Salt separation at super-critical condition is a promising technology to separate dissolved salts from water by utilizing sharp changes in thermal and physical properties of water close to its critical point in a tube in tube separator. To capture flow complexity and geometric asymmetry, a three-dimensional CFD model of salt separator is developed in Fluent ver 16. Simulation results are compared and validated with experimental work by Schubert et al. [19]. The axial temperature profiles predicted by model at different wall temperature are well in agreement with the reported data [19]. The model provides insight to axial and radial flow field, temperature gradients, and so on within the salt separator. The blurred boundary between super-critical and sub-critical regions is captured by accounting sharp changes in physical properties of water close to critical temperature and pressure. Sensitivity of key process parameters (e.g., vessel wall temperature, feed pre-heat temperature, flow rates and forced cooling in cold region) was carried out to check effect of operating parameters on deviation in performance of salt separator. No pre-heat feed condition (25 degrees C) is best since it ensures no salt deposition in dip tube without affecting the salt separator performance. Optimum wall temperature lies between 390 degrees C to 470 degrees C to avoid salt deposition and maintain desired temperature gradient between hot and cold section. The modelling framework will aid in efficient design and scale up of salt separator.