Elliptical tube cross section

Schematic representation of three tubular plate designs (a) cylindrical tube cross section (b) elliptical tube cross section (c) strap grid tubular plate construction.

The most frequently applied mechanical manometers in ventilation applications are fluid manometers, bur the following types are also used. The Bourdon tube is a small-voiume tube with an elliptic cross-section bent to the shape of a circular arc, the C-type. One end is open to the applied pressure while the other end is closed. The pressure inside the tube causes an elastic defonnation ot the tube and displaces the closed end, which is then converted, by means of a linkage mechanism, into the movement of a pointer. The Bourdon tube may be of a spiral or helical design as well. 

It is a simple and reliable gage covering six decades of pressure (not with one gage). Below 1 torr, its sensitivity is very low. The gage is usually made up of a bended flexible metallic tube (see Fig. 1.27) of elliptic cross-section. When pressure inside the tube is different for the outside (atmospheric) pressure, the tube bends. A gear and lever system moves the needle. 

As an illustration of this a tube of elliptical cross-section may be considered. If the major and minor semi-axes are a and b respectively... 

It is well known that for a given pressure drop, the flow is greater in a circular tube than in an elliptical one of the same area, and if in the Taylor diffusion coefficient a2 is replaced by the area of cross-section (na2 for the circle and nab for the ellipse) the constant k is least for e = 0. Thus the dispersion in a circular tube is less than in an elliptical tube of the same area. 

A difficulty associated with this method is that of obtaining capillary tubing of uniform bore (slight ellipticity is not important). Thermometer tubing is useful in this respect. Alternatively, one can adjust the height of the reservoir liquid so as to locate the meniscus at a particular level in the capillary where the cross-sectional area is accurately known. 

The bourdon tube pressure instrument is one of the oldest pressure sensing instruments in use today. The bourdon tube (refer to Figure 2) consists of a thin-walled tube that is flattened diametrically on opposite sides to produce a cross-sectional area elliptical in shape, having two long flat sides and two short round sides. The tube is bent lengthwise into an arc of a circle of 270 to 300 degrees. 

Badr, H.M.. Mixed Convectioh from a Straight Isothermal Tube of Elliptic Cross-Section Ini. J. Heat and Mass Jransfer, Vol. 37, p. 2343-2365. 1994. 

An accurately circular cross-section is not necessary some workers have laid unnecessary stress on the attainment of this. The height of rise is proportional to the sum of the reciprocals of the principal radii of curvature of the meniscus, which will be nearly equal to the major and minor semi-axes of the tube, rx and r2, if the section is elliptical the error in the... 

The Bourdon110 tube gauge (range 1 mbar to 0.1 Mbar) measures the deflections, due to pressure, on a solid barrier connected to a semicircular hollow tube of elliptical cross-section, whose contraction is amplified mechanically in a needle dial. It is used for pressures in various ranges, with an accuracy of 0.1% of the calibration. 

It is interesting to compare structural features of the zeolites mor-denite and faujasite in relation to aging. Mordenite, with ncnintercon-necting channels, can be visualized as a bundle of tubes with elliptical (6.96 X 5.81A) cross-section. If an obstruction develops within such a tube, access to catalytic sites can be decreased (Scheme lOA) or completely blocked (Scheme lOB), depending on its location. In faujasite. 

For a tube of elliptic cross-section with constant temperature on the wall, the perimeter-average Nusselt number in the heat stabilization region (far from the input cross-section) is determined by [341]... 

A series of parallel spines (current collectors) are connected at the upper end to a common connector bar (connector bus) which ends with a plate lug. The spines are positioned in the centre of tubes made of either woven, braided or felt acid-resistant glass wool or synthetic organic fibres. Depending on their shape (cross-sectional geometry), tubes may be cylindrical (round), elliptical (oval) or rectangular (square). Cylindrical tubes with the spines (current... 

A.L. Hazel, M. Heil, The steady propagation of a semi-inflnite bubble into a tube of elliptical or rectangular cross-section. Journal of Fluid Mechanics, 2002, 470, 91-114. 

The hydraulic diameter of the elliptic cross-section tube can be calculated by using the expression for its perimeter. For a not more than three times larger than b an approximation... 

Table 2.1 The friction factor of an elliptic tube for different cross-sections (bja ratios)...

Bourdon gauge An instrument used to measure gas or vapour pressure. It consists of a tube curved in a circular arc that has an elliptical cross section. One end is fixed while the... 

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