Analytical Solution for Unsteady Heat Transfer in a Pipe

1988 ◽  
Vol 110 (4a) ◽  
pp. 850-854 ◽  
Author(s):  
J. Sucec
Keyword(s):  
Heat Transfer ◽  
Pipe Wall ◽  
Ambient Medium ◽  
Sudden Change ◽  
Thermal Capacity ◽  
Surface Heat ◽  
Unsteady Heat Transfer ◽  
Adequate Accuracy ◽  
Steady Solutions ◽  
Temperature Surface

Under consideration is transient, convective heat transfer to a fluid flow within a pipe due to a sudden change in the temperature of the ambient medium outside the pipe. A solution is developed by the Laplace transformation, for the fastest portion of the transient, which gives the pipe wall temperature, surface heat flux, and fluid bulk mean temperature. These analytical results are compared with available finite difference results and with quasi-steady solutions. A criterion is developed that indicates when the zero thermal capacity wall solution can be used with adequate accuracy.

Unsteady Stagnation Point Heat Transfer with Blowing or Suction

1981 ◽  
Vol 103 (3) ◽  
pp. 448-452 ◽  
Author(s):  
Takao Sano
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Prandtl Number ◽  
Asymptotic Solution ◽  
Stagnation Point ◽  
Wall Temperature ◽  
Step Change ◽  
Surface Heat ◽  
Unsteady Heat Transfer ◽  
Prandtl Numbers

The effects of blowing and suction on unsteady heat transfer at a stagnation point due to a step change in wall temperature are examined. Two asymptotic solutions for the temperature field at large and small Prandtl numbers are presented. It is shown that the asymptotic solution for large Prandtl number gives sufficiently accurate results for the surface heat transfer even for the moderate values of Prandtl number if Euler transformation is applied to the series.

Improved Convective Heat Transfer in a Fluid with Artificially Modified Turbulence

1973 ◽  
Vol 15 (1) ◽  
pp. 61-72 ◽  
Author(s):  
R. G. Boothroyd ◽  
H. Haque
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Fine Particles ◽  
Pipe Wall ◽  
Vortex Motion ◽  
Thermal Capacity ◽  
Fluid Mixing ◽  
Wall Heat Transfer ◽  
Erosion Effect ◽  
Large Scale Vortex

Although a flowing gas loaded with fine particles can give a considerably higher wall heat transfer coefficient compared with the flow of gas alone, earlier studies have shown that this improvement is less than might be realized due to dampening of turbulence near the heat transfer surface by the particles. This paper reports an investigation into off-setting the effect by adding fine fibres to a suspension of 5–40 μm particles in air flowing in tubes of 1, 2 and 3 in diameter. The results indicate that in most situations a fibre-particle suspension is likely to be superior as a coolant compared with a suspension of particles flowing alone. The purpose of the fibres is (1) to induce a large-scale vortex motion near the pipe wall where normal turbulent fluid mixing is inadequate; (2) to promote controlled residence time of wall-contact of particles of high thermal conductivity and high thermal capacity and (3) to keep heat transfer surfaces clean with the minimum erosion effect.

Stagnation-Point Heat Transfer: The Effect of the First Damko¨hler Similarity Parameter

1972 ◽  
Vol 94 (4) ◽  
pp. 410-414 ◽  
Author(s):  
A. Alkidas ◽  
P. Durbetaki
Keyword(s):  
Heat Transfer ◽  
Blunt Body ◽  
Combustible Mixture ◽  
Surface Heat ◽  
Arrhenius Law ◽  
Governing Equations ◽  
Similarity Parameter ◽  
Stagnation Region ◽  
Kinetics Of ◽  
Temperature Surface

The present study considers the heat interaction between a combustible mixture and a constant-temperature surface near the stagnation region of a blunt body. The steady-state governing equations have been solved numerically for the case of Le = 1. A second-order Arrhenius law is assumed to describe the chemical kinetics of the mixture. The first Damko¨hler similarity parameter is shown to critically influence the surface heat transfer. The parameter represents a measure of the convective time to the chemical time.

Unsteady heat transfer in compressible boundary layers

1965 ◽  
Vol 61 (2) ◽  
pp. 555-567 ◽  
Author(s):  
N. Riley
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Steady State ◽  
Boundary Layers ◽  
Laminar Boundary Layer ◽  
Wall Temperature ◽  
Sudden Change ◽  
General Boundary ◽  
Unsteady Heat Transfer ◽  
Compressible Boundary Layers

AbstractThe flow following a sudden change in the wall temperature in a laminar boundary layer, which was originally incompressible and steady, is studied. The temperature to which the wall is raised is supposed large enough to bring about density changes in the boundary layer. The details of the flow immediately after the change in wall temperature are analysed for a general boundary layer. Two specific examples are considered and for these the manner in which the new steady state is achieved is also investigated.

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