Immersion depth

Optimum depth of immersion depends on pitch-line speed. Deep immersion is permissible at low speeds because power losses from churning are low, but at moderate speeds the immersion depth should not be more than three times the tooth height. At the highest speeds, only the addenda of the teeth need be submerged (Figure 52.8). 

The hydrostatic pressure pstat corresponds to the density p of the liquid multiplied by the gravity constant g multiplied by the immersion depth of the capillary hE but can be eliminated by using a parallel second capillary with much larger radius [49] or by relative measurements of p [50], Usually, capillaries with radii of 0.5-2.5 mm and gas flow rates of 5-20 ml/min are used while the pressure difference is below 1000 Pa (100,000 Pa = 1 bar). 

Recently, a very practical bubble pressure tensiometer was developed using elegant pressure transducer mechanics which only needs one capillary made from a high-tech polymer [51, 52]. The tensiometer is able to measure at different immersion depths but needs calibration in order to make the resulting data comparable to surface tension values from other sources. It was shown in a series of measure-... 

A better method uses two capillaries of differing radius, at the same immersion depth, and involves measuring the differential maximum bubble pressure between the two capillaries. In this case the two (Apgt) terms cancel out and the differential pressure is the difference between the two (2y/b) terms where b is the radius of curvature at the apex of the bubble. 

Figure 5.14. (A) Influence of US intensity on calcium carbonate crystallization expressed as free [Ca ]. US intensity (m) 250 W/cm, (o) 105 W/cm (horn tip diameter and immersion depth 3 mm and 3 cm, respectiveiy). (B) Variation of the crystaiiization rate of caicium carbonate with the US intensity at variabie horn tip diameters (m) 3 mm, fAj 14 mm, ( ) 22 mm (horn immersion depth 3 cm). (C) Variation of the crystaiiization rate of caicium carbonate with the product of the US intensity and square root of the horn tip area. Horn tip diameter and immersion depth as in B. (D) Variation of the particie size of hydroxyapatite as a function of the US power (Reproduced with permission of Eisevier, Refs. [142], [144].)...

With a US homogenizer, the flow pattern of the liquid depends on the distance from the horn tip. Since flow pattern (mixing) is the physical effect of US irradiation, any change in the flow pattern due to horn immersion may affect the crystallization rate. There is an optimal, specific horn immersion depth for each US device and irradiated medium which must be established experimentally on a case by case basis. 

It should be noted that on the receding cycle the wet plate surface has previously interacted with water molecules for a different period of time depending on the immersion depth of the plate. Therefore, the bottom deeper immersed portions of the plate interact with the water molecules for a longer period than the shallow immersed portions closer to the top of the plate. This causes small but continuous changes in the meniscus shape even after the three-phase contact line starts to move in the advancing and receding processes. 

Intrinsic hysteresis is a direct result of surface configuration change, which occurs as a result of wetting the surface with water. The plates were purposely immersed to a deeper immersion depth in the second cycle to observe the extent of intrinsic hysteresis. Significant surface configuration change affects the calculated contact angles on immersion and emersion, which violates the assumption of... 

Altenbach C, Greenhalgh DA, Khorana HG, Hubbell WL. A collision gradient-method to determine the immersion depth of nitrox-ides in lipid bilayers. Application to spin-labeled mutants of bac-teriorhodopsin. Proc. Natl. Acad. Sci. U.S.A. 1994 91 1667-1671. Fanucci GE, Cafiso DS. Recent advances and applications of site-directed spin labeling. Curr. Opin. Struct. Biol. 2006 16 644-653. 

A special water-cooled furnace lid was used for the capillary support. A micrometric screw, fixed on the lid, determined the position for the exact contact of the capillary with the liquid surface and gave the desired immersion depth with an accuracy of 0.01 mm. 

In surface tension measurements using the maximum bubble pressure method several sources of error may occur. As mentioned above, the exact machining of the capillary orifice is very important. A deviation from a circular orifice may cause an error of 0.3%. The determination of the immersion depth with an accuracy of 0.01 mm introduces an error of 0.3%. The accuracy of 1 Pa in the pressure measurement causes an additional error of 0.4%. The sum of all these errors gives an estimated total error of approximately 1%. Using the above-described apparatus, the standard deviations of the experimental data based on the least-squares statistical analysis were in the range 0.5% < sd > 1%. 

Figure 8.12. Basic geometty of the four-electrode method with double immersion, a, b, c, d - electrodes, AW- distance in the immersion depth, Vi, V2 - voltage, I, I2- current.

As it follows from Eq. (8.70), only the distance in the electrodes depth of immersion must be known. When the temperature of the measured liquid is changed, the change in the surface level (new depths of immersions) need not be measured. Ohta et al. (1981) also discussed the role of different parameters, i.e. the ratio between the electrode diameter and their distances, the material of the cmcible, electrode displacement from the center of the cmcible, the depth of measured liquid, immersion depth, the frequency of the measuring current, etc. 

In Fig. 1.20 the power numbers Ne for three different radially working stirrers in baffled and unbaffled vessels are represented as a function of the geometric parameters d/D and Hb/D (where is the immersion depth of the baffles). The agreement between measurements and predictions is excellent. 

Xd is evaluated (the electrode surface is estimated from the measurement of the immersion depth h of the electrode in the electrolyte). 

The method is based on Wilhelmy s plate technique for measuring DCAs. The technique involves the measurement of force as a plate is (automatically) immersed into and then emersed from a liquid at a constant rate. The forces (weight) can be plotted as a function of the immersion depth, and, from this, contact angles calculated (Figure 1.29a,b). 

For the second alternative, the net force, Fnet, is kept constant in the instrument while changing the immersion depth, h, by the movement of the container. The immersion depth may be measured from the level displacement or by a goniometer. For this modification, we have from Equations (424) and (495)... 

By raising the test liquid level, the sample is immersed, and the buoyant force increases to cause a decrease in the total force on the balance. Advancing contact angle is calculated from this force-immersion depth line. 

Figure 4.22 Scheme showing an installation for the preparation of carbon onions in molten alkali halogenide. The kind of carbon material obtained depends on the immersion depth of the graphite electrode. 

Immersion Depth and Position of Antifoams. In addition to the stability of the pseudoemulsion film, several factors influence the efficiency of the various antifoams. 

---