The study considers industrially applicable nozzles which are used as an auxiliary equipment in pneumatic pulsator systems for unclogging outlets of silos for loose materials. The aim is to determine the amount of heat (energy loss) which is generated during one work cycle of the system. Presented study compares energy loss during compressible (max. M = 1.7) and transient airflow through two types of nozzles: with and without a baffle. Investigation in this field has not been carried out so far and present-day designing process is significantly based on heuristic knowledge. The energy loss is calculated by using results of numerical simulation. The OpenFOAM CFD toolbox with the finite volume method has been used for that purpose with thermodynamically ideal gas model. The energy analysis and heat generation calculation have been based on the first principles of thermodynamics. For initial and boundary condition, authors’ previous work, which considered rapid airflow from a vessel to the atmosphere, has been partially utilized. Instantaneous results of simulation indicate the high energy rates but they are available for a very short time frame. The values of the total heat generated during gas conversion within the nozzle show that both nozzle produces a small amount of energy loss which would cause a slight warm-up of them.