Vortex tube separates inlet pressurized gas into hot and cold streams to let out at the two ends. It is mainly used for spot cooling purposes. In the hitherto studies on vortex tube, either cold temperature or temperatures difference of outlet gas was considered the response variable. In this work, suggesting that vortex tube can also be used for heating applications, the two response variables viz., cold-outlet air temperature and hot-outlet air temperature are optimized simultaneously using Taguchi method and grey relational analysis. Various input controllable parameters / factors may be conceived, the values (levels) of whom may affect the response variables. Five controllable parameters with three levels each and L-27 Orthogonal Array are used for experimentation in the present work. Grey Relational Grades are computed. Except hot-tube Length, all the parameters considered are found significant from ANOVA table. Through confirmatory test, experimental results are validated.