Summary of Tests for Mass and Heat Transfer Effects

5 Summary of Tests for Mass and Heat Transfer Effects 

the following is a summary of the methods at our disposal to check for mass and heat transfer effects. 

With slurry-phase systems, the mixing capability is increased until the reaction rate is independent of mixing - external gradients are then assumed to be gone. With gas/solid reactions in a CSTR, the internal recycle rate or the spinning speed of the catalyst basket can be increased to eliminate external gradients [9-11]. A Damkohler number can then be estimated to see if fj is sufficiently close to unity. 

In a fixed-bed PFR, the flow rate is varied at constant space time and if the rate remains constant, external mass transfer effects are assumed to be unimportant however, this test can become insensitive at low Reynolds number [61]. 

The catalyst particle size can be varied, and an increase in rate as the particles become smaller shows that internal (pore) diffusion is affecting the rates, assuming that external mass transfer limitations have been removed. Diffusion control may remain in even the smallest particles if the pore diameters are too small. 

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