. 1070-1080 ◽  
Author(s):  
Debashis Pramanik ◽  
Sujoy K. Saha
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Laminar Flows ◽  
Short Length ◽  
Full Length ◽  
Twisted Tape ◽  
Twisted Tapes ◽  
Square Ducts ◽  
Better Than

The heat transfer and the pressure drop characteristics of laminar flow of viscous oil through rectangular and square ducts with internal transverse rib turbulators on two opposite surfaces of the ducts and fitted with twisted tapes have been studied experimentally. The tapes have been full length, short length, and regularly spaced types. The transverse ribs in combination with full-length twisted tapes have been found to perform better than either ribs or twisted tapes acting alone. The heat transfer and the pressure drop measurements have been taken in separate test sections. Heat transfer tests were carried out in electrically heated stainless steel ducts incorporating uniform wall heat flux boundary conditions. Pressure drop tests were carried out in acrylic ducts. The flow was periodically fully developed in the regularly spaced twisted-tape elements case and decaying swirl flow in the short-length twisted tapes case. The flow characteristics are governed by twist ratio, space ratio, and length of twisted tape, Reynolds number, Prandtl number, rod-to-tube diameter ratio, duct aspect ratio, rib height, and rib spacing. Correlations developed for friction factor and Nusselt number have predicted the experimental data satisfactorily. The performance of the geometry under investigation has been evaluated. It has been found that on the basis of both constant pumping power and constant heat duty, the regularly spaced twisted-tape elements in specific cases perform marginally better than their full-length counterparts. However, the short-length twisted-tape performance is worse than the full-length twisted tapes. Therefore, full-length twisted tapes and regularly spaced twisted-tape elements in combination with transverse ribs are recommended for laminar flows. However, the short-length twisted tapes are not recommended.

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