When using compressed air for cooling you should use some system that either makes the compressed air cooler or makes it more efficient by maximizing mass flow. For this you have two choices: vortex tube technology or air amplification technology. Both have its particular range of application as this video explains. The picture shows the use of a vortex tube used to cool the inside of a blow molded part. In this case the vortex tube technology works best because it is inside an enclosed area.