Measurements of wetting

Another measure of wetting character in the field is the dimensionless capillary number N, which is the ratio of viscous to capillary forces. One expression for this number is (24)... 

Prior to the use of MR to investigate holdup and wetting, while direct measurements of macroscopic holdup could be made gravimetrically, only indirect measurements of surface wetting had been reported. Such indirect measurements of wetting include chemical methods based on reaction rates (90) and tracer (91),... 

The parameters for measurement of wet granulation equipment would include the following. Some would occur when the equipment is loaded, whereas other tests might occur when it is unloaded. 

In the West, dry deposition is a similar level as wet deposition for S and N in many areas, except near sources and in arid-desert conditions where wet deposition is negligible. Since measurements of wet deposition are taken in valleys with low precipitation, they underestimate the wet component somewhat for alpine (ecologically susceptible) conditions. The alpine and subalpine areas in the West have much higher annual precipitation rates than lower elevations. 

Figure 8 The contact angle between a solid and a liquid arises from differences in surface tensions and is used for a quantitative measurement of wetting ability...

A torque rheometer is a device that provides an off-line measurement of torque required to rotate the blades of the device and this torque can be used to assess rheological properties of the granulation. It has been extensively used for end-point determination.The torque values thus obtained were termed as measure of wet mass consistency. ° ... 

Fig. 11.1). The test foot is applied against the test surface, the actuating (pneumatic) cylinder causes swinging (slippage) motion of the test foot, and the instrument displays the slip index on its protractor scale. It ensures consistent operation by the application of uniform force for each test, and permits reliable metering of inclined surfaces such as ramps. The application of vertical and horizontal forces is simultaneous, thus avoiding residence -time and permitting reliable measurement of wet surfaces.

Measurements of wet-only precipitation between August and November 1985 at 10 sites in the Seoul area were reported by Shin et al (1989). The volume weighted... 

The rate of reaction of blast furnace slag and fly ash differs strongly To show this. Figure 1.8 compares electrical resistivity measurements of wet cured concrete with a water/cement ratio of 0.45 made with Portland, Portland fly ash and blast furnace slag cements. The development of resistivity of concrete at an early age... 

Figure 9.8 Principle of electrochemical measurement of wet time in the study of atmospheric corrosion. (A) is a zero-resistance ammeter, (B) is the electrochemical cell, ((a) electrodes, (h) insulation layers), and (C) is a direct current source with constant voltage. (After Kucera and Gullman [9.13].)...

The following methods have become widespread for the determination of the moisture content of gases determination of the absolute value of moisture content by gravimetry or barometry (direct method), measurement of wet gas particles in air by determination of the dry and wet bulb temperatures and the dew point temperature (indirect method), and measurement of a property of the wet gas that depends on the moisture content, such as the absorptivity of the wet gas to electromagnetic waves. 

The adhesion and uniformity of a film are also influenced by the forces that act between the coating formulation that is in solution form and the core surface of the film-coated surface. The measure of wetting behavior is the contact or wetting angle, which forms between a liquid droplet and the surface of the solid body to which it is applied. 

This is a rapid non-destructive method for in situ measurements of wet density, water content and the determination of dry density of soil and soil aggregate mixtures. 

C. Local Measurements. Local measurements of wet chlorine gas pressures below 10 or 15 kPa can be made with U-tube manometers filled with water. Process connections should minimize the collection of condensate in the manometers. A simple but not foolproof technique is to make a connection in the upper half of the header and force the tubing to rise for some distance before descending to the manometer. 

Local measurements of wet chlorine temperature use tantalum-sheathed flanged thermowells with bimetallic dial thermometers. The insertion length should be selected to place the tip about one third of the diameter into the piping or into an elbow. 

Bulk modification of paint and varnish coatings is achieved by the incorporation of various additives in the paint or varnish. In particle adhesion tests on certain coatings modified by this method, simultaneous measurements of wetting angle were made. The results obtained on chlorovinyl KhV-124 and penta-phthalic PF-115 coatings are listed in Table VIII.3, and those on chlorinated PVC coatings in Table VIII.4. 

Hydrophobicity is measured through the contact angle (0) of a water droplet on the aerogel surface as shown in Fig. 6.1. Contact angle, 0, is a quantitative measure of wetting of a soUd by a liquid. It is defined geometrically as the angle formed by a... 

Many materials have been used over the years in an effort to correct this weakness in paper. If water can be prevented from reaching the sites of the bonding by sizing or coating the sheet, then a measure of wet strength may be attained. 

Feed enthalpy feedforward is, rather fortunately, not often of great benefit. Changes in enthalpy are usually small compared to reboiler duty. If feedforward is justified then measuring enthalpy may present a problem. Provided the feed is below its bubble point or above its dew point then, provided its composition and pressure are reasonably constant, it is sufficient to use temperature as the DV. However if the feed is partially vaporised a measurement of wetness is not possible. Since change in wemess represents a large change in enthalpy it is probably not realistic to make any assumption about its value. 

The above values can be roughly used as a measure of wetting of the substrate by water (glass being completely wetted and PTFE very difficult to wet). 

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