Vertical Eccentricity Research Articles

LAMINAR NATURAL CONVECTION HEAT TRANSFER IN AN ECCENTRIC RHOMBIC ANNULUS

The effect of vertical eccentricity on natural convection in a rhombic annulus is studied numerically for enclosure gap values (ER) of 0.5 and 0.75, eccentricity (ϵ) values from -0.25 lo 0.25, and Rayteigh numbers (Ra) from I04 to 108 Negative values of t (inner rhombus displaced downward) lead to an increase in heat transfer. At low Ra there is a critical positive e for which the flow strength is a maximum. At high Ra, increasing positive e results in a decrease in the flow strength and heat transfer. For any ϵ > 0 there is a critical Ra, beyond which there is a decrease in the total heat transfer. This critical Ra increases with decreasing ER values.

Experimental analysis of thermal fields in horizontally eccentric cylindrical annuli

This paper presents new experimental results on thermal field and heat transfer in a two-dimensional annulus between horizontally eccentric cylinders. The study is conducted by means of optical techniques, for 1.07×104≤Ra L≤8.27×104 and a wide eccentricity range. The horizontal eccentricity of the inner cylinder substantially alters the thermal field and the geometry of the plume, but, in analogy to the behaviour for vertical eccentricity, the average Nu is slightly affected in the investigated range of eccentricity. The concentric geometry is also considered mainly to validate the experimental technique and evaluate the accuracy of the adopted methodology by comparison with available results. Both shearing interferometer and reference beam interferometer are obtained by means of Wollaston prisms with appropriate splitting angles, so that the temperature and local Nu distributions may be evaluated quantitatively from the original pictures via digital image processing.

Influence of baffles upon natural-convective steady-state heat transfers inwards across horizontal eccentric annuli

Flow patterns, temperature distributions and steady-state heat transfers inwards across a horizontal annular, atmospheric-pressure, air-filled eccentric cavity have been determined. Several different configurations of two low-conductivity baffles (arranged symmetrically with respect to the vertical plane through the centre-lines of the pipes), inserted across the cavity and extending its whole length, were tested. With the horizontal inner pipe located at a vertical eccentricity of −0·65 (i.e. in the lower region of the outer pipe), the optimal inclination of the two baffles, corresponding to the least rate of convective heat exchange, was achieved at ±140° from the vertically downwards radius vector emanating from the centre of the inner pipe. This enabled a reduction of ∼6% in the steady-state convective heat leak to be achieved compared with that for the plain eccentric annulus under similar temperature differences between the pipes. However, by using a vertical baffle (i.e. at an angle of 0°), an increase of ∼ 14% in the convective heat leak through the air occurred. The results agree qualitatively with those expected on the basis of previous studies for the inverse case (of a concentric annulus) with the heat flowing outwards.

Stiffness and damping coefficients of spherical spiral grooved bearings: Influences of vertical eccentricity and compressibility of lubricant

The dynamic characteristics of a spherical spiral groove bearing have been analysed using a narrow groove hypothesis for the cases of incompressible fluid film and isothermal gas film. The usefulness of the proposed method is demonstrated by a comparison of results with those obtained using established methods. The method is especially efficient for optimization design and other analysis problems for which other available calculation methods require significant computational effort. The influence of bearing parameters and compressibility of the fluid on dynamic performance and stability are presented.

Analysis of Dynamic Performances of Spiral Grooved Spherical Bearings : Influences of Vertical Eccentricity and Compressibility of Lubricant

Analysis of Dynamic Performances of Spiral Grooved Spherical Bearings : Influences of Vertical Eccentricity and Compressibility of Lubricant

Variation of the magnitude of the horizontal-vertical illusion with retinal eccentricity

The horizontal-vertical illusion was studied as a function of retinal eccentricity. It was found that the relation of illusion magnitude to vertical eccentricity is described by a U-shaped function with large amounts of reversed illusion for the more eccentric positions. Substantial effects due to horizontal eccentricity were also obtained, but these were not consistent across subjects. It is suggested that the flattening of the peripheral zones of the refracting surfaces of the eye may be involved in the variation of the illusion with retinal position, and that the astigmatic properties of the central portions of these surfaces may be a prime factor in the usual horizontal-vertical illusion.