Energy efficiency tends to be a crucial issue in engineering since energy costs have started permanent growth. Because of that exergy analyses are applied in the fields where they have not been utilized so far. In this study energy efficiency is determined by calculation of exergy destruction during transient and compressible flow phenomena. The investigated object is a pneumatic pulsator system which utilizes energy of compressed air for destruction of agglutinations, which come from cohesion forces, in loose materials and make the outlets of silos unobstructed. A type of pneumatic pulsator was developed during an R&D project in which fast effect of a pulsator performance was in focus. The results of this study show how much energy can be converted into work during the pulsator operating. A method was developed for exergy destruction calculation during one work cycle of pulsator. The method was based on the validated simulation results. The flow proceeded within less than 0.4 s with the highest Mach number M = 3. It has been found that 11.4% of accumulated energy, which equals 2160 MWh for one silo in heavy industry, is irreversibly lost. It is a significant amount of energy by which the pneumatic pulsator efficiency is reduced. (C) 2017 Elsevier Ltd. All rights reserved.