Horizontal contacting method

The coefficient of linear expansion can be measured as an average over tens of °C to reasonable precision using a precision cathetometer. Most contact methods of measuring length are not suitable because of the low stiffness of rubber and, for the same reason, it is often necessary to support the test piece in a horizontal position. A convenient procedure is to lay a test piece on smooth rollers in a glass-sided bath, but it must be emphasised that only moderate precision can normally be obtained, unless an extremely sensitive optical measuring device is employed, and friction can never be eliminated. 

Many reservoirs are now being exploited by horizontal wells, which have long horizontal contact with the reservoir. Solids control methods for horizontal wells have been adapted from those used in vertical wells. Special techniques and equipment have been developed to remove deposited solids from horizontal wells. 

To investigate the influence of swelhng of the substrate by the contacting liquid, the contact angle 6 of sessile drops of tricresylphosphate, TCP (drop volume 2 p,L, viscosity t = 70 cP, surface tension = 40.9 mN m ), has been measured as a function of time after deposition, t, on flat, smooth, horizontal surfaces of soft and rigid solids at 20°C. The method of measurement of contact angle is the same as in Section Ill.A. 

An interesting class of exact self-similar solutions (H2) can be deduced for the case where the newly formed phase density is a function of temperature only. The method involves a transformation to Lagrangian coordinates, based upon the principle of conservation of mass within the new phase. A similarity variable akin to that employed by Zener (Z2) is then introduced which immobilizes the moving boundary in the transformed space. A particular case which has been studied in detail is that of a column of liquid, initially at the saturation temperature T , in contact with a flat, horizontal plate whose temperature is suddenly increased to a large value, Tw T . Suppose that the density of nucleation sites is so great that individual bubbles coalesce immediately upon formation into a continuous vapor film of uniform thickness, which increases with time. Eventually the liquid-vapor interface becomes severely distorted, in part due to Taylor instability but the vapor film growth, before such effects become important, can be treated as a one-dimensional problem. This problem is closely related to reactor safety problems associated with fast power transients. The assumptions made are ... 

UMEs used in our laboratory were constructed by sealing of carbon fibre into low viscosity epoxy resin (see Fig. 32.4) [118]. This method is simple, rapid and no specialised instrumentation is required. Firstly, the fibres are cleaned with this aim. They are immersed in dilute nitric acid (10%), rinsed with distilled water, soaked in acetone, rinsed again with distilled water and dried in an oven at 70°C. A single fibre is then inserted into a 100- iL standard micropipette tip to a distance of 2 cm. A small drop of low-viscosity epoxy resin (A. R. Spurr, California) is carefully applied to the tip of the micropipette. Capillary action pulls the epoxy resin, producing an adequate sealing. The assembly is placed horizontally in a rack and cured at 70°C for 8h to ensure complete polymerization of the resin. After that, the electric contact between the carbon fibre and a metallic wire or rod is made by back-filling the pipette with mercury or conductive epoxy resin. Finally, the micropipette tip is totally filled with epoxy resin to avoid the mobility of the external connection. Then, the carbon fibre UME is ready. An optional protective sheath can be incorporated to prevent electrode damage. 

In gas-phase processes, gaseous ethylene or propylene is contacted with solid catalysts, sometimes dispersed in dry polymer powder. The industry uses two different methods of carrying out this reaction, depending on the method of heat removal. In one class of processes, a fluidized bed is used, and in the other, a mechanically agitated dry powder bed is used with evaporative cooling in vertical and horizontal autoclaves. The advantage of a gas-phase process is that no solvent recovery is necessary so that the energy requirement is less. 

For the production of white wine, it is almost universally accepted that a relatively clear juice of 0.5-2.0 percent suspended solids is desired for fermentation. This is achieved by separating the juice from the skins, pulp, and seeds. Many of the small wineries use a horizontal basket press to receive their fresh must. These presses utilize either an inflatable bladder or a movable piston to press the crushed grapes. In many cases, the must is pumped directly to these presses from the crusher-stemmer. An exception to this method of operation in small wineries is the case where skin contact is desired. Several wineries will allow maceration for from four hours to twenty-four hours for V. vinifera cultivars Chardonnay and Gewiirztraimer. 

The surface energy (critical surface tension) of solids is measured by a method developed by Zisman.9 In this method a series of contact angle measurements are made with various liquids with known surface tensions on the solid to be tested. The contact angle 9 is plotted as a function of the yLV of the test liquid. The critical surface tension is defined as the intercept of the horizontal line cos 9=1 (i.e., when the contact angle is 0°) with the extrapolated straight-line plot of cos 9 against yLV of the liquids. The yLV at this intersection point (i.e., where a hypothetical test liquid would just spread over the substrate) is defined as the critical surface tension of the solid. 

Another method is to measure the thickness of a drop of liquid resting on a horizontal plate, or of a bubble underneath a plate. If the bubble or drop is large, so that the curvature at the apex can be neglected and this part of the surface treated as flat, the contact angle is given by the equation8... 

Ferguson4 has also devised two ingenious methods for determining the surface tension of very small amounts (I or 2 cu. mm.) of liquid. The pressure required to force the meniscus, located at the end of a capillary tube, to a plane form, is measured it is equal to 2yjr for tubes so narrow that the meniscus would naturally be spherical. In one method the tube is vertical in the other it is horizontal, and in this modification the density of the liquid need not be determined. The contact angle must be zero, as in all variants of the capillary height method. 

The method is independent of the angle of contact between the liquid and the plate, provided that this is not so variable as to distort the bubbles or drop seriously from the form of a figure of revolution about a vertical axis, to which alone the calculations apply. With bubbles under a plate, it is almost necessary to use very slightly concave plates, or it becomes impossible to retain the bubble in position.6 A measuring microscope with a very good vertical travel is desirable for the measurement of h, and it should also be capable of horizontal... 

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