Impeller rotation causes acceleration of refrigerant vapor in the impeller streaks, increasing speed and kinetic energy.
Accelerated refrigerant vapor exits the impeller and enters the diffuser plate passages. These passages start small and become wider as the soda passes through them. As the size of the passages increases, the velocity, and hence the kinetic energy of the refrigerant, decreases.
The first law of thermodynamics says that energy is not lost, it is converted from one form to another. Thus, the kinetic energy of the refrigerant is converted to potential or pressure energy.
Soda, now at a higher pressure, moves to the volute, the largest space region. The volute also becomes wider as the refrigerant moves through it. Again, as the size of the volute increases, the kinetic energy is converted to potential energy.
