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.

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.

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 Investigations of the Compact Exhaust Heat Exchanger With Twisted Tape Inserts for Automotive Waste Heat Utilization

2020 ◽  
Vol 13 (4) ◽  
Author(s):  
Dhruv Raj Karana ◽  
Rashmi Rekha Sahoo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Internal Heat ◽  
Decisive Role ◽  
Twisted Tape ◽  
Twisted Tapes ◽  
Exhaust Heat

Abstract Thermoelectric-based waste heat recovery is a competent technique to reduce the exhaust emissions and fuel consumption of automobiles. Thermal and hydraulic characteristics of the exhaust heat exchanger plays a decisive role in the extent of waste heat recovery from the exhaust gas. In this study, the exhaust heat exchanger having twisted tape inserts is proposed to increase the internal heat transfer coefficient. The dimensionless Nusselt number and friction factor were evaluated experimentally for different designs of the twisted tapes. The experiments were performed for the Reynolds number in the range 2300–25000. The considered geometric parameters of the twisted rib explored were the pitch fraction, twist fraction, and slope. The obtained results were compared to reveal the best feasible design of the twisted tape. The maximum net thermohydraulic efficiency factor achieved for the system in the present analysis is 1.93. With the use of twisted tapes, the area of the exhaust heat exchanger can be greatly reduced for the same power output as flat geometry. This would help for the integration of the waste heat recovery with the engine, where the space available is very limited.

scholarly journals Heat Transfer Enhancement by Using Different Types of Inserts

2014 ◽  
Vol 6 ◽  
pp. 250354 ◽  
Author(s):  
S. Tabatabaeikia ◽  
H. A. Mohammed ◽  
N. Nik-Ghazali ◽  
B. Shahizare
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Low Cost ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Thermal Systems ◽  
Twisted Tapes ◽  
High Efficient

Heat transfer enhancement has been always a significantly interesting topic in order to develop high efficient, low cost, light weight, and small heat exchangers. The energy cost and environmental issue are also encouraging researchers to achieve better performance than the existing designs. Two of the most effective ways to achieve higher heat transfer rate in heat exchangers are using different kinds of inserts and modifying the heat exchanger tubes. There are different kinds of inserts employed in the heat exchanger tubes such as helical/twisted tapes, coiled wires, ribs/fins/baffles, and winglets. This paper presents an overview about the early studies on the improvement of the performance of thermal systems by using different kinds of inserts. Louvered strip insert had better function in backward flow compared to forward one. Modifying the shape of twisted tapes led to a higher efficiency in most of the cases excpet for perforated twisted tape and notched twisted tape. Combination of various inserts and tube with artificial roughness provided promising results. In case of using various propeller types, heat transfer enhancement was dependent on higher number of blades and blade angle and lower pitch ratio.

Experimental Analysis on Heat Transfer Enhancement of Double Pipe Heat Exchanger Using Alumina/Water Nanofluid and Baffled Twisted Tape Inserts

2015 ◽  
Vol 752-753 ◽  
pp. 458-465
Author(s):  
P.C. Sreekumar ◽  
K. Krishnamoorthy ◽  
R. Ratheesh
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Convective Heat Transfer Coefficient ◽  
Twisted Tape ◽  
Twisted Tapes ◽  
Twist Ratio ◽  
Double Pipe ◽  
Pipe Heat

Heat transfer augmentation techniques ultimately results in the reduction of thermal resistance in a conventional heat exchanger by generating higher convective heat transfer coefficient. Present study with the use of Alumina (Al2O3)/water nanofluid and baffled twisted tape inserts in double pipe heat exchanger as compound augmentation technique. Experiments were conducted to evaluate the heat transfer coefficient and friction factor for the flow through the inner tube of heat exchanger in turbulent flow range (8000<Re<60000). The effect of rectangular, circular, triangular baffled twisted tape having twist ratio (y/w) 4.2 and twisted tapes without baffles of twist ratio (y/w) 4.2 and 5.2 were studied. Experiments were conducted for both water and 0.1% volume concentration Alumina/water nanofluid. It is found that the enhancement of heat transfer coefficient by using rectangular baffled twisted tape and nanofluid is about 20%. Performance evaluation criteria were found for water and nanofluid and it was observed that rectangular baffled twisted tape performs better than other twisted tapes.

scholarly journals Evaluation of Multiple Semi-Twisted Tape Inserts in a Heat Exchanger Pipe Using Al2O3 Nanofluid

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1570
Author(s):  
Yongfeng Ju ◽  
Tiezhu Zhu ◽  
Ramin Mashayekhi ◽  
Hayder I. Mohammed ◽  
Afrasyab Khan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Base Fluid ◽  
Average Nusselt Number ◽  
Three Dimensions ◽  
Twisted Tape ◽  
Twisted Tapes

The hydrothermal performance of multiple semi-twisted tape inserts inside a heat exchanger pipe is numerically examined in three-dimensions. This study aims to find the optimum case for having the highest heat transfer enhancement with the lowest friction factor using nanofluid (Al2O3/water). A performance evaluation criterion (PEC) is defined to characterize the performance based on both friction factor and heat transfer. It was found that increasing the number of semi-twisted tapes increases the number of swirl flow streams and leads to an enhancement in the local Nusselt number as well as the friction factor. The average Nusselt number increases from 15.13 to 28.42 and the average friction factor enhances from 0.022 to 0.052 by increasing the number of the semi-twisted tapes from 0 to 4 for the Reynolds number of 1000 for the base fluid. By using four semi-twisted tapes, the average Nusselt number increases from 12.5 to 28.5, while the friction factor reduces from 0.155 to 0.052 when the Reynolds number increases from 250 to 1000 for the base fluid. For the Reynolds number of 1000, the increase in nanofluid concentration from 0 to 3% improves the average Nusselt number and friction factor by 6.41% and 2.29%, respectively. The highest PEC is equal to 1.66 and belongs to the Reynolds number of 750 using four semi-twisted tape inserts with 3% nanoparticles. This work offers instructions to model an advanced design of twisted tape integrated with tubes using multiple semi-twisted tapes, which helps to provide a higher amount of energy demand for solar applications.

Numerical study of turbulent nanofluid heat transfer in a tubular heat exchanger with twin twisted-tape inserts

2017 ◽  
Vol 132 (1) ◽  
pp. 741-759 ◽  
Author(s):  
Rahim Hosseinnezhad ◽  
Omid Ali Akbari ◽  
Hamid Hassanzadeh Afrouzi ◽  
Mohit Biglarian ◽  
Ali Koveiti ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Twisted Tape ◽  
Tubular Heat Exchanger

scholarly journals EXPERIMENTAL STUDY ON IN-POND HEAT EXCHANGER PROVIDED WITH TWISTED TAPES

2017 ◽  
Vol 10 (13) ◽  
pp. 467
Author(s):  
Karunamurthy K ◽  
Nayan Singh ◽  
Vivek Singh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Saline Water ◽  
Salinity Gradient ◽  
Swirl Flow ◽  
Laboratory Model ◽  
Solar Ponds ◽  
Twisted Tapes ◽  
Twist Ratio

In-pond heat exchangers (IHE) are used in salinity gradient solar ponds (SGSP), to transfer heat from hot saline water of the lower convective zone to the heat transfer medium. The performance of the SGSP depends on the performance of the IHE, which in turn depends on the method of heat transfer augmentation. A laboratory model IHE was fabricated to augment the heat transfer using helical twisted tapes (HTTs). The effects of varying twist ratio and double TTs on pressure drop and heat transfer were studied in this experimental work. Conventional HTTs of three twist ratios (Y=7, 9, 11), twin TTs of co-swirl flow (CoTT), and counter-swirl TTs (CTT) with Y=7 were provided in the flow path of the heat exchanger tube for analysis. From the results, it is observed that TTs with less twist ratio yielded higher rate of heat transfer by sacrificing the pressure drop. Compared to single TT, double TT provided better thermal performance. The pressure drop and rate of heat transfer for CTT are more compared to all other cases, including double TT with co-swirl flow.

scholarly journals Heat transfer enhancement in tubular heat exchanger with double V-ribbed twisted-tapes

2016 ◽  
Vol 7 ◽  
pp. 14-24 ◽  
Author(s):  
Sombat Tamna ◽  
Yingyong Kaewkohkiat ◽  
Sompol Skullong ◽  
Pongjet Promvonge
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Enhancement ◽  
Transfer Enhancement ◽  
Tubular Heat Exchanger ◽  
Twisted Tapes
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