Heat Transfer of rGO/CO3O4 Hybrid Nanomaterial-Based Nanofluids and Twisted Tape Configurations in a Tube

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
L. Syam Sundar ◽  
E. Venkata Ramana ◽  
Zafar Said ◽  
António M.B. Pereira ◽  
Antonio C.M. Sousa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Graphene Oxide ◽  
Friction Factor ◽  
Thermal Performance ◽  
Twisted Tape ◽  
Particle Loading ◽  
Hybrid Nanomaterial ◽  
Reduced Graphene ◽  
Plain Tube

Abstract The friction factor, thermal performance, and heat transfer are experimentally analyzed for reduced-graphene oxide/cobalt oxide (rGO/CO3O4) hybrid nanomaterial-based nanofluid circulating in a plain tube with and without twisted tape inserts having different pitches. The reduced-graphene oxide/cobalt oxide (rGO/CO3O4) hybrid nanomaterial is prepared using in situ/chemical reduction technique and then characterized with transmission electron microscope, X-ray diffraction, and magnetometry. The experiments were conducted with different values of particle loading (0.05%, 0.1%, and 0.2%) and Reynolds number (2000–2,020,000). Three twisted tape inserts of helixes 285 mm, 190 mm, and 95 mm were used. The nanofluids was produced from the addition of the hybrid nanomaterial to water yield an increase, as compared to the basefluid (water), of the Nusselt number, which is further enhanced by increasing the nanoparticle loading. Therefore, when compared to water, the Nusselt number is enhanced by 25.65%, with no twisted tape and by 79.16% with twisted tape with helix of 95 mm for the nanofluid of 0.2% volume concentration. However, when compared to water, there is a slight friction factor penalty with the 0.2% particle loading of 1.11-times and 1.49-times for the plain tube and for the 95-mm twisted tape helix, respectively. The thermal performance factor gets enhanced by increasing the nanoparticles concentration of the hybrid nanofluids with or without twisted tape inserts, and it is always higher than one. Based on the experimental data, regression equations were developed for the Nusselt number and friction factor.

scholarly journals Internal Flow in an Enhanced Tube Having Square-cut Twisted Tape Insert

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 306 ◽  
Author(s):  
Agung Wijayanta ◽  
Pranowo ◽  
Mirmanto ◽  
Budi Kristiawan ◽  
Muhammad Aziz
Keyword(s):  
Nusselt Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Single Phase ◽  
Internal Flow ◽  
Working Fluid ◽  
Twisted Tape ◽  
Number Range ◽  
Enhanced Tube ◽  
Plain Tube

In this study, a numerical simulation has been conducted in order to evaluate the thermal hydraulic performance of a turbulent single-phase flow inside an enhanced tube equipped with a square-cut twisted tape (STT) insert. The classical twisted tape (CTT) insert was also investigated for comparison. The k-ε renormalized group turbulence model has been utilized as the turbulent model. Various twist ratios (y/W) of 2.7, 4.5, and 6.5 were investigated for the Reynolds number range of 8000–18,000, with water as the working fluid. The numerical results indicated that, in comparison with the plain tube (PT), the tube equipped with the STT with the twist ratios of 2.7, 4.5, and 6.5 led to an increase in the values of the Nusselt number and friction factor in the inner tube by 45.4–80.7% and 2.0–3.3 times, respectively; in addition, the highest thermal performance of 1.23 has been obtained. The results further indicated that the tube equipped with the CTT of the same twist ratios improved the Nusselt number and friction factor in the inner tube by 40.3–74.4% and 1.7–3.0 times, respectively, in comparison with the PT; further, the maximum thermal performance of 1.18 was achieved.

Influence of Corrugated Booster Reflectors in a Centrally Finned Twist Inserted Solar Thermal Collector on Heat Transfer and Thermal Performance Characteristics

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
M. Murugan ◽  
R. Vijayan ◽  
A. Saravanan ◽  
S. Jaisankar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Performance Characteristics ◽  
Solar Thermal ◽  
Experimental Result ◽  
Solar Thermal Collector ◽  
Plain Tube ◽  
Experimental Trials

In this present work, the influence of corrugated booster reflectors (CBR) in a centrally finned twist (CFT) inserted solar thermal collector (SC) on heat transfer and thermal performance characteristics has been approached experimentally. The experimental trials have been made with two different twist ratios (Y = 3 and 6) for typical twist (TT) and CFT under same working conditions. The results were compared with the plain tube SC with CBR plain and also with the plain tube SC with flat booster reflectors (FBR plain). The experimental result of the CBR plain has been verified with the standard equations and found the deviations within ±10.05% for Nusselt number and ±9.42% for friction factor. The CBR has 1.6% higher effective reflection area than the FBR. Hence, the CBR augmented the Nusselt number around 8.25% over the FBR. When compared to the CBR plain, the CFT of minimum twist ratio (Y = 3) offered 10.09% higher thermal efficiency. In addition, empirical correlations have been derived for predicting the Nusselt number and friction factor. The deviations of the predicted value from the experiment value fall within ±10.62% for Nusselt number and ±11.28% for friction factor.

scholarly journals Numerical Studies on Thermo-Hydraulic Characteristics of Turbulent Flow in a Tube with a Regularly Spaced Dimple on Twisted Tape

CFD letters ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 20-31
Author(s):  
Birlie Fekadu ◽  
Harish H.V ◽  
Manjunath. K
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Thermal Performance ◽  
Numerical Study ◽  
Constant Heat Flux ◽  
Twisted Tape ◽  
Performance Factor ◽  
Thermal Performance Factor

Heat transfer augmentation is an important concern due to the increase in heat management problems in thermal systems. There are many techniques for enhancement of heat transfer, by active and passive techniques. A commonly used passive technique to enhance heat transfer is by inserting twisted tapes in tubes. This work presents a numerical study on Nusselt number, friction factor, and thermal performance characteristics through a circular pipe built-in with/without dimples on twisted tape. The analysis results for a turbulent flow range of 4500≤Re≤20000 are obtained with a twist ratio of the strip is 3.0. The analysis is carried for full-length tape with constant heat flux. The governing equations are numerically solved by a finite volume method using the RNG κ–ε model. The simulation results of Nusselt number versus Reynolds number of the plain, plain twisted tape and dimple twisted tape tube with the experimental data give a variation of 4.15%, 3.89%, and 7.65%. The friction factor of the dimple twisted tape tube is 60 to 70% higher than that of the plain twisted tube at different Reynolds numbers. The thermal performance factor of the dimple twisted tape and plain twisted tape tube is 30 to 35% respectively higher than that of the plain tube. Due to thermal performance factor is above unity yields a promising heat transfer enhancement. By the present study, an optimum geometrical parameter can be selected for use in heat exchangers.

scholarly journals CFD Simulation of Heat Transfer and Friction Factor Augmentation in a Circular Tube Fitted with Elliptic-Cut Twisted Tape Inserts

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Sami D. Salman ◽  
Abdul Amir H. Kadhum ◽  
Mohd S. Takriff ◽  
Abu Bakar Mohamad
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Cfd Simulation ◽  
Swirling Flow ◽  
Fluid Flows ◽  
Twisted Tape ◽  
Plain Tube ◽  
Cut Depth

This paper presents the application of a mathematical model for simulation of the swirling flow in a tube induced by elliptic-cut and classical twist tape inserts. Effects of the twist ratio (y=2.93, 3.91, and 4.89) and cut depth (w=0.4, 0.8, and 1.4 cm) on heat transfer enhancement (Nu) and friction factor (f) in laminar flow are numerically investigated. The simulation is carried out using commercial CFD package (FLUENT-6.3.26) to grasp the physical behaviour of the thermal and fluid flows of a constant heat-fluxed tube fitted with elliptic-cut twist tape in the laminar flow regime for the Reynolds number ranging from 200 to 2100. The simulated results matched the literature correlations of plain tube for validation with 8% variation for Nusselt number and 10% for friction factor. The results show that the heat transfer rate and friction factor in the tube equipped with elliptic-cut twist tape (ECT) are significantly higher than those fitted with classical twist tape (CTT). Moreover the results also reveal that the Nusselt number and the friction factor in the tube with elliptic-cut twisted tape (ECT) increase with decreasing twist ratios (y) and cut depths (w).

Thermal Performance Assessment of Turbulent Flow Through Dimpled Tubes

2010 ◽  
Author(s):  
Pornchai Nivesrangsan ◽  
Somsak Pethkool ◽  
Kwanchai Nanan ◽  
Monsak Pimsarn ◽  
Smith Eiamsa-ard
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Staggered Arrangement ◽  
Plain Tube ◽  
Pitch Ratio ◽  
Surface Patterns

This paper presents the heat transfer augmentation and friction factor characteristics by means of dimpled tubes. The experiments were conducted using the dimpled tubes with two different dimpled-surface patterns including aligned arrangement (A-A) and staggered arrangement (S-A), each with two pitch ratios (PR = p/Di = 0.6 and 1.0), for Reynolds number ranging from 9800 to 67,000. The experimental results achieved from the dimpled tubes are compared with those obtained from the plain tube. Evidently, the dimpled tubes with both arrangements offer higher heat transfer rates compared to the plain tube and the dimpled tube with staggered arrangement shows an advantage on the basis of heat transfer enhancement over the dimpled tube with aligned arrangement. The increase in heat transfer rate with reducing pitch ratio is due to the higher turbulent intensity imparted to the flow between the dimple surfaces. The mean heat transfer rate offered by the dimpled tube with staggered arrangement (S-A) at the lowest pitch ratio (PR = 0.6), is higher than those provided by the plain tube and the dimpled tube with aligned arrangement (A-A) at the same PR by around 127% and 8%, respectively. The empirical correlations developed in terms of pitch ratio (PR), Prandtl number (Pr) and Reynolds number, are fitted the experimental data within ±8% and ±2% for Nusselt number (Nu) and friction factor (f), respectively. In addition, the thermal performance factors under an equal pumping power constraint of the dimple tubes for both dimpled-surface arrangements are also determined.

Effect of Groove Dimension on Thermal Performance of Turbulent Fluid Flow in Internally Grooved Tube

2016 ◽  
Author(s):  
Sogol Pirbastami ◽  
Samir Moujaes
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Kinetic Energy ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulent Kinetic Energy ◽  
Thermal Performance ◽  
Tube Length ◽  
Pitch Length

A Computational Fluid Dynamics (CFD) study of heat enhancement in helically grooved tubes was carried out by using a 3-dimensional simulation with the STARCCM+ simulation package software. The k-ε model selected for turbulent flow simulation and the governing equations were solved by using the finite volume method. Geometric models of the current study include 3 rectangular grooved tubes with different groove width (w) and depth (e) which varies from 0.2 mm to 0.6 mm for the same tube length of 2.0m and diameter of 7.1 mm. The simulations were performed in the Reynolds number (Re) range of 4000–10000 with a uniform wall heat flux of 3150 w/m2 applied as a boundary condition on the surface of each tube. The purpose of this research is to investigate the effect of different groove dimensions on the thermal performance and pressure drop of water inside the grooved tubes and clarify the structural nature of the flow in regards to flow swirl and turbulent kinetic energy distributions. It was found that the highest performance belongs to the groove with these dimensions (w = 0.2 mm and e = 0.2 mm) which was considered for further study. Then, for these same groove dimensions four pitch size to tube diameter (p/D) ratios ranging from 1 to 18 were simulated for the same 2.0 m length tube. The results for Nusselt number (Nu) and friction factor (f) showed that by increasing the (p/D) ratio both the Nu numbers and the friction factors (f) values decrease. With a smaller pitch length (p) the turbulence intensity generated by the internal groove was also found to increase. The physical behavior of the turbulent flow and heat transfer characteristics were observed by contour plots which showed an increasing swirl flow and turbulent kinetic energy as p/D decreases. With an increase of the Nu number for smaller p/D ratio, a penalty of a higher pressure drop was obtained. The results were validated with a previous experimental work and the average error between the experimental and CFD Nu numbers and f were 13% and 8% respectively. A higher level of turbulent kinetic energy is observed near the grooves, as compared to the smooth areas of the pipe surface away from the grooves, which are expected to lead to higher levels of heat transfer. The effect of pitch length (p) on the flow pattern were plotted by streamlines along the tubes, by decreasing the pitch size (p/D ratio) an increase in the swirl is noticed as evidenced by the plots of the path lines. Finally, empirical correlations for Nusselt number and friction factor were provided as a function of p/D and Re number. This study indicates that the incorporation of the internal groove, of particular dimensions, can lead to an improvement of performance in heat exchanger devices. A limited variation of the groove dimensions was conducted and it was found that the values of Nu and f do not improve with an increase of (w) nor with that of (e) from 0.2–0.6 mm.

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.

scholarly journals Numerical Investigation of the Effect of Inserted Twisted Tape inside Submerged Bundle Tubes on its Thermal Performance

2018 ◽  
Vol 24 (3) ◽  
pp. 42
Author(s):  
Kamal Mohammed Ali ◽  
Abdalrazzaq K. Abbas
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Reynolds Numbers ◽  
Twisted Tape ◽  
Ansys Fluent ◽  
Twist Ratio ◽  
Plain Tube ◽  
Exit Temperature ◽  
Inner Diameter ◽  
Film Heat Transfer

Twisted tape insertion in smooth plain tube is one of types of passive methods that is used to enhance heat transfer. Swirl fluid flow inside tube and related heat transfer characteristics are very complex. ANSYS FLUENT (V 16.1) and ASPEN industrial program are used in analyzing this technique for enhancement heat transfer. A circular plain tube has length L=8534mm and 17 mm inner diameter with twisted tape has twist ratio of y = (H/D) = (150/17) =8.8 along with a plain tube were considered for this study. Eight Reynolds numbers (Re) of 784, 1000, 2000, 3000, 4000, 5000, 6000 and 7000 are used to analyze the response of thermal performance. Crude oil API 28 exit temperature, film heat transfer coefficient, Nusselt number and overall enhancement ratio results are presented for both empty and inserted plain tube with comparison between the two cases. An increase of 0.76 to 2.36 overall enhancement is predicted with twist ratio 8.8 for Reynolds number 784 to 7000 respectively.  

Numerical and experimental thermal performance with entropy generation analysis on tube with helical screw tape inserts at number of strips in turbulent flow

2020 ◽  
pp. 095440622093773
Author(s):  
Shashank Ranjan Chaurasia ◽  
RM Sarviya
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Entropy Generation ◽  
Thermal Performance ◽  
Twisted Tape ◽  
Maximum Enhancement ◽  
Twist Ratio ◽  
Plain Tube ◽  
Volume Method ◽  
Single Strip

In the heat exchangers, twisted tape insert is a technique to enhance heat transfer. In this paper, the experimental and numerical investigations are arranged to analyze thermal performance with entropy generation analysis on single and double strip helical screw tape inserts. The finite volume method is used with shear stress transport K-ω model to analyze fluid flow in tube with inserts. The Nusselt number attained enhancement with double strip as compared to single strip helical screw inserts at decreased values of twist ratio and increased values of Reynolds number. However, the Nusselt number attained maximum enhancement of 112% with double strip helical screw insert than plain tube at 4000 of Reynolds number (Re). The common correlations for Nusselt number and friction factor are generated with respect to Reynolds number, number of the strips and twist ratio. Entropy generation analysis is also performed. The thermal performance factor attained its enhancement with double strip than single strip helical screw inserts at twist ratio of 2.5 and 3; whereas, double strip helical screw insert attained maximum value of 1.5 at twist ratio of 2.5 and Reynolds number of 16000. The double strip helical screw inserts are suitable for miniaturization of heat exchanger.

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.

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