The principal constraint to high Reynolds number operation is due to boundary layer instability in the radial inflow region. Therefore, a modified model has been built to study the influence of inlet wall heating with the water flow model. This wall heated model of the radial inflow region has been adapted with additional thermocouples, plus insulation of the rim. The data continue to indicate highly stable flow conditions up to the maximum test Reynolds numbers. Work is continuing to further increase the system flow rate.