The current research compared the efficiency of the new generation refrigerants, propane (R290) and propene (R1270), for cooling applications. The refrigerants’ flow and phase change properties in a helical capillary tube are simulated using ANSYS Fluent 2021 R2 CFD software. For this virtual experiment, a helical capillary tube with an inner diameter of 1.2 mm and a total length of 2100 mm is used. The flashing phenomenon, in which the refrigerants undergo a phase change, is simulated using a finite volume-based mixture model. The Zwart–Gerber–Belamri model is utilized to estimate mass transfer during flashing, which adheres to a homogeneous equilibrium strategy. A set of user-defined functions (UDF) are created to access the refrigerant properties and implement the cavitation model. Bilinear interpolation is used to calculate the fluid’s characteristics at a particular cell pressure and temperature. Available numerical and experimental results are used to verify the constructed numerical model. The investigation shows that under the same operating conditions, R290 refrigerant maintains a higher mass flow through the helical capillary tube than R1270. R1270 produces a lower temperature vapour-liquid mixture at the exit of the capillary tube in comparison to R290. CFD simulations have generated information and data that are helpful in choosing proper refrigerants for different purposes.