Results illustrate that increasing the nozzle
numbers causes a temperature drop and the optimum nozzle
diameter corresponds to quarter of working tube diameter. Rafiee
and Rahimi [11] performed an experimental work on convergence
ratio of nozzles and in their work a three dimensional computational fluid dynamic model was introduced as a predictive tools to
obtain the maximum cold temperature difference. Also they proved
that energy separation procedure inside the vortex tube can be
improved by using convergent nozzle.