In this study, we employed the computational fluid dynamic (CFD) technique in conjunction with a thermodynamic EOS package to investigate the liquid hydrocarbon recovery of dehydration/NGL recovery unit. The effect of modification in dehydration/NGL recovery unit using the supersonic separator was studied. The Peng-Robinson equation of state in conjunction with the thermodynamic process modeling package were used to simulate the heavy hydrocarbon separation in the supersonic separator. The kappa-epsilon turbulence model was used to simulate the natural gas flow in supersonic separator and the behavior of gas pressure reduction on refrigeration performance was studied under the conditions of specified boundary layers. The CFD modeling results revealed a satisfactory agreement with the measured data reported in literature. The results showed that cooling performance was improved for this system compared to J-T valve and turbo-expander. The performance of this system can be further intensified by comparing the refrigeration effect in the same pressure difference. Furthermore, the condensation process of natural gas stream was investigated with the modification of design of dehydration/NGL recovery unit. Compared to the Joule-Thomson valve, this new method derives about 2.85 time higher of C-3(+). The results showed that, when the pressure reduction of this device is equal to that of Joule-Thomson valve, the supersonic separator has a better cooling and separation performance. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.