scholarly journals Statistical and Simulation Analysis on Dimple Configurations Performance of Heat Dissipation

2021 ◽  
Vol 86 (2) ◽  
pp. 74-90
Author(s):  
Mohd Shahir Kasim ◽  
Nur Husnina Najeah Husshini ◽  
Raja Izamshah ◽  
Hema Nanthini Ganesan ◽  
Muhamad Ammar Farhan Maula Mohd Azam ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Structure ◽  
Heat Dissipation ◽  
Simulation Analysis ◽  
Air Flow ◽  
Orientation Angle ◽  
Cooling Time ◽  
Cooling Effect ◽  
Staggered Arrangement

This paper presents an investigation on cooling effect and flow structure of the spherical dimple configuration during air flow on the Aluminium surface. It is prominently known that applying dimples profile causes an enhancement in heat transfer over a plain surface. A three level of Box-Behnken response surface methodology was performed to find the correlation between the input and output variables. A total of 17 different combinations of these inputs were performed throughout the experiment. The variable inputs to be investigated namely: dimple diameter of 10 - 14 mm, dimple orientation angle of 60°- 90°, and airflow velocity of 16 - 18 m/s to observe the response on the cooling time. The Aluminium block was heated to 60°C and cooled down by air flow at room temperature. The ANOVA was used to identify the significant effect of each parameter. CFD software was used as a simulation tool to analyze the flow structure and Reynolds number that associate with the heat transfer rate to support the statistical findings. Based on the result, all the input parameters are found to be significantly dominated by air flow velocity. Staggered arrangement dimple profile surface improves cooling effect by 63% over the plain flat surface. The increment in Reynolds number will increase the heat transfer which then shortening the cooling time.

scholarly journals Cooling Effect Efficiency Prediction of Aluminum Dimples Block using DOE Technique

2018 ◽  
Vol 7 (4.30) ◽  
pp. 152
Author(s):  
Ganesan H. N ◽  
Kasim M. S ◽  
Izamshah R ◽  
Anand T.J. S ◽  
Hafiz M. S. A ◽  
...  
Keyword(s):  
Heat Dissipation ◽  
Orientation Angle ◽  
Cooling Time ◽  
Cooling Effect ◽  
Average Error ◽  
Stream Velocity ◽  
Air Stream ◽  
Enhancement Method ◽  
Air Flow Velocity ◽  
The Mathematical Model

The main aim of the present work is to study the effect of heat enhancement method on the cooling process of a spherical dimple profile. It was prominently known that introducing dimples configuration causes an enhancement in heat transfer over a surface. In this project, an experimental investigation was carried out to examine the cooling effect of the spherical dimple profile during steady laminar flow in a wind tunnel. Seventeen different sets of parameters related to dimple diameter (mm), dimple orientation (angle) and air stream velocity (m/s) were studied. The Box-Behnken of Response Surface Methodology (RSM) was used as design of experiments (DoE) tool to evaluate these parameters on cooling time. This work deals with the analysis of variance (ANOVA) in order to establish the significant effect of input parameters. The result reveals that an increase in dimple diameter and air stream velocity increase heat dissipation. The shortest cooling time of 7 minutes can be achieved when the dimple diameter is 12 mm; the dimple orientation is 60° and air flow velocity at 18 m/s. The mathematical model has been rendered where the model has been experimentally validated with the average error of 6%.

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.

Local Swirl Chamber Heat Transfer and Flow Structure at Different Reynolds Numbers

1999 ◽  
Vol 122 (2) ◽  
pp. 375-385 ◽  
Author(s):  
C. R. Hedlund ◽  
P. M. Ligrani
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Structure ◽  
Flow Behavior ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Local Flow ◽  
Flux Boundary Condition ◽  
Nusselt Numbers ◽  
Swirl Chamber

Local flow behavior and heat transfer results are presented from two swirl chambers, which model passages used to cool the leading edges of turbine blades in gas turbine engines. Flow results are obtained in an isothermal swirl chamber. Surface Nusselt number distributions are measured in a second swirl chamber (with a constant wall heat flux boundary condition) using infrared thermography in conjunction with thermocouples, energy balances, and in situ calibration procedures. In both cases, Reynolds numbers Re based on inlet duct characteristics range from 6000 to about 20,000. Bulk helical flow is produced in each chamber by two inlets, which are tangent to the swirl chamber circumference. Important changes to local and globally averaged surface Nusselt numbers, instantaneous flow structure from flow visualizations, and distributions of static pressure, total pressure, and circumferential velocity are observed throughout the swirl chambers as the Reynolds number increases. Of particular importance are increases of local surface Nusselt numbers (as well as ones globally averaged over the entire swirl chamber surface) with increasing Reynolds number. These are tied to increased advection, as well as important changes to vortex characteristics near the concave surfaces of the swirl chambers. Higher Re also give larger axial components of velocity, and increased turning of the flow from each inlet, which gives Go¨rtler vortex pair trajectories greater skewness as they are advected downstream of each inlet. [S0889-504X(00)00502-X]

scholarly journals Local Swirl Chamber Heat Transfer and Flow Structure at Different Reynolds Numbers

1999 ◽  
Author(s):  
C. R. Hedlund ◽  
P. M. Ligrani
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Structure ◽  
Flow Behavior ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Local Flow ◽  
Flux Boundary Condition ◽  
Nusselt Numbers ◽  
Swirl Chamber

Local flow behavior and heat transfer results are presented from two swirl chambers, which model passages used to cool the leading edges of turbine blades in gas turbine engines. Flow results are obtained in an isothermal swirl chamber. Surface Nusselt number distributions are measured in a second swirl chamber (with a constant wall beat flux boundary condition) using infrared thermography, in conjunction with thermocouples, energy balances, and in situ calibration procedures. In both cases, Reynolds numbers Re based on inlet duct characteristics range from 6000 to about 20000. Bulk helical flow is produced in each chamber by two inlets which ore tangent to the swirl chamber circumference. Important changes to local and globally-averaged surface Nusselt numbers, instantaneous flow structure from flow visualizations, and distributions of static pressure, total pressure, and circumferential velocity are observed throughout the swirl chambers as the Reynolds number increases. Of particular importance are increases of local surface Nusselt numbers (as well as ones globally-averaged over the entire swirl chamber surface) with increasing Reynolds number. These are tiad to increased advection, as well as important changes to vortex characteristics near the concave surfaces of the swirl chambers. Higher Re also give larger axial components of velocity, and increased turning of the flow from each inlet, which gives Görtler vnrtex pair trajectories greater skewness as they are advected downstream of each inlet.

scholarly journals Numerical Simulation and Optimization of Waste Heat Recovery in a Sinter Vertical Tank

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 385 ◽  
Author(s):  
Chenyi Xu ◽  
Zhichun Liu ◽  
Shicheng Wang ◽  
Wei Liu
Keyword(s):  
Heat Transfer ◽  
Power Consumption ◽  
Flow Rate ◽  
Heat Dissipation ◽  
Waste Heat ◽  
Air Flow ◽  
Particle Diameter ◽  
Exergy Destruction ◽  
Air Flow Rate ◽  
Simulation And Optimization

In this paper, a two-dimensional steady model is established to investigate the gas-solid heat transfer in a sinter vertical tank based on the porous media theory and the local thermal non-equilibrium model. The influences of the air flow rate, sinter flow rate, and sinter particle diameter on the gas-solid heat transfer process are investigated numerically. In addition, exergy destruction minimization is used as a new principle for heat transfer enhancement. Furthermore, a multi-objective genetic algorithm based on a Back Propagation (BP) neural network is applied to obtain a combination of each parameter for a more comprehensive performance, with the exergy destruction caused by heat transfer and the one caused by fluid flow as the two objectives. The results show that the heat dissipation and power consumption both gradually increase with an increase of the air mass flow rate. Additionally, the increase of the sinter flow rate results in a decrease of the heat dissipation and an increase of the power consumption. In addition, both heat dissipation and power consumption gradually decrease with an increase of the sinter particle diameter. For the given structure of the vertical tank, the optimal operating parameters are 2.99 kg/s, 0.61 kg/s, and 32.8 mm for the air flow rate, sinter flow rate, and sinter diameter, respectively.

Flow and Heat Transfer of Confined Impingement Jets Cooling

2000 ◽  
Author(s):  
Ting Wang ◽  
Mingjie Lin ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Structure ◽  
Experimental Studies ◽  
Cross Flow ◽  
Jet Impingement ◽  
Target Surface ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Behavior

Experimental studies on heat transfer and flow structure in confined impingement jets were performed. The objective of this study was to investigate the detailed heat transfer coefficient distribution on the jet impingement target surface and flow structure in the confined cavity. The distribution of heat transfer coefficients on the target surface was obtained by employing the transient liquid crystal method coupled with a 3-D inverse transient conduction scheme under Reynolds number ranging from 1039 to 5175. The results show that the average heat transfer coefficients increased linearly with the Reynolds number as Nu = 0.00304 Pr0.42Re. The effects of cross flow on heat transfer were investigated. The flow structure were analyzed to gain insight into convective heat transfer behavior.

scholarly journals Convective heat transfer and drag of two side-by-side tubes in the narrow channel at different Reynolds number

2019 ◽  
Vol 62 (6) ◽  
pp. 756-762
Author(s):  
Yu. V. Zhukova ◽  
A. M. Теrekh ◽  
A. I. Rudenko
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Flow Structure ◽  
Convective Heat ◽  
Narrow Channel ◽  
Hydraulic Performance ◽  
Circular Tubes

We studied numerically and experimentally convective heat transfer and drag of two side-by-side tubes in different arrangements in the narrow channel at the Reynolds number ranging from 8000 to 40000 in comparison with circular tubes. The visualization results of the flow structure in the wake behind the arrangements of the investigated tubes are presented. It is shown that the thermal and hydraulic performance of side-by-side drop-shaped tubes is by a factor of 1.2–2 higher than that of circular tubes due to a lower drag of drop-shaped tubes.

scholarly journals Experimental and Numerical Study Effect of Using Nanofluids in Perforated Plate Fin Heat Sink for Electronics Cooling

2018 ◽  
Vol 24 (8) ◽  
pp. 1
Author(s):  
Kadhum Audaa Jehhef
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Volume Fraction ◽  
Numerical Study ◽  
Perforated Plate ◽  
Processing Unit ◽  
Transfer Enhancement

An experimental and numerical investigation of the effect of using two types of nanofluids with suspending of (Al2O3 and CuO) nanoparticles in deionized water with a volume fraction of (0.1% vol.), in addition to use three types of fin plate configurations of (smooth, perforated, and dimple plate) to study the heat transfer enhancement characteristics of commercial fin plate heat sink for cooling computer processing unit. All experimental tests under simulated conditions by using heat flux heater element with input power range of (5, 16, 35, 70, and 100 W). The experimental parameters calculated are such as water and nanofluid as coolant with Reynolds number of (7000, 8000, 9400 and 11300); the air is blown in the inlet duct across the heat sink with Reynolds number of (10500, 12300, 14200 and 16000). The distance fin-to-fin is kept constant at (2.00 mm), and the channel employed in this work has a square cross-section of (7 cm) inside. It was observed that the average effectiveness and Nusselt number of the nanofluids are higher compared with those of using conventional liquid cooling systems. However, the perforated fin plate showed higher air heat dissipation than the other configuration plate fin employed in this study. The experimental results were supported by numerical results which gave a good indication to heat transfer enhancement in studied ranges.  

Heat Transfer of Compressed Air Flow in a Spanwise Rotating Four-Pass Serpentine Channel

1999 ◽  
Vol 121 (3) ◽  
pp. 583-591 ◽  
Author(s):  
G. J. Hwang ◽  
S. C. Tzeng ◽  
C. P. Mao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Air Flow ◽  
Density Ratio ◽  
Local Heat Transfer ◽  
Operating Conditions ◽  
Compressed Air ◽  
Grashof Number ◽  
Serpentine Channel

Convective heat transfer of compressed air flow in a radially rotating four-pass serpentine channel is investigated experimentally in the present study. The coolant air was compressed at 5 atmospheric pressure to achieve a high rotation number and Reynolds number simultaneously. The main governing parameters are the Prandtl number, the Reynolds number for forced convection, and the rotation number for the Coriolis-force-induced cross-stream secondary flow and the Grashof number for centrifugal buoyancy. To simulate the operating conditions of a real gas turbine, the present study kept the parameters in the test rig approximately the same as those in a real engine. The air in the present serpentine channel was pressurized to increase the air density for making up the low rotational speed in the experiment. The air flow was also cooled to increase the density ratio before entering the rotating ducts. Consequently, the order of magnitude of Grashof number in the present study was the same as that in real operating conditions. The local heat transfer rate on the walls of the four-pass serpentine channel are correlated and compared with that in the existing literature.

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