Methods and systems for liquid desiccant air conditioning

Abstract

Liquid desiccant air conditioning methods and systems are operable in multiple modes to efficiently treat air streams provided to a space.

1 . A liquid desiccant air-conditioning system operable in a plurality of operation modes, the system comprising:
 a conditioner for treating a first air stream flowing therethrough and provided to a space, said conditioner using a heat transfer fluid and a liquid desiccant to treat the first air stream;   a regenerator connected to the conditioner such that the liquid desiccant can be circulated between the regenerator and the conditioner, the regenerator causing the liquid desiccant to desorb water vapor to a second air stream or to absorb water vapor from the second air stream depending on a selected mode of operation of the system;   a refrigerant system;   a first refrigerant-to-heat transfer fluid heat exchanger connected to the conditioner and the refrigerant system for exchanging heat between the refrigerant heated or cooled by the refrigerant system and the heat transfer fluid used in the conditioner;   a second refrigerant-to-heat transfer fluid heat exchanger connected to the regenerator and the refrigerant system for exchanging heat between the refrigerant heated or cooled by the refrigerant system and the heat transfer fluid used in the regenerator;   an air-cooled heat exchanger connected indirectly to the refrigerant system via the first refrigerant-to-heat transfer fluid heat exchanger or the second refrigerant-to-heat transfer fluid heat exchanger, said air-cooled heat exchanger directly or indirectly exchanging heat between the refrigerant and the second air stream after the second air stream has exited the regenerator in a first setting; and   a valve system for selectively controlling flow of the refrigerant or the heat transfer fluid among the first refrigerant-to-heat transfer fluid heat exchanger, the second refrigerant-to-heat transfer fluid heat exchanger, and the air-cooled heat exchanger in accordance with a given mode of operation of the system.   
     
     
         2 . The system of  claim 1 , wherein the air-cooled heat exchanger is connected to the second refrigerant-to-heat transfer fluid heat exchanger in series. 
     
     
         3 . The system of  claim 1 , wherein the air-cooled heat exchanger is connected to the second refrigerant-to-heat transfer fluid heat exchanger in series or in parallel. 
     
     
         4 . The system of  claim 1 , wherein in a frost-free heating mode, the air-cooled coil provides sensible cooling of the second air stream. 
     
     
         5 . The system of  claim 1 , wherein in an advanced dehumidification mode, the air-cooled coil generates a cooling load in the refrigerant system to increase the concentration of the liquid desiccant in the regenerator. 
     
     
         6 . The system of  claim 1 , further comprising a second air-cooled heat exchanger connected directly to the refrigerant system, said air-cooled heat exchanger directly or indirectly exchanging heat between the refrigerant and an outside air stream to reduce the energy available for the regenerator in a cooling mode and increasing the sensible load of a compressor in the refrigerant system in a heating mode. 
     
     
         7 . The system of  claim 6 , wherein in a hot and humid weather mode, the air-cooled coil is disconnected from the first and second refrigerant-to-heat transfer fluid heat exchangers, and the second air-cooled coil is used to increase the humidity level of the first air stream by reducing the heat available to the regenerator. 
     
     
         8 . The system of  claim 6 , wherein in a hot and dry weather mode, heat from the refrigerant system is rejected through the second air-cooled coil. 
     
     
         9 . The system of  claim 8 , wherein the flow of heat transfer fluid through the regenerator is reduced. 
     
     
         10 . The system of  claim 8 , wherein flow of liquid desiccant through the conditioner is reduced. 
     
     
         11 . The system of  claim 1 , wherein in a cool and humid weather mode, the air-cooled coil provides a load to the refrigerant system to increase energy available to the regenerator to increase liquid desiccant concentration in the regenerator. 
     
     
         12 . The system of  claim 11 , wherein the conditioner dehumidifies the first air stream adiabatically. 
     
     
         13 . The system of  claim 11 , wherein the conditioner dehumidifies and reduces enthalpy of the first air stream. 
     
     
         14 . The system of  claim 6 , wherein in a non-freezing and humid weather mode, only the second air-cooled coil is used to provide a sensible load to the refrigerant system to heat the first air stream without humidification. 
     
     
         15 . The system of  claim 1 , wherein in a cold weather mode, the air-cooled coil is used to provide an additional sensible load to the refrigerant system by cooling dehumidified air from the regenerator to inhibit frost formation on the air-cooled coil, and to heat and humidify the first air stream. 
     
     
         16 . The system of  claim 1 , further comprising a damper to provide outside air to the air-cooled coil while the air-cooled coil is connected to the second refrigerant-to-heat transfer fluid heat exchanger in a second setting whereby the second air stream is exhausted from the regenerator. 
     
     
         17 . A liquid desiccant air-conditioning system operable in a plurality of operation modes, the system comprising:
 a conditioner for treating a first air stream flowing therethrough and provided to a space, said conditioner using a heat transfer fluid and a liquid desiccant to treat the first air stream;   a regenerator connected to the conditioner such that the liquid desiccant can be circulated between the regenerator and the conditioner, the regenerator causing the liquid desiccant to desorb water vapor to a second air stream or to absorb water vapor from the second air stream depending on a selected mode of operation of the system;   a refrigerant system;   a first refrigerant-to-heat transfer fluid heat exchanger connected to the conditioner and the refrigerant system for exchanging heat between the refrigerant heated or cooled by the refrigerant system and the heat transfer fluid used in the conditioner;   a second refrigerant-to-heat transfer fluid heat exchanger connected to the regenerator and the refrigerant system for exchanging heat between the refrigerant heated or cooled by the refrigerant system and the heat transfer fluid used in the regenerator;   an air-cooled heat exchanger connected either (i) directly to the refrigerant system or (ii) indirectly to the refrigerant system via the first refrigerant-to-heat transfer fluid heat exchanger or the second refrigerant-to-heat transfer fluid heat exchanger, said air-cooled heat exchanger directly or indirectly exchanging heat between the refrigerant and the second air stream after the second air stream has exited the regenerator in a first setting; and   a valve system for selectively controlling flow of the refrigerant or the heat transfer fluid among the first refrigerant-to-heat transfer fluid heat exchanger, the second refrigerant-to-heat transfer fluid heat exchanger, and the air-cooled heat exchanger in accordance with a given mode of operation of the system.   
     
     
         18 . The system of  claim 17 , wherein the air-cooled heat exchanger is connected to the second refrigerant-to-heat transfer fluid heat exchanger in series. 
     
     
         19 . The system of  claim 17 , wherein the air-cooled heat exchanger is connected to the second refrigerant-to-heat transfer fluid heat exchanger in series or in parallel. 
     
     
         20 . The system of  claim 17 , wherein in a frost-free heating mode, the air-cooled coil provides sensible cooling of the second air stream. 
     
     
         21 . The system of  claim 17 , wherein in an advanced dehumidification mode, the air-cooled coil generates a cooling load in the refrigerant system to increase the concentration of the liquid desiccant in the regenerator. 
     
     
         22 . The system of  claim 17 , further comprising a second air-cooled heat exchanger connected indirectly to the refrigerant system via the first refrigerant-to-heat transfer fluid heat exchanger or the second refrigerant-to-heat transfer fluid heat exchanger, said air-cooled heat exchanger directly or indirectly exchanging heat between the refrigerant and an outside air stream to reduce the energy available for the regenerator in a cooling mode and increasing the sensible load of a compressor in the refrigerant system in a heating mode. 
     
     
         23 . The system of  claim 22 , wherein in a hot and humid weather mode, the air-cooled coil is disconnected from the first and second refrigerant-to-heat transfer fluid heat exchangers, and the second air-cooled coil is used to increase the humidity level of the first air stream by reducing the heat available to the regenerator. 
     
     
         24 . The system of  claim 22 , wherein in a hot and dry weather mode, heat from the refrigerant system is rejected through the second air-cooled coil. 
     
     
         25 . The system of  claim 17 , wherein in a cool and humid weather mode, the air-cooled coil provides a load to the refrigerant system to increase energy available to the regenerator to increase liquid desiccant concentration in the regenerator. 
     
     
         26 . The system of  claim 25 , wherein the conditioner dehumidifies the first air stream adiabatically. 
     
     
         27 . The system of  claim 25 , wherein the conditioner dehumidifies and reduces enthalpy of the first air stream. 
     
     
         28 . The system of  claim 22 , wherein in a non-freezing and humid weather mode, only the second air-cooled coil is used to provide a sensible load to the refrigerant system to heat the first air stream without humidification. 
     
     
         29 . The system of  claim 17 , wherein in a cold weather mode, the air-cooled coil is used to provide an additional sensible load to the refrigerant system by cooling dehumidified air from the regenerator to inhibit frost formation on the air-cooled coil, and to heat and humidify the first air stream. 
     
     
         30 . The system of  claim 17 , further comprising a damper to provide outside air to the air-cooled coil while the air-cooled coil is connected to the second refrigerant-to-heat transfer fluid heat exchanger in a second setting whereby the second air stream is exhausted from the regenerator. 
     
     
         31 . A liquid desiccant air-conditioning system, comprising:
 a conditioner for treating a first air stream flowing therethrough and provided to a space, said conditioner using a heat transfer fluid and a liquid desiccant to cool the first air stream to a desired temperature and to control the humidity of the first air stream to a desired humidity level;   a regenerator connected to the conditioner such that the liquid desiccant can be circulated between the regenerator and the conditioner, the regenerator causing the liquid desiccant to desorb water vapor to a second air stream or to absorb water vapor from a second air stream to concentrate or dilute the liquid desiccant as needed in the conditioner to maintain the desired humidity level of the first air stream;   a refrigerant system for cooling the heat transfer fluid in the conditioner, said refrigerant system rejecting heat through the regenerator; and   a liquid desiccant dilution system for selectively controlling water addition to the liquid desiccant in the regenerator to increase the humidity level and decrease the temperature of the first air stream to the desired temperature and humidity level.   
     
     
         32 . The system of  claim 31 , wherein the liquid desiccant dilution system dilutes the liquid desiccant directly by adding demineralized water to a liquid desiccant tank to maintain a constant level in the tank and a given minimum level of relative humidity of the first air stream. 
     
     
         33 . The system of  claim 31 , wherein the liquid desiccant dilution system dilutes a flow of the liquid desiccant using a membrane module. 
     
     
         34 . The system of  claim 33 , wherein the membrane module comprises a vapor transition membrane or a forward osmosis membrane. 
     
     
         35 . The system of  claim 31 , wherein the liquid desiccant dilution system indirectly dilutes the liquid desiccant by increasing the humidity of the air stream entering the regenerator. 
     
     
         36 . The system of  claim 35 , wherein humidity of the air stream is increased by an indirect evaporator or a mist forming nozzle. 
     
     
         37 . The system of  claim 31 , wherein in a hot and dry weather mode, the liquid desiccant dilution system is used to increase both the absolute and relative humidity levels of the first air stream. 
     
     
         38 . The system of  claim 31 , the liquid desiccant dilution system is used to reduce the temperature and absolute humidity of the first air stream, while increasing its relative humidity. 
     
     
         39 . The system of  claim 31 , wherein in a cold and dry weather mode, the liquid desiccant dilution system is used to humidify the first air stream.