How do we calculate the space velocity of gas in a tube?

Question

the tube is a reacotr filled with catalyst, and we are passing a gas at a certain flow rate.

Answer 1

Pass a measured amount of gas through the tube, collect the passed amount from the other tube end, measure the time taken to get the gas , then the flow rate will be m^3/sec, knowing the cross sectional area of the tube , then divide the flow rate by the cross area , that will give you the gas velocity in the tube.