scholarly journals Numerical Study of Heat Transfer and Flow Bifurcation of CuO Nanofluid in Sudden Expansion Microchannel Using Two-Phase Model

2017 ◽  
Vol 07 (02) ◽  
pp. 57-72 ◽  
Author(s):  
Farhad A. Abbassi ◽  
Mohsen Nazari ◽  
Mohammad Mohsen Shahmardan
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Phase Model ◽  
Sudden Expansion ◽  
Two Phase ◽  
Flow Bifurcation

scholarly journals Experimental and Numerical Study of the Flow and Heat Transfer in a Bubbly Turbulent Flow in a Pipe with Sudden Expansion

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2735 ◽  
Author(s):  
Pavel Lobanov ◽  
Maksim Pakhomov ◽  
Viktor Terekhov
Keyword(s):  
Heat Transfer ◽  
Liquid Velocity ◽  
Numerical Study ◽  
Bubbly Flow ◽  
Fluid Phase ◽  
Reynolds Stress Model ◽  
Sudden Expansion ◽  
Two Phase ◽  
Carrier Fluid ◽  
Carrier Liquid

The flow patterns and heat transfer of a downstream bubbly flow in a sudden pipe expansion are experimentally and numerically studied. Measurements of the bubble size were performed using shadow photography. Fluid phase velocities were measured using a PIV system. The numerical model was employed the Eulerian approach. The set of RANS equations was used for modelling two-phase bubbly flows. The turbulence of the carrier liquid phase was predicted using the Reynolds stress model. The peak of axial and radial fluctuations of the carrier fluid (liquid) velocity in the bubbly flow is observed in the shear layer. The addition of air bubbles resulted in a significant increase in the heat transfer rate (up to 300%). The main enhancement in heat transfer is observed after the point of flow reattachment.

scholarly journals Effect of Prandtl number on heat transfer characteristics in an axisymmetric sudden expansion: A numerical study

2007 ◽  
Vol 11 (4) ◽  
pp. 171-178
Author(s):  
Khalid Alammar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Numerical Study ◽  
Sudden Expansion ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Simulated Effect

Using the standard k-e turbulence model, an incompressible, axisymmetric turbulent flow with a sudden expansion was simulated. Effect of Prandtl number on heat transfer characteristics downstream of the expansion was investigated. The simulation revealed circulation downstream of the expansion. A secondary circulation (corner eddy) was also predicted. Reattachment was predicted at approximately 10 step heights. Corresponding to Prandtl number of 7.0, a peak Nusselt number 13 times the fully-developed value was predicted. The ratio of peak to fully-developed Nusselt number was shown to decrease with decreasing Prandtl number. Location of maximum Nusselt number was insensitive to Prandtl number.

scholarly journals Numerical study on the boiling heat transfer induced by two heated plates

2020 ◽  
Vol 24 (Suppl. 1) ◽  
pp. 257-265
Author(s):  
Xiaopeng Shan ◽  
Geng Guan ◽  
Deming Nie
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Numerical Study ◽  
Present System ◽  
Two Phase ◽  
Before And After ◽  
Flow Features ◽  
Boltzmann Method ◽  
Departure Behavior ◽  
Heated Plates

A two-phase lattice Boltzmann method was used to numerically study the boiling heat transfer related to the liquid-vapor transition induced by two heated plates. The effects of the gravity force as well as the separation between the heated plates were examined. The focus is on the bubble departure behavior resulting from the interaction between bubbles, which can be roughly classified into four types of pat?tern according to the separation between plates. In particular, it is shown that the bubble merging may take place twice in one cycle when the separation is close to a certain value. This is referred to as the pattern of alternation of bubble merging before and after departure, for which a sudden jump is seen in the bubble release period. Furthermore, the heat flux and the flow features are also shown to illustrate the behavior of heat transfer in the present system.

Numerical study of mixed convection heat transfer inside a vertical microchannel with two-phase approach

2018 ◽  
Vol 135 (2) ◽  
pp. 1119-1134 ◽  
Author(s):  
Mohammad Reza Tavakoli ◽  
Omid Ali Akbari ◽  
Anoushiravan Mohammadian ◽  
Erfan Khodabandeh ◽  
Farzad Pourfattah
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Two Phase ◽  
Phase Approach ◽  
Mixed Convection Heat Transfer ◽  
Vertical Microchannel

Phase Change Process Inside a Small-radii Cylinder Subjected to Cyclic Convective Boundary Conditions: a Numerical Study

2021 ◽  
Author(s):  
Yousef Kanani ◽  
Avijit Karmakar ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Phase Change ◽  
Phase Change Materials ◽  
Numerical Study ◽  
Convective Boundary Condition ◽  
Freezing Process ◽  
Fourier Number ◽  
Two Phase ◽  
Convective Boundary

Abstract We numerically investigate the melting and solidi?cation behavior of phase change materials encapsulated in a small-radii cylinder subjected to a cyclic convective boundary condition (square wave). Initially, we explore the effect of the Stefan and Biot numbers on the non-dimensionalized time required (i.e. reference Fourier number Tref ) for a PCM initially held at Tcold to melt and reach the cross?ow temperature Thot. The increase in either Stefan or Biot number decreases Tref and can be predicted accurately using a correlation developed in this work. The variations of the PCM melt fraction, surface temperature, and heat transfer rate as a function of Fourier number are reported and analyzed for the above process. We further study the effect of the cyclic Fourier number on the periodic melting and freezing process. The melting or freezing front initiates at the outer periphery of the PCM and propagates towards the center. At higher frequencies, multiple two-phase interfaces are generated (propagating inward), and higher overall heat transfer is achieved as the surface temperature oscillates in the vicinity of the melting temperature, which increases the effective temperature difference driving the convective heat transfer.

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