Ammonia refrigeration system

Abstract

In accordance with the present disclosure there is provided an efficient refrigeration system for cooling an environment using ammonia and sodium thiocyanate using a low grade heat source. The refrigeration system comprises a condenser for condensing vaporous ammonia to liquid ammonia coupled to an evaporator. The condenser condenses the ammonia vapour using a heat exchanger. The evaporator evaporates liquid ammonia to vaporous ammonia by absorbing heat from the cooling environment. An absorber absorbs the vaporous ammonia into an ammonia sodium thiocyanate solution and adsorbs vaporous ammonia on to sodium thiocyanate salts. The absorber is coupled to a regenerator through a solution pump for pumping ammonia sodium thiocyanate solution with dissolved ammonia from the absorber to the regenerator. The regenerator regenerates ammonia vapour from the pumped solution and supplies the regenerated ammonia vapour to the condenser and the concentrated solution back to the absorber.

1 . A refrigeration system for cooling a cooling environment using a low grade heat source, the refrigeration system comprising:
 a condenser for condensing vaporous ammonia to liquid ammonia using a first heat exchanger;   an evaporator coupled to the condenser through a first valve, the evaporator for evaporating liquid ammonia to vaporous ammonia by absorbing heat from the cooling environment, the evaporator receiving the liquid ammonia from condenser;   an absorber coupled to the evaporator, the absorber for absorbing vaporous ammonia into an ammonia sodium thiocyanate solution and for adsorbing vaporous ammonia onto sodium thiocyanate salts, the absorber receiving the vaporous ammonia from the evaporator;   a regenerator for regenerating ammonia vapour from the ammonia sodium thiocyanate solution with the absorbed vaporous ammonia, the regenerator coupled to the condenser for supplying the regenerated ammonia vapour to the condenser; and the regenerator further coupled to the absorber for returning the concentrated thiocyanate solution to the absorber; and   a solution pump for pumping the ammonia sodium thiocyanate solution with dissolved ammonia from the absorber to the regenerator.   
     
     
         2 . The refrigeration system as claimed in  claim 1 , wherein the regenerator is coupled to the absorber through a second valve and a second heat exchanger, the second heat exchanger cooling the ammonia sodium thiocyanate solution 
     
     
         3 . The refrigeration system as claimed in  claim 2 , wherein the first and second heat exchanger dissipate the heat with a cooling medium. 
     
     
         4 . The refrigeration system as claimed in  claim 3 , wherein the cooling medium is water, anti-freezing agent or air. 
     
     
         5 . The refrigeration system as claimed in  claim 1 , wherein the first valve comprises a first energy recuperator for recovering energy from the expansion of the liquid ammonia, the recovered energy providing energy to the solution pump. 
     
     
         6 . The refrigeration system as claimed in  claim 2 , wherein the second valve comprises a second energy recuperator for recovering energy from the flow of the concentrated ammonia sodium thiocyanate solution, the recovered energy providing additional energy to power the solution pump. 
     
     
         7 . The refrigeration system as claimed in  claim 1 , further comprising a compressor coupled between the expander and the absorber for compressing the vaporous ammonia. 
     
     
         8 . The refrigeration system as claimed in  claim 1 , further comprising a third heat exchanger coupled between the expander and the absorber for dissipating heat from the vaporous ammonia. 
     
     
         9 . An absorber for use in a refrigeration system comprising:
 an outer shell comprising:
 an outlet for removing ammonia sodium thiocyanate solution; 
 an inlet for adding concentrated ammonia sodium thiocyanate solution to the absorber; and 
 an inner cavity for holding:
 ammonia sodium thiocyanate solution for absorbing ammonia vapour, and 
 sodium thiocyanate salts for adsorbing ammonia vapour; 
 
   an inner tube having an inlet and outlet end, the inner tube located within the inner cavity of the outer shell; and   a gas duct for transporting ammonia vapour into the ammonia sodium thiocyanate solution within the inner tube from the inlet end to the outlet end.   
     
     
         10 . The absorber as claimed in  claim 9 , wherein the inner cavity further holds anti-fouling particles that are of a similar density of the ammonia sodium thiocyanate solution. 
     
     
         11 . The absorber as claimed in  claim 9 , wherein the gas duct comprises a gas nozzle for bubbling the ammonia vapour into the ammonia sodium thiocyanate solution. 
     
     
         12 . The absorber as claimed in  claim 9 , wherein the outer shell is made of one of aluminium;
 steel;   stainless steel; and   titanium.   
     
     
         13 . A regenerator for regenerating ammonia vapour from a solution of ammonia sodium thiocyanate for use in a refrigeration system using a low grade heat source, the regenerator comprising:
 an outer shell having an inner cavity and a circulation means for circulating a heat transfer medium from the inner cavity to a low grade heat exchanger for exchanging heat from the low grade heat source to the heat transfer medium;   an inner tube having:
 an inlet portion at a first end for receiving a solution of ammonia sodium thiocyanate; 
 an outlet portion at an other end for recovering regenerated ammonia vapour and separating the regenerated ammonia vapour from the concentrated ammonia sodium thiocyanate solution, and 
 a heat transfer portion arranged between the inlet portion and the outlet portion, the heat transfer portion located within the inner cavity of the outer shell; and 
   wherein the ammonia thiocyanate solution absorbs heat from the heat transfer medium within the heat transfer portion of the inner tube and regenerates the ammonia vapour.   
     
     
         14 . The regenerator as claimed in  claim 13 , further comprising a plurality of inner tubes located partially within the inner cavity of the outer shell. 
     
     
         15 . The regenerator as claimed in  claim 14 , wherein longitudinal axes of the inner tubes are arranged substantially parallel to a longitudinal axis of the outer shell. 
     
     
         16 . The regenerator as claimed in  claim 15 , wherein the inner tubes are made from one of:
 aluminium;   steel;   stainless steel; and   titanium.   
     
     
         17 . The regenerator as claimed in  claim 16 , wherein the inner tubes have a diameter in the range of 0.75 to 1 inch 
     
     
         18 . The regenerator as claimed in  claim 17 , wherein the low grade heat source is one of:
 a solar heat source;   process waste heat;   engine exhaust heat;   generator exhaust heat;   a biomass heat source; and   a geothermal heat source.