Thermal Transport From a Heated Moving Surface

1986 ◽  
Vol 108 (4) ◽  
pp. 728-733 ◽  
Author(s):  
M. V. Karwe ◽  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Thermal Transport ◽  
Conjugate Problem ◽  
Moving Surface ◽  
Practical Applications ◽  
Thermal Fields ◽  
Heated Body ◽  
Wide Range ◽  
Surface Heat Transfer Coefficient ◽  
Transfer Mechanisms

A numerical and analytical study of the transport process arising due to the movement of a continuous heated body has been carried out. The relevant heat transfer mechanisms are of interest in a wide variety of practical applications, such as continuous casting, extrusion, hot rolling, and crystal growing. The conjugate problem, which involves a coupling between the heat transfer in the moving material and the transport in the fluid, is considered. The thermal fields in the material and in the fluid are computed. The temperature level is found to decay gradually with distance along the moving material, as expected. Results are obtained for a wide range of governing parameters, particularly the Peclet number Pe and the parameter R, which depends on the properties of the fluid and the material. The results obtained are compared with those for the idealized cases of an assumed surface heat transfer coefficient and of a moving isothermal surface. Of particular interest were the nature of the flow generated by the moving surface and the resulting thermal transport. The results obtained are also considered in terms of the underlying physical processes in the problem.

scholarly journals Cooling Performance of Arrays of Vibrating Cantilevers

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Mark Kimber ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Vibration Amplitude ◽  
Past Research ◽  
Resonant Mode ◽  
Operating Conditions ◽  
Infrared Thermal Imaging ◽  
Practical Applications ◽  
Wide Range ◽  
Piezoelectric Fans

Piezoelectric fans are vibrating cantilevers actuated by a piezoelectric material and can provide heat transfer enhancement while consuming little power. Past research has focused on feasibility and performance characterization of a single fan, while arrays of such fans, which have important practical applications, have not been widely studied. This paper investigates the heat transfer achieved using arrays of cantilevers vibrating in their first resonant mode. This is accomplished by determining the local convection coefficients due to the two piezoelectric fans mounted near a constant heat flux surface using infrared thermal imaging. The heat transfer performance is quantified over a wide range of operating conditions, including vibration amplitude (7.5–10 mm), distance from heat source (0.01–2 times the fan amplitude), and pitch between fans (0.5–4 times the amplitude). The convection patterns observed are strongly dependent on the fan pitch, with the behavior resembling a single fan for small fan pitch and two isolated fans at a large pitch. The area-averaged thermal performance of the fan array is superior to that of a single fan, and correlations are developed to describe this enhancement in terms of the governing parameters. The best thermal performance is obtained when the fan pitch is 1.5 times its vibration amplitude.

Finite Element Simulation of Magnetohydrodynamic Mixed Convection in a Double-Lid Driven Enclosure With a Square Heat-Generating Block

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
M. M. Rahman ◽  
M. M. Billah ◽  
N. A. Rahim ◽  
R. Saidur ◽  
M. Hasanuzzaman
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Mixed Convection ◽  
Convection Flow ◽  
Weighted Residuals ◽  
Thermal Fields ◽  
Flow And Heat Transfer ◽  
Element Simulation ◽  
Wide Range ◽  
Element Technique

Magnetohydrodynamic (MHD) mixed-convection flow and heat transfer characteristics inside a square double-lid driven enclosure have been investigated in this study. A heat-generating solid square block is positioned at the centre of the enclosure. Both of its vertical walls are lid-driven and have temperature Tc and uniform velocity V0. In addition, the top and bottom surfaces are kept adiabatic. Discretization of governing equations is achieved using finite element technique based on Galerkin weighted residuals. The computation is carried out for a wide range of pertinent parameters such as Hartmann number, heat-generating parameter, and Richardson number. Numerical results are reported for the effects of aforesaid parameters on the streamline and isotherm contours. In addition, the heat transfer rate in terms of the average Nusselt number and temperature of the fluid as well as block center are presented for the mentioned parametric values. The obtained results show that the flow and thermal fields are influenced by the above-mentioned parameters.

scholarly journals Simulation of Natural Convection Heat Transfer in a 2-D Trapezoidal Enclosure

2019 ◽  
Vol 16 (4) ◽  
pp. 7375-7390 ◽  
Author(s):  
K. Venkatadri ◽  
S. Abdul Gaffar ◽  
Ramachandra Prasad V. ◽  
B. Md. Hidayathulla Khan ◽  
O. Anwar Beg
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Prandtl Number ◽  
Vertical Wall ◽  
Convection Heat Transfer ◽  
Side Wall ◽  
Practical Applications ◽  
Wide Range ◽  
Trapezoidal Enclosure

Natural convection within trapezoidal enclosures finds significant practical applications. The natural convection flows play a prominent role in the transport of energy in energyrelated applications, in case of proper design of enclosures to achieve higher heat transfer rates. In the present study, a two-dimensional cavity with adiabatic right side wall is studied. The left side vertical wall is maintained at the constant hot temperature and the top slat wall is maintained at cold temperature. The dimensionless governing partial differential equations for vorticity-stream function are solved using the finite difference method with incremental time steps. The parametric study involves a wide range of Rayleigh number, Ra, 103 ≤ Ra ≤ 105 and Prandtl number (Pr = 0.025, 0.71 and 10). The fluid flow within the enclosure is formed with different shapes for different Pr values. The flow rate is increased by enhancing the Rayleigh number (Ra = 104 ). The numerical results are validated with previous results. The governing parameters in the present article, namely Rayleigh number and Prandtl number on flow patterns, isotherms as well as local Nusselt number are reported. 

Boiling Heat Transfer for Freon R21 in Rectangular Minichannel

2006 ◽  
Author(s):  
V. V. Kuznetsov ◽  
A. S. Shamirzaev
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Patterns ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Modified Model ◽  
Wide Range ◽  
Nucleation Boiling ◽  
The Heat Transfer Coefficient ◽  
Transfer Mechanisms

In this paper we study the boiling heat transfer of upward flow of R21 in a vertical mini-channel with size 1.6×6.3 mm. The heat transfer coefficient was measured as a function of heat flux for a wide range of vapor quality and for two levels of mass flow rate, G = 215 kg/m2s and G = 50 kg/m2s. The temperature dispersions over channel perimeter and in time were calculated. Different heat transfer mechanisms were revealed for different flow patterns. We distinguish the dominant nucleation boiling and the joint mode of nucleation boiling and convective evaporation. We also found the modes when the evaporation of thin liquid films makes the main contribution to heat transfer. The modified model of Liu and Winterton describes the experimental data for the flow patterns when the nucleation boiling and convective transfer make the most contribution to the heat transfer.

scholarly journals Differentiated heated lid driven cavity interacting with tube: A lattice Boltzmann study

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 89-104 ◽  
Author(s):  
Rachid Bennacer ◽  
Marcelo Reggio ◽  
Nicolas Pellerin ◽  
Xiaoyan Ma
Keyword(s):  
Heat Transfer ◽  
Lattice Boltzmann ◽  
Vertical Wall ◽  
Distribution Model ◽  
Heat Conducting ◽  
Driven Cavity ◽  
Thermal Fields ◽  
Wide Range ◽  
Multiple Relaxation Time ◽  
The Right

The multiple-relaxation-time (MRT) lattice-Boltzmann method is implemented to investigate combined natural and forced convection occurring in a two-dimensional square cavity. The top wall slides to the right at constant speed, while the other three remain stationary. The solution is performed for a left vertical wall at a constant temperature, which is higher than of the right wall. This yields a ?cooperating? case, in which dynamic and buoyancy forces are added together. The enclosure is filled with air and contains a heat conducting circular cylinder, which is placed at various positions. The double distribution model used in lattice Boltzmann methods has been adopted to simulate the hydrodynamic and thermal fields, with the D2Q9 and D2Q5 lattices selected to perform the corresponding computations. Simulations have been conducted over a wide range of Rayleigh (Ra) and Reynolds (Re) numbers, and the features of dynamic and thermal fields are presented for the spectra of this mixed convection phenomenon. The flow and heat transfer characteristics of the cylinder position are described and analyzed in terms of the average Nusselt number (Nu). The computed results show the influence of the cylinder on the corresponding heat transfer in the enclosure. It has been found that the power (i.e. shear stress) needed to lid the upper surface will depend on the governing parameters.

Shape Optimization With Isoperimetric Constraints for Isothermal Pipes Embedded in an Insulated Slab

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Theodoros Leontiou ◽  
Marios M. Fyrillas
Keyword(s):  
Heat Transfer ◽  
Heat Conduction Problem ◽  
Classical Problem ◽  
Lower Surface ◽  
Optimum Shape ◽  
Practical Applications ◽  
Wide Range ◽  
Geometrical Constraints ◽  
Isoperimetric Constraint ◽  
Isoperimetric Constraints

In this paper, we consider the heat transfer from a periodic array of isothermal pipes embedded in a rectangular slab. The upper surface of the slab is sustained at a constant temperature while the lower surface is insulated. The particular configuration is a classical heat conduction problem with a wide range of practical applications. We consider both the classical problem, i.e., estimating the shape factor of a given configuration, and the inverse problem, i.e., calculating the optimum shape that maximizes the heat transfer rate associated with a set of geometrical constraints. The way the present formulation differs from previous formulations is that: (i) the array of pipes does not have to be placed at the midsection of the slab and (ii) we have included an isoperimetric constraint (not changing in perimeter) through which we can control the deviation of the optimum shape from that of a circle. This is very important considering that most of the applications deal with buried pipes and a realistic shape is a practical necessity. The isoperimetric constraint is included through the isoperimetric quotient (IQ), which is the ratio between the area and the perimeter of a closed curve.

Numerical Simulation of the Transient Temperature Field during Gas Quenching

2013 ◽  
Vol 683 ◽  
pp. 275-279
Author(s):  
Zi Liang Li ◽  
Mei Hong Liu
Keyword(s):  
Heat Transfer ◽  
Phase Transformation ◽  
Temperature Field ◽  
Transient Temperature ◽  
Transfer Phase ◽  
Practical Applications ◽  
Transient Temperature Field ◽  
Surface Heat Transfer Coefficient ◽  
Gas Quenching ◽  
Nonlinear Surface

Based on the theory of heat transfer, phase transformation and thermal non-elasticity, a nonlinear coupling heat-conduction equation considering phase transformation, nonlinear surface heat transfer coefficient and variable physical properties during gas quenching is proposed and solved by means of Finite Element Method (F.E.M). The transient temperature field is obtained and the influencing factors are analyzed and discussed. It might be valuable for some practical applications and for the development of theory.

Modeling and Design of Micro Groove Falling Film Evaporators

2004 ◽  
Author(s):  
Shohei Hasebe ◽  
Naoki Shikazono ◽  
Nobuhide Kasagi
Keyword(s):  
Heat Transfer ◽  
Gravitational Force ◽  
Gravitational Effect ◽  
Pressure Effects ◽  
Falling Film ◽  
Thermal Fields ◽  
Runge Kutta Method ◽  
Wide Range ◽  
Region Model ◽  
Study Heat Transfer

In the present study, heat transfer in a falling film micro groove evaporator has been simulated by an analytical model. The flow and thermal fields were divided in two regions, i.e. macroscopic flow inside the groove and the microscopic flow where intensive evaporation takes place at the thin film interline region. For the micro region model, pressure in the liquid film was expressed as a sum of surface tension and disjoining pressure effects. The film thickness profile was obtained by solving the 4th order differential equation by Runge-Kutta method. Then, this micro region model was combined with the macro region model. Macro region model solves one dimensional bulk flow inside the groove with gravitational effect taken into account. Constant curvature of the liquid vapor surface was assumed for the macro flow. It is shown that the gravitational force is essential for providing the liquid to wide range of heat transfer area. Thus, diverging branch evaporator is investigated. It is demonstrated that this concept has large potentiality for improving the performance of the micro groove falling film evaporator.

Coupling Between Heat and Momentum Transfer Mechanisms for Drag-Reducing Polymer and Surfactant Solutions

1999 ◽  
Vol 121 (4) ◽  
pp. 796-802 ◽  
Author(s):  
G. Aguilar ◽  
K. Gasljevic ◽  
E. F. Matthys
Keyword(s):  
Heat Transfer ◽  
Momentum Transfer ◽  
Direct Coupling ◽  
Surfactant Solutions ◽  
Wide Range ◽  
Momentum And Heat Transfer ◽  
Local Measurements ◽  
Friction Measurements ◽  
Heat And Momentum Transfer ◽  
Transfer Mechanisms

Drag-reducing solutions exhibit simultaneous friction and heat transfer reductions, yet it has been widely believed that there is no direct coupling between the two. In this work, we have conducted a study to re-examine this issue, using measurements of friction and heat transfer over a wide range of flow conditions from onset to asymptotic, various pipe diameters, and several polymer and surfactant solutions. Contrary to some earlier suggestions, our tests show that no decoupling of the momentum and heat transfer mechanisms was seen at the onset of drag reduction, nor upon departure from the asymptotes, but rather that the friction and heat transfer reductions change simultaneously in those regions. For asymptotic surfactant and polymer solutions, the ratio of heat transfer and drag reductions was seen to be constant over a large range of Reynolds numbers, if modified definitions of the reduction parameters are used. In the nonasymptotic region, however, the ratio of heat transfer to drag reductions is higher and is a function of the reduction level, but is approximately the same for polymer and surfactant solutions. This variation is consistent with the concept of a direct coupling through a nonunity constant Prt, as also suggested by our local measurements of temperature and velocity profiles. We also saw that our diameter scaling technique for friction applies equally well to heat transfer. These findings allow us to predict directly the heat transfer from friction measurements or vice versa for these drag-reducing fluids, and also suggest that a strong coupling exists between the heat and momentum transfer mechanisms.

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