Hydraulic turbocharger is a common energy recovery device used in reverse osmosis water desalination plants to recover the stored energy in brine. Also, it can be used to control the pressure variation due to the change of plant operating conditions. The aim of the current work is to apply the computational fluid dynamics (CFD) to investigate the balance between the hydraulic turbocharger turbine and pump sections. The effect of changing the rotor speed and the effect of auxiliary line size and valve opening on the performance of the hydraulic turbocharger are also investigated. In addition, the effect of these changes on the plant specific energy consumption (SEC) is discussed. The results of the current work present the variation of the hydraulic turbocharger performance with the rotor speed. It also shows that increasing the turbine auxiliary line diameter reduces the turbine inlet pressure. The CFD results show that opening the auxiliary line reduces the turbine inlet pressure which reduces the rotor speed and the pump boosting pressure. (C) 2015 Elsevier B.V. All rights reserved.