Wall heat transfer in shock tubes at long test times

In recent years in our laboratory, relatively long chemical kinetics experiments are being employed behind reflected shock waves [1,2]. These experiments are performed in upwards of 15-ms test times with the common assumption that the region behind the reflected shock wave can be considered isothermal prior to the main chemical reaction. While the isothermal assumption is applicable to short test times as heat transfer between the hot gas and the cold walls can be neglected, there is some concern that longer test times may allow significant heat loss to the walls of the shock tube, thus creating observable deviations from the isothermal assumption.