Oil management in refrigeration systems

Abstract

A refrigeration assembly includes a receiver tank, a heat exchanger, a first piping assembly, and a second piping assembly. The receiver tank has a fluid outlet and a fluid inlet that receives a working fluid. The heat exchanger is disposed within the receiver tank. The heat exchanger has coiled tubing that is fluidly coupled to the fluid inlet and to the fluid outlet. The first piping assembly is disposed between and is fluidly coupled to the fluid inlet and the coiled tubing. The first piping assembly has a first double riser and a first P-trap. The second piping assembly is disposed between and is fluidly coupled to the fluid outlet and the coiled tubing. The second piping assembly includes a second double riser and a second P-trap.

What is claimed is: 
     
         1 . A refrigeration assembly comprising:
 a receiver tank comprising a fluid outlet and a fluid inlet configured to receive a working fluid;   a heat exchanger disposed within the receiver tank, the heat exchanger comprising coiled tubing fluidly coupled to the fluid inlet and to the fluid outlet;   a first piping assembly disposed between and fluidly coupled to the fluid inlet and the coiled tubing, the first piping assembly comprising a first double riser and a first P-trap;   a second piping assembly disposed between and fluidly coupled to the fluid outlet and the coiled tubing, the second piping assembly comprising a second double riser and a second P-trap.   
     
     
         2 . The refrigeration assembly of  claim 1 , wherein the working fluid comprises a mixture of refrigerant and oil, and the first P-trap and the second P-trap are configured to retain oil accumulated during flowing of the working fluid through the refrigeration assembly. 
     
     
         3 . The refrigeration assembly of  claim 2 , wherein each of the first piping assembly and the second piping assembly are configured to flow, during different load conditions of the refrigeration assembly, the oil from the respective P-traps toward the fluid outlet of the heat exchanger. 
     
     
         4 . The refrigeration assembly of  claim 2 , wherein the coiled tubing comprises a first end attached to the first double riser and a second end attached to the second double riser, the first end residing at a first elevation and the second end residing at a second elevation lower than the first elevation. 
     
     
         5 . The refrigeration assembly of  claim 4 , wherein the first double riser is configured to flow oil received from the first P-trap to the coiled tubing, the second P-trap configured to receive oil from the coiled tubing, and the second double riser configured to flow oil received from the second P-trap to the fluid outlet of the heat exchanger. 
     
     
         6 . The refrigeration assembly of  claim 4 , wherein the refrigeration assembly is configured to operate under a first load condition and a second load condition higher than the first load condition, a first riser of the first double riser configured to increase a flow speed of the working fluid with the first P-trap substantially blocked by accumulated oil during the first load condition, and a second riser of the second double riser configured to increase a flow speed of the working fluid with the second P-trap substantially blocked by accumulated oil during the first load condition. 
     
     
         7 . The refrigeration assembly of  claim 1 , wherein the first P-trap is configured to retain oil received from the fluid inlet during a low-load condition of the refrigeration assembly, and the second P-trap is configured to retain oil received from the coiled tubing during the low-load condition of the refrigeration assembly. 
     
     
         8 . The refrigeration assembly of  claim 1 , wherein the fluid inlet is fluidly coupled to a supply suction line comprising a first diameter and the fluid outlet is fluidly coupled to a return suction line comprising a second diameter substantially equal to the first diameter. 
     
     
         9 . The refrigeration assembly of  claim 1 , wherein the first double riser and the second double riser each comprise a first riser comprising a first diameter and a second riser comprising a second diameter larger than the first diameter, the second riser comprising the respective P-trap, and each of the first riser and second riser attached to the respective fluid outlet or fluid inlet of the heat exchanger. 
     
     
         10 . The refrigeration assembly of  claim 1 , wherein the receiver tank comprises a flash tank of a CO 2  refrigeration assembly, the heat exchanger coil configured to flow CO 2  as refrigerant and the receiver tank configured to retain a liquid phase of the CO 2  refrigerant in thermal contact with the heat exchanger coil, the fluid inlet of the flash tank configured to receive CO 2  refrigerant from one or more evaporators, and the fluid outlet configured to route the CO 2  refrigerant to one or more compressors. 
     
     
         11 . The refrigeration assembly of  claim 10 , where the first piping assembly and the second piping assembly are in thermal contact with the fluid inside the receiver tank such that the working fluid flowing through the first piping assembly and the second piping assembly transfers heat to the liquid inside the receiver tank or the liquid inside the receiver tank transfers heat to the first piping assembly and the second piping assembly. 
     
     
         12 . A refrigeration assembly comprising:
 a receiver tank defining a volume configured to retain a liquid; and   a heat exchanger disposed within the receiver tank and in thermal contact with the liquid, the heat exchanger configured to flow a working fluid there through and transfer heat from the working fluid to the liquid, the heat exchanger comprising:
 coiled tubing, 
 a fluid inlet fluidly coupled to the coiled tubing and configured to receive the working fluid, 
 a piping assembly disposed between and fluidly coupled to the fluid inlet and the coiled tubing, the piping assembly comprising a riser and an oil trap, and 
 a fluid outlet fluidly coupled to the coiled tubing, the fluid outlet configured to flow the working fluid received from coiled tubing out of the receiver tank. 
   
     
     
         13 . The refrigeration assembly of  claim 12 , wherein the riser comprises a second coiled tubing in thermal communication with the liquid inside the receiver tank, the second coiled tubing disposed between the fluid inlet and the fluid outlet of the heat exchanger. 
     
     
         14 . The refrigeration assembly of  claim 12 , wherein the oil trap is disposed downstream of the riser and resides between the riser and the coiled tubing. 
     
     
         15 . The refrigeration assembly of  claim 12 , wherein the riser is attached, at a fluid connection, to a pipe connected to the outlet, the fluid connection disposed between the fluid outlet and the coiled tubing. 
     
     
         16 . The refrigeration assembly of  claim 12 , wherein the working fluid comprises a mixture of refrigerant and oil, the oil trap configured to retain oil accumulated during flowing of the refrigerant through the heat exchanger, and the piping assembly configured to flow, during different load conditions of the refrigeration assembly, the oil from the oil trap toward the fluid outlet of the heat exchanger. 
     
     
         17 . The refrigeration assembly of  claim 16 , wherein the coiled tubing comprises a first end attached to the fluid outlet and a second end attached to the fluid inlet, the first end residing at a first elevation and the second end residing at a second elevation lower than the first elevation, the riser configured to flow oil received from the oil trap to the fluid outlet of the heat exchanger. 
     
     
         18 . The refrigeration assembly of  claim 12 , further comprising a second piping assembly attached to and residing between the coiled tubing and the fluid outlet, the piping assembly attached to and residing between the coiled tubing and the fluid inlet, the piping assembly comprising a second riser attached to the oil trap, and the second piping assembly comprising a second oil trap, a third riser, and a fourth riser attached to the oil trap. 
     
     
         19 . The refrigeration assembly of  claim 18 , wherein the refrigeration assembly is configured to operate under a first load condition and a second load condition higher than the first load condition, the riser configured to increase a flow speed of the working fluid with the oil trap substantially blocked by accumulated oil during the first load condition, and the second riser configured to increase a flow speed of the working fluid with the second oil trap substantially blocked by accumulated oil during the first load condition. 
     
     
         20 . The refrigeration assembly of  claim 12 , wherein the fluid inlet is fluidly coupled to a supply suction line comprising a first diameter and the fluid outlet is fluidly coupled to a return suction line comprising a second diameter substantially equal to the first diameter.