The Free Convection of Heat from a Vertical Plate to Several Non-Newtonian “Pseudoplastic” Fluids

1972 ◽  
Vol 94 (1) ◽  
pp. 64-72 ◽  
Author(s):  
J. D. Dale ◽  
A. F. Emery
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Power Law ◽  
Vertical Plate ◽  
Numerical Solutions ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Minor Importance ◽  
Large Tank ◽  
Pseudoplastic Fluids

The local heat transfer, temperature, and velocity profiles were measured and numerically predicted for the free convection of heat from a vertical constant flux plate to several concentrations of carboxymethylcellulose (CMC) and carboxypolymethylene (Carbopol) powders in water. The fluids were found to have the thermal properties of water and in the shear stress range of interest to follow the power law of Ostwald–de Waele with flow indices varying from 0.395 to 1.0 and with fluid consistencies of 30 to 2300 times that of water. The tests were conducted using either of two plates (12 and 24 in. high) immersed in such a large tank (3000 lb of fluid) that the viscometric properties of the fluid remained unchanged, even for the long test periods used. All fluids, including those with yield stresses and those which suffered free surface effects, were found to transfer heat which could be correlated by the generalized Newtonian correlation Nux=C(Grx*Prx*n)13n+2 which suggests that the precise velocity characteristics of the fluid are of minor importance in determining the heat transfer performance of the system. The numerical solutions, based upon the boundary layer assumptions and the power-law model, were in excellent agreement with the experimental measurements.

Effects of Microstructure on the Conjugated Mixed Forced and Free Convection-Conduction Analysis of Heat Transfer in a Vertical Plate Fin

1986 ◽  
Vol 108 (3) ◽  
pp. 580-584 ◽  
Author(s):  
Fue-Sang Lien ◽  
Cha’o-Kuang Chen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Free Convection ◽  
Transfer Coefficient ◽  
Micropolar Fluid ◽  
Vertical Plate ◽  
Numerical Solutions ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient

A conjugated convection-conduction analysis has been made for a vertical plate fin which exchanges heat with its micropolar fluid environment by mixed forced and free convection. The analysis is based on a one-dimensional model for the plate fin whereby the heat conduction equation for the fin is solved simultaneously with the conservation equations for mass, momentum, angular momentum, and energy in the micropolar fluid boundary layer adjacent to the fin. The local heat transfer coefficient is not specified in advance but is one of the results of the numerical solutions. Numerical results of the overall heat transfer rate, the local heat transfer coefficient, the local heat flux, and the fin temperature distribution for Pr = 5 are presented for various values of Δ (dimensionless material parameter), Nc (conjugated convection-conduction parameter), and Ω (buoyancy parameter).

scholarly journals Heat Transfer From a Rotating Disc

1990 ◽  
Author(s):  
G. H. Dibelius ◽  
M. Heinen
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Rotating Disc ◽  
Reynolds Analogy ◽  
Inlet Swirl ◽  
Additional Influence ◽  
Run Up ◽  
Cooling Air

The local heat transfer from a plane rotating disc enclosed in a casing has been studied experimentally. The disc of 800 mm diameter can be run up to 2000 min−1 at axial distances between disc and casing varied between 5 and 55 mm. Centrifugal or alternatively centripetal flow of cooling air at rates up to ṁ = 1 kg/s can be applied, both with or without an inlet swirl. With the disc rotating in a closed casing (ṁ = 0 kg/s) the influence of the characteristic dimensionless groups on the local heat transfer has been investigated. At a fixed radius, a variation of the local Reynolds Number by either speed or density results in corresponding changes of the heat transfer. However, with a variation of the radius different heat transfer-Re relations are found. In fact, the temperature distribution in the gas caused by the heat flux results in an additional influence of free convection, to be expressed by a Grashof Number. This is confirmed by a comparison of the experimental results with calculations based on Reynolds Analogy and measured friction coefficients. The discrepancies found can be explained only, if in addition to the limitations of the analogy, the influence of free convection is taken into account. Additional results of ongoing experiments concerning the influence of the geometry of the cavity between disc and casing, of the coolant flow rate and of the swirl are presented.

Radiant Interchange Between Circular Disks Having Arbitrarily Different Temperatures

1961 ◽  
Vol 83 (4) ◽  
pp. 494-502 ◽  
Author(s):  
E. M. Sparrow ◽  
J. L. Gregg
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Local Heat Transfer ◽  
Disk Surface ◽  
Radiant Heat ◽  
Local Heat ◽  
Radiant Heat Transfer ◽  
Disk Radius ◽  
Integral Equation Formulation ◽  
Different Temperatures

The problem of radiant heat transfer between parallel disks has been analyzed by generalizing the standard gray-body enclosure theory. In particular, the assumption that the radiant flux leaving a surface and the local heat flux are uniformly distributed over the surface has been lifted by an integral equation formulation. It has been shown that the general problem of disks at arbitrarily different temperatures can be conveniently broken down into two subproblems, each of which can be solved independently of the temperature level. Numerical solutions of the governing integral equations have been carried out for spacing ratios h/R (h = spacing, R = disk radius) ranging from 5.0 to 0.05 and for emissivities ranging from 0.1 to 0.9. Local heat-transfer results have been presented which, depending on spacing and emissivity, display marked variations over the disk surface. Over-all heat-transfer results have been calculated and compared with the predictions of the standard simplified enclosure theory. These predictions of the simplified theory were found to be unexpectedly good, especially in view of the large surface variations of the local heat transfer.

A Comparison Between the Local Free Convection Heat Transfer Coefficients of Horizontal Cylinders in Vertical and Inclined Arrays

2006 ◽  
Author(s):  
Mehdi Ashjaee ◽  
Tooraj Yousefi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Rayleigh Number ◽  
Free Convection ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Horizontal Cylinder ◽  
Convection Heat ◽  
Free Convection Heat

Laminar free convection heat transfer from vertical and inclined arrays of horizontal isothermal cylinders in air was investigated experimentally and numerically. Experiments were carried out using Mach-Zehnder interferometer and the FLUENT code was used for numerical study. Investigation was performed for vertical and horizontal cylinder spacing from 2 to 5 and to 2 cylinder diameter respectively. The Rayleigh number based on the cylinder diameter varied between 103 and 3×103. The effect of vertical and horizontal cylinder spacing and Rayleigh number on the local heat transfer from each individual cylinder was investigated. It was seen that the local heat transfer coefficient of each cylinder strongly depends on its position relative to the others. This variation of the local heat transfer coefficient was explained by the interaction of plume’s temperature and velocity profiles.

Natural Convection Heat Transfer From a Staggered Vertical Plate Array

1993 ◽  
Vol 115 (4) ◽  
pp. 938-945 ◽  
Author(s):  
G. Tanda
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Vertical Plate ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

An experimental study was performed to evaluate the natural convection heat transfer characteristics of an array of four staggered vertical plates. The thermal input at each plate was the same or differed from plate to plate depending on various heating modes. The effects of the interplate spacing and the plate-to-ambient temperature difference were investigated. The experiments were performed in air. Convective interactions among the plates were identified by examining the per-plate heat transfer coefficients and the local heat transfer coefficients along the vertical sides of plates. Local heat transfer results were obtained by means of the schlieren quantitative technique. Comparison of local heat transfer coefficients along the plate assembly with those of a continuous vertical plate (having the same height) showed enhancements up to a factor of two. Comparison of average heat transfer results with those for a parallel plate channel having the same exchanger size showed only little reductions in heat transfer rate, despite a 28 percent reduction in heat transfer area, with enhancements, in terms of specific heat flux, up to 30 percent.

scholarly journals Effects of Conjugate Heat Transfer on Steady MHD Mixed Convective Heat Transfer Flow over a Thin Vertical Plate Embedded in a Porous Medium with High Porosity

2012 ◽  
Vol 2012 ◽  
pp. 1-19 ◽  
Author(s):  
Ahmet Kaya
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Mixed Convection ◽  
Conjugate Heat Transfer ◽  
Vertical Plate ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
High Porosity ◽  
Local Skin

This study investigates mixed convection heat transfer about a thin vertical plate in the presence of magneto and conjugate heat transfer effects in the porous medium with high porosity. The fluid is assumed to be incompressible and dense. The nonlinear coupled parabolic partial differential equations governing the flow are transformed into the nonsimilar boundary layer equations, which are then solved numerically using the Keller box method. The effects of the conjugate heat transfer parameterp, the porous medium parameterk1, the Forchheimer parameterF*, the mixed convection parameter Ri, the magnetic parameter Mn, and the electric field parameterE1on the velocity and temperature profiles as well as on the local skin friction and local heat transfer are presented and analyzed. The validity of the methodology and analysis is checked by comparing the results obtained for some specific cases with those available in the literature.

Laminar Free Convection From a Sphere

1964 ◽  
Vol 86 (4) ◽  
pp. 537-541 ◽  
Author(s):  
T. Chiang ◽  
A. Ossin ◽  
C. L. Tien
Keyword(s):  
Heat Transfer ◽  
Surface Heat Flux ◽  
Numerical Solutions ◽  
Local Heat Transfer ◽  
Thermal Conditions ◽  
Local Heat ◽  
Surface Heat ◽  
Sphere Surface ◽  
Free Convective Flow ◽  
Boundary Layer Equations

The present paper is concerned with the solution to the problem of external free-convective flow from a sphere with various prescribed thermal conditions on the surface. Exact numerical solutions and heat-transfer results of the boundary-layer equations were obtained for the case of uniform surface temperature and the case of uniform surface heat flux, both at a Prandtl number of 0.70. Temperature and velocity profiles at various angular positions along the sphere surface and local heat-transfer results are presented. A comparison between the exact solution and the approximate solution from the integral method is also presented.

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