scholarly journals Radiation-Conduction Interaction of Steady Streamwise Surface Temperature Variations on Vertical Free Convection

2011 ◽  
Vol 2011 ◽  
pp. 1-11
Author(s):  
Md. Kutub Uddin ◽  
Rabindra Nath Mondal
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Heated Surface ◽  
Leading Edge ◽  
Mean Value ◽  
Physical Parameters ◽  
Convective Boundary ◽  
Temperature Variations ◽  
Local Shear ◽  
Layer Flow

The combined effects of the steady free convective boundary-layer flow induced by a vertical heated surface in the presence of sinusoidal surface temperature variations about a constant mean value with the effect of radiation are examined. The problem is studied using fully numerical techniques. The surface rate of heat transfer eventually alternates in sign with distance from the leading edge, but no separation occurs unless the amplitude of the thermal modulation is sufficiently high. Numerical results are obtained for different values of the physical parameters, the radiation parameter Rd, the Prandtl number Pr, and the surface temperature wave amplitude a. It is found that both the local shear stress and the rate of heat transfer decrease when values of Rd increase.

Hydromagnetic Effects on Hybrid Nanofluid (Cu–Al2O3/Water) Flow with Convective Heat Transfer Due to a Stretching Sheet

2020 ◽  
Vol 9 (4) ◽  
pp. 293-301
Author(s):  
V. Rajesh ◽  
M. Srilatha ◽  
Ali J. Chamkha
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Stretching Sheet ◽  
Numerical Technique ◽  
Physical Parameters ◽  
Hybrid Nanofluid ◽  
Convective Boundary ◽  
Layer Flow ◽  
Field Setting

In this paper, transient free convective boundary layer flow of a viscous hybrid nanofluid due to a vertical stretching sheet with MHD effects is studied numerically using the Crank Nicolson finite difference numerical technique. To explore the properties of heat transfer and the flow field due to a vertical stretching sheet in the existence of a Lorentz force, two different fluids, specifically Cu–Al2O3/water and Cu/water, are utilized. The results of different physical parameters and the practical quantities of concern that they affect are investigated. According to this article’s results, Cu–Al2O3/water has a superior heat transfer rate than Cu/water in a magnetic field setting. Various other nano mixtures can be attempted to attain the optimal heat transfer rate.

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.

scholarly journals Coaxial Thermocouples for Heat Transfer Measurements in Long-Duration High Enthalpy Flows

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5254
Author(s):  
Shizhong Zhang ◽  
Qiu Wang ◽  
Jinping Li ◽  
Xiaoyuan Zhang ◽  
Hong Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Thermal Effusivity ◽  
Fast Response ◽  
Test Time ◽  
Physical Parameters ◽  
Fourier Number ◽  
High Enthalpy ◽  
Long Duration

Coaxial thermocouples have the advantages of fast response and good durability. They are widely used for heat transfer measurements in transient facilities, and researchers have also considered their use for long-duration heat transfer measurements. However, the model thickness, transverse heat transfer, and changes in the physical parameters of the materials with increasing temperature influence the accuracy of heat transfer measurements. A numerical analysis of coaxial thermocouples is conducted to determine the above influences on the measurement deviation. The minimum deviation is obtained if the thermal effusivity of chromel that changes with the surface temperature is used to derive the heat flux from the surface temperature. The deviation of the heat flux is less than 5.5% when the Fourier number is smaller than 0.255 and 10% when the Fourier number is smaller than 0.520. The results provide guidance for the design of test models and coaxial thermocouples in long-duration heat transfer measurements. The numerical calculation results are verified by a laser radiation heating experiment, and heat transfer measurements using coaxial thermocouples in an arc tunnel with a test time of several seconds are performed.

scholarly journals Numerical investigation of passive stabilization of the surface temperature using PCM and metal foam

2018 ◽  
Vol 240 ◽  
pp. 05027
Author(s):  
Mirosław Seredyński
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Energy Transport ◽  
Metal Foam ◽  
Liquid Fraction ◽  
Heated Surface ◽  
General Purpose ◽  
Ansys Fluent ◽  
Proposed Model ◽  
Strong Relation

Stabilization of the temperature of PVs is of great importance, due to strong relation between operating temperature and its efficiency. Due to low thermal conductivity of PCM, intensification of heat transfer to the operating material is needed. The four fully passive PV’s temperature stabilization systems, based on the phase change material (PCM) are numerically investigated in this paper. Apart from the natural convection promotion, intensification of heat transfer is done with aluminium fins and aluminium foam. The simplified computational model based on the equilibrium formulation of energy transport equation, taking into account viscous and inertial fluid flow resistances in the porous material, is formulated and solved with the general purpose software - ANSYS Fluent. Proposed model is succesfully verified by comparing the results with available in literature numerical solutions.Simulations outcomes are presented, the temperature and liquid fraction distributions in proposed geometry configurations, temperature variations determined in selected points and averaged on the heated surface temperature plots. Presented results help to assign the best configuration.

Heat Transfer in a Couple Stress Fluid over a Continuous Moving Surface with Internal Heat Generation and Convective Boundary Conditions

2012 ◽  
Vol 67 (5) ◽  
pp. 217-224 ◽  
Author(s):  
Tasawar Hayat ◽  
Zahid Iqbal ◽  
Muhammad Qasim ◽  
Omar M. Aldossary
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Heat Generation ◽  
Couple Stress ◽  
Couple Stress Fluid ◽  
Physical Parameters ◽  
Series Solutions ◽  
Convective Boundary Conditions ◽  
Convective Boundary ◽  
Moving Surface

This investigation reports the boundary layer flow and heat transfer characteristics in a couple stress fluid flow over a continuos moving surface with a parallel free stream. The effects of heat generation in the presence of convective boundary conditions are also investigated. Series solutions for the velocity and temperature distributions are obtained by the homotopy analysis method (HAM). Convergence of obtained series solutions are analyzed. The results are obtained and discussed through graphs for physical parameters of interest.

scholarly journals UNSTEADY BOUNDARY LAYERS: CONVECTIVE HEAT TRANSFER OVER A VERTICAL FLAT PLATE

2009 ◽  
Vol 50 (4) ◽  
pp. 541-549 ◽  
Author(s):  
ROBERT A. VAN GORDER ◽  
K. VAJRAVELU
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Numerical Solutions ◽  
Approximate Solutions ◽  
Shear Thinning ◽  
Momentum Equation ◽  
Physical Parameters ◽  
Flow And Heat Transfer ◽  
Special Cases ◽  
Layer Flow

AbstractIn this paper, we extend the results in the literature for boundary layer flow over a horizontal plate, by considering the buoyancy force term in the momentum equation. Using a similarity transformation, we transform the partial differential equations of the problem into coupled nonlinear ordinary differential equations. We first analyse several special cases dealing with the properties of the exact and approximate solutions. Then, for the general problem, we construct series solutions for arbitrary values of the physical parameters. Furthermore, we obtain numerical solutions for several sets of values of the parameters. The numerical results thus obtained are presented through graphs and tables and the effects of the physical parameters on the flow and heat transfer characteristics are discussed. The results obtained reveal many interesting behaviours that warrant further study of the equations related to non-Newtonian fluid phenomena, especially the shear-thinning phenomena. Shear thinning reduces the wall shear stress.

Heat Transfer Studies on the Interior Surfaces of Cooled Nozzle Guide Vane in a Linear Cascade

2015 ◽  
Author(s):  
Arun Kumar Pujari ◽  
Bhamidi Prasad ◽  
Nekkanti Sitaram
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Guide Vane ◽  
Internal Heat ◽  
Leading Edge ◽  
Internal Surface ◽  
Transfer Coefficients ◽  
Computational Data ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Experimental and computational heat transfer investigations are reported in the interior side of a nozzle guide vane (NGV) subjected to combined impingement and film cooling. The domain of study is a two dimensional five-vane cascade having four passages. Each vane has a chord length of 228 mm and the pitch distance between the vanes is 200 mm. The vane internal surface is cooled by dry air supplied through the two impingement inserts: the front and the aft. The mass flow through the impingement chamber is varied, for a fixed spacing (H) to jet diameter (d) ratio of 1.2. The surface temperature distributions, at certain locations of the vane interior, are measured by pasting strips of liquid crystal sheets. The vane interior surface temperature distribution is also obtained by computations carried out by using Shear stress transport (SST) k-ω turbulence model in the ANSY FLUENT-14 flow solver. The computational data are in good agreement with the measured values of temperature. The internal heat transfer coefficients are thence determined along the leading edge and the mid span region from the computational data.

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