Optimum Turbomachine Selection for Power Regeneration in Vapor Compression Cool Production Plants

Abstract — Power Regeneration in Refrigeration Plant concept has been analyzed and has been shown to be capable of saving about 25% power in Cryogenic Plants with the Power Regeneration System (PRS) running under nominal conditions. The innovative component Compressor Expander Group (CEG) based on turbomachinery has been designed and built modifying CETT compressor and expander, both selected for optimum plant performance. Experiments have shown the good response of the turbomachines to run with R404a as working fluid. Power saving up to 12% under PRS derated conditions (50% loading) has been demonstrated. Such experiments allowed predicting a power saving up to 25% under CEG full load. Keywords — Compressor, Expander, Power Saving, Refrigeration Plant, Turbine, Turbomachinery Selection, Vapor Pressure Booster. I. I NTRODUCTION APOR compression based refrigeration plants are worldwide extensively used for domestic applications, air conditioning and industrial processes. The various applications are characterized by different values of the evaporator temperature and working fluids. While the upper condensing temperatures depend on the environment, into which the Heat Power (HP) is rejected. An enormous amount of electric energy (also primary energy) is worldwide consumed by the various plants whose Cool Power (CP) ranges from a few hundred Watts to more than 10 MW per unit. The worldwide consumed electric energy by Vapor Compression Refrigeration Systems (VCRSs) is an enormous quantity being some 15%, corresponding to some 4.5% of the greenhouse effect total gas emissions. The millions liters (huge value) of fossil fuels (gasoline, diesel fuel, liquigas, natural gas and coal) that are burned to power air conditioners and refrigerators for cars, trucks and ships, must be added to the above consumption [1], [2]. It can be easily understood that a small percentage of power saving per unit of produced cool leads to saving an enormous amount of primary energy and of CO