scholarly journals Comparative Studies on Thermal Performance of Conic Cut Twist Tape Inserts with SiO2and TiO2Nanofluids

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Sami D. Salman ◽  
Abdul Amir H. Kadhum ◽  
Mohd S. Takriff ◽  
Abu Bakar Mohamad
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Thermal Performance ◽  
Volume Concentration ◽  
Twisted Tape ◽  
Maximum Heat ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Maximum Heat Transfer ◽  
Twist Ratio

This paper presents a comparison study on thermal performance conic cut twist tape inserts in laminar flow of nanofluids through a constant heat fluxed tube. Three tape configurations, namely, quadrant cut twisted tape (QCT), parabolic half cut twisted tape (PCT), and triangular cut twisted (VCT) of twist ratioy= 2.93 and cut depthde= 0.5 cm were used with 1% and 2% volume concentration of SiO2/water and TiO2/water nanofluids. Typical twist tape with twist ratio ofy= 2.93 was used for comparison. The results show that the heat transfer was enhanced by increasing of Reynolds number and nanoparticles concentration of nanofluid. The results have also revealed that the use of twist tape enhanced the heat transfer coefficient significantly and maximum heat transfer enhancement was achieved by the presence of triangular cut twist tape insert with 2% volume concentration of SiO2nanofluid. Over the range investigated, the maximum thermal performance factor of 5.13 is found with the simultaneous use of the SiO2nanofluid at 2% volume concentration VCT at Reynolds number of 220. Furthermore, new empirical correlations for Nusselt number, friction factor, and thermal performance factor are developed and reported.

scholarly journals Simulation approach on turbulent thermal performance factor of Al2O3-Cu/water hybrid nanofluid in circular and non-circular ducts

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Ing Jiat Kendrick Wong ◽  
Ngieng Tze Angnes Tiong
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Hybrid Nanofluid ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
The Heat Transfer Coefficient

AbstractThis paper presents the numerical study of thermal performance factor of Al2O3-Cu/water hybrid nanofluid in circular and non-circular ducts (square and rectangular). Turbulent regime is studied with the Reynolds number ranges from 10000 to 100000. The heat transfer performance and flow behaviour of hybrid nanofluid are investigated, considering the nanofluid volume concentration between 0.1 and 2%. The thermal performance factor of hybrid nanofluid is evaluated in terms of performance evaluation criteria (PEC). This present numerical results are successfully validated with the data from the literature. The results indicate that the heat transfer coefficient and Nusselt number of Al2O3-Cu/water hybrid nanofluid are higher than those of Al2O3/water nanofluid and pure water. However, this heat transfer enhancement is achieved at the expense of an increased pressure drop. The heat transfer coefficient of 2% hybrid nanofluid is approximately 58.6% larger than the value of pure water at the Reynolds number of 10000. For the same concentration and Reynolds number, the pressure drop of hybrid nanofluid is 4.79 times higher than the pressure drop of water. The heat transfer performance is the best in the circular pipe compared to the non-circular ducts, but its pressure drop increment is also the largest. The hybrid nanofluid helps to improve the problem of low heat transfer characteristic in the non-circular ducts. In overall, the hybrid nanofluid flow in circular and non-circular ducts are reported to possess better thermal performance factor than that of water. The maximum attainable PEC is obtained by 2% hybrid nanofluid in the square duct at the Reynolds Number of 60000. This study can help to determine which geometry is efficient for the heat transfer application of hybrid nanofluid.

scholarly journals Numerical Investigation of Heat Transfer and Friction Factor Characteristics in a Circular Tube Fitted with V-Cut Twisted Tape Inserts

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Sami D. Salman ◽  
Abdul Amir H. Kadhum ◽  
Mohd S. Takriff ◽  
Abu Bakar Mohamad
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Investigation ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Twisted Tape ◽  
Maximum Heat ◽  
High Heat Transfer ◽  
Maximum Heat Transfer ◽  
Twist Ratio

Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y=2.93) and different cut depths (w=0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y=2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratioy=2.93and cut depthw=0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration.

scholarly journals Investigation of Heat Transfer and Pressure Drop in Microchannel Heat Sink Using Al2O3 and ZrO2 Nanofluids

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1796
Author(s):  
Muhammad Zia Ullah Khan ◽  
Emad Uddin ◽  
Bilal Akbar ◽  
Naveed Akram ◽  
Ali Ammar Naqvi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Factor Analysis ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Particle Concentration ◽  
Dean Vortices ◽  
Performance Factor ◽  
Thermal Performance Factor

A new micro heat exchanger was analyzed using numerical formulation of conjugate heat transfer for single-phase fluid flow across copper microchannels. The flow across bent channels harnesses asymmetric laminar flow and dean vortices phenomena for heat transfer enhancement. The single-channel analysis was performed to select the bent channel aspect ratio by varying width and height between 35–300 μm for Reynolds number and base temperature magnitude range of 100–1000 and 320–370 K, respectively. The bent channel results demonstrate dean vortices phenomenon at the bend for Reynolds number of 500 and above. Thermal performance factor analysis shows an increase of 18% in comparison to straight channels of 200 μm width and height. Alumina nanoparticles at 1% and 3% concentration enhance the Nusselt number by an average of 10.4% and 23.7%, respectively, whereas zirconia enhances Nusselt number by 16% and 33.9% for same concentrations. On the other hand, thermal performance factor analysis shows a significant increase in pressure drop at high Reynolds number with 3% particle concentration. Using zirconia for nanofluid, Nusselt number of the bent multi-channel model is improved by an average of 18% for a 3% particle concentration as compared to bent channel with deionized water.

scholarly journals Turbulent heat transfer enhancement in tubular heat exchangers with different twisted tape inserts

2021 ◽  
Vol 15 (3) ◽  
pp. 8364-8378
Author(s):  
SADMAN HASSAN LABIB ◽  
M. R. A. Himel ◽  
J.I. Ali ◽  
A.R. Mim ◽  
M.J. Hossain ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Twisted Tape ◽  
Performance Factors ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Heat Transfer Behavior ◽  
Transfer Behavior

Experimental and numerical analyses are carried out to investigate the influence of twisted tape inserts on the heat transfer and the flow behavior in double tube heat exchangers. First, all the performance factors, namely the Nusselt number, friction factor, and thermal performance factor, were studied for a basic heat exchanger (BHE). Afterwards, twisted tapes with three different twist ratios (7.5, 6, and 4.5) were inserted inside the inner tube of the BHE, which resulted in three different modified heat exchangers (MHEs). For the numerical study, a 3D numerical model is developed with the k-ε RNG turbulent model to visualize the flow and the heat transfer behavior inside the heat exchangers. In both studies, turbulent flow field is maintained, ranging Reynolds number from 15000 to 50000.  From the experimental result, an enhanced heat transfer, characterized by the performance factors, is found for all the MHEs compared to the BHE. The most enhanced thermal performance factor is achieved for the MHE with the lowest twist ratio. Finally, a good agreement between obtained numerical and experimental results reveals that the present numerical model can reliably predict the flow and heat transfer behavior in double tube heat exchangers.

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 Numerical Analysis of Flow and Heat Transfer Enhancement in A Horizontal Pipe with Plain and Dimple Twisted Tape

2021 ◽  
Vol 82 (2) ◽  
pp. 106-119
Author(s):  
Harish H. V. ◽  
Manjunath K. ◽  
Rangaswamy T.
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Constant Heat Flux ◽  
Hydraulic Performance ◽  
Twisted Tape ◽  
Horizontal Pipe ◽  
Circular Duct ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Plain Tube

In order to improve thermo-hydraulic performance of laminar flow various techniques has been used among which a plain tube with twisted tape insert is widely used. The main objective is to numerically study flow field in order to enhance heat transfer, through a circular pipe built in with/without Dimples on twisted strip. Effect of plain and dimple strip on thermo hydraulic performance discussed. The analysis results for laminar range of 800<Re<2000 is obtained with twist ratio of the strip is 3.0. Analysis is carried for full length tape with constant heat flux. The simulation results of Nusselt number versus Reynolds number of the plain, plain twisted tape and Dimple twisted tape with the experimental data give variation of 2.5, 5.75 and 9.5%. The friction factor of Dimple twisted tape tube is 6 to 13 times that of the plain tube. The thermal performance factor of the Dimple twisted tape and plain twisted tape tube is 4 to 15% and 3 to 12 % respectively higher than that of plain tube. Due to increase in thermal performance factor of induced strip with dimples there is an intensification of heat transfer obtained through circular duct with dimple twisted tape insert than that of plain twisted tape and plain pipe. The use of a twisted tube compounded with dimples is feasible in terms of energy saving at lower Reynolds numbers. Present study is applicable for design of compact heat exchanger in order to optimize energy consumption.

Heat Transfer and Pressure Measurements in a Lattice-Cooled Trailing Edge of a Turbine Airfoil

2008 ◽  
Author(s):  
Krishnendu Saha ◽  
Shengmin Guo ◽  
Sumanta Acharya ◽  
Chiyuki Nakamata
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Reynolds Numbers ◽  
Matrix Structure ◽  
Trailing Edge ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Cooling Passage

An experimental study of the heat transfer distribution and pressure drop through a converging lattice-matrix structure has been performed. This structure represents a gas turbine blade trailing-edge cooling passage. Stationary tests were performed on a scaled up model under three Reynolds numbers (24000&lt;Re&lt;60000). To obtain the wall temperature, the narrow band liquid crystal technique was used, and the heat transfer coefficient value was obtained using the transient method. It’s found that the Nusselt number ratio (Nu/Nu0) is around 4–5, comparing to the channel flow of similar hydraulic diameter and Re, for the whole lattice-matrix structure. Under the impingement and turning areas, the ratio can be as high as 7–8. Pressure data are taken throughout the lattice structure following the flow direction. The pressure drop increases with Reynolds number and as a result there is a decrease in the thermal performance factor at higher Reynolds number. In the present study thermal performance factor is found to be around 1–1.2. For comparison, pin fin based trailing edge configuration has a typical thermal performance factor of 0.7 to 0.85 under the same Reynolds numbers.

scholarly journals Augmentation of Heat Transfer in a Circular Channel with Inline and Staggered Baffles

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8593
Author(s):  
Muneerah Al Nuwairan ◽  
Basma Souayeh
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Working Fluid ◽  
Solar Air Heater ◽  
Circular Channel ◽  
Maximum Enhancement ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Sst Model ◽  
Inlet Length

This numerical investigation presents the effects of the position of baffles in the shape of a circle’s segment placed inside a circular channel to improve the thermal and flow performance of a solar air heater. Three different baffles’ positions with Reynolds number varying between 10,000 to 50,000 were investigated computationally. The k-omega SST model was used for solving the governing equations. Air was taken as the working fluid. Three pitch ratios (Y = 3, 4, and 5) were considered, while the height of the baffles remained fixed. The result showed an enhancement in Nusselt number, friction factor, j-factor, and thermal performance factor. Staggered exit-length baffles showed maximum enhancement in heat transfer and pressure drop, while inline inlet-length baffles showed the least enhancement. For a pitch ratio of Y = 3.0, the enhancement in all parameters was the highest, while for Y = 5.0, the enhancement in all parameters was the least. The highest thermal performance factor of 1.6 was found for SEL at Y = 3.0.

scholarly journals Numerical study of gas dynamics and heat transfer in matrix channels at various rib angles

2021 ◽  
Vol 2057 (1) ◽  
pp. 012026
Author(s):  
A V Barsukov ◽  
V V Terekhov ◽  
V I Terekhov
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Gas Dynamics ◽  
Average Velocity ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Separation Flow ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract The results of numerical simulation of the separation flow in matrix channels by the RANS method are presented. The simulation is performed at the Reynolds number Re = 12600, determined by the mass-average velocity and the height of the channel. The distribution of the local Nusselt number is obtained for various Reynolds numbers in the range of 5÷15⋅103 and several rib angles. It is shown that the temperature distribution on the surface is highly nonuniform; in particular, the maximum heat transfer value is observed near the upper edge facets, in the vicinity of which the greatest velocity gradient is observed.

Sign in / Sign up

Export Citation Format

Share Document