Abstract: The refrigeration principle of "thermal separator" is analyzed in light of unsteady flow dynamics and a simplified physical model is presented to improve the refrigeration efficiency. The analytical study shows that it is necessary to control the pressure ratio P4/P1 properly and to match the length of working pipes with the size and revolution speed of the unit in order to increase its efficiency. The unit may be used for recovery of petroleum gas, cold storage and central airconditioning.