scholarly journals Calculation of evaporation length of a liquid bridge flowing between inclined hot tubes

2021 ◽  
Vol 2119 (1) ◽  
pp. 012056
Author(s):  
P I Geshev
Keyword(s):  
Nonlinear Integral Equation ◽  
Boundary Integral Equations ◽  
Boundary Integral ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Method Of Boundary Elements ◽  
Hydrostatic Equation ◽  
Velocity And Temperature Fields ◽  
Energy Equations ◽  
Surface Tension Forces

Abstract The bridge consists of liquid held by surface tension forces between two inclined tubes in an LNG heat exchanger. The shape of the bridge is calculated by the hydrostatic equation, which is reduced to a nonlinear integral equation and resolved by the Newton method. The velocity and temperature fields in the bridge are described by the Navier-Stokes and energy equations, respectively. They are reduced to the boundary integral equations and calculated by the method of boundary elements. Heat transfer coefficient is calculated for evaporating bridge and the length of total bridge evaporation is estimated.

scholarly journals Convective Flow of Blood in Square and Circular Cavities

2018 ◽  
Vol 26 (2) ◽  
pp. 209-230 ◽  
Author(s):  
P. Senel ◽  
M. Tezer-Sezgin
Keyword(s):  
Cross Sections ◽  
Axial Velocity ◽  
Boundary Integral Equations ◽  
Boundary Integral ◽  
Numerical Results ◽  
Heated Wall ◽  
Navier Stokes ◽  
Source Pressure ◽  
Magnetic Source ◽  
Energy Equations

Abstract In this study, the fully developed, steady, laminar ow of blood is studied in a long pipe with square and circular cross-sections subjected to a magnetic field generated by an electric wire. Temperature difference between the walls causes heat transfer within the fluid by the displacement of the magnetizable fluid particles in the cavity. The governing equations are the coupled Navier-Stokes and energy equations including magnetization terms. The axial velocity is also computed with the obtained plane velocity. The Dual Reciprocity Boundary Element Method (DRBEM) is used by taking all the terms other than Laplacian as in- homogeneity which transforms the partial differential equations into the boundary integral equations. Numerical results are given for increasing values of Magnetic (Mn) and Rayleigh (Ra) numbers. The numerical results reveal that an increase in Mn accelerates the plane velocity in the cavity but decelerates the axial velocity around the magnetic source. Pressure increases through the channel starting from the magnetic source. Isotherms show the cooling of the channel with high Mn and Ra only leaving a thin hot layer near the top heated wall. As Ra increases viscous effect is reduced leaving its place to convection in the channel. The use of DRBEM has considerably small computational expense compared to domain type methods.

Influence of temperature dependent physical properties on liquid metal droplet impact dynamics

2021 ◽  
pp. 1-15
Author(s):  
Akash Chowdhury ◽  
Anandaroop Bhattacharya ◽  
Partha Bandyopadhyay
Keyword(s):  
Surface Tension ◽  
Numerical Solutions ◽  
Substrate Surface ◽  
Metal Droplet ◽  
Navier Stokes ◽  
Complex Flow ◽  
Liquid Metal Droplet ◽  
Aluminium Copper ◽  
Energy Equations ◽  
Surface Tension Forces

Abstract The dynamics of a metal droplet impacting on a substrate surface has been studied in the paper numerically. Numerical solutions of the Navier-Stokes and Energy equations show the evolution of the droplet as it spreads upon impact with the substrate while simultaneously undergoing solidification. The interplay of the different forces including inertia, viscous and surface tension, coupled with solidification of the molten material in layers lead to complex flow dynamics. The change in density and viscosity owing to change in temperature resulting from the cooling process, is found to influence the spreading of the droplet significantly. The model was exercised for three different materials viz. aluminium, copper and nickel to determine the final splat radius as well as spreading time. The surface tension forces as well as solidification rates were found to be the dominant factors in determining the above parameters as well as the shape of the splat during spreading. The results were found to be in good agreement with existing analytical model.

scholarly journals Numerical Computation of Turbulent Flow and Heat Transfer in a Radially Rotating Channel with Wall Conduction

2001 ◽  
Vol 7 (3) ◽  
pp. 209-222
Author(s):  
Frank K. T. Lin ◽  
G. J. Hwang ◽  
S.-C. Wong ◽  
C. Y. Soong
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Computation ◽  
Experimental Models ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Turbine Blade Cooling ◽  
Flow And Heat Transfer ◽  
Energy Equations ◽  
Rotating Channel

This work is concerned with numerical computation of turbulent flow and heat transfer in experimental models of a radially rotating channel used for turbine blade cooling. Reynolds-averaged Navier-Stokes and energy equations with a two-layer turbulence model are employed as the computational model of the flow and temperature fields. The computations are carried out by the software package of “CFX-TASCflow”. Heat loss from the channel walls through heat conduction is considered. Results at various rotational conditions are obtained and compared with the baseline stationary cases. The influences of the channel rotation, through-flow, wall conduction and the channel extension on flow and heat transfer characteristics are explored. Comparisons of the present predictions and available experimental data are also presented.

Analysis of Convective Heat Transfer for Laminar Flow in a Pin Fins Array

2005 ◽  
Author(s):  
H. Shokouhmand ◽  
M. Moghari
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Structural Unit ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Pin Fins ◽  
Pass Through ◽  
Energy Equations

In this paper, convective heat transfer for fully developed laminar flow in a pin fins array using a two-dimensional periodic model of porous structure has been studied. A macroscopically uniform flow is assumed to pass through an array of circular pin fins placed regularly in an infinite space. Due to periodicity of the model, only one structural unit is taken for a calculation domain to resolve an entire domain of pin fins array. In the structural unit, pin fins surface are maintained at constant temperature, and Continuity, Navier-Stokes and energy equations are solved numerically to describe the microscopic velocity and temperature fields at a pore scale. The numerical results thus obtained are integrated over the structural unit to evaluate the dimensionless macroscopic pressure gradient and the thermal diffusivity tensors. Finally, the obtained results compared with available numerical and experimental data.

Dendritic growth of an elliptical paraboloid with forced convection in the melt

1989 ◽  
Vol 208 ◽  
pp. 575-593 ◽  
Author(s):  
Ramagopal Ananth ◽  
William N. Gill
Keyword(s):  
Reynolds Number ◽  
Dendritic Growth ◽  
Moving Boundary ◽  
Solid Phase ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Energy Equations ◽  
Theory And Experiments ◽  
Elliptical Paraboloid

All experimental observations of the growth of fully developed dendritic ice crystals indicate that the shape of the tip region is an elliptical paraboloid. Therefore, moving-boundary solutions of the three-dimensional Navier-Stokes and energy equations are obtained here for the shape-preserving growth of isothermal elliptical paraboloids by using the Oseen approximation which is valid for the low-Reynolds-number viscous flows which prevail in dendritic growth. Explicit expressions for the flow and the temperature fields are derived in a simple way using Ivantsov's method. It is shown that the growth Péclet number, PG, is a function of the aspect ratio A, the Stefan number St, the Reynolds number Re, and the Prandtl number Pr. As the Reynolds number increases PG becomes linear in St, less dependent on A and ultimately varies roughly as Re½.A comparison between the exact solutions given here and the experiments of Kallungal (1974) indicate that A decreases as Re increases. This result agrees qualitatively with the experiments of Kallungal (1974) and Chang (1985). The differences between theory and experiments for Re > 10−3 may be due to attachment kinetic resistance to growth along the c-axis and capillary effects at the tip which make ice dendrites non-isothermal and create conduction in the solid phase. However, more accurate simultaneous measurements of R1 and R2 are needed to determine definitively the mechanisms responsible for these deviations between theory and experiment.

scholarly journals Hydromagnetic Flow Over a Heated Stretching Surface

2021 ◽  
pp. 332-338
Author(s):  
Kotagiri Srihari
Keyword(s):  
Differential Equations ◽  
Stretching Sheet ◽  
Viscous Incompressible Fluid ◽  
Temperature Fields ◽  
Hydromagnetic Flow ◽  
Stretching Surface ◽  
Nusselt Numbers ◽  
Similarity Transformations ◽  
Velocity And Temperature Fields ◽  
Energy Equations

In the present paper on steady flow of a viscous incompressible fluid past a heated stretching sheet with thermal radiation is studied. Magnetic field is applied normal to the flow. With suitable similarity transformations, the momentum and energy equations are reduced to ordinary differential equations. The governing differential equations with corresponding boundary conditions are solved numerically using MATLAB inbuilt solver bvp4c,. Graphical results for velocity and temperature fields, tabular values of Skin-friction and Nusselt numbers are presented and discussed. It is found the temperature of the fluid increases for the increasing values of radiation parameter.

scholarly journals A Pore-Scale Investigation of the Transient Response of Forced Convection in Porous Media to Inlet Ramp Inputs

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Rabeeah Habib ◽  
Bijan Yadollahi ◽  
Nader Karimi
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Forced Convection ◽  
Transient Response ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Pore Scale ◽  
Staggered Arrangement ◽  
Energy Equations ◽  
Convection In Porous Media

Abstract This paper investigates the transient response of forced convection of heat in a reticulated porous medium through taking a pore-scale approach. The thermal system is subject to a ramp disturbance superimposed on the entrance flow temperature/velocity. The developed model consisted of ten cylindrical obstacles aligned in a staggered arrangement with set isothermal boundary conditions. A few types of fluids, along with different values of porosity and Reynolds number, are considered. Assuming a laminar flow, the unsteady Navier Stokes and energy equations are solved numerically. The temporally developing flow and temperature fields as well as the surface-averaged Nusselt numbers are used to explore the transient response of the system. Also, a response lag ratio (RLR) is defined to further characterize the transient response of the system. The results reveal that an increase in amplitude increases the RLR. Nonetheless, an increase in ramp duration decreases the RLR, particularly for high-density fluids. Interestingly, it is found that the Reynolds number has almost negligible effects upon RLR. This study clearly reflects the importance of conducting pore-scale analyses for understanding the transient response of heat convection in porous media.

Effects of Important Parameters on the Transition from Forced to Mixed Convection Flow in a Square Cavity

2021 ◽  
Vol 406 ◽  
pp. 36-52
Author(s):  
Sofiane Boulkroune ◽  
Omar Kholai ◽  
Brahim Mahfoud
Keyword(s):  
Reynolds Number ◽  
Prandtl Number ◽  
Mixed Convection ◽  
Forced Convection ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Convection Flow ◽  
Square Cavity ◽  
Left Wall ◽  
Energy Equations

Combined free and forced convection in a square cavity filled with a viscous fluid characterized by a small Prandtl number is studied numerically. The left wall is moving with a constant velocity v and is maintained at a local cold temperature Tc, while the right wall is fixed and maintained at a local hot temperature Th (Tc <Th). The top and bottom walls of the cavity is assumed to be adiabatic. The governing Navier-Stokes, and energy equations along with appropriate boundary conditions are solved using the finite-volume method. The flow and temperature fields are presented by stream function and isotherms, respectively. The effects of important parameters such as Reynolds number, Prandtl number, and Grashof number on the transition from forced convection to mixed convection are investigated. Results indicate that increasing Reynolds number results to fluid acceleration and, thus, to flow transition. Results also show that Grashof and Prandtl's numbers influenced the conditions for the transition to the mixed convection regime.

scholarly journals A numerical study of flow and temperature fields in circular tube heat exchanger with elliptic vortex generators

2008 ◽  
Vol 12 (2) ◽  
pp. 129-136 ◽  
Author(s):  
Ehsan Mohseni-Languri ◽  
Mofid Gorji-Bandpy ◽  
Reza Masoodi
Keyword(s):  
Nusselt Number ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Circular Tube ◽  
Numerical Study ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Computational Domain ◽  
Tube Heat Exchanger ◽  
Energy Equations

The two-dimensional fluid flow and heat transfer in a circular tube heat exchanger with two elliptic obstacles at the back is studied numerically. The computational domain consists of a circular tube and two elliptic obstacles that are situated after the tube, such that the angle between their centerlines and the direction of free coming flow is 45 degrees. The numerical solution is achieved by numerical integration of full Navier-Stokes and energy equations over the computational domain, using finite volume method. The fluid flow is assumed to be laminar, incompressible and steady-state with constant thermo-physical characteristics. In this study major thermo-fluid parameters such as temperature, pressure and velocity fields as well as Nusselt number and friction factor variations are computed and some results are presented in the graphs. It is shown that using of elliptic obstacles leads to an increase in the average Nusselt number and also pressure. .

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