Analytical Prediction of Heat Transfer in Tape Generated Swirl Flow

2017 ◽  
Author(s):  
R. J. Yadav ◽  
Sandeep Kore ◽  
V. N. Riabhole
Keyword(s):  
Heat Transfer ◽  
Circular Tube ◽  
Swirl Flow ◽  
Twisted Tape ◽  
Analytical Prediction ◽  
Transfer Coefficients ◽  
Numerical Predictions ◽  
Twisted Tapes ◽  
Wide Range ◽  
Prandtl Numbers

Heat transfer and pressure drop characteristics in a circular tube with twisted tapes have been investigated experimentally and numerically using different working fluids by many researchers for wide range of Reynolds number. The swirl was generated by tape inserts of various twist ratios. The various twist ratios are considered Many researchers formed generalized correlations to predict friction factors and convective heat transfer coefficients with twisted tapes in a tube for a wide range of Reynolds numbers and Prandtl numbers. Satisfactory agreement was obtained between the present correlations and the data of others validate the proposed correlations. The experimental or numerical predictions were compared with earlier correlations revealing good agreement between them. From the literature review it is observed that most studies are mainly focused on the heat transfer enhancement using twisted tape by experimental or numerical solution. An investigation with analytical approach is rarely reported. Therefore, the main aim of the present work is to form a correlation from theoretical approach for Nusselt number for circular tube with twisted tape. Application of dimensional analysis to heat transfer in tape generated swirl flow is carried out.

Thermohydraulic Study of Laminar Swirl Flow Through a Circular Tube Fitted With Twisted Tapes

2001 ◽  
Vol 123 (3) ◽  
pp. 417-427 ◽  
Author(s):  
S. K. Saha ◽  
A. Dutta
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Friction Factor ◽  
Circular Tube ◽  
Swirl Flow ◽  
Short Length ◽  
Full Length ◽  
Twisted Tape ◽  
Twisted Tapes

Heat transfer and pressure drop characteristics in a circular tube fitted with twisted tapes have been investigated experimentally. Laminar swirl flow of a large Prandtl number 205<Pr<518 viscous fluid was considered. The swirl was generated by short-length twisted-tape inserts; regularly spaced twisted-tape elements with multiple twists in the tape module and connected by thin circular rods; and smoothly varying (gradually decreasing) pitch twisted-tapes. The heat transfer test section was heated electrically imposing axially and circumferentially constant wall heat flux (UHF) boundary condition. Reynolds number, Prandtl number, twist ratio, space ratio, number of tuns in the tape module, length of the twisted-tape and smoothness of the swirling pitch govern the characteristics. Friction factor and Nusselt number are lower for short-length twisted-tape than those for full-length twisted-tape. On the basis of constant pumping power and constant heat duty, however, short-length twisted-tapes are found to perform better than full-length twisted-tapes for tighter twists. Thermohydraulic performance shows that twisted-tapes with multiple twists in the tape module is not much different from that with single twist in the tape module. Friction factor and Nusselt number are approximately 15 percent lower for twisted-tapes with smooth swirl having the average pitch same as that of the uniform pitch (throughout) twisted-tape and the twisted-tapes with gradually decreasing pitch perform worse than their uniform-pitch counterparts.

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part II—Transition and Turbulent Flows

1993 ◽  
Vol 115 (4) ◽  
pp. 890-896 ◽  
Author(s):  
R. M. Manglik ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flows ◽  
Published Data ◽  
Twisted Tape ◽  
Heating And Cooling ◽  
Twisted Tapes ◽  
Family Of Curves ◽  
Wide Range ◽  
Limiting Case

Thermal-hydraulic design correlations are developed to predict isothermal f and Nu for in-tube, turbulent flows with twisted-tape inserts. Experimental data taken for water and ethylene glycol, with y = 3.0, 4.5, and 6.0, are analyzed, and various mechanisms attributed to twisted tapes are identified. Tube blockage and tape-induced vortex mixing are the dominant phenomena that result in increased heat transfer and pressure drop; for loose- to snug-fitting tapes, the fin effects are insignificant. The limiting case of a straight tape insert correlates with the hydraulic-diameter-based smooth tube equation. Tape twist effects are thus isolated by normalizing the data with the asymptotic predictions for y = ∞, and the swirl effects are found to correlate with Re and l/y. The validity of the final correlations is verified by comparing the predictions with previously published data, which include both gases and liquids, under heating and cooling conditions and a wide range of tape geometries, thereby establishing a very generalized applicability. Finally, correlations for laminar (presented in the companion Part I paper) and turbulent flows are combined into single, continuous equations. For isothermal f, the correlation describes most of the available data for laminar-transition-turbulent flows within ±10 percent. For Nu, however, a family of curves is needed due to the nonunique nature of laminar-turbulent transition.

Prediction of Swirl Flow and Heat Transfer through Square Duct with Twisted Tape Insert

2013 ◽  
Vol 284-287 ◽  
pp. 888-893 ◽  
Author(s):  
Ho Keun Kang ◽  
Soo Whan Ahn ◽  
Myung Sung Lee
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Flow Direction ◽  
Swirl Flow ◽  
Hydraulic Diameter ◽  
Twisted Tape ◽  
Square Duct ◽  
Square Channel ◽  
Numerical Predictions ◽  
Commercial Code

Numerical predictions of characteristics of turbulent flows through a square duct (30 30 mm) with twisted tape inserts and with twisted tape inserts plus interrupted ribs are conducted to investigate regionally averaged heat transfer and friction factors by using CFX 11.0 commercial code. The validity of the numerical results is confirmed by measurement. Reynolds numbers are varied between 8,900 and 29,000. A rib height-to-channel hydraulic diameter (e/Dh) of 0.067 and a length-to hydraulic diameter (L/Dh) of 30 are considered. The square ribs are arranged to follow the trace of the twisted tape and along the flow direction defined as axial interrupted ribs. The twisted tape is 0.1 mm thick carbon steel sheet with diameter of 28mm, length of 900mm and 2.5 turns. Each wall of the square channel is composed of the isolated aluminum section. The present study demonstrates that the twisted tape with interrupted ribs provides a greater overall heat transfer performance over the twisted tape with no ribs in the square duct.

scholarly journals CFD Analysis for Heat Transfer Enhancement inside a Circular Tube with Half-Length Upstream and Half-Length Downstream Twisted Tape

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
R. J. Yadav ◽  
A. S. Padalkar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Circular Tube ◽  
Swirl Flow ◽  
Twisted Tape ◽  
Turbulent Regime ◽  
Cfd Analysis ◽  
Transfer Enhancement ◽  
Plain Tube ◽  
Half Length

CFD investigation was carried out to study the heat transfer enhancement characteristics of air flow inside a circular tube with a partially decaying and partly swirl flow. Four combinations of tube with twisted-tape inserts, the half-length upstream twisted-tape condition (HLUTT), the half-length downstream twisted-tape condition (HLDTT), the full-length twisted tape (FLTT), and the plain tube (PT) with three different twist parameters (, 0.27, and 0.38) have been investigated. 3D numerical simulation was performed for an analysis of heat transfer enhancement and fluid flow for turbulent regime. The results of CFD investigations of heat transfer and friction characteristics are presented for the FLTT, HLUTT, and the HLDTT in comparison with the PT case.

scholarly journals The Effect of Off-center Placement of Twisted Tape on Flow and Heat Transfer Characteristics in a Circular Tube

2020 ◽  
Author(s):  
Li Wang ◽  
Peiyong Ni ◽  
Guannan Xi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Circular Tube ◽  
Flow Distribution ◽  
Hydraulic Performance ◽  
Twisted Tape ◽  
Twisted Tapes ◽  
Plain Tube ◽  
And Performance ◽  
High Reynolds

Abstract This study is conducted to investigate the effect of off-center placement of twisted tape on flow distribution and heat transfer in a circular tube. The effect of tape width of 20, 18, 16, 14 and 12 mm on the heat transfer performance is discussed under the same twist ratio of 2.0. The numerical analysis of the flow field, average Nusselt number, friction factor and thermo-hydraulic performance parameter of the tube are discussed with Reynolds number ranged from 2600 to 8760. The results indicate that the Nusselt number of the tube fitted with center-placed twisted tapes at various width is 7~51% higher than the plain tube, and performance in low Reynolds region was found more effective than that in high Reynolds region. The heat transfer for circular tube with twisted tape attached to the wall shows better performance than that for the tube with center-placed twisted tape. With a smaller tape width, a higher increasing ratio of Nu-wall/Nu-center is obtained. The increasing ratio for Nusselt number ranged from 3 to 18%. However, the use of twisted tape inserts is not beneficial for energy saving. The thermo-hydraulic performance parameters for convective heat transfer of helium gas flowing in a circular tube are below unity for the calculated Reynolds region.

A review study on the performance of a parabolic trough receiver using twisted tape inserts

2021 ◽  
pp. 095440892110371
Author(s):  
Sashank Thapa ◽  
Sushant Samir ◽  
Khushmeet Kumar
Keyword(s):  
Heat Transfer ◽  
Extensive Study ◽  
Twisted Tape ◽  
Wide Field ◽  
Parabolic Trough ◽  
Flow Paths ◽  
Twisted Tapes ◽  
Wide Range ◽  
Performance Conditions ◽  
Passive Techniques

Heat transfer in concentrating solar collectors like parabolic troughs has proven nowadays a very efficient method by using different passive techniques to increase the heat transfer rate. The use of passive techniques also increases the pumping power requirements to make the flow through the receiver. So, a number of researchers are working to find out the optimum performance conditions for parabolic trough receivers by using different types of inserts in flow paths. This paper presents a wide range of literature available for solar parabolic troughs in one place. Based on this extensive study, it is found that twisted tape inserts is a very wide field for investigation and the use of different shapes, pitch value, free space, and angle of twist tape are the parameters that can be considered for further studies to improve the performance of solar troughs. Also, various combinations of perforation and cuts on twisted tapes can be used to achieve enhanced performance.

The Influence of Twisted Tapes in Subcritical, Once-Through Vapor Generators in Counter flow

1974 ◽  
Vol 96 (3) ◽  
pp. 365-370 ◽  
Author(s):  
M. Cumo ◽  
G. E. Farello ◽  
G. Ferrari ◽  
G. Palazzi
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Exchanger ◽  
Joule Heating ◽  
Swirl Flow ◽  
Twisted Tape ◽  
Counter Flow ◽  
Tubular Heat Exchanger ◽  
Annular Gap ◽  
Twisted Tapes

The swirl flow of Freon 12 in a tubular heat exchanger, indirectly heated by forced convection of water in an annular gap, is studied. Two identical situations are compared, with and without a twisted tape, to deduce the influence of the swirl flow in the particularly interesting boundary condition of indirect heating by another fluid (and not simply of uniform Joule heating). The heat transfer is greatly increased by the swirl flow, up to a factor of two at the burnout or dryout point.

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