HIGH-PRESSURE FAST-FLOW TECHNIQUE FOR GAS-PHASE KINETICS STUDIES

A fast-flow technique suitable for measuring elementary rate constants over a wide range of pressures has been developed. The method operates under turbulent flow conditions, in contrast to laminar flow which characterizes the conventional low pressure technique. Flow visualization, velocity profile measurements, and tracer pulse studies have been carried out in a flow tube reactor to investigate the dynamics of both laminar and turbulent flow for chemical kinetics purposes. Furthermore, the wall collision frequency for the reactants has been determined: at the higher pressures it is greatly reduced in comparison with the frequency characteristic of the conventional low pressure laminar flow technique. Also, to test and validate the technique the bimolecular rate constants for the reactions H + Cl2 and H + O3 have been measured at total pressures in the 3-300 torr range; at pressures below 5 torr, as well as above 50 torr in the turbulent flow regime the agreement with the recommended literature values is excellent.