Flow and diffusion in the reactor

The Axial Purge Flow. The reactor should be purged of reaction products between flashes. Although the conversion per flash is small, the large number of flashes necessary to accumulate an adequate signal would 

FLASH PHOTOLYSIS WITH TIME-RESOLVED MASS SPECTROMETRY 

In the absence of diffusion or flow, the dimensionless concentration that the pinhole would sample is given by 

Flow Toward the Sampling Orifice. The assumption that flow toward the sampling orifice is unlikely to significantly distort the reactor flow or to be a factor in reactant sampling can be justified with compressible flow arguments. For isentropic flow of an ideal gas the temperature and pressure are related to the Mach number by Eqs. 7 and 8 [40]  

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Figure 5. The source of sampling error caused by flow and diffusion in the reactor.

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