Experimental techniques continued velocity measurement

The main developments in experimental techniques for measuring high pressure to obtain reliable pressure sensors are extensively discussed by Decker et al. [42]. These include (1) the establishment of a primary pressure scale using a free piston gauge (2) the selection and precise measurement of identifiable phase transitions as fixed pressure points and (3) the use of interpolation and extrapolation techniques for continuous-pressure calibration based on changes in resistance, volume, or optical spectra (based on an equation of state). An alternative method of estimating absolute pressure in isotropically compressed materials is based on measurements of ultrasonic velocity [43, 44]. 

Although the method proposed here is based on idealized models of two-phase flow, it does provide a means for estimating more realistic vapor fractions. Further research is necessary in order to fully understand the conditions under which the technique can be applied. It is obvious that exact measurements on vapor fractions are necessary in order to check the reliability and the accuracy of the proposed method. Experimental work is continuing with motion picture studies on two-phase flow during cool-dowm. This will provide further information on the mechanisms of two-phase flow as well as the two-phase fluid velocities. 

Plug flow was further investigated in various channel sizes of different material for both liquid-liquid flow systems, i.e. ionic liquid-deionised water (Table 4.1), and TBP/ionic liquid (30 % v/v)-nitric acid solutions (Table 3.2). Experiments were carried out at various mixmre velocities (0.0028-0.067 m s ) and volume fractions (eil = 0.4-1). In the Teflon channels plug flow was established in all cases with the aqueous phase flowing as non-continuous plugs within the TBP/ionic liquid phase (30 %, v/v) (carrier phase), whilst in the glass microchannel experiments were carried out with the aqueous phase as the carrier fluid as well. The experimental procedure and the techniques followed for these measurements are explained in Sects. 3.4 and 3.5. The setup used for the measurements is shown in Fig. 3.2. 

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