Heat dissipation system with hygroscopic working fluid

Abstract

A system and method for transferring heat from a process source and dissipating it to the ambient atmosphere. The system uses a low-volatility, hygroscopic working fluid to reject thermal energy directly to ambient air. Direct-contact heat exchange allows for the creation of large interfacial surface areas for effective heat transfer. Heat transfer is further enhanced by water vapor pressure gradients present between the equilibrium moisture content of the working fluid and the ambient air. Cyclic absorption and evaporation of atmospheric moisture dampens variations in cooling capacity because of ambient temperature changes. The low-volatility and hygroscopic nature of the working fluid prevents complete evaporation of the fluid and a net consumption of water.

1 . A method for heat dissipation comprising:
 providing a low-volatility hygroscopic working fluid,   removing heat from a process heat exchanger to absorb thermal energy for dissipation using the low-volatility hygroscopic working fluid,   providing a working fluid-air contactor,   enabling combined heat dissipation from the low-volatility hygroscopic working fluid to the air using the fluid-air contactor, and   enabling a bidirectional moisture mass transfer between the low-volatility hygroscopic working fluid and the air using the working fluid-air contactor.   
     
     
         2 . The method for heat dissipation according to  claim 1 , wherein the hygroscopic working fluid comprises an aqueous solution including at least one of sodium chloride (NaCl), calcium chloride (CaCl 2 ), lithium chloride (LiCl), lithium bromide (LiBr), zinc chloride (ZnCl 2 ), sulfuric acid (H 2 SO 4 ), sodium hydroxide (NaOH), sodium sulfate (Na 2 SO 4 ), potassium chloride (KCl), calcium nitrate (Ca[NO 3 ] 2 ), potassium carbonate (K 2 CO 3 ), ammonium nitrate (NH 4 NO 3 ), ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, dipropylene glycol, and any combination thereof. 
     
     
         3 . The method for heat dissipation according to  claim 1 , wherein the process heat exchanger comprises one of a condenser of a thermodynamic power production or a refrigeration cycle. 
     
     
         4 . The method for heat dissipation according to  claim 1 , wherein the fluid-air contactor operates in at least one relative motion including countercurrent, cocurrent, or cross-flow operation. 
     
     
         5 . The method for heat dissipation according to  claim 1 , wherein the fluid-air contactor is enhanced by at least one of the forced or induced draft of ambient air by a powered fan; the natural convection airflow generated from buoyancy differences between heated and cooled air; and the induced flow of air generated by the momentum transfer of sprayed working fluid into the air. 
     
     
         6 . The method for heat dissipation according to  claim 1 , wherein said ambient airstream is supplemented with additional humidity from at least one of:
 a spray, mist, or fog of water directly into the airstream,   an exhaust gas stream from a drying process,   an exhaust gas stream consisting of high-humidity rejected air displaced during the ventilation of conditioned indoor spaces,   an exhaust airstream from a wet evaporative cooling tower, and   an exhaust flue gas stream from a combustion source and any associated flue gas treatment equipment.   
     
     
         7 . The method for heat dissipation according to  claim 1 , wherein the overall heat-transfer performance is enhanced by addition of moisture to the hygroscopic working fluid using any one of:
 direct addition of liquid water to the hygroscopic working fluid and   absorption of vapor-phase moisture by the working fluid from a moisture-containing gas stream outside of the process air contactor, where the moisture-containing gas stream could include ambient air into which water has been evaporated by spraying or misting, flue gas from a combustion source and its associated flue gas treatment equipment, exhaust gas from a drying process, rejected high-humidity air displaced during ventilation of conditioned indoor air, or the exhaust airstream from a wet evaporative cooling tower.   
     
     
         8 . The method for heat dissipation according to  claim 1 , wherein the process heat exchanger is cooled by a flowing film of said hygroscopic working fluid enabling both sensible and latent heat transfer to occur during thermal energy absorption from the process fluid. 
     
     
         9 . The method for heat dissipation according to  claim 8 , wherein the process heat exchanger is placed at the inlet to said air contactor for raising inlet airflow humidity levels. 
     
     
         10 . The method for heat dissipation according to  claim 8 , wherein the process heat exchanger is placed at the outlet of said air contactor for receiving air dehumidified with respect to the ambient air atmosphere. 
     
     
         11 . A heat dissipation method comprising:
 removing heat from a process heat exchanger absorbing thermal energy using a low-volatility hygroscopic working fluid,   enabling combined heat dissipation from the low-volatility hygroscopic working fluid to the air using a fluid-air contactor, and   enabling a bidirectional moisture mass transfer between the low-volatility hygroscopic working fluid and the air using the working fluid-air contactor.   
     
     
         12 . The method for heat dissipation according to  claim 11 , wherein the hygroscopic working fluid comprises an aqueous solution including at least one of sodium chloride (NaCl), calcium chloride (CaCl 2 ), lithium chloride (LiCl), lithium bromide (LiBr), zinc chloride (ZnCl 2 ), sulfuric acid (H 2 SO 4 ), sodium hydroxide (NaOH), sodium sulfate (Na 2 SO 4 ), potassium chloride (KCl), calcium nitrate (Ca[NO 3 ] 2 ), potassium carbonate (K 2 CO 3 ), ammonium nitrate (NH 4 NO 3 ), ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, dipropylene glycol, and any combination thereof. 
     
     
         13 . The method for heat dissipation according to  claim 11 , wherein the process heat exchanger comprises one of a condenser of a thermodynamic power production or a refrigeration cycle. 
     
     
         14 . The method for heat dissipation according to  claim 11 , wherein the fluid-air contactor operates in at least one relative motion including countercurrent, cocurrent, or cross-flow operation. 
     
     
         15 . The method for heat dissipation according to  claim 11 , wherein the fluid-air contactor is enhanced by at least one of the forced or induced draft of ambient air by a powered fan; the natural convection airflow generated from buoyancy differences between heated and cooled air; and the induced flow of air generated by the momentum transfer of sprayed working fluid into the air. 
     
     
         16 . The method for heat dissipation according to  claim 11 , wherein said ambient airstream is supplemented with additional humidity from at least one of a spray, mist, or fog of water directly into the airstream, an exhaust gas stream from a drying process, an exhaust gas stream consisting of high-humidity rejected air displaced during the ventilation of conditioned indoor spaces, an exhaust airstream from a wet evaporative cooling tower, and an exhaust flue gas stream from a combustion source and any associated flue gas treatment equipment. 
     
     
         17 . The method for heat dissipation according to  claim 11 , wherein the overall heat-transfer performance is enhanced by addition of moisture to the hygroscopic working fluid using at least one of direct addition of liquid water to the hygroscopic working fluid and absorption of vapor-phase moisture by the working fluid from a moisture-containing gas stream outside of the process air contactor, where the moisture-containing gas stream could include ambient air into which water has been evaporated by spraying or misting, flue gas from a combustion source and its associated flue gas treatment equipment, exhaust gas from a drying process, rejected high-humidity air displaced during ventilation of conditioned indoor air, or the exhaust airstream from a wet evaporative cooling tower. 
     
     
         18 . The method for heat dissipation according to  claim 11 , wherein the process heat exchanger is cooled by a flowing film of said hygroscopic working fluid enabling both sensible and latent heat transfer to occur during thermal energy absorption from the process fluid. 
     
     
         19 . The method for heat dissipation according to  claim 18 , wherein the process heat exchanger is placed at the inlet to said air contactor for raising inlet airflow humidity levels. 
     
     
         20 . The method for heat dissipation according to  claim 18 , wherein the process heat exchanger is placed at the outlet of said air contactor for receiving air dehumidified with respect to the ambient air atmosphere.