New Model Turbo Chiller, AART Series, Contributes to the Reduction of Energy Consumption under Year- Round Operation

Among turbo chillers loaded with alternative refrigerant (HFC134a), the AART Series is one of the world's most efficient. This paper discusses the technology used in the New AART Series, a lineup of Turbo Chillers upgraded through the introduction of a two-stage inlet guide vane control mechanism and a vane-less diffuser to enhance performance during partial loads. A high-end, high-speed control panel and inverter-driven motor are combined with a variable-speed control logic. The design takes advantage of the aerodynamic characteristic of the compressor and brings about optimal operational control under changing loads and outside temperatures throughout the year. Compared to the conventional variable-speed machines of the NART-I Series, the new AART Series is expected to save considerably more energy in year-round operation. Turbo chillers are a category of cold heat source ma- chines. Most in service today are used for heat storage, air-conditioning for factories and commercial facilities, process cooling in chemical plants, and district heating and cooling with heat-supply services. In recent years, from the view of protection of the Earth's ozone layer, the use of CFCs which was used as refrigerant has been completely eliminated, and efforts are underway to abol- ish the use of HCFCs in future. Since 2000, Mitsubishi Heavy Industries, Ltd. (MHI) has been trying to improve the performance of machines using HFC-134a, a specific refrigerant with an ozone depletion potential (ODP) of zero. With success in this endeavor, MHI will save more energy and help conserve the global environment. Fig. 1