scholarly journals Experimental study of developing turbulent flow and heat transfer in ribbed convergent/divergent rectangular ducts

2015 ◽  
Vol 19 (6) ◽  
pp. 2219-2231 ◽  
Author(s):  
Sivakumar Karthikeyan ◽  
Natarajan Elumalai ◽  
Kulasekharan Narasingamurthi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Square Duct ◽  
Convergent Channel ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Mean Diameter

The article represents an experimental investigation of friction and heat transfer characteristics of divergent / convergent rectangular ducts with an inclination angle of 1? in the y-axis. Measurements were taken for a convergent / divergent rectangular duct of aspect ratio AR at inlet1.25 and outlet in convergent channel 1.35; but in case of divergent duct it can be reversed. The four uniform rib heights, e = 3, 6, 9 and 12 mm the ratio between rib height to hydraulic mean diameter (e/Dm) are 34.8, 69.7, 104.6 and 138.7 a constant rib pitch distance, P = 60 mm has been used. The flow rate in terms of average Reynolds number based on the hydraulic mean diameter (Dm) is 86 mm of the channel was in a range of 20,000 to 50,000. The two ceramic heating strip of 10 mm thickness is used as a heating element have attached on top and bottom surfaces for the test sections. The heat transfer performance of the divergent / convergent ducts for 3, 6, 9 and 12 mm ribs was conducted under identical mass flow rate based on the Reynolds number. In our experiments has totally 8 different ducts were used. In addition, the acceleration / deceleration caused by the cross section area, the divergent duct generally shows enhanced heat transfer behavior for four different rib sizes, while the convergent duct has an appreciable reduction in heat transfer performance. From result point view divergent duct with 3 mm height ribbed square duct gets maximum heat transfer coefficient with minimum friction loss over the other convergent / divergent ducts.

scholarly journals Optimization of heat transfer and pressure drop of the channel flow with baffle

2021 ◽  
Vol 40 (1) ◽  
pp. 286-299
Author(s):  
Behzad Ghobadi ◽  
Farshad Kowsary ◽  
Farzad Veysi
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract In this article, the numerical analysis has been carried out to optimize heat transfer and pressure drop in the horizontal channel in the presence of a rectangular baffle and constant temperature in two-dimension. For this aim, the governing differential equation has been solved by computational fluid dynamics software. The Reynolds numbers are in the range of 2,000 < Re < 10,000 and the working fluid is water. While the periodic boundary condition has been applied at the inlet, outlet, and the channel wall, axisymmetric boundary condition has been used for channel axis. For modeling and optimizing the turbulence, k–ω SST model and genetic algorithm have been applied, respectively. The results illustrate that adding a rectangular baffle to the channel enhances heat transfer and pressure drop. Hence, the heat transfer performance factor along with maximum heat transfer and minimum pressure drop has been investigated and the effective geometrical parameters have been introduced. As can be seen, there is an inverse relationship between baffle step and both heat transfer and pressure drop so that for p/d equal to 0.5, 1, and 1.25, the percentage of increase in Nusselt number is 141, 124, and 120% comparing to a simple channel and the increase in friction factor is 5.5, 5, and 4.25 times, respectively. The results of modeling confirm the increase in heat transfer performance and friction factor in the baffle with more height. For instance, when the Reynolds number and height are 5,000 and 3 mm, the Nusselt number and friction factor have been increased by 35% and 2.5 times, respectively. However, for baffle with 4 mm height, the increase in the Nusselt number and friction factor is 68% and 5.57 times, respectively. It is also demonstrated that by increasing Reynolds number, the maximum heat transfer performance has been decreased which is proportional to the increase in p/d and h/d. Moreover, the maximum heat transfer performance in 2,000 Reynolds number is 1.5 proportional to p/d of 0.61 and h/d of 0.36, while for 10,000 Reynolds number, its value is 1.19 in high p/d of 0.93 and h/d of 0.15. The approaches of the present study can be used for optimizing heat transfer performance where geometrical dimensions are not accessible or the rectangular baffle has been applied for heat transfer enhancement.

Investigations on the Influence of Flow Migration on Flow and Heat Transfer in Oblique Fin Microchannel Array

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Nasi Mou ◽  
Yong Jiun Lee ◽  
Poh Seng Lee ◽  
Pawan K. Singh ◽  
Saif A. Khan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Secondary Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Profile Analysis ◽  
Flow Distribution ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Microchannel Array

In order to scrutinize the coolant mass distribution and its effect to the heat transfer in oblique fin microchannel array, extensive numerical studies are performed on planar oblique fin configuration. Full-domain simulations using common-flow down (CFD) approach are employed to provide better insights into the flow distribution, flow stability, and heat transfer performance at a global level. The flow field and temperature profile analysis shows that nonuniform coolant distribution and coolant migration occur in the oblique fin microchannel, and the heat transfer performance for both edges of the heat sink is affected due to changing secondary flow rate. However, the flow migration does not affect the local coolant velocity and temperature profiles significantly in the middle region (0.2 < Z′ < 0.8). Meanwhile, it is also found that Reynolds number affects the coolant migration, the stability of the fluid flow, and heat transfer performance significantly. Higher Reynolds number increases the percentage of secondary flow rate and, hence, enhances the heat transfer for fin surfaces in secondary channels.

scholarly journals Effects of Coil Pitch Spacing on Heat Transfer Performance of Nanofluid Turbulent Flow through Helical Microtube Heat Exchanger

2019 ◽  
Vol 7 (4.14) ◽  
pp. 356
Author(s):  
A. H. Rasheed ◽  
H. Alias ◽  
S. D. Salman
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Transfer Performance ◽  
Ansys Fluent ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Momentum And Heat Transfer

This article provides Numerical simulation on forced convective heat transfer performance of Nanofluid flowing through copper helical microtube of inner diameter of 1.5 mm with different pitch using ANSYS-FLUENT 18.0. The simulation was performed for water, CuO/water, Al2O3/water Nanofluid with 1-2% volume concentration and different pitch of microtube (10, 14 and 18 mm) for turbulent flow regime of Reynolds number varied 5000 to 20000 and governing equations of mass, momentum and heat transfer were solved simultaneously, using the k-e two equations turbulence model. Based on the obtained results, regardless of the concentrations used, the nanofluids exhibited a higher transfer rate than water. This is mainly attributed to the nanoparticles that are in the used nanofluids. The friction factor and the heat transfer rate were enhanced considerably due to the shape and size of the tube, which in this case is a helical microtube. Moreover, the maximum heat transfer performance has been conducted by Al2O3/water Nanofluid with 2% volume concentration and microtube pitch of 18 mm.    

Influence of Different Rib Height on Heat Transfer Augmentation in Rectangular Convergent / Divergent Channels With Continuous Ribs on Bottom Surface

2013 ◽  
Author(s):  
K. Sivakumar ◽  
E. Natarajan ◽  
N. Kulasekharan
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Rectangular Channel ◽  
Bottom Surface ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Smooth Channel ◽  
Mean Diameter

The work reported in this paper is a systematic experimental study of friction and heat transfer characteristics of divergent /convergent rectangular ducts with an inclination angle of 1° in the y-direction. Measurements were taken for a convergent / divergent rectangular channel of aspect ratio, AR = 1.25 to 1.35 with three uniform rib heights, e = 3, 6 and 9 mm the ratio between rib height (e) to hydraulic mean diameter (Dm) are 0.0348, 0.0697 and 0.1046, a constant rib pitch distance, P = 60 mm. The flow rate in terms of average Reynolds numbers based on the hydraulic mean diameter (Dm) of the channel was in a range of 20000 to 50,000 is 0.085 m. A ceramic strip of 10 mm thickness is used as a heating coil has been attached on top and bottom surfaces for the test sections. The heat transfer characteristics degraded with increase in the rib height in 90° attached ribs over smooth channel. The heat transfer performance of the divergent/convergent ducts for 3, 6 and 9 mm ribs was conducted under identical mass flow rate based on the Reynolds number. In convergent duct having three test sections each having three different size ribs 3, 6, and 9mm. Similarly, divergent section is also three different rib heights duct. So, in our experiments has totally 6 different ducts were used. In addition, the acceleration / deceleration caused by the cross section area, the divergent duct generally shows enhanced heat transfer behavior for three different rib sizes, while the convergent duct has an appreciable reduction in heat transfer performance.

Numerical Study and Optimization of Corrugation Height and Angle of Attack of Vortex Generator in the Wavy Fin-and-Tube Heat Exchanger

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Wei Li ◽  
Tariq Amin Khan ◽  
Weiyu Tang ◽  
W. J. Minkowycz
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Transfer Performance ◽  
Maximum Heat ◽  
Tube Heat Exchanger ◽  
Multi Objective ◽  
Maximum Heat Transfer

Wavy fins have been considered as an alternative of the straight fins in compact heat exchangers (CHEs) for better heat transfer performance, which can be augmented by considering vortex generators (VGs). This work is related to numerical investigation and optimization of corrugation height of fin and angle of attack of delta winglet type VGs in a wavy fin-and-tube heat exchanger. For this purpose, three-dimensional (3D) Reynolds-averaged Navier-Stokes analysis and a multi-objective genetic algorithm (MOGA) with surrogate modeling are performed. Numerical simulation is carried out to study the effect of delta winglets with varying the corrugation height of wavy fin in three rows of tubes with staggered tube arrangements. The corrugation height (H) and angle of attack (α) vary from 0.3 mm to 1.8 mm and 15 deg to 75 deg, respectively. Results are illustrated by investigating the flow structures and temperature contours. Results show that increasing the corrugation height of wavy fin and angle of attack of delta winglets enhances the heat transfer performance of heat exchanger while friction factor is also increased. Employing delta winglets has augmented the thermal performance for all corrugation heights and superior effect is observed at a higher corrugation. To achieve a maximum heat transfer enhancement and a minimum pressure drop, the optimal values of these parameters (H and α) are calculated using the Pareto optimal strategy. For this purpose, computational fluid dynamics (CFD) data, a surrogate model (neural network), and a multi-objective GA are combined. Results show that optimal orientation of delta winglets with respect to corrugation height can improve both the thermal and hydraulic performance of the heat exchanger.

Performance Analysis of a Solar Collector Using Nanofluids

2013 ◽  
Vol 832 ◽  
pp. 107-112 ◽  
Author(s):  
Mohammad Abdul Alim ◽  
Rahman Saidur ◽  
Mohammad Alam Khairul ◽  
Nasrudin A. Rahim ◽  
Zainul Abdin
Keyword(s):  
Heat Transfer ◽  
Solar Collector ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Solar Collectors ◽  
Thermal Systems ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Energy And Exergy ◽  
Qualitative Performance

The Efficiency of Energy and Exergy is Generally Used as the Mostimportant Parameter in Order to Introduce and Compare the Thermal Systems Offlat Plate Solar Collectors. the First Law of Thermodynamics is Not Solelycapable of Demonstrating Quantitative and Qualitative Performance of Suchsystems, so the Second Law is Required to Illustrate the Performances. in Thispaper, an Analysis was Done for Heat Transfer Performance and Exergy Efficiencyof Flat Plate Solar Collectors Using Four Types of Nanofluids, e.g. Zno/water,CeO2/water, Nio and Coo/water. these Nanofluids were Used Withdifferent Nanoparticle Volume Fractions in the Range of 1% to 4%. Besides this,the Present Work also Focuses on the Performance of Solar Collector Withdifferent Volume Flow Rates. Investigation Consequences are also Compared Withthe Presently Available Literature for Conventional Solar Collectors. Thehighest Heat Transfer Performance and Exergy Efficiency were Obtained for CeO2/waternanofluid among all Nanofluids. Nio/water and Coo/water Nanofluids Representalmost same Performance but Higher than Water. the Results Reveal that, CeO2/waternanofluid Indicates Maximum Heat Transfer with Maximum Exergy.

Experimental Study on Flow Friction and Heat Transfer in a Square-Duct Heat Exchanger with Winglet Turbulators

2014 ◽  
Vol 931-932 ◽  
pp. 1183-1187
Author(s):  
Supattarachai Suwannapan ◽  
Panuwat Hoonpong ◽  
Pongjet Promvonge ◽  
Sirisawat Juengjaroennirachon ◽  
Monsak Pimsarn
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Pressure Loss ◽  
Experimental Result ◽  
Airflow Rate ◽  
Square Duct ◽  
Maximum Heat ◽  
Maximum Heat Transfer

The paper presents an experimental study on airflow friction and heat transfer behaviors in a heat exchanger square-duct fitted with winglet turbulators. The experiments are carried out by varying the airflow rate in terms of Reynolds number from 4000 to 25,000. The winglets were mounted in tandem with three attack angles (α=30o, 45o and 60o), two winglet-pitch to duct-height ratios, (called pitch ratio, PR=P/H=1.0 and 1.5) and a single winglet-to duct-height ratio, (called blockage ratio, BR=e/H=0.2). Effects of the winglet parameters on heat transfer and pressure loss in terms of Nusselt number and friction factor are investigated. The experimental result reveals that the application of the winglets provides considerably higher heat transfer and pressure loss values than the smooth duct alone. The winglet at α=60o and PR=1 gives the maximum heat transfer and pressure loss but the one at α = 30o and PR=1.5 yields the highest thermal enhancement factor of about 1.49 at the lowest Reynolds number.

scholarly journals Heat transfer performance of multiple holes impingement cooling technique

2018 ◽  
Vol 7 (4.13) ◽  
pp. 43
Author(s):  
M F Mohd Zulkeple ◽  
A R Abu Talib ◽  
E Gires ◽  
M T Hameed Sultan ◽  
M S Ramli
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Jet Impingement ◽  
Design Parameters ◽  
Transfer Performance ◽  
Transfer Condition ◽  
Maximum Heat ◽  
Impingement Cooling ◽  
Maximum Heat Transfer ◽  
Cooling Technique

This research presents the possibility of the jet impingement cooling technique configuration for stator of turbine blade under the transient heat transfer condition. The main goal of this study is to investigate the impingement cooling plate holes configuration and Reynolds number (Re) effect on the heat transfer which can be observed from the color play of the thermochromic liquid crystal (TLC). The findings proved that with the present of the small holes in between the main larger holes capable to enhance the heat transfer across the target surface. However, some criteria of the design need to be taken into count as it may produce different heat transfer performance of the impingement cooling technique. Therefore, in the range of predetermined design parameters, only several combinations that prevailed to achieve maximum heat transfer across the target plate. 

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