Low pressure refrigeration system with membrane purge

Abstract

Disclosed is a refrigeration system including a heat transfer fluid circulation loop configured to allow a refrigerant to circulate through the circulation loop. A purge gas outlet is in operable communication with the heat transfer fluid circulation loop. The system also includes at least one gas permeable membrane having a first side in operable communication with the purge gas outlet and a second side. The membrane includes a separation layer including a porous inorganic material with pores of a size to allow passage of contaminants through the membrane and restrict passage of the through the membrane, and a polymer coating over the separation layer. A permeate outlet is in operable communication with the second side of the membrane.

1 . A refrigeration system comprising
 a heat transfer fluid circulation loop configured to allow a refrigerant to circulate therethrough;   a purge gas outlet in operable communication with the heat transfer fluid circulation loop;   at least one gas permeable membrane having a first side in operable communication with the purge gas outlet and a second side, said membrane comprising a separation layer comprising a porous inorganic material with pores of a size to allow passage of contaminants through the membrane and restrict passage of the refrigerant through the membrane, and a polymer coating over said separation layer; and   a permeate outlet in operable communication with the second side of the membrane.   
     
     
         2 . The refrigeration system of  claim 1 , further comprising a prime mover operably coupled to the permeate outlet, the prime mover configured to move gas from the second side of the membrane to an exhaust port leading outside the fluid circulation loop. 
     
     
         3 . The refrigeration system of  claim 1 , wherein the heat transfer fluid circulation loop comprises a compressor, a heat rejection heat exchanger, an expansion device, and a heat absorption heat exchanger, connected together in order by conduit;
 wherein the purge gas outlet is in operable communication with at least one of the heat rejection heat exchanger, the heat absorption heat exchanger, or the membrane.   
     
     
         4 . The refrigeration system of  claim 2  wherein the prime mover comprises a vacuum pump in operable communication with the second side of the membrane. 
     
     
         5 . The refrigeration system of  claim 1 , further comprising a filter in operable communication with the purge outlet and the first side of the membrane. 
     
     
         6 . The refrigeration system of  claim 1 , wherein the separation layer comprises a ceramic material. 
     
     
         7 . The refrigeration system of  claim 6 , wherein the membrane comprises zeolite. 
     
     
         8 . The refrigeration system of  claim 1 , wherein the at least one gas permeable membrane comprises a plurality of gas permeable membranes; wherein the plurality of gas permeable membranes are arranged in serial or parallel communication. 
     
     
         9 . The refrigeration system of  claim 1 , wherein the polymer layer comprises a polymer selected from a silicone rubber, fluorosilicone or polyimide. 
     
     
         10 . The refrigeration system of  claim 1 , wherein the polymer layer has a thickness of 0.05 μm to 50 μm. 
     
     
         11 . The refrigeration system of  claim 1 , further comprising a controller configured to operate the fluid circulation loop in response to a cooling demand signal and to operate the prime mover in response to a determination of contaminants in the fluid circulation loop. 
     
     
         12 . The refrigeration system of  claim 11 , wherein the controller is configured to activate a purge back-flush mode in which gas is transported from the second side of the membrane to the first side of the membrane. 
     
     
         13 . The refrigeration system of  claim 11 , wherein the controller is configured to activate a heat source to heat the membrane to a temperature to remove contaminants. 
     
     
         14 . A method of operating a refrigeration system, comprising
 circulating a refrigerant through a heat transfer fluid circulation loop in response to a cooling demand signal;   collecting purge gas comprising contaminants from a purge outlet in the fluid circulation loop;   transferring the contaminants across a permeable molecular sieve membrane with a prime mover, said membrane comprising a porous inorganic or metal organic framework with pores of a size to allow passage of the contaminants through the membrane and restrict passage of the refrigerant through the membrane; and   periodically back-flushing the membrane by transporting gas from the second side of the membrane to the first side of the membrane, or periodically heating the membrane to a temperature to remove contaminants, or both periodically transporting gas from the second side of the membrane to the first side of the membrane and periodically heating the membrane to a temperature to remove contaminants.   
     
     
         15 . The method of  claim 14 , comprising periodically back-flushing the membrane by transporting gas from the second side of the membrane to the first side of the membrane. 
     
     
         16 . The method of  claim 14  comprising periodically heating the membrane to a temperature to remove contaminants. 
     
     
         17 . The method of  claim 14 , further comprising passing the purge gas through a filter before reaching the membrane. 
     
     
         18 . The method of  claim 14 , further comprising transporting the contaminants through a polymer coating on the inorganic or metal organic framework membrane. 
     
     
         19 . The method of  claim 14 , further comprising collecting the purge gas in a purge gas collector between the purge outlet and the membrane. 
     
     
         20 . The method of  claim 14 , further comprising returning refrigerant from the first side of the membrane to the fluid circulation loop.