Oil-free liquid chiller

A centrifugal chiller comprising:

• a condenser, said condenser condensing refrigerant gas to the liquid state when said chiller is in operation;
• a metering device, said metering device receiving refrigerant from said condenser and reducing the pressure thereof;
• an evaporator, said evaporator receiving refrigerant from said metering device and causing liquid refrigerant to evaporate when said chiller is in operation;
• a compressor, said compressor receiving refrigerant from said evaporator and delivering refrigerant in the gaseous state to said condenser when said chiller is in operation, said compressor having a shaft and a motor, at least one impeller and the rotor of said motor being mounted on said shaft, said shaft being rotatably supported by at least one bearing of other than the magnetic, hydrostatic or hydrodynamic type, said bearing having rolling elements and being lubricated exclusively by refrigerant, the rolling elements of said bearing having a lower density, a higher modulus of elasticity and being less sensitive to thermal expansion than rolling elements fabricated from steel, refrigerant delivered to said at least one bearing for lubrication purposes being at least primarily in the liquid state and a portion of the refrigerant used in the lubrication of said at least one bearing vaporizing at the location of said at least one bearing as a result of the bearing lubrication process;
• a reservoir, said reservoir being the location from which refrigerant is supplied to said at least one bearing for the lubrication thereof;
• and
• means for replenishing the liquid refrigerant in said reservoir when said chiller is in operation.