Non-intrusive measurements

The fluidized bed systems have been utilized extensively in many physical, chemical, petrochemical, electrochemical, and biochemical processes. Successful applications of the fluidization systems lie in a comprehensive understanding of hydrodynamics, heat and mass transfer properties, and mixing. Various non-intrusive measurement techniques, such as electric capacitance tomography and radioactive particle tracking technique, are available to advance the fundamental understanding of the microscopic and macroscopic phenomena of fluidization. Till date, the... 

Natrajan VK, Christensen KT (2010) Non-intrusive measurements of convective heat transfer in smooth-and rough-wall microchannels laminar flow. Exp Fluids 49 1021-103710... 

In the main, flow visualization with TLCs offers some elementary advantages. It is a non-intrusive measurement technique, the TLCs are easy to handle, the measurement is nearly instantaneous and the TLCs can also be used as tracers for 2D and 3D micro PIV to determine the velocity profile. 

PIV is an optical whole-field, non-intrusive measurement technique to measure fluid velocity by recording the displacement of small tracer particles added to the fluid. PIV has been extensively reviewed in past [5], and can be divided into pattern matching velocimetry (PMV) and particle tracking velocimetry (PTV). PIV offers more flow information per interrogation, and thus substantially more work has been done in this field compared to LDV and ODT. 

Several workers have inferred the existence of a radial velocity profile in a packed bed of low tube-to-particle diameter ratio from measurements of the fluid velocity at the bed exit [30]. However, their results are in considerable disagreement. A semi-theoretical study, using a modified Brinkmann model [31], indicates the existence of a steep maximum in the velocity next to the wall, but this remains unsubstantiated. Non-intrusive measurements of gas velocity within the packed bed are needed before a proper evaluation of the interactions of radial velocity, radial heat transfer, conversion and reaction selectivity are forthcoming. 

In the thermochromic liquid crystal (TLC) the dominant reflected wavelength is temperature-dependent and it has been employed for full-field mapping of temperature fields for over three decades. Although it is non-intrusive and cost effective, there are some problems in applying it to micro-scale measurements, because of size (typically tens of micrometers) and time response (from a few milliseconds to several hundred milliseconds depending on the material and the form). Examples of application are micro-fabricated systems (Chaudhari et al. 1998 Liu et al. 2002) and electronic components (Azar et al. 1991). 

Information on particle size may be obtained from the sedimentation of particles in dilute suspensions. The use of pipette techniques can be rather tedious and care is required to ensure that measurements are sufficiently precise. Instruments such as X-ray or photo-sedimentometers serve to automate this method in a non-intrusive manner. The attenuation of a narrow collimated beam of radiation passing horizontally through a sample of suspension is related to the mass of solid material in the path of the beam. This attenuation can be monitored at a fixed height in the suspension, or can be monitored as the beam is raised at a known rate. This latter procedure serves to reduce the time required to obtain sufficient data from which the particle size distribution may be calculated. This technique is limited to the analysis of particles whose settling behaviour follows Stokes law, as discussed in Section 3.3.4, and to conditions where any diffusive motion of particles is negligible. 

In the geosciences Raman spectroscopy has traditionally been a laboratory tool for structural analysis of minerals. Recent developments in instrumentation make possible the use of Raman spectroscopy as a tool for routine identification of minerals in field situations. The following advantages characterize Raman analysis of minerals no sample preparation in situ real time measurement non-destructive and non-intrusive sampling samples may be transparent or opaque spectra are well resolved and with high information content. 

Ultrasonic meters are finding increasing application because of their ability to measure clear and dirty liquids in difficult situations. They are usually non-intrusive and present little or no obstruction to the flow. They are effective also in measuring flow in open channels (Section 6.2.5) and in partially filled pipes. They are, however, highly sensitive to flow conditions and should be calibrated with care. 

Although ECVT is a promising non-intrusive technique, this system is limited to measuring bubbles greater than the voxel resolution. A bubble smaller than the voxel resolution cannot be measured by the ECVT. A potential solution to this issue is to increase the number of sensor electrodes and modify the related sensitivity which could increase the resolution to track the smaller, single bubble. 

Summary. Spectroscopic techniques, in particular laser induced fluorescence, appear as a good analytical tool for complexation measurements since they are non-intrusive methods, they allow to work at low level of cation concentration (in the case of TRLIF), in particular below the solubility limits permitting to cover a large range of pH and they also allows the use of low humic acid concentrations to avoid aggregation phenomena. From the conditional interaction constants measured by these techniques, the following trend of actinides for humic acids is deduced ... 

The bubble size distribution was also measured at a cell potential of 3.3V and is given in figure 3. To that purpose backlighting or shadowgraphy, being an in situ and non-intrusive optical measurement technique, was used. 

Scattering techniques are non intrusive, non-destructive and have particular advantages in the characterisation of the surface and porous properties of materials containing either closed or molecular sized pores and where outgass-ing pre-treatment may result in irreversible changes in microstructure. Measurements may be carried out, indeed, in the presence of a gas or with hydrated materials and there is no need to evacuate the sample. 

Figure 24 shows the evolution of the CN concentration field. A noticeable amount of CN is observed at t > 7 ms. The concentrations of CN are usually small, except in the secondary flame, thereby serving as a good indication of the flame position. Parr and Hanson-Parr [23] conducted pioneering measurements of the transient flame structure of RDX using both UV-visible absorption and non-intrusive planar laser-induced fluorescence (PLIF). The experiments were... 

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