Liquid Impingement Flow and Heat Transfer of a Cone Heat Sink With Filet Profiles

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Zhiguo Tang ◽  
Feng Zhang ◽  
Shoucheng Wang ◽  
Jianping Cheng
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Sink ◽  
Pressure Coefficient ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Bottom Edge ◽  
Convex Surfaces ◽  
Flow And Heat Transfer ◽  
Heat Transfers

Abstract Jet impingement is a technique for removing heat efficiently. A liquid jet impingement on a cone heat sink was investigated numerically to explore the effect of filet profiles at the top and bottom edge of conical protuberances on fluid flow and heat transfer. An adopted turbulence model was validated through an experiment as described in the literature. Numerical results of pressure coefficient and Nusselt number were obtained for cases with and without filet profiles for variable jet Reynolds numbers and conical angles. Results showed that the flow and heat transfer of conical protuberances with small tip filet profiles are similar to that of the original cone. Pressure coefficient curves are similar to that of convex surfaces, and the average heat transfer slightly increases when the radius of the tip filet profiles exceeds 1 mm. A small filet profile of a conical bottom edge can improve the average Nusselt number. A secondary jet that enhanced the overall heat transfer was demonstrated, and the heat transfers of convex surfaces, as the comparison, with small angles were enhanced in most cases.

Numerical study of liquid jet impingement flow and heat transfer of a cone heat sink

2019 ◽  
Vol 29 (11) ◽  
pp. 4074-4092 ◽  
Author(s):  
Zhiguo Tang ◽  
Hai Li ◽  
Feng Zhang ◽  
Xiaoteng Min ◽  
Jianping Cheng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Sink ◽  
Numerical Study ◽  
Cone Angle ◽  
Jet Impingement ◽  
Bottom Edge ◽  
Content Type ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer

Purpose The purpose of this paper is to explore the flow and heat transfer characteristics of the jet impingement onto a conical heat sink and evaluate the ability of heat transfer enhancement. Design/methodology/approach A numerical study of the flow and heat transfer of liquid impingement on cone heat sinks was conducted, and transition SST turbulence model was validated and adopted. The flow and thermal performances were investigated with the Reynolds number that ranges from 5,000 to 23,000 and cone angle that ranges from 0° to 70° in four regions. Findings Local Nusselt numbers are large, and pressure coefficients drop rapidly near the stagnation point. In the conical bottom edge, a secondary inclined jet was observed, thereby introducing a horseshoe vortex that causes drastic fluctuations in the curves of the flow and heat transfer. The average Nusselt numbers are higher in a conical protuberance than in flat plates in most cases, thus indicating that the heat transfer performance of jet impingement can be improved by a cone heat sink. The maximum increase is 13.6 per cent when the cone angle is 60°, and the Reynolds number is 23,000. Originality/value The flow and heat transfer behavior at the bottom edge of the cone heat sink is supplemented. The average heat transfer capacity of different heat transfer radii was evaluated, which provided a basis for the study of cone arrays.

Experimental Investigation on Convective Heat Transfer Enhancement of Laminar Slot Jet Impingement in the Presence of Porous Medium

2016 ◽  
Author(s):  
Sampath Kumar Chinige ◽  
Arvind Pattamatta
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Porous Medium ◽  
Porous Media ◽  
Nusselt Number ◽  
Heat Sink ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Transfer Enhancement ◽  
Porous Obstacle

An experimental study using Liquid crystal thermography technique is conducted to study the convective heat transfer enhancement in jet impingement cooling in the presence of porous media. Aluminium porous sample of 10 PPI with permeability 2.48e−7 and porosity 0.95 is used in the present study. Results are presented for two different Reynolds number 400 and 700 with four different configurations of jet impingement (1) without porous foams (2) over porous heat sink (3) with porous obstacle case (4) through porous passage. Jet impingement with porous heat sink showed a deterioration in average Nusselt number by 10.5% and 18.1% for Reynolds number of 400 and 700 respectively when compared with jet impingement without porous heat sink configuration. The results show that for Reynolds number 400, jet impingement through porous passage augments average Nusselt number by 30.73% whereas obstacle configuration enhances the heat transfer by 25.6% over jet impingement without porous medium. Similarly for Reynolds number 700, the porous passage configuration shows average Nusselt number enhancement by 71.09% and porous obstacle by 33.4 % over jet impingement in the absence of porous media respectively.

scholarly journals Investigating the impacts of included angles on flow and heat transfer in cross-corrugated triangular ducts with field synergy principle

2013 ◽  
Vol 17 (3) ◽  
pp. 823-832 ◽  
Author(s):  
Zuoyi Chen ◽  
Lizhi Zhang ◽  
Han Song
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Field Synergy ◽  
Field Synergy Principle ◽  
Included Angle ◽  
Flow And Heat Transfer ◽  
Performance Evaluation Criterion ◽  
Vital Effect

Included angles (?) have vital effect on the flow and heat transfer in cross-corrugated triangular ducts. The friction factor and Nusselt number were estimated at different Reynolds numbers from both experiments and simulations. Results show that the flow in the duck with ?=90 has the largest friction factor and Nusselt number. However, the included angle influences the flow and heat transfer in cross-corrugated triangular ducts in different ways. The field synergy principle was used to explore the mechanism of the different impacts of the included angle. Results show that the flow in the cross-corrugated triangular duct with ?=90o has the smallest domain averaged included angle (?m), which implies the best synergy performance. The results of the field synergy principle were also validated by analyzing the performance evaluation criterion and studying the velocity vector and temperature distributions.

scholarly journals Turbulent fluid flow and heat transfer analysis of heated rectangular blocks encountered in electronics enclosures

2020 ◽  
Vol 184 ◽  
pp. 01027
Author(s):  
B Ch Nookaraju
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Kinetic Energy ◽  
Vertical Channel ◽  
Reynolds Numbers ◽  
Heat Transfer Analysis ◽  
Computational Investigation ◽  
Turbulent Fluid Flow ◽  
Flow And Heat Transfer ◽  
Pressure Fall

Computational investigation of steady, two-dimensional heat transfer attributes for forced convective chaotic discharge in a vertical channel of cluster of heated rectangular sections is performed. The discharge is deemed to be periodic fully developed so that the issue is determined for two extending zone and explanation is developed to more number of sections. This structure reproduces the driven convective cooling of a cluster of engraved circuit panels confronted in computerize belongings. Two mathematical statements for k- ℇ model is used for modeling for the turbulence and the finite volume methodology is used. Computations are performed for Reynolds numbers ranging from 6000-12000, Prandtl number of 0.7 and various geometric parameters characterizing the problem. As Reynolds number steps up the Nusselt Number increases. Re-circulations undermine the local Nusselt number when matched with comparing variation from a identical plate. The velocity contours, temperature distributions, variation of turbulent kinetic energy and kinetic energy dissipation rates in a vertical channel is found. With the blocks in the cluster, pressure fall is higher in resemblance to plane duct.

Direct Numerical Simulation of Flow and Heat Transfer From a Sphere in a Uniform Cross-Flow

2000 ◽  
Vol 123 (2) ◽  
pp. 347-358 ◽  
Author(s):  
P. Bagchi ◽  
M. Y. Ha ◽  
S. Balachandar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Vortex Shedding ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Flow And Heat Transfer

Direct numerical solution for flow and heat transfer past a sphere in a uniform flow is obtained using an accurate and efficient Fourier-Chebyshev spectral collocation method for Reynolds numbers up to 500. We investigate the flow and temperature fields over a range of Reynolds numbers, showing steady and axisymmetric flow when the Reynolds number is less than 210, steady and nonaxisymmetric flow without vortex shedding when the Reynolds number is between 210 and 270, and unsteady three-dimensional flow with vortex shedding when the Reynolds number is above 270. Results from three-dimensional simulation are compared with the corresponding axisymmetric simulations for Re>210 in order to see the effect of unsteadiness and three-dimensionality on heat transfer past a sphere. The local Nusselt number distribution obtained from the 3D simulation shows big differences in the wake region compared with axisymmetric one, when there exists strong vortex shedding in the wake. But the differences in surface-average Nusselt number between axisymmetric and three-dimensional simulations are small owing to the smaller surface area associated with the base region. The shedding process is observed to be dominantly one-sided and as a result axisymmetry of the surface heat transfer is broken even after a time-average. The one-sided shedding also results in a time-averaged mean lift force on the sphere.

An Experimental Investigation of Forced Convection Heat Transfer From an Isothermal V-Shaped Plate

2010 ◽  
Author(s):  
Tooraj Yousefi ◽  
Saeed Ebrahimi ◽  
Masood Bigharaz ◽  
Sajjad Mahmoodi Nezhad
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Nusselt Number ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Plate Spacing ◽  
Internal Surfaces

An experimental study has been carried out to investigate heat transfer characteristics on internal surfaces of a V-shaped plate exposed to a slot jet impingement of air. A square-edged nozzle is mounted parallel with V-shaped plate axis and jet flow impinges on the bottom of the V-shaped plate. The study is focused on Rayleigh number 159000, angle of V-shaped plate ranging from 22.5 to 45 degree, low Reynolds numbers ranging from 29.05 to 60.41, and slot-to-(V-shaped plate) spacing from 17 to 21 of the slot width. A Mach-Zehnder interferometer is used for measurement of local Nusselt number on the V-shaped plate. It is observed that the local Nusselt number and average Nusselt number decrease with increasing the jet spacing and increase with increasing the Reynolds number. Also the local Nusselt number and average nusselt number increase with rising the angle of V-shaped plate.

Impingement Heat Transfer on a Cylindrical, Concave Surface With Varying Jet Geometries

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
C. Neil Jordan ◽  
Lesley M. Wright ◽  
Daniel C. Crites
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Leading Edge ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Hole Shape ◽  
Impingement Heat Transfer ◽  
Cylindrical Holes

Jet impingement is often employed within the leading edge of turbine airfoils to combat the heat loads incurred within this region. This experimental investigation employs a transient liquid crystal technique to obtain detailed Nusselt number distributions on a concave, cylindrical surface that models the leading edge of a turbine airfoil. The effect of hole shape and differing hole inlet and exit conditions are investigated. Two hole shapes are studied: cylindrical and racetrack-shaped holes; for each hole shape, the hydraulic diameter and mass flow rate into the array of jets is conserved. As a result, the jet's Reynolds number varies between the two jet arrays. Reynolds numbers of 13,600, 27,200, and 40,700 are investigated for the cylindrical holes, and Reynolds numbers of 11,500, 23,000, and 34,600 are investigated for the racetrack holes. Three inlet and exit conditions are investigated for each hole shape: a square edged, a partially filleted, and a fully filleted hole. The ratio of the fillet radius to hole hydraulic diameter is set at 0.25 and 0.667 for the partially and fully filleted holes, respectively, while all other geometrical features remain constant. Results show the Nusselt number is directly related to the Reynolds number for both cylindrical and racetrack-shaped holes. The racetrack holes are shown to provide enhanced heat transfer compared to the cylindrical holes. The degree of filleting at the inlet and outlet of the holes affects whether the heat transfer on the leading edge model is further enhanced or degraded.

Experimental Heat Transfer and Discharge Coefficients for Single Confined Jet Impingement Normal to a Surface at Close Distances

2008 ◽  
Author(s):  
J. D. Shapiro ◽  
M. E. Taslim
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Discharge Coefficient ◽  
Jet Impingement ◽  
Ambient Air ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Gap Size ◽  
Discharge Coefficients

Heat transfer and flow discharge coefficients for confined jet impingement are being investigated for a single round jet impinging normal to a target surface less than one hole diameter from the jet origin. A search of open literature resulted in the availability of no discharge coefficient information, and limited heat transfer information, especially for the configuration of a confined jet in close surface impingement. The experiment has been conducted for a developing jet and utilizes liquid crystal thermography for heat transfer measurements. Nusselt numbers were obtained for jet Reynolds numbers between 15000 and 30000 with a gap to hole diameter ratio of 0.3 to 3. Discharge coefficient data were obtained for jet Reynolds numbers between 11000 and 59000, with a gap to hole diameter ratio of 0.2 to infinity. The heat transfer data obtained shows a secondary Nusselt number peak and similar trends to those seen in other close surface impingement studies. The data also show a crossover of Nusselt number at increasing radial distance from the jet stagnation point with increasing gap size which could be indicative of ambient air entrainment. The discharge coefficient data obtained show a decrease in discharge coefficient for a decrease in gap size. At constant pressure ratio conditions a large decrease in discharge coefficient is observed between pressure ratios of 1.05 and 1.11. The results of this study are applicable to many industrial applications. However, a discussion of close surface impingements applicability to gas turbines has been included, as well as a comparison of the experimental and numerical results.

Investigations on Fluid Flow and Heat Transfer Performances Within a Real Turbine Blade Channel

2014 ◽  
Author(s):  
Zhaoqing Ke ◽  
Jian Pu ◽  
Jianhua Wang ◽  
Lei Wang ◽  
Zhiqiang Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Secondary Flow ◽  
Reynolds Numbers ◽  
Numerical Investigations ◽  
Serpentine Channel ◽  
Flow And Heat Transfer ◽  
Working Medium

The characteristics of fluid flow and heat transfer within a smooth three-pass channel of a real low pressure (LP) turbine blade have been investigated through experimental and numerical approaches. The serpentine channel consists of two inlet passes, two dividing walls, two 180 degree bends, twenty-five exits at the trailing edge, and two exits at the blade tip. In the experiments, purified water was used as working medium, the secondary flow patterns at five cross-sections were captured by a particle image velocimetry (PIV) system, the inlet Reynolds number was controlled by a turbine flow meter, and the mass flow rate ejected from each exit was measured by rotameters. Using the commercial software ANSYS CFX 13.0, numerical investigations were carried out. The practicability of four turbulence models, the SSG RSM, SST k-ω, RNG k-ε and standard k-ε models, were estimated. Through qualitative and quantitative comparisons of the secondary flow patterns, local velocity variation trends and mass flow rates between the experimental data and numerical results, the SSG RSM was selected as the most appropriate model in the following numerical investigations. Using ideal gas as working medium, the impacts of Reynolds numbers and rotation numbers on the heat transfer performances were numerically investigated. The numerical results predicted three interesting phenomena: 1) The locally averaged Nusselt number increases generally with the inlet Reynolds numbers. However, the increasing amplitude is significantly different from the correlation suggested by Dittus-Boelter, Nuo = 0.023Re0.8Pr0.4. The effect of the Reynolds number on the Nusselt number is substantially enhanced due to the serpentine channel design with two 180 degree-bends. The enhancement amplitude is described by two fitted coefficients based on Dittus-Boelter correlation. 2) Under a rotation condition, in the 1st and 3rd passes, the enhancement amplitude of the average Nusselt number on the pressure side (PS) is more significant than that on the suction side (SS), whereas in the 2nd pass, the enhancement amplitude on the PS is lower than that on the SS. 3) In the 3rd pass, a higher rotation number leads to a more uniform distribution of the local Nusselt number along the streamwise direction on both the PS and SS.

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