Heat Transfer in Engineering

The advancements in research related to heat transfer has gathered much attention in recent decades following the quest for efficient thermal systems, interdisciplinary studies involving heat transfer, and energy research. Heat transfer, a fundamental transport phenomenon, has been considered one of the critical aspects for the development and advancement of many modern applications, including cooling, thermal systems which contain symmetry analysis, energy conservation and storage, and symmetry-preserving discretization of heat transfer in a complex turbulent flow. The objective of this book is to present recent advances, as well as up-to-date progress in all areas of heat transfer in engineering and its influence on emerging technologies

Analysis of heat transfer for unsteady MHD free convection flow of rotating Jeffrey nanofluid saturated in a porous medium

In this article, the influence of thermal radiation on unsteady magnetohydrodynamics (MHD) free convection flow of rotating Jeffrey nanofluid passing through a porous medium is studied. The silver nanoparticles (AgNPs) are dispersed in the Kerosene Oil (KO) which is chosen as conventional base fluid. Appropriate dimensionless variables are used and the system of equations is transformed into dimensionless form. The resulting problem is solved using the Laplace transform technique. The impact of pertinent parameters including volume fraction φ, material parameters of Jeffrey fluid λ1, λ, rotation parameter r, Hartmann number Ha, permeability parameter K, Grashof number Gr, Prandtl number Pr, radiation parameter Rd and dimensionless time t on velocity and temperature profiles are presented graphically with comprehensive discussions. It is observed that, the rotation parameter, due to the Coriolis force, tends to decrease the primary velocity but reverse effect is observed in the secondary velocity. It is also observed that, the Lorentz force retards the fluid flow for both primary and secondary velocities. The expressions for skin friction and Nusselt number are also evaluated for different values of emerging parameters. A comparative study with the existing published work is provided in order to verify the present results. An excellent agreement is found

Heat transfer in combined convective magnetohydrodynamic motion of nanofluid holding different shapes of nanoparticles in a channel under the influence of heat source

87-98Heat transfer in mixed convection unsteady MHD flow of an incompressible nanofluid in a channel under the influence of heat source is studied. The channel with non-uniform walls temperature is taken in a perpendicular direction with a transverse magnetic field. Based on the substantial boundary conditions, three different flow conditions are examined. The problem is formed in PDEs with substantial boundary conditions. Four different forms of nanoparticles of identical volume fraction are employed in traditional base fluid water (H2O). Solutions for momentum and energy are attained by the perturbation method and examined graphically in different graphs. It is established that viscosity and thermal conductivity are the mainly well-known variables accountable for different results of velocity and temperature. It is also found that increasing heat source leads to an increase in nanofluid velocity and temperature and nano-size particles instance platelet and blade shapes have lesser momentum as related to brick and cylinder size of nanoparticles

Radiative heat transfer in MHD mixed convection flow of nanofluids along a vertical channel

Over the past few decades, nanofluids have emerged as a promising technology for the enhancement of the intrinsic thermophysical properties of many convectional heat transfer fluids such as water and oil. Many researchers have been investigated the merits of dispersing nanometer-sized particles into base fluids to enhance heat transfer, thermal conductivity and viscosity of the fluids. Therefore, this research focused on radiative heat transfer in magnethohydrodynamics mixed convection flow in a channel filled with nanofluids containing different type of nanoparticles. Five types of nanoparticles (Al2O3, 3 4Fe O , Cu, 2 TiO , and Ag) with five different shapes (platelet, blade, cylinder, brick and spherical) were used in water 2 (H O) and ethylene glycol 2 6 2 (C H O), as conventional base fluid. An important subtype of nanofluids called ferrofluids 3 4 (Fe O in water based nanofluids) was also studied. Four different problems were modelled as partial differential equations with physical boundary conditions. In the first three problems, the channel walls were taken rigid, while the fourth problem the walls were chosen permeable where suction or injection was taking place. Perturbed type analytical solutions for velocity and temperature were obtained and discussed graphically in various graphs. Results for skin friction and Nusselt number were also computed and presented in tabular forms. This study showed that 2 6 2 C H O was the better convectional base fluid compared to 2 H O because of the higher viscosity and thermal conductivity. Ag nanoparticles had the highest thermal conductivity and viscosity compared to other type of nanoparticles. Increasing nanoparticles size had caused variation in velocity. It was also observed that, variation in velocity for Ag nanoparticles was obtained at low volume concentration, whereas for 2 3 Al O nanoparticles, this variation was observed only at high volume concentration. Velocity increases with increasing Grashof number, radiation, heat generation and permeability parameters, but decreases with increasing magnetic parameter and volume fraction of nanoparticles. However, the effects of these parameters were quite different in the case of suction and injection. Results had also shown that, temperature increases with increasing radiation and heat generation parameters. In this study, the temperature of ferrofluids was found smaller when compared to the temperature of nanofluids

Heat transfer in combined convective magnetohydrodynamic motion of nanofluid holding different shapes of nanoparticles in a channel under the influence of heat source

Heat transfer in mixed convection unsteady MHD flow of an incompressible nanofluid in a channel under the influence of heat source is studied. The channel with non-uniform walls temperature is taken in a perpendicular direction with a transverse magnetic field. Based on the substantial boundary conditions, three different flow conditions are examined. The problem is formed in PDEs with substantial boundary conditions. Four different forms of nanoparticles of identical volume fraction are employed in traditional base fluid water (H2O). Solutions for momentum and energy are attained by the perturbation method and examined graphically in different graphs. It is established that viscosity and thermal conductivity are the mainly well-known variables accountable for different results of velocity and temperature. It is also found that increasing heat source leads to an increase in nanofluid velocity and temperature and nano-size particles instance platelet and blade shapes have lesser momentum as related to brick and cylinder size of nanoparticles

Numerical investigation of the nanoparticles nature effect on the MHD behavior in a square cavity with a metallic obstacle

In this paper, a study is conducted to determine numerically the effect of the nanoparticles nature (Al2O3, CuO, and Fe3O4) on the thermo-magnetohydrodynamic behavior of a nanofluid in a square cavity with a circular obstacle. The left wall of this cavity is movable and provided with a cold temperature (Tc) and the right wall is exposed to a hot temperature (Th). However, the upper and lower walls are considered adiabatic. The purpose of this paper is to highlight the effect of aluminum dioxide, copper oxide, and iron trioxide nanoparticles on the thermal and hydrodynamic behavior under the influence of different volume fractions(0 ≤ φ ≤ 0.1), different Hartmann numbers (0 ≤ Ha ≤ 75) and Richardson number (0 ≤ Ri ≤5). The system of governing équations was solved by the finite element method adopting the Galerkine discretization. The obtained results showed that the CuO nanoparticles improve the heat transfer at the fluid and obstacle, in addition, the increase of Hartmann number reduces the heat capacity, especially with the use of Fe3O4 nanoparticles. This study falls within the context of improving the cooling rate of industrial equipment.

Mixed Convection of Unsteady Nanofluids Flow Past A Vertical Plane With Entropy Generation

A fully developed mixed convection nanofluid flow past accelerating vertical plane in the presence of a uniform transverse magnetic field has been studied. Three different types of water-based Nanofluids containing Titanium (iv) oxide, Copper and aluminum (iii) oxide are taken into consideration. The governing equations are solved numerically by shooting technique coupled with Runge-Kutta-Fehlberg integration scheme. Effects of the pertinent parameters on the nanofluid temperature and velocity are shown in figures followed by a quantitative discussion. The expression for entropy generation number and the Bejan number are also obtained based on the profiles. It is found that the magnetic field tends to decrease the nanofluid velocity. Keywords: Nanofluids, Magnetohydrodynamics, Mixed convection, Heat transfer, Entropy generation. DOI: 10.7176/MTM/9-3-04 Publication date: March 31st 201

Similarity solutions of boundary layer flows in a channel filled by non-newtonian fluids

Similarity solutions of non-Newtonian fluids are getting much attention to researchers because of their practical importance in the field of science and engineering. Currently, most of researchers focus their work on non-Newtonian fluids over a sheet. However, only a few of them pay their attention towards the geometry of channel due to the complexity of governing equations. Therefore, this study attempts to investigate the numerical solutions of new problems of laminar incompressible Nanofluids, Casson fluids and Micropolar fluids under various fluid flow conditions. Each considered fluid involves porous channel walls, stretching or shrinking walls, and expanding or contracting walls with the influence of various physical parameters. Mathematical formulations such as the law of conservation, momentum or angular momentum, heat and mass transfer are performed on the new problems. After the mathematical formulation is developed, the governing fluid flow equations of partial differential equations are then transformed into boundary value problems (BVPs) of nonlinear ordinary differential equations (ODEs) by using the suitable similarity transformations. After converting high order BVPs into the equivalent first order system of BVPs, shootlib function in Maple 18 software is employed to obtain the similarity solutions of nonlinear ODEs. The numerical results in this study are compared with the existing solutions in literature for the purpose of validation. The results are found to be in good agreement with the existing solutions. Multiple solutions of some of the problems particularly in porous channel with expanding or contracting walls also exist for the case of strong suction. This study has successfully find the numerical solutions of the new problems for various fluid flow conditions. The results obtained from this study can serve as a theoretical reference in related fields

ADM solution for Cu/CuO –water viscoplastic nanofluid transient slip flow from a porous stretching sheet with entropy generation, convective wall temperature and radiative effects

A mathematical modelis presented for entropy generation in transient hydromagnetic flow of an electroconductive magnetic Casson (non-Newtonian) nanofluid over a porous stretching sheet in a permeable medium. The Cattaneo-Christov heat flux model is employed to simulate non-Fourier (thermal relaxation) effects. A Rosseland flux model is implemented to model radiative heat transfer. The Darcy model is employed for the porous media bulk drag effect. Momentum slip is also included to simulate non-adherence of the nanofluid at the wall. The transformed, dimensionless governing equations and boundary conditions (featuring velocity slip and convective temperature) characterizing the flow are solved with the Adomian Decomposition Method (ADM). Bejan’s entropy minimization generation method is employed. Cu-water and CuO-water nanofluids are considered. Extensive visualization of velocity, temperature and entropy generation number profiles is presented for variation in magnetic field parameter, unsteadiness parameter, Casson parameter, nanofluid volume fraction, permeability parameter, suction/injection parameter, radiative parameter, Biot number, relaxation time parameter, velocity slip parameter, Brinkman number (dissipation parameter), temperature ratio and Prandtl number. The evolution of skin friction and local Nusselt number (wall heat transfer rate) are also studied. The ADM computations are validated with simpler models from the literature. The solutions show that with elevation in volume fraction of nanoparticle and Brinkman number, the entropy generation magnitudes are increased. An increase in Darcy number also increases the skin friction and local Nusselt number. Increasing magnetic field, volume fraction, unsteadiness, thermal radiation, velocity slip, Casson parameters, Darcy and Biot numbers are all observed to boost temperatures. However, temperatures are reduced with increasing non-Fourier (thermal relaxation) parameter. Greater flow acceleration is achieved for CuO-water nanofluid compared with Cu-water nanofluid although the contrary response is computed in temperature distributions. The simulations are relevant to the high temperature manufacturing fluid dynamics of magnetic nanoliquids, smart coating systems etc