Showing papers on "Nusselt number published in 2010"
TL;DR: In this article, a similarity solution is presented which depends on the Prandtl number Pr, Lewis number Le, Brownian motion number Nb and thermophoresis number Nt.
1,565 citations
TL;DR: In this paper, the authors studied the natural convective boundary-layer flow of a nanofluid past a vertical plate and found that the reduced Nusselt number is a decreasing function of each of Nr, Nb and Nt.
1,218 citations
TL;DR: In this paper, the heat transfer coefficient and friction factor of the TiO 2 -water nanofluids flowing in a horizontal double tube counter-flow heat exchanger under turbulent flow conditions, experimentally.
623 citations
TL;DR: In this paper, Wang et al. used the Poincare section to analyze the fluid mixing in three-dimensional wavy microchannels with rectangular cross-sections and found that the quantity and the location of the vortices may change along the flow direction, leading to chaotic advection.
423 citations
TL;DR: In this paper, the steady boundary-layer flow of a nanofluid past a moving semi-infinite flat plate in a uniform free stream is investigated, where the plate is assumed to move in the same or opposite directions to the free stream.
362 citations
TL;DR: In this paper, a three-dimensional laminar flow and heat transfer with two different nanofluids, Al 2 O 3 and CuO, in an ethylene glycol and water mixture circulating through the flat tubes of an automobile radiator have been numerically studied to evaluate their superiority over the base fluid.
343 citations
TL;DR: In this paper, a two-phase Eulerian model has been implemented for the first time to study a forced convective of a nanofluid that consists of water and Al2O3 in horizontal tubes.
340 citations
TL;DR: In this paper, the effect of multiple v-rib roughness on heat transfer coefficient and friction factor in an artificially roughened solar air heater duct was investigated, and correlations for Nusselt number and friction factors in terms of roughness geometry and flow parameters were developed.
334 citations
TL;DR: In this paper, the authors derived a lower bound estimate for the minimum number of computational mesh nodes required to conduct accurate numerical simulations of moderately high (BL-dominated) turbulent Rayleigh-Benard (RB) convection, in the thermal and kinetic boundary layer (BL) close to the bottom and top plates.
Abstract: Results on the Prandtl–Blasius-type kinetic and thermal boundary layer (BL) thicknesses in turbulent Rayleigh–Benard (RB) convection in a broad range of Prandtl numbers are presented. By solving the laminar Prandtl–Blasius BL equations, we calculate the ratio between the thermal and kinetic BL thicknesses, which depends on the Prandtl number only. It is approximated as for and as for , with . Comparison of the Prandtl–Blasius velocity BL thickness with that evaluated in the direct numerical simulations by Stevens et al (2010 J. Fluid Mech. 643 495) shows very good agreement between them. Based on the Prandtl–Blasius-type considerations, we derive a lower-bound estimate for the minimum number of computational mesh nodes required to conduct accurate numerical simulations of moderately high (BL-dominated) turbulent RB convection, in the thermal and kinetic BLs close to the bottom and top plates. It is shown that the number of required nodes within each BL depends on and and grows with the Rayleigh number not slower than . This estimate is in excellent agreement with empirical results, which were based on the convergence of the Nusselt number in numerical simulations
321 citations
320 citations
TL;DR: In this article, a numerical approach has been used to study the heat and mass transfer from a vertical plate embedded in a porous medium experiencing a first-order chemical reaction and exposed to a transverse magnetic field.
TL;DR: In this article, the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior.
Abstract: This paper deals with the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior. Measurement of convective heat fluxes must be performed by means of a thermal sensor, where temperatures have to be measured with proper transducers. By correctly choosing the thermal sensor, IR thermography can be successfully exploited to resolve convective heat flux distributions with both steady and transient techniques. When comparing it to standard transducers, the IR camera appears very valuable because it is non-intrusive, it has a high sensitivity (down to 20 mK), it has a low response time (down to 20 μs), it is fully two dimensional (from 80 k up to 1 M pixels, at 50 Hz) and, therefore, it allows for better evaluation of errors due to tangential conduction within the sensor. This paper analyses the capability of IR thermography to perform convective heat transfer measurements and surface visualizations in complex fluid flows. In particular, it includes the following: the necessary radiation theory background, a review of the main IR camera features, a description of the pertinent heat flux sensors, an analysis of the IR image processing methods and a report on some applications to complex fluid flows, ranging from natural convection to hypersonic regime.
TL;DR: In this article, the results from direct numerical simulation (DNS) for three-dimensional Rayleigh-Benard convection in a cylindrical cell of aspect ratio 1/2 and Prandtl number Pr=0.7 are presented.
Abstract: Results from direct numerical simulation (DNS) for three-dimensional Rayleigh–Benard convection in a cylindrical cell of aspect ratio 1/2 and Prandtl number Pr=0.7 are presented. They span five decades of Rayleigh number Ra from 2 × 106 to 2 × 1011. The results are in good agreement with the experimental data of Niemela et al. (Nature, vol. 404, 2000, p. 837). Previous DNS results from Amati et al. (Phys. Fluids, vol. 17, 2005, paper no. 121701) showed a heat transfer that was up to 30% higher than the experimental values. The simulations presented in this paper are performed with a much higher resolution to properly resolve the plume dynamics. We find that in under-resolved simulations the hot (cold) plumes travel further from the bottom (top) plate than in the better-resolved ones, because of insufficient thermal dissipation mainly close to the sidewall (where the grid cells are largest), and therefore the Nusselt number in under-resolved simulations is overestimated. Furthermore, we compare the best resolved thermal boundary layer profile with the Prandtl–Blasius profile. We find that the boundary layer profile is closer to the Prandtl–Blasius profile at the cylinder axis than close to the sidewall, because of rising plumes close to the sidewall
TL;DR: In this paper, the influence of the oblique delta-winglet twisted tape (O-DWT) arrangement on thermal performance was investigated in a uniform wall heat flux tube.
TL;DR: In this article, the influence of twin-counter/co-twisted tapes on heat transfer rate (Nu), friction factor (f) and thermal enhancement index (η) were experimentally determined.
TL;DR: In this article, a numerical study is conducted to investigate the transport mechanism of mixed convection in a lid-driven enclosure filled with nanofluids, where two vertical walls of the enclosure are insulated while the horizontal walls are kept at constant temperatures with the top surface moving at a constant speed.
TL;DR: In this article, a laminar flow convective heat transfer and friction factor characteristics of Al2O3/water nanofluid flowing through a uniformly heated horizontal tube with and without wire coil inserts is presented.
TL;DR: The variation of local Nusselt number along the length and circumference at the wall of a helical pipe is brought out and a correlation to predict the local values of Nusselst number as a function of angular location of the point is presented.
TL;DR: In this article, experimental heat transfer data are obtained for single phase flow (water-to-water) configurations in a commercial plate heat exchanger for symmetric 30°/30°, 60°/60°, and mixed 30° /60° chevron angle plates.
TL;DR: In this paper, a numerical study of the effect of the magnetic field with inclined angle on the flow and heat transfer rate of liquid gallium in a square cavity is presented, where the penalty finite element method with bi-quadratic rectangular elements is used to solve the non-dimensional governing equations.
TL;DR: In this paper, heat transfer enhancement in a square cavity subject to different side wall temperatures using water/SiO 2 nanofluid has been investigated in the presence of an experimental setup.
TL;DR: In this article, the authors focused on the study of natural convection heat transfer characteristics in a differentially-heated enclosure filled with a CuOeEGeWater nanofluid for different published variable thermal conductivity and variable viscosity models.
TL;DR: In this paper, the impingement heat transfer characteristics of a synthetic jet are studied and the behavior of the average heat transfer coefficient of the impinged heated surface with variation in the axial distance between the jet and the heated surface is measured.
TL;DR: In this paper, a mathematical model is analyzed in order to study the heat and mass transfer characteristics in mixed convection boundary layer flow about a linearly stretching vertical surface in a porous medium filled with a viscoelastic fluid, by taking into account the diffusion-thermo (Dufour) and thermal diffusion (Soret) effects.
TL;DR: In this paper, the authors present an experimental study of turbulent heat transfer and flow friction characteristics in a circular tube equipped with two types of twisted tapes: (1) typical twisted tapes and (2) alternate clockwise and counterclockwise twisted tapes (C-CC twisted tapes).
TL;DR: In this article, the effect of twisted tape with serrated-edge insert on heat transfer and pressure loss behaviors in a constant heat-fluxed tube was investigated, and the results showed that the heat transfer rate in terms of Nusselt number, Nu increases with the rise in the depth ratio but decreases with raising the width ratio.
TL;DR: In this paper, the authors evaluated the forced convective heat transfer at the surfaces of a cube immersed in a turbulent boundary layer, for applications in atmospheric boundary layer (ABL) wind flow around surface-mounted obstacles such as buildings.
TL;DR: In this article, a coiled wire inserted tube in turbulent flow regime was experimentally investigated and the results revealed that the best operating regime of all wire inserts is detected at low Reynolds number, leading to more compact heat exchanger.
TL;DR: In this paper, the authors investigated the magnetohydrodynamic (MHD) two-dimensional flow with heat and mass transfer over a stretching sheet in the presence of Joule heating and thermophoresis.
TL;DR: In this paper, the effects of peripherally-cut twisted tape insert on heat transfer, friction loss and thermal performance factor characteristics in a round tube were investigated, and the experimental results revealed that both heat transfer rate and friction factor in the tube equipped with the peripherally cut twisted tapes were significantly higher than those of the tube fitted with the typical twisted tape and plain tube, especially in the laminar flow regime.