Abstract: A vapor compression refrigeration system has a main refrigerant circuit having a primary compressor group, a gas cooler or condenser, an expansion device, a liquid receiver, and at least one evaporator. An emergency circulation duct fluidically connects the liquid receiver to the main circuit to allow a flow of refrigerant from the liquid receiver to the gas cooler. An emergency compressor group in the emergency circulation duct is activatable when pressure inside the liquid receiver or in the duct upstream of the emergency compressor group meets or exceeds a predefined emergency pressure threshold. An uninterruptible power supply powers the emergency compressor group and expansion device during a shutdown of the refrigeration system. When pressure inside the liquid receiver or in the duct upstream of the emergency compressor group equals or exceeds the predefined emergency pressure threshold, an emergency circulation of refrigerant fluid is activated through the emergency circulation duct.

Abstract: A refrigeration plant with multiple evaporation levels, operating according to a vapour compression cycle and including a circuit having a high-pressure branch HP, wherein is arranged at least one heat exchanger, and two or more low-pressure branches, each of which operates at a different evaporation level to serve users having different refrigeration requirements. In each of the low-pressure branches the plant comprises an expansion device, at least one evaporator and a compressor group. At least one evaporator of each low-pressure branch is connected directly to the high-pressure branch. At least a first low-pressure branch comprises a liquid separator fluidically connected: to the evaporator outlet to collect the liquid exiting the evaporator when operating in overfeeding conditions; and to the intake of the compressor group. Such liquid separator is fluidically connected to a second low-pressure branch upstream of the expansion device of such second low-pressure branch through a first connection duct.