Heat transfer from a cylinder in a time-dependent cross flow at low Peclet number

1985 ◽  
Vol 28 (12) ◽  
pp. 3451 ◽  
Author(s):  
B. J. Bayly
Keyword(s):  
Heat Transfer ◽  
Peclet Number ◽  
Cross Flow ◽  
Time Dependent ◽  
Péclet Number

scholarly journals HEAT EXCHANGE IN A PLANE CHANNEL IN A TURBULENT FLOW REGIME IN THE CASE OF SMALL VALUES OF PRANDTL NUMBER ACCORDING TO DATA OF DIRECT NUMERICAL SIMULATION

2021 ◽  
Vol 56 ◽  
pp. 57-60
Author(s):  
Yurii G. Chesnokov ◽  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Prandtl Number ◽  
Direct Numerical Simulation ◽  
Transfer Process ◽  
Peclet Number ◽  
Plane Channel ◽  
Heat Transfer Process ◽  
Flat Channel ◽  
Péclet Number

Using the results obtained by the method of direct numerical simulation of the heat transfer process in a flat channel by various authors, it is shown that at small values of Prandtl number quite a few characteristics of the heat transfer process in a flat channel depend not on Reynolds and Prandtl numbers separately, but on Peclet number. Peclet number is calculated from the so-called dynamic speed

Numerical Analysis of Heat Transfer Enhancement in a Micro-Channel Due to Mechanical Stirrers

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
M. Sreejith ◽  
S. Chetan ◽  
S. N. Khaderi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Peclet Number ◽  
Periodic Case ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Fluidic Channel ◽  
Enhancement Of Heat Transfer ◽  
Péclet Number

Abstract Using two-dimensional numerical simulations of the momentum, mass, and energy conservation equations, we investigate the enhancement of heat transfer in a rectangular micro-fluidic channel. The fluid inside the channel is assumed to be stationary initially and actuated by the motion imparted by mechanical stirrers, which are attached to the bottom of the channel. Based on the direction of the oscillation of the stirrers, the boundary conditions can be classified as either no-slip (when the oscillation is perpendicular to the length of the channel) or periodic (when the oscillation is along the length of the channel). The heat transfer enhancement due to the motion of the stirrers (with respect to the stationary stirrer situation) is analyzed in terms of the Reynolds number (ranging from 0.7 to 1000) and the Peclet number (ranging from 10 to 100). We find that the heat transfer first increases and then decreases with an increase in the Reynolds number for any given Peclet number. The heat transferred is maximum at a Reynolds number of 20 for the no-slip case and at a Reynolds number of 40 for the periodic case. For a given Peclet and Reynolds number, the heat flux for the periodic case is always larger than the no-slip case. We explain the reason for these trends using time-averaged flow velocity profiles induced by the oscillation of the mechanical stirrers.

Heat Transfer From a Translating Droplet at High Peclet Numbers: Revisiting the Classic Solution of Kronig & Brink

2005 ◽  
Vol 128 (7) ◽  
pp. 648-652 ◽  
Author(s):  
Douglas L. Oliver ◽  
Adham W. Souccar
Keyword(s):  
Heat Transfer ◽  
Peclet Number ◽  
Numerical Techniques ◽  
Droplet Transfer ◽  
Péclet Number ◽  
Classic Solution ◽  
Droplet Phase

More than five decades ago Kronig and Brink published a classic analysis of transport from translating droplets. Their analysis assumed that the bulk of the resistance to transfer was in the droplet phase. It considered the limiting solution as the Peclet number became very large. Their work has been cited in many subsequent studies of droplet transfer. The present work revisits their solution using numerical techniques that were not then available. It was found that only the first mode of their solution is mathematically accurate. Hence, their solution is accurate only at large times.

Nanofluid Impinging Jets in Porous Media

2016 ◽  
Vol 7 ◽  
pp. 84-113
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
D. Ricci
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Rayleigh Number ◽  
Peclet Number ◽  
Pure Water ◽  
Particle Diameter ◽  
Target Surface ◽  
Impinging Jets ◽  
Local Thermal Equilibrium ◽  
Péclet Number

Heat transfer enhancement technology has the aim to develop more efficient systems as demanded in many applications in the fields of automotive, aerospace, electronics and process industry. A possible solution to obtain efficient cooling systems is represented by the use of confined impinging jets. Moreover, the introduction of nanoparticles in the working fluids can be considered in order to improve the thermal performances of the base fluids. In this paper a numerical investigation on mixed convection in confined slot jets impinging on a porous media by considering pure water or Al2O3/water based nanofluids is described. A two-dimensional model is developed and different Peclet numbers and Rayleigh numbers were considered. The particle volume concentrations ranged from 0% to 4% and the particle diameter is equal to 30 nm. The target surface is heated by a constant temperature value, calculated according to the value of Rayleigh number. The distance of the target surface is five times greater than the slot jet width. A single-phase model approach has been adopted in order to describe the nanofluid behaviour while the hypothesis of non-local thermal equilibrium is considered in order to simulate the behaviour in the porous media which is featured by a porosity value of 0.87. The aim consists into study the thermal and fluid-dynamic behaviour of the system. Results show increasing values of the convective heat transfer coefficients for increasing values of Peclet number and particle concentration. This behaviour is more evident at low Peclet number values and Rayleigh number ones.

Accurate Boundary Element Solutions for Highly Convective Unsteady Heat Flows

2005 ◽  
Vol 127 (10) ◽  
pp. 1138-1150 ◽  
Author(s):  
M. M. Grigoriev ◽  
G. F. Dargush
Keyword(s):  
Boundary Element ◽  
Peclet Number ◽  
Iterative Solvers ◽  
Heat Diffusion ◽  
Time Dependent ◽  
Time Interval ◽  
Spatial Integration ◽  
Péclet Number ◽  
Heat Flows ◽  
Analytic Integration

Several recently developed boundary element formulations for time-dependent convective heat diffusion appear to provide very efficient computational tools for transient linear heat flows. More importantly, these new approaches hold much promise for the numerical solution of related nonlinear problems, e.g., Navier–Stokes flows. However, the robustness of these methods has not been examined, particularly for high Peclet number regimes. Here, we focus on these regimes for two-dimensional problems and develop the necessary temporal and spatial integration strategies. The algorithm takes advantage of the nature of the time-dependent convective kernels, and combines analytic integration over the singular portion of the time interval with numerical integration over the remaining nonsingular portion. Furthermore, the character of the kernels lets us define an influence domain and then localize the surface and volume integrations only within this domain. We show that the localization of the convective kernels becomes more prominent as the Peclet number of the flow increases. This leads to increasing sparsity and in most cases improved conditioning of the global matrix. Thus, iterative solvers become the primary choice. We consider two representative example problems of heat propagation, and perform numerical investigations of the accuracy and stability of the proposed higher-order boundary element formulations for Peclet numbers up to 105.

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