FORCED CONVECTION BASED HEAT TRANSFER ANALYSIS OF SPHERICAL DIMPLE AND PROTRUSION SURFACE IN TURBULENT FLOW

2017 ◽  
Vol 41 (5) ◽  
pp. 771-786 ◽  
Author(s):  
Ashif Perwez ◽  
Shreyak Shende ◽  
Rakesh Kumar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Vortex Flow ◽  
Rectangular Channel ◽  
Heat Transfer Analysis ◽  
Flow Structures ◽  
Transfer Enhancement ◽  
Heat Transfer Augmentation ◽  
Thermal Boundary Conditions

An experimental and numerical investigation is performed to study the effect of dimple and protrusion geometry on the heat transfer enhancement and the friction factor of surfaces with dimples and protrusions subjected to turbulent flow. The parameters used to compare the spherical dimples and protrusions are Nusselt Number, friction factor, and flow pattern. These parameters are obtained for a Reynolds number of 10500-60900. The spherical dimple results showed the greater heat transfer, which is about 6.97% higher and pressure loss which is 5.07% lower than the spherical protrusion. The realistic heat transfer augmentation capabilities of channels with dimples and protrusions can be studied from the experimental results. The comparison is made with respect to the smooth rectangular channel under the same flow and thermal boundary conditions. The numerical analysis is performed which shows the different vortex flow structures of the spherical dimples and protrusions channel.

scholarly journals Influence of Narrow Rectangular Channel ( AR = 1 : 4 ) on Heat Transfer and Friction for V- and W-Shaped Ribs in Turbine Blade Applications

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Karthik Krishnaswamy ◽  
Suresh Sivan ◽  
Hafiz Muhammad Ali
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Rectangular Channel ◽  
Hydraulic Diameter ◽  
Transfer Enhancement ◽  
Maximum Enhancement ◽  
Heat Transfer Augmentation ◽  
Nominal Pressure

Effective cooling of blades with a nominal pressure drop is essential for performance augmentation and thermal management of gas turbines. Hence, present work is aimed at determining the heat transfer enhancement and friction for W- and V-shaped ribs inside a rectangular cooling channel having hydraulic diameter ( D h ) of 0.048 m and aspect ratio ( AR ) 1 : 4. Ribs are fixed facing downstream with angle of attack ( α ) 45° on opposite walls. Pitch ( P ) between two successive ribs is 25 mm for both cases. Continuous V- and W-shaped ribs with height to channel hydraulic diameter ratio ( e / D h ) 0.052 and 0.0416 and pitch to height ratio ( P / e ) 10 and 12.5, respectively, have been examined for Reynolds number ( Re ) range 20000-80000. Heat transfer augmentation achieved at Re 80000 is 1.94 and 1.8 times higher than Re 20000 for V- and W-shaped ribs, respectively. Streamwise and spanwise variations in local Nusselt number ratio are highest for V-shaped ribs, which are estimated to be 31% and 12%. For W-shaped ribs, variations are 17.5% and 3.5%. Nusselt number ( Nu ) is highest along span length 0.5 w for V-shaped ribs due to dominance of apex induced secondary flow. For W-shaped ribs, Nusselt number along the span lengths is found to be nearly same view uniformity in secondary flow. Maximum enhancement ( Nu / N u o ) estimated for both the rib shapes is 3.9 at Re 20000. Due to increased rib height, friction losses for V-shaped ribs are higher than W-shaped ribs. Maximum friction loss increment is estimated to be 85% for V-shaped ribs and 42% for W-shaped ribs between Re 20000 and 40000. For both rib shapes, impact of ribs is found to be greatest at Re 40000. Thermohydraulic performance ( THP ) for W-shaped ribs is superior to V-shaped ribs. Best THP achieved for W- and V-shaped ribs are 3.7 and 3.4 at Re 20000.

scholarly journals 2D Numerical Study of Heat Transfer Enhancement Using Fish-Tail Locomotion Vortex Generators

2021 ◽  
Vol 8 (3) ◽  
pp. 386-392
Author(s):  
Ahmed Hashim Yousif ◽  
Hakim T. Kadhim ◽  
Kadhim K. Idan Al-Chlaihawi
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Number Range ◽  
Maximum Value ◽  
Fluid Flow Characteristics

In this paper, a numerical simulation is performed to study the effect of two types of concave vortex generators (VGs), arranged as fish-tail locomotion in a rectangular channel. The heat transfer and fluid flow characteristics with and without VGs are examined over the Reynolds number range 200≤Re≤2200.The two proposed types of the VGs are selected based on the speed of the fish movement which is arranged in different distances between them (d/H=0.6, 1, 1.3). The results show that the use of VGs can significantly enhance the heat transfer rate, but also increases the friction factor. The heat transfer performance is enhanced by (4-21.1%) reaching the maximum value by using the first type of the VGs at (d/H=1.3) due to better mixing of secondary flow and the new arrangement of the VGs which lead to decreasing the friction factor with an easy flow of fluid.

Experimental Investigations on Heat Transfer Enhancement in a Horizontal Tube Using Converging and Diverging Conical Strip Inserts

2014 ◽  
Vol 592-594 ◽  
pp. 1590-1595 ◽  
Author(s):  
Naga Sarada Somanchi ◽  
Sri Rama R. Devi ◽  
Ravi Gugulothu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Heat Transfer Enhancement ◽  
Friction Factor ◽  
Working Fluid ◽  
Experimental Investigations ◽  
Transfer Enhancement ◽  
Enhancement Of Heat Transfer

The present work deals with the results of the experimental investigations carried out on augmentation of turbulent flow heat transfer in a horizontal circular tube by means of tube inserts, with air as working fluid. Experiments were carried out initially for the plain tube (without tube inserts). The Nusselt number and friction factor obtained experimentally were validated against those obtained from theoretical correlations. Secondly experimental investigations using three kinds of tube inserts namely Rectangular bar with diverging conical strips, Rectangular bar with converging conical strips, Rectangular bar with alternate converging diverging conical strips were carried out to estimate the enhancement of heat transfer rate for air in the presence of inserts. The Reynolds number ranged from 8000 to 19000. In the presence of inserts, Nusselt number and pressure drop increased, overall enhancement ratio is calculated to determine the optimum geometry of the tube insert. Based on experimental investigations, it is observed that, the enhancement of heat transfer using Rectangular bar with converging and diverging conical strips is more effective compared to other inserts. Key words: Heat transfer, enhancement, turbulent flow, conical strip inserts, friction factor, pressure drop.

A New Estimation Method of Turbulent Flow Structures Effective for Impingement Heat Transfer Augmentation.

2001 ◽  
Vol 34 (9) ◽  
pp. 1136-1140 ◽  
Author(s):  
SHINYA KISHIMOTO ◽  
JIANXING ZHENG ◽  
TAKAYUKI OCHI ◽  
TOKUO YOSHIMURA ◽  
NAOTO OHMURA ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Estimation Method ◽  
Flow Structures ◽  
Heat Transfer Augmentation ◽  
Impingement Heat Transfer

Numerical Analysis for Performance Evaluation of Round Tubes Inserted With Corrugated Twisted Tape

2019 ◽  
Author(s):  
Kalpana Gupta ◽  
Raj Kumar Singh ◽  
Naman Choudhary ◽  
Subham Mukhopadhyay
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Transfer Enhancement ◽  
Friction Factor ◽  
Evaluation Criteria ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Round Tube ◽  
Heat Transfer Augmentation ◽  
Plain Tube

Abstract Varieties of heat transfer enhancement techniques developed by different researchers. Heat transfer augmentation techniques refer to different methods used to increase rate of heat transfer and basically divided into active, passive and compound heat transfer enhancement technique. Use of twisted tape is one such promising passive heat transfer augmentation technique. In this work a novel design of twisted tape is introduced. An attempt has been made to analyze the effect of newly designed twisted tape on heat transfer enhancement using computational Fluid Dynamics (CFD) Techniques. Physical time and energy considered for experimentation will be more so in present work simulation has been carried out using ANSYS FLUENT software to find performance of novel twisted tape. The tape considered here is corrugated twisted tape in which corrugations are given longitudinally with fixed angle of corrugation then it is twisted. Comparison in performance of tube without tape, with plain twisted tape and twisted corrugated tape has been done. Verification of model has been done using available correlations for plain tube and tube with plain twisted tape. Range of Reynolds varied from 10,000 to 60,000. Heat transfer and pressure drop characteristics studied using computational analysis. Nusselt Number and friction factor of round tube with CTT insert is found to be 1.79–1.94 times and 2.5–3.5 times higher respectively compared to round tube without any insert. Thermal performance factor chosen as performance evaluation criteria keeping pumping power constant. Performance of tube with corrugated twisted tape insert found to be better than plain tube (improvement in TPF up to 31%) taking into account both heat transfer and friction factor.

Flow Structure and Heat Transfer Characteristics of a Rectangular Channel With Pin Fins and Dimples With Different Shapes

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Lei Luo ◽  
Han Yan ◽  
Wei Du ◽  
Songtao Wang ◽  
Changhai Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Flow Structure ◽  
Rectangular Channel ◽  
Horseshoe Vortex ◽  
Heat Transfer Characteristics ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Transfer Characteristics ◽  
Pin Fins

Abstract In this study, numerical simulations are conducted to investigate the effects of pin fin and dimple shape on the flow structure and heat transfer characteristics in a rectangular channel. The studied shapes for dimple and pin fin are circular, spanwise-elliptical, and streamwise-elliptical, respectively. The flow structure, friction factor, and heat transfer performance are obtained and analyzed with Reynolds number ranging from 10,000 to 50,000. Channel with circular pin fin and dimple is chosen as the Baseline. Channels with spanwise-elliptical pin fins have the best heat transfer augmentation, while also accompanied with the largest friction factor. Spanwise-elliptical pin fin generates the strongest horseshoe vortex which is responsible for the best heat transfer augmentation. Besides, channels with streamwise-elliptical pin fins show the worst heat transfer augmentation and the smallest friction factors. Dimple plays an important role in improving the heat transfer. Spanwise-elliptical dimple yields the best heat transfer augmentation which is attributed to the strongest counter-rotating vortex, while streamwise-elliptical dimple shows the worst heat transfer enhancement.

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