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MHI Develops Lubricant Oil-free Centrifugal Chillers Through Adoption of Magnetic Bearing System
- "ETI-40MB and 50MB" Models Added to Built-in Inverter "ETI Series" -

No.1707
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Tokyo, August 21, 2013 - Mitsubishi Heavy Industries, Ltd. (MHI) has developed two models of highly efficient centrifugal chillers featuring a totally lubricant oil-free magnetic bearing system. The adoption of the new magnetic bearing system - the first application in Japan in commercial-use centrifugal chillers - eliminates the need for lubricant oil. As no oil changes are required, significant reductions are realized in both maintenance work and related costs. The two newly developed models - the "ETI-40MB and 50MB" - offer cooling capacities ranging from 350 to 500 refrigeration tons*1 (RT). They will be launched into the Japanese domestic market this fall as new additions to the company's "ETI Series" of compact centrifugal chillers with built-in inverters.

Centrifugal
In the compressor of the new models - which is the core component of centrifugal chillers - MHI has adopted a magnetic bearing system for the rotation shaft of the impeller; this system causes the shaft to float, enabling reduction in friction drag to a minimal level. The impeller blades have also been newly designed. Through these innovations, the new models have achieved even higher compressor efficiency. Adoption of the magnetic bearing configuration also significantly reduces both maintenance work and related costs by eliminating the need for lubricating oil and oil filter changes.

The ETI-40MB/50MB, chillers having a 400 RT refrigeration capacity, achieve a rated COP (coefficient of performance)*2 of 6.7 and IPLV (integrated part load value)*3 of 10.8. The new models, which use HFC-134a, a chlorine-free and zero ozone depletion potential (ODP) refrigerant, achieve higher energy-saving performance than the pre-existing ETI-40 models, and will enable further reductions in energy consumption for customers while at the same time contributing to efforts to prevent global warming through lower CO2 emissions. They also require less installation space and weigh less (by 15% and 20%, respectively) owing to the reduction in the number of compressors to only one, in contrast to the two needed in the ETI-40 models. These advantages not only enable downsizing but also facilitate carrying-in and installation work.

MHI launched the ETI Series, initially with cooling capacities from 150 to 500 RT, in May 2008. The original models offered outstanding efficiency and compact size responding to the needs of customers who require centrifugal chillers with lower carbon emission levels, reduced energy requirements and smaller installation space needs. Subsequently, in 2011 the company enhanced its product portfolio up to 700 RT in tandem with expansion of the market for inverter models, resulting in expansion of its customer base.

Following the market launch of the ETI-40MB/50MB, going forward MHI will now pursue commercialization of larger systems incorporating magnetic bearings, in its ongoing quest to respond to an ever-broader range of customer needs for centrifugal chillers.

Notes: 

1) Refrigeration ton represents the refrigerating capacity for turning 2000 lb of 0°C water into 0°C ice in 24 hours. 1 RT = 3,024 Kcal/hr.
2) Coefficient of performance (COP) indicates the ratio of a system's useful energy output versus its energy input. The higher a system's COP, the higher is its energy-saving efficiency. In the case of refrigeration systems, COP = rated cooling capacity (kW) / electricity consumption (kW). The cited value was calculated based on Air-Conditioning, Heating and Refrigeration Institute Standards (AHRI).
3) Integrated part load value (IPLV) measures the efficiency of air-conditioners under a variety of conditions: several partial operational load ratios and coolant water temperatures similar to those in actual usage, to reflect seasonal changes in operational conditions. The cited value was calculated based on AHRI.