Tracer gas

If there is substantial airflow through the pathway, the peppermint oil odor could be diluted so that it is imperceptible. Tracer gases such as sulfur hexafluoride (SF ) can provide qualitative and quantitative information on pollutant pathways and ventilation rates. Use of tracer gases to obtain quantitative results requires considerable technical expertise. If it appears that a sophisticated study of pathways (or ventilation rates) is required, you need to use trained investigators. 

Sometimes the real contaminant cannot be used for the determination of the capture efficiency, for example, if there is no suitable analysis method available for the real covitaminant, or if the analysis method is too expensive. In these cases, tracer gases can be used (see Section 10.2.3.3). 

In the case of gaseous contaminants, the tracer gas is selected to simu late as well as possible the properties (density, temperature) and momentum of the real contaminant. It is essential to ensure that the tracers arc nontoxic, chemically nonreactive, nonadsorptive on indoor surfaces, and inexpensive. The mixing of the tracer with the actual gaseous contaminant before its release or the release of the tracer with a density near that of the air will improve the validity of the simulation. With tracers, the most difficult task in practice is the relationship of the discharge between the tracer and the real contaminant. Case-by-case techniques to release the tracer are necessary in practice. With tracer gases, the procedure for capture efficiency is described in detail in the European Standard. - The tracer gas concentrations are measured in the exhaust duct for two release locations as illustrated in Fig. 10.108. 

Tracer gases Gases used with an instrument to determine the air change rate within a space. 

Mass transfer coefficients (kw and fca) have been empirically defined based on experimental studies using tracer gases [71-77] and converted to values for PAHs using differences in diffusivities. The magnitude of K0i for individual PAHs typically ranges from 0.05 to 0.7 m/d (e.g. [78]). 

Instrument, Netherlands) for regulation of carrier and tracer gases, a six-way sampling valve... 

Morookaef al. (M42) studied the effect of gas adsorption on mass transfer between bubbles and emulsion phase, while measuring the residence time distributions of tracer gases for helium, carbon dioxide. Freon 12, and Freon 22 in 12- and 19-cm-diam. free and baffled beds of cracking catalyst. The kob b values are calculated from the distributions for different gases according to the two-phase model, providing for the adsorption equilibrium. 

Horita, T., Yamaji, K., Sakai, N., Xiong, Y.P., Kato, T., Yokokawa, H., Kawada, T. Determination of proton and oxygen movements in solid oxides by the tracer gases exchange technique and secondary ion mass spectrometry. Appl. Surf. Sci. 2003, 203, 634-8. 

Li, Y.C. Zhang, S.Q. Zhang, S. 2013. The qualitative identification of air leakage channels in goaf based on the tracer gases. Safety in Coal Mines 44(1) 185-188. 

The mounding of groundwater is essentially the measure of water table encroachment into the vadose zone. Other measures of the radius/zone of influence are possible, including the measurement of VOC vapors in the vadose zone, the increase of dissolved oxygen, the extent of tracer gases that may have been included in the air injection process, and the increase of overall soil gas pressure within the vadose zone. Caution should be exercised, however, when using vadose detection methods because differences exist between the permeabilities of the saturated zone and the vadose zone. Any type of measurement that requires... 

Radioactive gas mixtures. Tritium and carbon-14, usually mixed with inert gases, are commonly used as tracer gases. Krypton-85 mixed with air is used for diagnosing heart and brain disorders. 

One obvious deficiency of the D-A equation is that it does not approach the Henry type equation at lower concentrations. According to chromatographic measurement using helium gas as a carrier (Chihara, Suzuki and Kawazoe, 1978), the adsorption equilibrium coefficient of the Henry type equation, which was assumed to hold at an extreme of C=0, could be determined for MSC SA. The results are shown in Fig. 3.14. In this experiment, since helium gas exists in large excess compared with adsorbable tracer gas, the coadsorption effect of helium may not have been negligible, making it possible to assume the Henry type isotherm for the tracer gases. 

The second example deals with measurements made by Cheng et al, [14] using different tracer gases (helium,argon,hydrogen) in a carrier gas (nitrogen).The catalyst has the following characteristics ... 

In Figure 5 we show the apparent effective diffusivity as a function of the Reynolds number for several tracer gases.Again D increases with flowrate. 

We see on Fig.5 that the apparent effective dif fusivity for hydrogen is higher than for argon and helium.However the ratio of apparent diffusivities for two tracer gases is lower than the ratio of the corresponding diffusion coefficients.This may be due to the influence of intraparticle convective velocity.In fact,let us take a... 

A tracer gas can also be injected into the flowing gas-solid stream in order to study some of the details of the flow process. By watching the diffusion or dispersion mechanisms of tracer gases such as helium, the turbulent diffusivity of the gas-solid system can be found. This adds considerably to the understanding of the transport process in gas-solid flows. In addition to gas tracers, heat sources can be inserted in the flow and their dispersive behavior noted. The work of Bobkowicz and Gauvin (1965) is notable in this area. 

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