Convection Boundary Layer Heat Transfer Research Articles

Modified Adomian decomposition method for solving the problem of boundary layer convective heat transfer

In this paper, we apply a new modification of the Adomian decomposition method for solving the problem of boundary layer convective heat transfer with viscous dissipation and low pressure gradient over a at plate. The technique is based on the standard Adomian decomposition method and the Chebyshev pseudospectral method. Comparisons are made between the pro-posed technique, the standard Adomian decomposition method, and the numerical solutions to demonstrate the applicability, validity, and high accuracy of the present approach. The results demonstrate that the new modification is more efficient and converges faster than the Adomian decomposition method.

Analysis of forced convective heat transfer of nanofluids over a moving plate by the homotopy perturbation method

The steady-state two-dimensional laminar forced convection boundary layer heat transfer of various types of nanofluids over an impermeable isothermal moving flat plate is investigated. The governing partial differential equations of mass, momentum and energy conservations are transformed by using suitable similarity transformations to two nonlinear ordinary differential equations (ODEs). The resulting nonlinear ODEs are solved using the semi-analytical treatment of the homotopy perturbation method (HPM) for six types of nanoparticles, namely copper (Cu), alumina (Al2O3), titania (TiO2), copper oxide (CuO), silver (Ag) and silica (SiO2) in the water based fluid. The effects of solid nanoparticles volume fraction and nanoparticles type on the heat transfer characteristics are investigated and compared with previously published numerical results. The obtained results show that the local Nusselt number increases with the increase of the nanoparticles volume fraction.DOI: http://dx.doi.org/10.5755/j01.mech.22.6.12890

Unsteady natural convection boundary layer heat transfer of fractional Maxwell viscoelastic fluid over a vertical plate

In classical study on viscoelastic fluids, researchers commonly ignored the effects of nonlinear convection and dealt only with the cases when the governing equations are linear. This paper presents a research on unsteady boundary layer natural convection heat transfer of Maxwell viscoelastic fluid over a vertical plate. The fractional boundary layer governing equations are firstly formulated and derived. From such derivation, the model constitutes nonlinear coupled equations with mixed time–space derivatives in the convection terms, which are solved by a newly developed finite difference method combined with an L1-algorithm. Results show that both the velocity and the temperature boundary layer manifest a short-term memory and basic relaxation time characteristics. For example, for specified velocity and temperature fractional derivative α and β, the velocity profile has a maximum, which increases and goes from a far-field region to the vertical plate as a decreasing function of α, implying a loss in velocity boundary layer thickness. But the values of such maxima behave conversely for β. More effects of the fractional order parameters α and β on velocity and temperature fields are shown graphically and analyzed in detail.

Successive Linearization Solution of Boundary Layer Convective Heat Transfer over a Flat Plate

Successive Linearization Solution of Boundary Layer Convective Heat Transfer over a Flat Plate

On linearization method to MHD boundary layer convective heat transfer with low pressure gradient

Abstract: The paper highlights the application of a recent semi-numerical successive linearization method (SLM) in solving highly coupled, nonlinear boundary value problem. The method is presented in detail by solving the problem of boundary layer convective heat transfer with low pressure gradient in the presence of viscous dissipation and radiation effects. The effects of the parameters on the flow are investigated. The velocity, temperature, skin-friction, and heat transfer coefficients have been obtained and discussed for various physical parametric values.

Theoretical analysis of natural convection boundary layer heat and mass transfer of nanofluids: Effects of size, shape and type of nanoparticles, type of base fluid and working temperature

The problem of natural convection boundary layer heat transfer of nanofluids is theoretically analyzed. Different aspects of nanoparticles, such as size, shape and constructive material, as well as the type of the base fluid and the working temperature, are examined. The drift-flux model of nanofluids, including the effects of Brownian motion, thermophoresis, and the local volume fraction of nanoparticles, is adopted to model the boundary layer heat and mass transfer of nanofluids. Following the state-of-the-art, the thermo-physical properties are extracted from five different synthesized types of nanofluids. A new non-dimensional parameter, the enhancement ratio, indicating the ratio of the convective heat transfer coefficient of the nanofluid to the base fluid, is introduced. The effect of the nanoparticles on the enhancement of natural convective heat transfer of nanofluids is discussed. The main findings of this study are as follows: (i) the type of the nanoparticles and the base fluid are the most important parameters affecting the heat transfer of nanofluids; (ii) in some cases, the presence of nanoparticles in the base fluid deteriorates the heat transfer rate; and (iii) the rise of the working temperature reduces the efficiency of the nanofluid, which is a crucial issue in applications of nanofluids as coolants.

Mixed convection heat transfer in power law fluids over a moving conveyor along an inclined plate

We study the mixed convection boundary layer heat transfer of power law fluid over a moving conveyor along an inclined plate. The effects of shear flow and power law viscosity on the temperature field are taken into account according to a modified Fourier law. Approximate analytical solutions are obtained by the homotopy analysis method (HAM). Results indicate that heat transfer is strongly dependent on the values of power law exponent, inclination angle, boundary velocity ratio and Prandtl number. Three distinct characteristics are found for power law exponents 0<n<1, n=1 and n>1, especially the nonlinear behavior due to skin friction and local Nusselt number shown in Figs. 4 and 17, which has never been reported before. The decrease of inclination angle causes the loss of velocity boundary layer but the gain of temperature boundary layer. Heat transfer efficiency is enhanced but skin friction is diminished with the increase in velocity ratio (the ratio of conveyor velocity/mean velocity of flow field). Critical ratio (with skin friction zero) is obtained which strongly depends on the power law exponent. The effects of involved parameters on the velocity and temperature fields are analyzed.

Adomian Decomposition Method for the Solution of Boundary Layer Convective Heat Transfer with Low Pressure Gradient over a Flat

This research work is aimed at obtaining solutions to the boundary layer convective heat transfer with viscous dissipation and low pressure gradient over a flat plate. The nonlinear equations of momentum and energy are transformed from partial differential equations into ordinary differential equations by using similarity transformation; the resulting equations were solved using Adomian decomposition method (ADM). An attempt was made to show the potentials and wide-range of applications of the Adomian decomposition method in the comparison with other methods used in solving heat transfer problems. The results were compared with numerical method (NM) and Homotopy perturbation method (HPM). It was observed from results obtained, that the ADM provides highly precise numerical solution for nonlinear differential equations. The results were accurate especially for ��≤�� using this method, a general equating terms of Eckert number (EC) and pressure gradient (�� ) is derived which can be used to investigate velocity and temperature profiles.

Boundary layer convective heat transfer with pressure gradient using Homotopy Perturbation Method (HPM) over a flat plate

Convective heat transfer equations of boundary layer with pressure gradient over a flat plate are solved using Homotopy Perturbation Method (HPM). This variation method is able to study the effects of Prandtl number ( Pr) and pressure gradient ( m) on both temperature and velocity distributions in the boundary layer. To this aim, the nonlinear equations of momentum and energy are solved simultaneously. Results of HPM in the absence of pressure gradient are in good agreement with results obtained from numerical methods. In addition, a general equation in terms of Re number, Pr number, and pressure gradient is derived using Nu number definition which can be used to obtain heat transfer coefficient for various situations.

Mathematical modelling of blood flow in curved arteries

We study the mixed convection boundary layer heat transfer of power law fluid over a moving conveyor along an inclined plate. The effects of shear flow and power law viscosity on the temperature field are taken into account according to a modified Fourier law. Approximate analytical solutions are obtained by the homotopy analysis method (HAM). Results indicate that heat transfer is strongly dependent on the values of power law exponent, inclination angle, boundary velocity ratio and Prandtl number. Three distinct characteristics are found for power law exponents 0 < n < 1, n = 1 and n > 1, especially the nonlinear behavior due to skin friction and local Nusselt number shown in Figs. 4 and 17, which has never been reported before. The decrease of inclination angle causes the loss of velocity boundary layer but the gain of temperature boundary layer. Heat transfer efficiency is enhanced but skin friction is diminished with the increase in velocity ratio (the ratio of conveyor velocity/mean velocity of flow field). Critical ratio (with skin friction zero) is obtained which strongly depends on the power law exponent. The effects of involved parameters on the velocity and temperature fields are analyzed.

The effect of transverse plate vibration on the mean laminar convective boundary layer heat transfer rate

Heat transfer experiments were conducted to ascertain the effects of transverse plate vibration on the local heat transfer rate, that is, the local Nusselt number. The nominal mean free-stream velocity for the main results presented in this paper is 4 m/s, giving a Reynolds number range up to 2.5 × 10 5. The plate vibration frequency is 60 Hz, and the typical plate vibration level at the excitation point of the heat transfer test plate ranges from 1.7 to 12 mm/s (peak). The effect of the plate vibration on the heat transfer is attributed to the stability characteristics of the induced boundary layer velocity oscillations. A detailed flow-field investigation indicates that the induced velocity oscillations in the laminar boundary layer are unstable. It is the nonlinear development of these unstable velocity oscillations and the resulting laminar-turbulent transition that produces an increase in the local heat transfer rate. The local heat transfer augmentation is in some cases as large as 290%. It is observed that at low levels of plate vibration the rate at which the local heat transfer increases with respect to the downstream direction is large and that the local heat transfer augmentation occurs mainly in the downstream region of the test plate. As the level of plate vibration is increased, the rate at which heat transfer increases with respect to the downstream direction is reduced, but the starting point at which heat transfer augmentation begins is moved upstream.

Thermal management of integrated microsensors

Thermal modeling techniques are demonstrated as they apply to a generic integrated microsensor with a heat source located on an anisotropically etched silicon diaphragm. One- and two-dimensional conduction formulas, boundary-layer convective heat transfer, a method of images approach for chip-level conduction, and the finite-element method are discussed, with examples, as they apply to the generic microsensor.

Laminar Free Convection Boundary Layer Heat Transfer over Non-Isothermal Surface

Accurate heat transfer results are provided for the case of nonisothermal objects. A steady, laminar, free convection boundary layer flow over two-dimensional or rotationally symmetrical bodies of nonuniform surface temperature situated in an ambient fluid of undisturbed temperature is considered analytically. The surface heat flux is given in terms of the Nusselt number and wall derivatives of universal functions for Prandtl numbers of 0.72 and 100 are provided. The method is shown to be valid up to a temperature/radius ratio of 130 deg.

Boundary-layer convective heat transfer in a convergent channel

In this paper the numerical solution of the heat transfer problem in a convergent channel with uniform and non-uniform wall temperatures under boundary-layer approximations has been presented. Also, a semi-analytical solution for uniform wall temperature has been obtained.

Predictive Capabilities of Series Solutions for Laminar Free Convection Boundary Layer Heat Transfer

Various types of series solutions for predicting laminar, free-convection boundary-layer heat transfer over both isothermal and nonisothermal boundaries are reviewed. The methods include finite difference, Merk series, Blasius series, and Goertler series. Comparative results are presented for heat transfer over an isothermal, horizontal, elliptical cylinder in both slender and blunt configurations.