Compressor for a refrigeration cycle, refrigeration cycle and method for operating the same

Abstract

A compressor ( 2 ) for a refrigeration cycle according to the invention comprises an inlet port ( 6 ), a compression element ( 10 ), an outlet port ( 18 ), wherein in operation a refrigerant flow ( 20 ) of a gaseous refrigerant carrying an amount of oil circulates through the inlet port ( 6 ), the compression element ( 10 ) and the outlet port ( 18 ), and an oil sump ( 8 ) in which part of the oil carried by the gaseous refrigerant collects. An oil circulation rate enhancement feature ( 16 ) is provided being configured so as to direct oil from the oil sump ( 8 ) to the refrigerant flow ( 20 ), when the oil in the oil sump ( 8 ) exceeds a predetermined oil sump level ( 24 ).

1 . A compressor for a refrigeration cycle comprising:
 an inlet port;   a compression element;   an outlet port;   wherein in operation a refrigerant flow of a gaseous refrigerant carrying an amount of oil circulates through the inlet port, the compression element and the outlet port; and   an oil sump in which part of the oil carried by the gaseous refrigerant collects,   characterized by an oil circulation rate enhancement feature configured so as to direct oil from the oil sump to the refrigerant flow, when the oil in the oil sump exceeds a predetermined oil sump level.   
     
     
         2 . The compressor of  claim 1 , wherein characterized in that the oil circulation rate enhancement feature is formed by the crankshaft rotatably driven by a motor, said crankshaft being configured so as to dip into the oil sump and to disperse an amount of oil to form an oil mist to be entrained by the refrigerant flow, when the oil in the oil sump reaches the predetermined oil sump level. 
     
     
         3 . The compressor of  claim 1 , wherein the oil circulation rate enhancement feature is formed by an oil dispersing element, especially a blade or a disk, fixed to the crankshaft and rotatably driven by a motor, said oil dispersing element being configured so as to dip into the oil sump and to disperse an amount of oil to form an oil mist to be entrained by the refrigerant flow, when the oil in the oil sump reaches the predetermined oil sump level. 
     
     
         4 . The compressor of  claim 1 , wherein  the oil circulation rate enhancement feature is formed by a bypass line extending between the oil sump substantially at a height of the predetermined oil sump level and the refrigerant flow at a position before the compression element internal or external to the compressor housing. 
     
     
         5 . The compressor of  claim 4 , wherein  an ejector is provided for transporting oil from the oil sump to the refrigerant flow. 
     
     
         6 . The compressor of  claim 4 , wherein  oil is transported from the oil sump to the refrigerant flow by static pressure entrainment. 
     
     
         7 . The compressor of  claim 4 , wherein the bypass line extends between the oil sump at the height of the predetermined oil sump level and the inlet port. 
     
     
         8 . The compressor of claim, wherein the bypass line extends between the oil sump at the height of the predetermined oil sump level and a suction line connecting to the inlet port (external). 
     
     
         9 . The compressor of any claim, wherein the bypass line extends between the oil sump at the height of the predetermined oil sump level and a compression element suction line or a compression element suction portion. 
     
     
         10 . (canceled) 
     
     
         11 . A refrigeration cycle, comprising:
 at least one lower suction pressure compressor, at least one higher suction pressure compressor, a heat-rejection heat exchanger, preferably a collecting container, at least one lower suction pressure evaporator having an expansion device connected upstream thereof, at least one higher suction pressure evaporator having an expansion device connected upstream thereof and conduits circulating a refrigerant therethrough;   wherein the at least one lower suction pressure compressor includes an inlet port, a compression element, an outlet port, and an oil sump, wherein in operation a refrigerant flow of a gaseous refrigerant carrying an amount of oil circulates through the inlet port, the compression element and the outlet port, wherein a part of the oil carried by the gaseous refrigerant collects within the oil sump, which lower suction pressure compressor is characterized by an oil circulation rate enhancement feature configured so as to direct oil from the oil sump to the refrigerant flow, when the oil in the oil sump exceeds a predetermined oil sump level.   
     
     
         12 . The refrigeration cycle of  claim 11 , further comprising compressors having different sizes. 
     
     
         13 . The refrigeration cycle of  claim 11 , wherein the at least one lower suction pressure compressor and the at least one higher suction pressure compressor are connected in parallel. 
     
     
         14 . The refrigeration cycle of  claim 11 , wherein the at least one lower suction pressure compressor and the at least one higher suction pressure compressor are connected in series. 
     
     
         15 . The refrigeration cycle of  claim 13 , wherein the lower suction pressure compressor and the higher suction pressure compressor are configured such that when the oil sump level of the lower suction pressure compressor is less than its predetermined oil sump level, its oil circulation rate is always lower than the oil circulation rate of the higher suction pressure compressor. 
     
     
         16 . The refrigeration cycle of  claim 15 , wherein the lower suction pressure compressor and the higher suction pressure compressor are configured such that when the oil sump level of the lower suction pressure compressor exceeds its predetermined oil sump level, its oil circulation rate is always higher than the oil circulation rate of the higher suction pressure compressor. 
     
     
         17 . The refrigeration cycle of  claim 11 , wherein the lower suction pressure compressor is configured such that when the oil sump level of the lower suction pressure compressor is less than its predetermined oil sump level its oil circulation rate is always lower than the oil circulation rate entering the lower suction pressure compressor. 
     
     
         18 . The refrigeration cycle of  claim 11 , wherein the lower suction pressure compressor is configured such that when the oil sump level of the lower suction pressure compressor exceeds its predetermined oil sump level its oil circulation rate is always higher than the oil circulation rate entering the lower suction pressure compressor. 
     
     
         19 . A method for operating a compressor of a refrigeration cycle, comprising:
 operating the compression element such that a refrigerant flow of a gaseous refrigerant carrying an amount of oil circulates through the inlet port, the compression element and the outlet port, and that part of the oil carried by the gaseous refrigerant collects in the oil sump,   characterized by the step of directing oil from the oil sump to the refrigerant flow, when the oil in the oil sump exceeds a predetermined oil sump level.   
     
     
         20 . A method for operating a refrigeration cycle, comprising:
 providing at least one lower suction pressure compressor and at least one higher suction pressure compressor connected in series and being configured such that when the oil sump level of the lower suction pressure compressor is less than its predetermined oil sump level, its oil circulation rate is always lower than the oil circulation rate of the higher suction pressure compressor and that when the oil sump level of the lower suction pressure compressor exceeds its predetermined oil sump level, its oil circulation rate is always higher than the oil circulation rate of the higher suction pressure compressor:   operating the compression elements such that a refrigerant flow of a gaseous refrigerant carrying an amount of oil circulates through the inlet port, the compression element and the outlet port, and that part of the oil carried by the gaseous refrigerant collects in the oil sump;   directing, in the lower suction pressure compressors, oil from the oil sump to the refrigerant flow and thus to the higher suction pressure compressors connected downstream, when the oil in the oil sump exceeds a predetermined oil sump level and thereby achieving a self-regulating balance of oil between the lower suction pressure compressors and the higher suction pressure compressors.