Hybrid double-absorption cooling system

A hybrid double-absorption air cooling system utilizing low grade thermal energy comprising:

• (a) an absorber;
• (b) a generator;
• (c) first and second conduits connecting the absorber and the generator;
• (d) a first heat exchanger adapted to place a first fluid flowing through the first conduit in heat exchange relationship with a second fluid flowing through the second conduit;
• (e) a condenser;
• (f) a third conduit connecting the generator and the condenser;
• (g) an evaporator;
• (h) a fourth conduit connecting the condenser and the evaporator;
• (i) a fifth conduit connecting the evaporator and the absorber;
• (j) an open absorber;
• (k) a sixth conduit connecting the generator with the open absorber;
• (l) a seventh conduit attached between the open absorber and the first conduit at a point between the absorber and the first heat exchanger;
• (m) a first pump located on the first conduit between the absorber and the junction of the first and seventh conduits;
• (n) a first expansion valve located in the second conduit between the first heat exchanger and the absorber;
• (o) a second heat exchanger adapted to place fluids flowing through the sixth and seventh conduits in heat exchange relationship;
• (p) a second expansion valve located in the seventh conduit between the junction of the first and seventh conduits and the second heat exchanger;
• (g) a second pump located in the sixth conduit between the open absorber and the heat exchanger;
• (r) a bleed valve located in the fourth conduit;
• (s) a third expansion valve located in the fourth conduit between the bleed valve and the evaporator;
• (t) a first cooling coil circuit adapted for circulating a working fluid between the open absorber and the evaporator;
• (u) a second cooling coil adapted to circulate cooling water through the condenser;
• (v) a third cooling coil adapted to circulate cooling water through the absorber;
• and
• (w) a heating coil adapted to circulate water heated by a low grade heat source through the generator.

A method of cooling a process air stream by utilizing low grade thermal energy comprising the steps of:

• (a) contacting a liquid desiccant with water to form a desiccant solution;
• (b) concentrating the desiccant solution by placing it in heat exchange relation at subatmospheric pressure with a low grade energy source so as to vaporize at least a portion of the water from the desiccant solution;
• (c) collecting and condensing the vaporized water;
• (d) revaporizing the condensed water while placing it in heat exchange relationship with a first working fluid;
• (e) diluting at least a portion of the concentrated desiccant solution by bringing it in contact with the process air stream so as to remove water from the process air stream;
• (f) placing the process air stream in heat exchange relation with the first working fluid;
• and
• (g) contacting the desiccant solution with the revaporized water.

A method of cooling a process air stream by utilizing low grade thermal energy comprising the steps of:

• (a) contacting a desiccant with water in an absorber to form a weak desiccant solution;
• (b) pumping the weak desiccant solution from the absorber to a generator;
• (c) mixing the weak desiccant solution with more weak desiccant solution returning from an open absorber prior to passing the mixture to a generator;
• (d) concentrating the weak desiccant solution in the generator by heating the solution by means of a low grade thermal energy source whereby water is vaporized from the desiccant;
• (e) transferring the water vapor from the generator to a condenser;
• (f) condensing the water vapor in the condenser by cooling the vapor by using a first stream of cooling water;
• (g) pressurizing and condensed water to approximately one atmosphere;
• (h) cooling the condensed water through expansion and passing said condensed water to an evaporator;
• (i) pressurizing at least a portion of the strong desiccant solution from the generator to approximately one atmosphere and then communicating it to the open absorber;
• (j) bringing the strong desiccant solution into direct contact with the process air stream in the open absorber by dispensing it in the form of a fine film, whereby the strong solution is weakened by the absorption of water from the air;
• (k) circulating water between the open absorber and the evaporator such that it absorbs heat from the process air stream in the open absorber and revaporizes the condensed water in the evaporator;
• and
• (l) transferring the revaporized water from the evaporator to the absorber.

A hybrid absorption system utilizing low grade thermal energy to cool process air comprising:

• an open absorber for contacting the process air with a liquid desiccant solution and having one end of a cooling coil in heat exchange relation with the process air;
• a generator in heat exchange relation with a low grade thermal energy source and having first and second conduits placing the generator in fluid communication with the open absorber for circulating the liquid desiccant solution between the generator and the open absorber;
• a condenser in fluid communication with the generator;
• an evaporator in fluid communication with the condenser and having the other end of the cooling coil in heat exchange relation with the evaporator;
• and
• an absorber in fluid communication with the evaporator and the generator.