The improvement of the physicochemical properties of heavy crudes for their better use has brought the application of new technologies and processes to the oil and gas industry. Hydrodynamic cavitation consists of cavitating the working crude oil as it passes through a reactor, which operates with specific process parameters such as flow rate, hydrogen donor percentage, and temperature. In this work, we will focus on the effect of temperature on the fluid dynamics of the crude oil inside the Vortex reactor. The process started with a 3D steady-state, multiphase liquid-vapour fluid flow modelling with k-ε turbulence model and Schnerr-Sauer cavitation in Ansys Fluent software. The results obtained for the different operating temperatures in the range of 92 °F to 350 °F allowed us to analyse the behaviour of the fraction of vapour generated by cavitation. The amount of vapour produced in the reactor increased notably when a certain temperature value of the crude oil is reached, and the vortex effect becomes stronger in the fluid dynamics of the crude oil. To have a better understanding of the physical phenomena, the possibility of further investigation of this equipment with different crude oils and operating parameters is open to determine the optimal operating points of the hydrodynamic cavitation nano reactor.