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.

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.

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.

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.

Thermohydraulics of Laminar Flow Through Rectangular and Square Ducts With Axial Corrugation Roughness and Twisted Tapes With Oblique Teeth

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Sujoy Kumar Saha
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Thermal Characteristics ◽  
Twisted Tape ◽  
Pumping Power ◽  
Twisted Tapes ◽  
Flux Boundary Conditions ◽  
The Individual ◽  
Square Ducts

The heat transfer and the pressure drop characteristics of laminar flow of viscous oil (175<Pr<538) through rectangular and square ducts with combined internal axial corrugations on all the surfaces of the ducts and with twisted-tape inserts with and without oblique teeth have been studied experimentally. The axial corrugations in combination with both twisted tapes with and without oblique teeth have been found to perform better than either axial corrugations or twisted-tape inserts 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 friction and thermal characteristics are governed by duct aspect ratio, corrugation angle, corrugation pitch, twist ratio, space ratio, length, tooth horizontal length and tooth angle of the twisted tapes, Reynolds number, and Prandtl number. 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 based on constant pumping power, up to 45% heat duty increase occurs for the combined axial corrugation and twisted-tape insert case compared with the individual axial corrugation and twisted-tape insert cases in the measured experimental parameters space. On the constant heat duty basis, the pumping power has been reduced up to 30% for the combined enhancement geometry than the individual enhancement geometries.

scholarly journals Thermo-Hydraulic Performance Analysis on the Effects of Truncated Twisted Tape Inserts in a Tube Heat Exchanger

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1652
Author(s):  
Mehdi Ghalambaz ◽  
Ramin Mashayekhi ◽  
Hossein Arasteh ◽  
Hafiz Muhammad Ali ◽  
Pouyan Talebizadehsardari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Tube Heat Exchanger ◽  
Twisted Tapes ◽  
Plain Tube

This paper investigates the convective heat transfer in a heat exchanger equipped with twisted tape elements to examine effects of the twisted tape truncation percentage, pitch value, position and Reynolds number using 3D numerical simulation. A symmetric heat flux is applied around the tube as the studied heat exchanger. Based on the influences in both heat transfer enhancement and pressure drop, the performance evaluation criterion (PEC) is utilized. Inserting twisted tape elements and reducing the pitch value significantly augment the Nusselt number, friction coefficient and PEC number compared to the plain tube. For the best case with a Reynolds number of 1000, the average Nusselt number increases by almost 151%, which is the case of fully fitted twisted tape at a pitch value of L/4. Moreover, increasing the twisted tape truncation percentage reduces both heat transfer and pressure drop. Furthermore, the highest heat transfer rate is achieved when the truncated twisted tape is located at the entrance of the tube. Finally, it is concluded that for P = L, L/2, L/3 and L/4, the optimum cases from the viewpoint of energy conservation are twisted tapes with truncation percentages of 75, 50, 50 and 0%, in which the related PEC numbers at a Reynolds number of 1000 are almost equal to 1.08, 1.24, 1.4 and 1.76, respectively.

Heat Transfer and Pressure Drop Characteristics of Laminar Flow in Rectangular and Square Plain Ducts and Ducts With Twisted-Tape Inserts

2004 ◽  
Vol 127 (9) ◽  
pp. 966-977 ◽  
Author(s):  
S. K. Saha ◽  
D. N. Mallick
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Friction Factor ◽  
Short Length ◽  
Full Length ◽  
Twisted Tape ◽  
Aspect Ratios ◽  
Twisted Tapes

Abstract The present paper reports the results of an experimental investigation of the heat transfer and pressure drop characteristics of laminar flow of viscous oil through horizontal rectangular and square plain ducts and ducts inserted with full-length twisted tapes, short-length twisted tapes, and regularly spaced twisted-tape elements. Isothermal pressure drop measurements were taken in acrylic ducts. Heat transfer measurements were taken in electrically heated stainless-steel ducts imposing uniform wall heat flux boundary conditions. The duct aspect ratios AR were 1, 0.5, and 0.333. The twist ratios of the twisted tapes were y=2.692, 5.385, 2.597, 5.193, 2.308, and 4.615. Short-length tapes were 0.9, 0.7, and 0.5 times the duct length. The space ratios were s=2.692, 5.385, 2.597, 5.193, 2.308, and 4.615. Both friction factor and Nusselt number increase with decreasing y and AR for AR⩽1 and increasing Re, Sw, and Pr. As the tape-length decreases, both friction factor and Nusselt number decrease. Friction factor increases as s decreases, and Nusselt number increases as s increases. Isothermal friction factor correlation and comprehensive Nusselt number correlation have been developed to predict data reasonably well in the entire range of parameters. Performance evaluation says that short-length twisted tapes are worse and regularly spaced twisted-tape elements are better than the full-length twisted tapes.

scholarly journals Investigation of Overlapped Twisted Tapes Inserted in a Double-Pipe Heat Exchanger Using Two-Phase Nanofluid

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1656 ◽  
Author(s):  
Mehdi Ghalambaz ◽  
Hossein Arasteh ◽  
Ramin Mashayekhi ◽  
Amir Keshmiri ◽  
Pouyan Talebizadehsardari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Performance Evaluation ◽  
Heat Exchanger ◽  
Evaluation Criterion ◽  
Twisted Tape ◽  
Performance Evaluation Criterion ◽  
Twisted Tapes ◽  
Double Pipe ◽  
Pipe Heat

This study investigated the laminar convective heat transfer and fluid flow of Al2O3 nanofluid in a counter flow double-pipe heat exchanger equipped with overlapped twisted tape inserts in both inner and outer tubes. Two models of the same (co-swirling twisted tapes) and opposite (counter-swirling twisted tapes) angular directions for the stationary twisted tapes were considered. The computational fluid dynamic simulations were conducted through varying the design parameters, including the angular direction of twisted tape inserts, nanofluid volume concentration, and Reynolds number. It was found that inserting the overlapped twisted tapes in the heat exchanger significantly increases the thermal performance as well as the friction factor compared with the plain heat exchanger. The results indicate that models of co-swirling twisted tapes and counter-swirling twisted tapes increase the average Nusselt number by almost 35.2–66.2% and 42.1–68.7% over the Reynolds number ranging 250–1000, respectively. To assess the interplay between heat transfer enhancement and pressure loss penalty, the dimensionless number of performance evaluation criterion was calculated for all the captured configurations. Ultimately, the highest value of performance evaluation criterion is equal to 1.40 and 1.26 at inner and outer tubes at the Reynolds number of 1000 and the volume fraction of 3% in the case of counter-swirling twisted tapes model.

scholarly journals Heat Enhancement Effectiveness Using Multiple Twisted Tape in Rectangular Channels

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 188
Author(s):  
M. Ziad Saghir ◽  
Ayman Bayomy ◽  
Md Abdur Rahman
Keyword(s):  
Pressure Drop ◽  
Heat Removal ◽  
Energy System ◽  
Twisted Tape ◽  
Heat Exchanger Design ◽  
Twisted Tapes ◽  
Rectangular Channels ◽  
Flow Through ◽  
The Subject ◽  
Energy Coefficient

Heat enhancement and heat removal have been the subject of considerable research in the energy system field. Flow-through channels and pipes have received much attention from engineers involved in heat exchanger design and construction. The use of insert tape is one of many ways to mix fluids, even in a laminar flow regime. The present study focused on the use of different twisted tapes with different pitch-to-pitch distances and lengths to determine the optimum design for the best possible performance energy coefficient. The results revealed that twisted tape of one revolution represented the optimal design configuration and provided the largest Nusselt number. The length of the tape played a major role in the pressure drop. The results revealed that the insertion of a shorter twisted tape can create mixing while minimizing the changes in the pressure drop. In particular, the best performance evaluation criterion is found for a short tape located towards the exit of the channel. The highest performance energy coefficient was obtained for the half-twisted tape for a Reynolds number varying between 200 and 600.

Modeling of Turbulent Flows Through the Annular Channel with Eccentricity and Rotating Inner Cilinder

2012 ◽  
Vol 7 (4) ◽  
pp. 79-86
Author(s):  
Evgeny Podryabinkin ◽  
Valeriy Rudyak
Keyword(s):  
Pressure Drop ◽  
Turbulent Flows ◽  
Transport Model ◽  
Reverse Flow ◽  
Axial Flow ◽  
Annular Channel ◽  
Rotational Flow ◽  
Concentric Annulus ◽  
Cylindrical Annulus ◽  
Wide Range

In this paper fully developed turbulent flows of Newtonian fluid in cylindrical annulus with eccentricity and rotating inner cylinder has been systematically studied. Modeling has been performed on the base of Menter Shear Transport model of turbulence in a wide range of Reynolds numbers, eccentricity, and radii ratio. As the result dependencies of flow field and pressure drop along the channel on geometrical and flow parameters have been found. It was shown that flow characteristics and dependence of the pressure drop are determined by which flow axial or rotational dominates and caused generation of turbulence. When rotational flow dominates the dependence of the pressure drop is almost linear. When axial flow dominates rotation practically has no impact on the pressure drop in concentric annulus. Appearance of the reverse flow in eccentric channel has a major impact on the pressure drop. In case when rotational flow dominates, appearance of the reverse flow is accompanied by threshold flow restructuring at some critical value of eccentricity. A correlation for determination of the pressure drop in various regimes has been developed for the case of concentric annulus

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