Numerical study on significance of wave amplitude, wavelength and aspect ratio on heat transfer and fluid flow characteristics in circular wavy MC heat sink design

2021 ◽  
pp. 095440622198937
Author(s):  
Valaparla Ranjith Kumar ◽  
Karthik Balasubramanian ◽  
K Kiran Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Aspect Ratio ◽  
Wave Amplitude ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Uniform Heat Flux ◽  
Uniform Heat ◽  
Fluid Flow Characteristics

In this study, hydrothermal characteristics in a circular wavy microchannel (CWMC) design under laminar flow conditions with uniform heat flux is numerically studied. Parametric studies in an innovative CWMC design were carried out at various wave amplitudes, wavelengths and aspect ratios. Three dimensional numerical study was performed in the Reynolds number (Re) range from 100 to 300 with uniform heat flux (50 W/cm2) applied at bottom of the channel, treating copper as channel material and water as working fluid. The obtained results were compared to sinusoidal wavy microchannel (SWMC).The results showed that heat transfer and fluid flow characteristics were significantly influenced by wave amplitude, wavelength and aspect ratio. Velocity vectors and contours were presented to understand the heat transfer and fluid flow characteristics. Stream-wise local Nusselt number, overall performance factor, span-wise velocity and temperature variation are also presented. It is concluded that CWMC with higher wave amplitude, smaller wave length and smaller aspect ratio gives higher heat transfer augmentation with corresponding pressure drop penalty.

Investigation on Convective Heat Transfer over a Rotating Disk with Bottom Wall Subjected to Uniform Heat Flux

2012 ◽  
Vol 249-250 ◽  
pp. 443-451
Author(s):  
Jing Zhou Zhang ◽  
Xiao Ming Tan ◽  
Xing Dan Zhu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Rotating Disk ◽  
Outer Radius ◽  
Bottom Wall ◽  
Uniform Heat Flux ◽  
Uniform Heat

A three-dimensional numerical study on the flow and heat transfer characteristics over a rotating disk with bottom wall subjected to uniform heat flux was conducted with the use of RNG k- turbulent model. And some experiments were also made for validation. The effects of rotating angular speed and pin configuration on the temperature maps and convective heat transfer characte-ristics on rotating surface are analyzed. As the increase of rotating velocity, the impingement of pumping jet on the centre of rotating disk became stronger and the transition from laminar to turbu-lent occurred at the outer radius of rotating disk, which resulted in heat transfer enhancement. The pins on the disk made the pumping action of a rotating disk weaker. Simultaneously, they also acted as disturbing elements to the cyclone flow near the rotating disk surface, which made the overall heat transfer to be enhanced. Under the same extend areas of different pins, needle pin has higher convective heat transfer capacity than the discrete ring pin.

scholarly journals Influence of fluid flow characteristics and heat transfer in a tube heat exchanger using H-shape inserts with circular ring

2021 ◽  
Author(s):  
Satyendra Singh ◽  
◽  
Tarun Joshi ◽  
Himanshi Kharkwal ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Flow Characteristics ◽  
Circular Ring ◽  
Main Section ◽  
Tube Heat Exchanger ◽  
Fluid Flow Characteristics

The heat transfer and fluid flow characteristics in a tube heat exchanger using H-shape inserts with circular ring (CRWHS) has been done by computationally and experimentally. In this investigation parameters like ratio of the diameters and pitches are considered. The value of diameter and pitch ratios are (DR=0.8, 0.9), (PR=3, 4) respectively. The main section in which investigation was done is 1.5m long and the hydraulic diameter of the tube is 68.1mm. 1000 W/m2 heat flux was provided in the main section. Heat flux was constant throughout the investigation. Air is used as a working medium in which 6000 to 21000 Reynolds number was used for the investigation. The observation revealed that the increment in heat transfer rate is 4.56 times as compare to smooth tube for the circular ring with H-shape inserts. In case of DR=0.8 and PR=3, maximum thermal performance factor was obtain which is 3.24. In GIT the deviation in Nusselt number & friction factor is limited to ±0.4% & ±0.1% respectively. CFD analysis result comparisons with experimental one are presented in which the maximum deviations for thermal performance factor are limited to ±3.6%.

Three Dimensional Numerical Simulation of Gas Heat Transfer in Rectangular Microchannels

2010 ◽  
Author(s):  
Xiaohong Yan ◽  
Qiuwang Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Wall Temperature ◽  
Three Dimensional ◽  
Uniform Heat Flux ◽  
Flux Boundary Condition ◽  
Uniform Heat ◽  
Heat Flux Boundary Condition

Rectangular microchannel is the typical component of the micro heat exchangers and micro heat sinks. Three-dimensional compressible Navier-Stokes equations are solved for gas flow and heat transfer in microchannels under uniform heat flux boundary condition. The numerical methodology is based on the control volume SIMPLE scheme. It is found that the heat removal characteristic for compressible flow is better than the incompressible flow and it is not suitable to use conventionally defined Nu to measure the heat transfer characteristic for compressible heat transfer. The effect of the aspect ratio (width to height) on the cross-sectional averaged wall temperature and the Nu is negligible under the uniform heat flux boundary condition. However, the local uniformity of the wall temperature is significantly influenced by the aspect ratio. The square cross-section exhibits the best local uniformity of the wall temperature.

Natural Convection in Vertical Annuli: A Numerical Study for Constant Heat Flux on the Inner Wall

1989 ◽  
Vol 111 (4) ◽  
pp. 909-915 ◽  
Author(s):  
J. A. Khan ◽  
R. Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Numerical Study ◽  
Outer Cylinder ◽  
Diameter Ratio ◽  
Uniform Heat Flux ◽  
Inner Diameter ◽  
Vertical Annuli

A numerical investigation has been conducted to evaluate the effects of diameter ratio and aspect ratio in natural convection of gases within vertical annuli. The inner cylinder is maintained at uniform heat flux and the outer cylinder at constant temperature. The horizontal top and bottom walls are insulated. Detailed results of heat transfer rate, temperature, and velocity fields have been obtained for 1 ≤ κ ≤ 15, 1 ≤ A ≤ 10, and 100 < RaL* < 107. The inner wall temperature is a function of diameter ratio and aspect ratio. The heat transfer results have been compared with those for isothermal heating, and have been found to be higher. The inner diameter is seen to be the appropriate length scale for high Rayleigh number flows and/or high radius ratios, and the radius ratio effect on heat transfer is seen to be insignificant for radius ratios greater than 10. The heat transfer results based on the inner diameter are in very good agreement with published experimental results, although these experiments were conducted for very high aspect ratio. Heat transfer correlations are provided.

Numerical Study on Effect of Volume Fraction of Nanoparticles on Rayleigh-Bernard Convection in Different Enclosures

2014 ◽  
Vol 592-594 ◽  
pp. 945-950 ◽  
Author(s):  
S. Senthil Kumar ◽  
S. Karthikeyan
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Boussinesq Approximation ◽  
Working Fluid ◽  
Volume Fractions ◽  
Aspect Ratios ◽  
Fluid Flow Characteristics

Numerical investigations of Rayleigh-Bernard convection in enclosures of different modified bottom and top surfaces filled with Au-Water Nanofluid with different volume fractions are presented. This paper describes a numerical predication of heat transfer and fluid flow characteristics inside enclosures bounded by modified bottom and top surfaces and two periodic straight vertical walls. Simulations are carried out for a Rayleigh number of 6×104 and two aspect ratios (0.25 & 0.5) with working fluid as Au-Water Nanofluid and The same analyses are performed with the Nanofluid having Au nanoparticles of same size and different volume fraction of φ = 5%, 10%, 15% and 20 % in order to see the effect of Nanofluid volume fraction on heat transfer. The Boussinesq approximation is used in order to take density change effect in the governing equations. The study investigates the effect of the nanoparticles volume fraction, and the aspect ratio on the heat transfer. The results are presented in terms of isotherms, streamlines local and average surface Nusselt numbers. Results show that the flow and isotherms are affected by the geometry shape and by the presence of nanoparticles with different volume fractions. It is also shown that for a fixed value of aspect ratio, the convective heat transfer is decreased for the increase in volume fraction of Nanofluid.

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