Energy consumption analysis of building air-conditioning systems using centrifugal compressor with gas bearing under annual operating conditions

The water chiller using centrifugal compressor with gas bearing is an important development direction for building energy saving, but the additional refrigerant cycle for bearing and motor colling leads to more complex performance especially under the various operating condition. Based on the heating and cooling loads of a building in Nanjing and the local climate conditions, this paper innovatively establishes an air conditioning system model using centrifugal compressor with gas bearings (CCGB), and analyzes the performance of air-cooling and water-cooling methods. Considering the heating and cooling loads, the annual energy consumption of two systems was compared consider the climate condition. The results show that the COP of watercooling system is larger than that of air-cooling system due to the better heat transfer condition. The larger power consumption of compressor for air-cooling system leads to the larger motor cooling load. The cooling methods have obvious influence on the vapor-injected mass flow rate, but have small impact on the mass flow rate of motor cooling and bearing gas supply. The energy efficiency of air-cooling and water-cooling system in summer are 3.77 and 5.12 respectively, and the total energy consumption in the whole year are 32.4 tons and 33.5 tons of standard coal.