Efficient, quiet and oil-free
Frictionless chiller technology sets new standard for efficiency and quiet operation
nergy efficiency is a key driver in HVAC technology development. Refrigerant compressors can require very large prime movers, so improvements to both compressor technology and prime mover technology are major goals for
HVAC research and development. Frictionless chillers, the newest generation of chiller technology, achieve both goals. Designed with oil-free magnetic bearing technology and highspeed impellers, McQuay® frictionless chillers can operate as low as 0.375 kW/ton IPLV, the most efficient performance in its tonnage range in the industry. Full load performance as low as 0.62 kW/ton IPLV is about 32 percent more efficient than screw compressor chillers. These IPLV, when applied in a
high efficiency HVAC system, can help save significant operating costs and earn points for Leadership in Energy and Environmental Design (LEED) Energy and Atmosphere, Credit 1.
Magnetic bearings eliminate noise and oil
The Danfoss Turbocor compressor behind frictionless chiller technology uses magnetic bearings—a technology already employed in advanced engineering applications such as the aerospace industry. At about one-fifth the weight of a conventional compressor, and with impeller speeds of 30,000 rpm on a three or four inch diameter impeller (compared to 3,600 rpm on a 40-inch diameter impeller), the magnetic bearing technology can significantly reduce HVAC operating costs. Traditional centrifugal compressors use roller bearings and hydrodynamic bearings; both types of bearings consume power, and both require oil and a lubrication system. Recently, ceramic roller bearings have been introduced to
The frictionless compressor shaft, the compressor’s only moving component, rotates on a levitated magnetic cushion. One axial and two radial magnetic bearings hold the shaft in position.
©2005 McQuay International
Frictionless Chiller 2
the HVAC industry, which avoid the oil issues and reduce some of the power consumption. However, magnetic bearing technology is significantly different from other bearing technologies. A digitallycontrolled magnetic bearing system, including both permanent magnets and electromagnets, replaces conventional lubricated bearings. The frictionless compressor shaft is the compressor’s only moving component, and it rotates on a levitated magnetic cushion. One axial and two radial magnetic bearings hold the shaft in position. When the magnetic bearings are energized, the motor and impellers become levitated in midair. Permanent magnetic bearings do the primary work, while five digitally controlled electromagnets provide the fine positioning. Four separate positioning signals hold the levitated assembly to a tolerance of 0.00005 inches. As the levitated assembly moves from the center point, the electromagnets’ intensity is adjusted to correct the position. These adjustments occur six millions times a minute. The software has been designed to auto-compensate for any out-ofbalance in the levitated assembly. Because the compressor rotor and impeller shaft float on a layer of air, there is no metal-to-metal contact noise or vibration common with conventional bearings. Measured according to ARI Standard 575, sound pressure ratings at one meter are as low as 77 dB(A) for
the McQuay frictionless chiller. Eliminating conventional lubricated bearings eliminates the need for oil, whose main function is to lubricate the compressor bearings. Gone, too, is the maintenance-intensive oil management hardware and the controls associated with them: oil pumps, coolers, heaters and filters; temperature control valves; temperature and pressure sensors; and interconnecting piping. Only a very small amount of oil is required to lubricate the other system components, such as seals and valves, and often even this small amount of oil is not...
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