Heat transfer in laminar flow. III. Application of the thermal boundary layer

1972 ◽  
Vol 37 (9) ◽  
pp. 2898-2906 ◽  
Author(s):  
K. Wichterle
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Laminar Flow ◽  
Thermal Boundary Layer

Heat Transfer in the Laminar Boundary Layer Over an Impulsively Started Flat Plate

1975 ◽  
Vol 97 (3) ◽  
pp. 482-484 ◽  
Author(s):  
C. B. Watkins
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Laminar Flow ◽  
Flat Plate ◽  
Constant Temperature ◽  
Laminar Boundary Layer ◽  
Temperature Difference ◽  
Thermal Boundary Layer ◽  
Numerical Solutions ◽  
Prandtl Numbers

Numerical solutions are described for the unsteady thermal boundary layer in incompressible laminar flow over a semi-infinite flat plate set impulsively into motion, with the simultaneous imposition of a constant temperature difference between the plate and the fluid. Results are presented for several Prandtl numbers.

Effect of Nanofluid on Heat Transfer Enhancement for Mixed Convection Flow Over a Corrugated Surface

2020 ◽  
Vol 45 (4) ◽  
pp. 373-383
Author(s):  
Nepal Chandra Roy ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Local Nusselt Number ◽  
Richardson Number ◽  
Thermal Boundary Layer ◽  
Volume Fraction ◽  
Convection Flow ◽  
Mixed Convection Flow

AbstractA mathematical model for mixed convection flow of a nanofluid along a vertical wavy surface has been studied. Numerical results reveal the effects of the volume fraction of nanoparticles, the axial distribution, the Richardson number, and the amplitude/wavelength ratio on the heat transfer of Al2O3-water nanofluid. By increasing the volume fraction of nanoparticles, the local Nusselt number and the thermal boundary layer increases significantly. In case of \mathrm{Ri}=1.0, the inclusion of 2 % and 5 % nanoparticles in the pure fluid augments the local Nusselt number, measured at the axial position 6.0, by 6.6 % and 16.3 % for a flat plate and by 5.9 % and 14.5 %, and 5.4 % and 13.3 % for the wavy surfaces with an amplitude/wavelength ratio of 0.1 and 0.2, respectively. However, when the Richardson number is increased, the local Nusselt number is found to increase but the thermal boundary layer decreases. For small values of the amplitude/wavelength ratio, the two harmonics pattern of the energy field cannot be detected by the local Nusselt number curve, however the isotherms clearly demonstrate this characteristic. The pressure leads to the first harmonic, and the buoyancy, diffusion, and inertia forces produce the second harmonic.

Vortex-Induced Vibration for Heat Transfer Enhancement

2014 ◽  
Author(s):  
Junxiang Shi ◽  
Steven R. Schafer ◽  
Chung-Lung (C. L. ) Chen
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Enhancement ◽  
Natural Frequency ◽  
Vortex Shedding ◽  
Pressure Loss ◽  
Thermal Boundary Layer ◽  
Transfer Enhancement ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

A passive, self-agitating method which takes advantage of vortex-induced vibration (VIV) is presented to disrupt the thermal boundary layer and thereby enhance the convective heat transfer performance of a channel. A flexible cylinder is placed at centerline of a channel. The vortex shedding due to the presence of the cylinder generates a periodic lift force and the consequent vibration of the cylinder. The fluid-structure-interaction (FSI) due to the vibration strengthens the disruption of the thermal boundary layer by reinforcing vortex interaction with the walls, and improves the mixing process. This novel concept is demonstrated by a three-dimensional modeling study in different channels. The fluid dynamics and thermal performance are discussed in terms of the vortex dynamics, disruption of the thermal boundary layer, local and average Nusselt numbers (Nu), and pressure loss. At different conditions (Reynolds numbers, channel geometries, material properties), the channel with the VIV is seen to significantly increase the convective heat transfer coefficient. When the Reynolds number is 168, the channel with the VIV improves the average Nu by 234.8% and 51.4% in comparison with a clean channel and a channel with a stationary cylinder, respectively. The cylinder with the natural frequency close to the vortex shedding frequency is proved to have the maximum heat transfer enhancement. When the natural frequency is different from the vortex shedding frequency, the lower natural frequency shows a higher heat transfer rate and lower pressure loss than the larger one.

Heat Transfer in a Magnetohydrodynamic Boundary Layer Flow of a Non-Newtonian Casson Fluid Over an Exponentially Stretching Magnetized Surface

2021 ◽  
Vol 10 (2) ◽  
pp. 172-185
Author(s):  
Golbert Aloliga ◽  
Yakubu Ibrahim Seini ◽  
Rabiu Musah
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Thermal Boundary Layer ◽  
Stretching Sheet ◽  
Casson Fluid ◽  
Heat Transfer Characteristics ◽  
Layer Flow ◽  
Exponentially Stretching ◽  
Concentration Equation

In this current paper, an investigation has been conducted on the magnetohydrodynamic boundary layer flow of non-Newtonian Casson fluids on magnetized sheet with an exponentially stretching sheet. The similarity approach has been used to transform the governing models for Casson fluid to ordinary differential equations. We presented numerical results for momentum, energy and concentration equation parameters. Effects of the magnetized sheet and varying all the emerged parameters on the flow of Casson fluid with respect to the friction between the fluid and the surface, temperature and concentration are presented in tables. As a result of the induced magnetization of the sheet, the thickness of the thermal boundary layer has been enhanced. This behaviour brings a considerable reduction to the heat transfer. The induced magnetized sheet has a similar influence on the skin friction, Nusselt number and the Sherwood number. We however proposed incorporation of magnetized surfaces in MHD flows for controlling the flow rate of the fluid and heat transfer characteristics.

On the Momentum and Thermal Structures of Turbulent Spots in a Favorable Pressure Gradient

2005 ◽  
Vol 128 (4) ◽  
pp. 689-698 ◽  
Author(s):  
T. P. Chong ◽  
S. Zhong
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Gradient ◽  
Velocity Component ◽  
Thermal Boundary Layer ◽  
Temperature Fluctuations ◽  
Turbulent Spots ◽  
Zone Length ◽  
Favorable Pressure Gradient ◽  
The Difference

This paper represents the results from an experimental investigation of the flow physics behind the difference in the transition zone length indicated by the momentum boundary layer and thermal boundary layer parameters observed on the suction surfaces of gas turbine blades. The experiments were carried out on turbulent spots created artificially in an otherwise laminar boundary layer developing over a heated flat plate in a zero pressure gradient and a favorable pressure gradient. A specially designed miniature triple wire probe was used to measure the streamwise velocity component U, transverse velocity component V and temperature T simultaneously during the passage of the spots. In this paper, the general characteristics of the ensemble-averaged velocity and temperature perturbations, rms fluctuations, and the second moment turbulent quantities are discussed and the influence of favorable pressure gradient on these parameters is examined. When a favorable pressure gradient is present, unlike in the velocity boundary layer where significant velocity fluctuations and Reynolds shear stress occur both on the plane of symmetry and the spanwise periphery, high temperature fluctuations (and turbulent heat fluxes) are confined in the plane of symmetry. The difference in the levels of velocity/temperature fluctuations at these two locations gives an indication of the effectiveness of momentum/heat transfer across the span of the spots. The results of this study indicate that the heat transfer within a spot is inhibited more than that of the momentum transfer at the presence of a favorable pressure gradient. This phenomenon is expected to slow down the development of a transitional thermal boundary layer, leading to a longer transitional zone length indicated by the heat transfer parameters as reported in the literature.

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