Refrigerant circuit and method for managing oil therein

Abstract

Refrigerant circuit ( 2 ) comprising a low pressure compressor unit ( 38 ) having a low pressure refrigerant outlet ( 42 ) in a low pressure sub-circuit ( 4 ) and a higher pressure compressor unit ( 8 ) having a higher pressure refrigerant inlet ( 12 ) in a higher pressure sub-circuit ( 6 ), wherein the low pressure refrigerant outlet ( 42 ) and the higher pressure refrigerant inlet ( 12 ) are fluidly connected with each other, further comprising an oil reservoir ( 56 ) connected by a low pressure oil inlet conduit ( 54 ) to the low pressure sub-circuit ( 4 ) for receiving oil therefrom and connected via an oil discharge ( 62 ) to the higher pressure sub-circuit ( 6 ).

1 . Refrigerant circuit comprising a low pressure compressor unit having a low pressure refrigerant outlet in a low pressure sub-circuit and a higher pressure compressor unit having a higher pressure refrigerant inlet in a higher pressure sub-circuit, wherein the low pressure refrigerant outlet and the higher pressure refrigerant inlet are fluidly connected with each other, further comprising an oil reservoir connected by a low pressure oil inlet conduit to the low pressure sub-circuit for receiving oil therefrom and connected via an oil discharge to the higher pressure sub-circuit and a receiver in the higher pressure sub-circuit, a pressurizing line connecting the receiver with the oils reservoir and a pressurizing valve in the pressurizing line. 
     
     
         2 . Refrigerant circuit according to  claim 1 , wherein the oil reservoir is connected to a tapping means for tapping excess oil from the low pressure compressor unit. 
     
     
         3 . Refrigerant circuit according to  claim 1 , wherein the oil reservoir is fluidly connected to the oil sump of the low pressure compressor unit so that the oil level in the oil reservoir and that of the oil sump in the low pressure compressor unit are same level during operation. 
     
     
         4 . Refrigerant circuit according to  claim 1 , further comprising a low pressure shut-off valve in the oil inlet conduit. 
     
     
         5 . Refrigerant circuit according to  claim 1 , wherein the oil reservoir further comprises a pressure release means. 
     
     
         6 . Refrigerant circuit according to  claim 5 , wherein the pressure relief means is a release conduit connecting the oil reservoir with a low pressure section line and comprising a release valve. 
     
     
         7 . Refrigerant circuit according to  claim 1 , further comprising a heater connected to the oil reservoir. 
     
     
         8 . Refrigerant circuit according to  claim 1 , further comprising a oil transfer conduit with an oil transfer valve connecting the higher pressure compressor unit to the oil reservoir. 
     
     
         9 . Refrigeration apparatus comprising a refrigerant circuit comprising a low pressure compressor unit having a low pressure refrigerant outlet in a low pressure sub-circuit and a higher pressure compressor unit having a higher pressure refrigerant inlet in a higher pressure sub-circuit wherein the low pressure refrigerant outlet and the higher pressure refrigerant inlet are fluidly connected with each other, further comprising an oil reservoir connected by a low pressure oil inlet conduit to the low pressure sub-circuit for receiving oil therefrom and connected via an oil discharge to the higher pressure sub-circuit and a receiver in the higher pressure sub-circuit, a pressurizing line connecting the receiver with the oils reservoir and a pressurizing valve in the pressurizing line. 
     
     
         10 . Method for managing oils in a refrigerant circuit comprising a low pressure compressor unit having a low pressure refrigerant outlet in a low pressure sub-circuit and a higher pressure compressor unit having a higher pressure refrigerant inlet in a higher pressure sub-circuit, wherein the low pressure refrigerant outlet and the higher pressure refrigerant inlet are fluidly connected with each other, further comprising a receiver in the higher pressure sub-circuit, a pressurizing line connecting the receiver with the oils reservoir and a pressurizing valve in the pressurizing line, comprising the step of collecting excess oil from the low pressure sub-circuit in an oil reservoir and pressurizing the oil in the oil reservoir for transferring oil into the higher pressure sub-circuit, wherein the step of pressurizing the oil reservoir comprises supplying refrigerant from the high pressure portion of the higher pressure sub-circuit into the oil reservoir. 
     
     
         11 . Method according to  claim 10 , further comprising the step of tapping excess oil from the low pressure compressor unit by means of a tapping means. 
     
     
         12 . Method according to  claim 10 , wherein the pressurizing is performed in intervals and further comprising the step of maintaining an equal oil level in the oil reservoir and the compressor unit at times where the oil in the reservoir is not pressurized. 
     
     
         13 . Method according to  claim 10 , further comprising the step of closing a shut-off valve in the oil inlet conduit to the oil reservoir before pressurizing the same. 
     
     
         14 . Method according to  claim 13 , further comprising the step of releasing pressure for the oil reservoir before opening the shut-off valve again. 
     
     
         15 . Method according to  claim 10 , wherein the step of pressurizing the oil reservoir comprises the heating thereof. 
     
     
         16 . Method according to  claim 10 , further comprising the step of transferring excess oil from the higher pressure sub-circuit to the oil reservoir.