Axial Temperature Profiles in MicroChannel Reactors

Because of the small diameter of microchannels (df 1 mm), a homogeneous temperature in radial direction can be assumed. In the gas phase, mass and heat transport have the same characteristic time. Exceptions are fast gas phase reactions with high activation energies such as combustions where radial temperature gradients exist. 

For the following discussion we consider ideal plug flow behavior of the microchannel reactor. The material balance for a small volume element (AV ) 

Assuming the cross sectional area to be constant, dV = iz,the above equation can be written as 

To simplify the energy balance, the work done on the reacting fluid is neglected and constant heat capacity and reaction enthalpy is assumed. The steady state temperature profile of the fluid without the influence of axial conductivity can be calculated by considering the energy balance (Equation 5.31) simultaneously with the material balance (Equation 5.32). 

Heat removed by maintaining constant cooling temperature 

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