Space Time (\(\tau\)) and Space Velocity (\(S\))

Space time (\(\tau\)) of a flow reactor is defined as the time necessary to process one reactor volume of fluid at the reactor inlet (i.e., feed): \[\tau= \frac{VC_{A0}}{F_{A0}} = \frac{V}{v_0} \qquad \equiv [\text{time}]\] A space time of 10 minutes means that every 10 minutes one reactor volume of feed at specified conditions is treated by the reactor. Space velocity (\(S\)) of a flow reactor is the reciprocal of space time (\(\tau\)). Space velocity gives the number of reactor volumes of fluid at the inlet conditions (i.e., feed) which can be processed in unit time. \[S=\frac{1}{\tau}= \frac{v_0}{V} \qquad \equiv [\text{time}^{-1}]\] A space velocity of 5 h\(^{-1}\) signifies that each hour, 5 reactor volumes of feed can be processed.

  • Space time and space velocity are the usual measures of processing rate in flow reactors.

  • Space time depends on the feed conditions.