Can I connect the output of a Vortex Tube to an Air Amplifier or Air Knife?
No, for proper operation, the Vortex Tube cold outlet should not be subjected to any restrictions that would produce backpressure in excess of 5 PSIG. The hot end exhaust can withstand pressure up to 30 PSIG (depending on the cold fraction). If backpressure exceeds 5 PSIG, then the performance of the Vortex Tube will deteriorate. The hot end exhaust can withstand pressure up to 30 PSIG (depending on the cold fraction).
An Air Amplifier or Air Knife would restrict the flow of a Vortex Tube to the point where the backpressure is excessive and severely limit the cooling capacity of the Vortex Tube.
If the goal were chilled airflow coming from an Air Amplifier or Air Knife, it would be unrealistic to expect a temperature decrease in the total output flow of either device with chilled compressed air. Compressed air will make up a small fraction of the total airflow output from these devices. The net temperature out will be a mix of compressed and ambient air with ambient air the majority of the volume. The net effect is that the airflow is going to be the same or very close to ambient temperature surrounding an Air Amplifier or Air Knife.