In this paper, the effects of number of inlets, tube length and diameter of cold outlet on temperature, flow rates passing through the vortex tube are investigated. The results including temperature of cold outlet and flow rates passing through the vortex tube are discussed. The effect of length, number of inlets, ranging from 1 to 5 inlets and the effect of cold outlet on the results are investigated. According to obtained results, we conclude that the passing flow rate from a cold outlet is increased as its diameter increase and by increasing the length of the vortex tube, the passing mass flow rates from the cold and hot cross sections slightly increased and slightly increased, respectively. Also, the temperatures at both outlets decreased as the number of inlets increased, while increases were observed as the radius of cold outlet increased and the temperature of exiting gas is considerably higher than hot and cold outlets compared to the case where more number of inlets with reduced diameters is used. As shown, for LID = 15 and as the radius of cold outlet is increased, the fraction of mass flow rate is decreased from 0.8 to 0.7 and then 0.6, from 0.65 to 0.58 and then 0.52, and from 0.42 to 0.32 and then 0.24 for n = 1, 3 and 5. (C) 2017 Elsevier Ltd. All rights reserved.