In the last decades, the theory of energy separation in vortex tubes is debated broadly based on the heat transfer and work transfer between core and peripheral flow layers. Many parameters were considered in the literature. However, the present study involves the inlet energy considered collectively towards energy separation. In this paper, three-dimensional computational fluid dynamic simulations are discussed in vortex tube to analyze the energy separation phenomena in different cases by varying the working medium such as hydrogen and air having specific heat variation. The energy at the inlet is maintained same in both cases by adjusting the inlet mass flow rate. The results from this study are validated with recently published literature using hydrogen as a working medium. Vortex tube with hydrogen as working medium yields a temperature separation of 8 K lower than air as working medium. Further studies on vortex tube with hydrogen as a working fluid is explored at different inlet temperatures relative to the room temperature. Vortex tube with hydrogen at an inlet temperature of 400 K gives better temperature separation as compared to other inlet temperatures considered in this study. © 2019 Hydrogen Energy Publications LLC