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.

Thermal Behaviors in a Square Duct with U-Ribbed Tape Inserts

2014 ◽  
Vol 931-932 ◽  
pp. 1208-1212
Author(s):  
Chitakorn Khanoknaiyakarn ◽  
Sompol Skullong ◽  
Pongjet Promvonge ◽  
Nuthvipa Jayranaiwachira
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Performance Enhancement ◽  
Thermal Characteristics ◽  
Longitudinal Vortex ◽  
Experimental Result ◽  
Airflow Rate ◽  
Constant Heat ◽  
Square Duct ◽  
The One

This paper presents an experimental study on thermal characteristics in a constant heat-fluxed square-duct heat exchanger with U-ribbed tape inserts. The experiments are carried out by varying airflow rate for Reynolds number ranging from 4000 to 38,000. The insertion of the U-ribbed tape is performed with an axial rib-pitch set to four times duct-height (4H) at a single attack angle, α=45° and the ribbed tape is diagonally inserted in the square duct in order to generate longitudinal vortex flows. Effects of five blockage ratios (e/H=0.1, 0.15, 0.2, 0.25 and 0.3) on heat transfer and friction loss are experimentally investigated. The experimental result shows that the insertion of the U-ribbed tape at e/H=0.3 provides the highest heat transfer and friction factor values but the one at e/H=0.25 yields the highest thermal performance enhancement.

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.

Thermal-Hydraulic Performance and Optimization of Tube Ellipticity in a Plate Fin-and-Tube Heat Exchanger

2018 ◽  
Author(s):  
Zhuo Yang ◽  
Tariq Amin Khan ◽  
Wei Li ◽  
Hua Zhu ◽  
Zhijian Sun ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Friction Factor ◽  
Pareto Optimal ◽  
Maximum Heat ◽  
Tube Heat Exchanger ◽  
Maximum Heat Transfer ◽  
Colburn Factor

The flow field inside the heat exchangers is associated with maximum heat transfer and minimum pressure drop. Designing a compact heat exchanger and employing various techniques to enhance its overall performance has been widely investigated and still an active research field. However, few researches deal with thermal optimization. The application of elliptic tube is an effective alternative to circular tube which can reduce the pressure drop significantly. In this study, numerical simulation and optimization of variable tube ellipticity is studied at low Reynolds numbers. The three-dimensional numerical analysis and a multi-objective genetic algorithm (MOGA) with surrogate modelling is performed. Two row tubes in staggered arrangement in fin-and-tube heat exchanger is investigated for combination of various elliptic ratio (e = minor axis/major axis) and Reynolds number. Tube elliptic ratio ranges from 0.2 to 1 and Reynolds number ranges from 150 to 750. The tube perimeters are kept constant while changing the elliptic ratio. The numerical model is derived based on continuum flow approach and steady-state conservation equations of mass, momentum and energy. The flow is assumed as incompressible and laminar due to low inlet velocity. Results are presented in the form of Colburn factor, friction factor, temperature contours and streamline contours. Results show that increasing elliptic ratio increases the friction factor due increased flow blocking area, however, the effect on the Colburn factor is not significant. Moreover, tube with lower elliptic ratio followed by higher elliptic ratio tube has better thermal-hydraulic performance. To achieve maximum heat transfer enhancement and minimum pressure drop, the Pareto optimal strategy is adopted for which the CFD results, Artificial neural network (ANN) and MOGA are combined. The tubes elliptic ratio (0.2 ⩽ e ⩽ 1.0) and Reynolds number (150 ⩽ Re ⩽ 750) are the design variables. The objective functions include Colburn factor (j) and friction factor (f). The CFD results are input into ANN model. Once the ANN is computed and its accuracy is checked, it is then used to estimate the model responses as a function of inputs. The final trained ANN is then used to drive the MOGA to obtain the Pareto optimal solution. The optimal values of these parameters are finally presented.

scholarly journals Review on Heat Transfer Enhancement by Louvered Fin

2021 ◽  
Vol 6 (1) ◽  
pp. 60-80
Author(s):  
Samsul Islam ◽  
Md. Shariful Islam ◽  
Mohammad Zoynal Abedin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Heat Transfer Enhancement ◽  
Vortex Generator ◽  
Transfer Enhancement ◽  
Maximum Heat ◽  
Louvered Fin ◽  
Heat Transfer Improvement ◽  
Better Than

The heat transfer enhancement is recycled in many engineering uses such as heat exchangers, refrigeration and air conditioning structures, chemical apparatuses, and automobile radiators. Hence many enhancing extended fin patterns are developed and used. In multi louvered fin, in this segment for multi-row fin and tube heat exchanger, an increase in heat transfer enhancement is found 58% for ReH = 350. When the Reynolds number is 1075, the temperature gradient is more distinct for greater louver angle that is the higher heat transfer enhanced for large louver angle. For variable louver angle heat exchanger, the maximum heat transfer improvement achieved by 118% Reynolds number at 1075. In the vortex generator for the delta winglet vortex generator, the extreme enhancement of heat transfer increased to 16% compared to the baseline geometry (at ReDh = 600). For a compact louvered heat exchanger, the results showed that a regular arrangement of louvered fins gives a 9.3% heat transfer improvement. In multi-region louver fins and flat tubes heat exchanger, the louver fin with 4 regions and the louver fin with 6 regions are far better than the conventional fin in overall performance. At the same time, the louver fin with 6 regions is also better than the louver fin with 4-region. The available work is in experimental form as well as numerical form performed by computational fluid dynamics.

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.

scholarly journals Numerical Study on Flow and Heat Transfer Mechanisms in the Heat Exchanger Channel with V-Orifice at Various Blockage Ratios, Gap Spacing Ratios, and Flow Directions

2019 ◽  
Vol 2019 ◽  
pp. 1-21 ◽  
Author(s):  
Amnart Boonloi ◽  
Withada Jedsadaratanachai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Numerical Results ◽  
Blockage Ratio ◽  
Maximum Heat ◽  
Flow And Heat Transfer ◽  
Maximum Heat Transfer ◽  
Smooth Channel ◽  
Gap Spacing

Numerical assessments in the square channel heat exchanger installed with various parameters of V-orifices are presented. The V-orifice is installed in the heat exchanger channel with gap spacing between the upper-lower edges of the orifice and the channel wall. The purposes of the design are to reduce the pressure loss, increase the vortex strength, and increase the turbulent mixing of the flow. The influence of the blockage ratio and V-orifice arrangement is investigated. The blockage ratio, b/H, of the V-orifice is varied in the range 0.05–0.30. The V-tip of the V-orifice pointing downstream (V-downstream) is compared with the V-tip pointing upstream (V-upstream) by both flow and heat transfer. The numerical results are reported in terms of flow visualization and heat transfer pattern in the test section. The thermal performance assessments in terms of Nusselt number, friction factor, and thermal enhancement factor are also concluded. The numerical results reveal that the maximum heat transfer enhancement is found to be around 26.13 times higher than the smooth channel, while the optimum TEF is around 3.2. The suggested gap spacing for the present configuration of the V-orifice channel is around 5–10%.

Study of Flow and Convective Heat Transfer in a Simulated Scaled Up Low Emission Annular Combustor

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Sunil Patil ◽  
Teddy Sedalor ◽  
Danesh Tafti ◽  
Srinath Ekkad ◽  
Yong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat ◽  
Swirling Flow ◽  
Numerical Study ◽  
Swirl Number ◽  
Maximum Heat ◽  
Number Range ◽  
Maximum Heat Transfer ◽  
Annular Combustor

Modern dry low emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the gas side difficult to predict and estimate. A coupled experimental–numerical study of swirling flow inside a DLE annular combustor model is used to determine the distribution of heat transfer on the liner walls. Three different Reynolds numbers are investigated in the range of 210,000–840,000 with a characteristic swirl number of 0.98. The maximum heat transfer coefficient enhancement ratio decreased from 6 to 3.6 as the flow Reynolds number increased from 210,000 to 840,000. This is attributed to a reduction in the normalized turbulent kinetic energy in the impinging shear layer, which is strongly dependent on the swirl number that remains constant at 0.98 for the Reynolds number range investigated. The location of peak heat transfer did not change with the increase in Reynolds number since the flow structures in the combustors did not change with Reynolds number. Results also showed that the heat transfer distributions in the annulus have slightly different characteristics for the concave and convex walls. A modified swirl number accounting for the step expansion ratio is defined to facilitate comparison between the heat transfer characteristics in the annular combustor with previous work in a can combustor. A higher modified swirl number in the annular combustor resulted in higher heat transfer augmentation and a slower decay with Reynolds number.

An Experimental Investigation of Heat Transfer Enhancement by Pulsating Laminar Flow in a Triangular Grooved Channel

2012 ◽  
Vol 516-517 ◽  
pp. 249-252 ◽  
Author(s):  
Bing Chang Yang ◽  
Dong Xu Jin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Strouhal Number ◽  
Enhancement Factor ◽  
Pulsating Flow ◽  
Transfer Enhancement ◽  
Maximum Heat ◽  
Pulsation Amplitude ◽  
Maximum Heat Transfer

Heat transfer enhancement by pulsating flow in a triangular grooved channel has been experimentally investigated. Effects of Reynolds number Re, Strouhal number St, pulsation amplitude A on the heat transfer enhancement were studied. The experimental results show that, the pulsating flow can significantly enhance heat transfer compared to the steady flow case, for instance, an enhancement of 115% is achieved at Re=400, A=0.5 and St=0.3. There exists an optimal Strouhal number corresponding to the maximum heat transfer enhancement factor. The heat transfer enhancement factor increases with the increase of Reynolds number and pulsation amplitude.

Heat Transfer Study of Staggered Thin Rectangular Blocks in a Channel Flow

1991 ◽  
Vol 113 (3) ◽  
pp. 294-300 ◽  
Author(s):  
Ching Jen Chen ◽  
Ramiro H. Bravo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Channel Flow ◽  
Vector Fields ◽  
Block Size ◽  
Navier Stokes ◽  
Maximum Heat ◽  
Flow And Heat Transfer ◽  
Maximum Heat Transfer ◽  
Energy Equations

In this study, fluid flow and heat transfer in two-dimensional staggered thin rectangular blocks in a channel flow heat exchanger is analyzed by the Finite Analytic Numerical Method. The heat exchanger consists of four staggered thin rectangular blocks at temperature T1 placed inside a channel which is formed by two plates maintained at constant temperature T0. The fluid is considered to be incompressible and the flow laminar. Flow and heat transfer from the inlet of the heat exchanger to the outlet are simulated by solving Navier-Stokes and energy equations. Results were obtained for different block spacing and different size of the blocks. Computations were made for Reynolds numbers 100, 500, and 1,000, and Prandtl numbers 0.7 and 4.0. The results are presented in the form of velocity vector fields, isotherms, and local and global Nusselt numbers. The characteristics of the heat transfer and pressure drop in different block size and block separation are analyzed. The optimal length of separation between thin blocks and the optimal block length for maximum heat transfer are determined.

Numerical Study of Shellside Performance of Heat Transfer and Flow Resistance for Heat Exchanger with Trefoil-Hole Baffles

2012 ◽  
Vol 557-559 ◽  
pp. 2141-2146
Author(s):  
Yong Hua You ◽  
Ai Wu Fan ◽  
Chen Chen ◽  
Shun Li Fang ◽  
Shi Ping Jin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Numerical Study ◽  
Shell Side ◽  
Tube Heat Exchanger

Trefoil-hole baffles have good thermo-hydraulic performances as the support of heat pipes, however the published research paper is relatively limited. The present paper investigates the shellside thermo-hydraulic characteristics of shell-and-tube heat exchanger with trefoil-hole baffles (THB-STHX) under turbulent flow region, and the variations of shellside Nusselt number, pressure loss and overall thermo-hydraulic performance (PEC) with Reynolds number are obtained for baffles of varied pitch with the numerical method. CFD results demonstrate that the trefoil-hole baffle could enhance the heat transfer rate of shell side effectively, and the maximal average Nusselt number is augmented by ～2.3 times that of no baffle, while average pressure loss increases by ～9.6 times. The PEC value of shell side lies in the range of 16.3 and 73.8 kPa-1, and drops with the increment of Reynolds number and the decrement of baffle pitch, which indicates that the heat exchanger with trefoil-hole baffles of larger pitch could generate better overall performance at low Reynolds number. Moreover, the contours of velocity, turbulent intensity and temperature are presented for discussions. It is found that shellside high-speed jet, intensive recirculation flow and high turbulence level could enhance the heat transfer rate effectively. Besides good performance, THB-STHXs are easily manufactured, thus promise widely applied in various industries.

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