Liquid desiccant air conditioning using air as heat transfer medium

Abstract

A liquid desiccant system includes a liquid desiccant circuit having an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, the liquid desiccant flowing between the absorber unit and the desorber unit. The liquid desiccant system includes a supply airflow path that passes through the absorber unit, forms an absorber liquid / air interface within the absorber unit, and forms a conditioned airflow exiting the absorber unit. The liquid desiccant system includes a regeneration gas flow path that passes through the desorber unit, forms a desorber liquid / air interface within the desorber unit, and forms an exhaust gas flow exiting the desorber unit. A heat exchanger is thermally coupled to the supply airflow path to remove heat from the supply airflow upstream of the absorber unit. A heat exchanger is thermally coupled to the regeneration gas stream path to add heat to the regeneration gas stream upstream of the desorber unit.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application No. 17,719,598, filed on April 13, 2022, entitled “Liquid Desiccant Air Conditioning Using Air As Heat Transfer Medium,” which is incorporated herein by reference in its entirety. Summary of the invention

[0003] The present disclosure generally relates to air dehumidification systems utilizing liquid desiccant.

[0004] The present disclosure relates to a liquid desiccant system in which heat and mass transfer occurs only at the liquid / air interface within the desorber unit and the absorber unit. The liquid desiccant system may not include a desiccant-liquid (such as water or refrigerant) heat exchanger, thereby reducing the complexity and cost of the liquid desiccant system while achieving a highly efficient air dehumidification system.

[0005] The present disclosure relates to a liquid desiccant system, the liquid desiccant system comprising a liquid desiccant loop having an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, the liquid desiccant flowing between the absorber unit and the desorber unit. The liquid desiccant system comprises a supply airflow path, the supply airflow path passing through the absorber unit, forming an absorber liquid / air interface in the absorber unit, and forming a conditioned airflow leaving the absorber unit. The liquid desiccant system comprises a regeneration airflow path, the regeneration airflow path passing through the desorber unit, forming a desorber liquid / air interface in the desorber unit, and forming an exhaust airflow leaving the desorber unit. A heat exchanger is thermally coupled to the supply airflow path to remove heat from the supply airflow upstream of the absorber unit. A heat exchanger is thermally coupled to the regeneration airflow path to add heat to the regeneration airflow upstream of the desorber unit. At least 95% or at least 99% of the total heat added to the liquid desiccant can be added at the desorber liquid / air interface.

[0006] The present disclosure relates to a liquid desiccant system, the liquid desiccant system comprising a liquid desiccant loop having an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, the liquid desiccant flowing between the absorber unit and the desorber unit. The liquid desiccant system comprises a supply airflow path, the supply airflow path passing through the absorber unit, forming an absorber liquid / air interface in the absorber unit, and forming a conditioned airflow leaving the absorber unit. The liquid desiccant system comprises a regeneration airflow path, the regeneration airflow path passing through the desorber unit, forming a desorber liquid / air interface in the desorber unit, and forming an exhaust airflow leaving the desorber unit. A heat exchanger is thermally coupled to the supply airflow path to remove heat from the supply airflow upstream of the absorber unit. The heat exchanger is also thermally coupled to the regeneration airflow path to add heat to the regeneration airflow upstream of the desorber unit. At least 95% or at least 99% of the total heat added to the liquid desiccant can be added at the desorber liquid / air interface.

[0007] The present disclosure relates to a method of conditioning an airflow, the method comprising circulating a liquid desiccant through a liquid desiccant loop, the liquid desiccant loop comprising an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, flowing supply air along a supply airflow path and through the absorber unit to form an absorber liquid / air interface within the absorber unit and to form a conditioned airflow leaving the absorber unit, and flowing regeneration air along a regeneration airflow path and through the desorber unit to form a desorber liquid / air interface within the desorber unit and to form an exhaust airflow leaving the desorber unit. The method comprises removing heat from the supply air upstream of the absorber unit and adding heat to the regeneration airflow upstream of the desorber unit. The liquid desiccant has a first temperature when leaving the desorber unit and a second temperature when entering the absorber unit, and the first temperature and the second temperature are within 5% of each other, or within 1% of each other, or are equal to each other. At least 95% or at least 99% of the total heat added to the liquid desiccant can be added at the desorber liquid / air interface.

[0008] The present disclosure relates to a method for conditioning an airflow, the method comprising circulating a liquid desiccant through a liquid desiccant loop, the liquid desiccant loop comprising an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, flowing supply air along a supply airflow path and through the absorber unit to form an absorber liquid / air interface within the absorber unit and form a conditioned airflow leaving the absorber unit, and flowing regeneration air along a regeneration airflow path and through the desorber unit to form a desorber liquid / air interface within the desorber unit and form an exhaust airflow leaving the desorber unit. The method comprises removing heat from the supply air upstream of the absorber unit and adding the heat to the regeneration airflow upstream of the desorber unit. The liquid desiccant has a first temperature when leaving the desorber unit and a second temperature when entering the absorber unit, and the first temperature and the second temperature are within 5% of each other, or within 1% of each other, or are equal to each other. At least 95% or at least 99% of the total heat added to the liquid desiccant can be added at the desorber liquid / air interface.

[0009] The present disclosure relates to a liquid desiccant system, the liquid desiccant system comprising a liquid desiccant loop having an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, the liquid desiccant flowing between the absorber unit and the desorber unit. The liquid desiccant system comprises a supply airflow path, the supply airflow path passing through the absorber unit, forming an absorber liquid / air interface in the absorber unit, and forming a conditioned airflow leaving the absorber unit. The liquid desiccant system comprises a regeneration airflow path, the regeneration airflow path passing through the desorber unit, forming a desorber liquid / air interface in the desorber unit, and forming an exhaust airflow leaving the desorber unit. A heat exchanger is thermally coupled to the supply airflow path to remove heat from the supply airflow upstream of the absorber unit. The heat exchanger is also thermally coupled to the regeneration airflow path to add heat to the regeneration airflow upstream of the desorber unit. The liquid desiccant loop does not include a refrigerant-liquid heat exchanger or a water-liquid desiccant heat exchanger.

[0010] The present disclosure relates to a method of conditioning an airflow, the method comprising circulating a liquid desiccant through a liquid desiccant loop, the liquid desiccant loop comprising an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, flowing supply air along a supply airflow path and through the absorber unit to form an absorber liquid / air interface within the absorber unit and to form a conditioned airflow exiting the absorber unit, and flowing regeneration air along a regeneration airflow path and through the desorber unit to form a desorber liquid / air interface within the desorber unit and to form an exhaust airflow exiting the desorber unit. The method comprises removing heat from the supply air upstream of the absorber unit and adding heat to the regeneration airflow upstream of the desorber unit. The liquid desiccant loop does not include a refrigerant-liquid heat exchanger or a water-liquid desiccant heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following discussion refers to the following drawings, wherein like reference numerals may be used to identify similar / identical components throughout the various figures. The drawings are not necessarily drawn to scale.

[0012] Figure 1 is a schematic diagram of an illustrative liquid desiccant system; and

[0013] Figure 2 is a schematic diagram of another illustrative liquid desiccant system. DETAILED DESCRIPTION

[0014] The present disclosure relates generally to heating, ventilation and air conditioning (HVAC) systems. In an exemplary embodiment, a gas-liquid vapor exchanger includes an absorber unit and a desorber unit to regenerate a liquid desiccant passing through the two units. These units can be used to absorb water vapor into and desorb water vapor from the liquid desiccant to dehumidify or humidify the air. The humidification and dehumidification can be used for HVAC heating and cooling applications.

[0015] Air conditioning systems can perform two functions simultaneously: a first function for dehumidification and a second function for cooling the forced airflow. Commonly used air conditioning systems use vapor compression, which can both dehumidify and cool the incoming air. However, given a humid airflow, vapor compression can rely on cooling the airflow to below its delivery temperature to condense moisture and achieve low absolute humidity, and then reheating the air to its delivery temperature. This moisture condensation process significantly increases the energy requirements of air conditioning, especially in humid climates. An alternative dehumidification method known as liquid desiccant dehumidification can significantly reduce the energy intensity of air conditioning and is the subject of the present disclosure.

[0016] Using a liquid desiccant to remove moisture from the air is an energy-efficient alternative to vapor compression because it minimizes or eliminates the need to cool and reheat the air stream. In a liquid desiccant dehumidification system, humid air exchanges water vapor with a liquid desiccant. A gas-liquid vapor exchanger (absorber unit) can be used to contact the humid air and the liquid desiccant and transfer the water vapor in the humid air to the liquid desiccant to form a loaded liquid desiccant. The loaded liquid desiccant can be regenerated in a gas-liquid vapor exchanger (desorber unit) by heating the loaded liquid desiccant to drive off the water vapor and returning the regenerated liquid desiccant to the absorber unit.

[0017] The present disclosure relates to a liquid desiccant system in which heat and mass transfer occurs only at the liquid / air interface within the desorber unit and the absorber unit. Heat is added or removed from the liquid desiccant only at the liquid / air interface within the desorber unit and the absorber unit. The liquid desiccant system may not include a desiccant-liquid (such as water or refrigerant) heat exchanger, thereby reducing the complexity and cost of the liquid desiccant system while achieving a highly efficient air dehumidification system.

[0018] In current liquid desiccant air conditioning systems, heat exchangers are used to cool and heat the liquid desiccant. These heat exchanges are typically countercurrent unit operations in which the heating or cooling liquid flows in a first direction and the liquid desiccant flows in the opposite direction and transfers heat through the heat exchanger conduit walls by thermal conduction. These heat exchangers are formed of exotic materials to handle the corrosive liquid desiccant and are therefore expensive and complex.

[0019] The present disclosure eliminates these desiccant-liquid heat exchangers while providing a highly efficient liquid desiccant air conditioning system. The present disclosure provides a simplified liquid desiccant air conditioning system that can be easily retrofitted to a conventional air conditioning system. The present disclosure describes a highly efficient liquid desiccant air conditioning system that utilizes standard air coils to heat and cool the air entering the absorber unit and the desorber unit. The air passing through the absorber unit and the desorber unit provides heating and cooling of the liquid desiccant. This simplifies the system architecture, removes expensive parts, and opens the door to liquid desiccant retrofits of existing conventional air conditioners.

[0020] Figure 1 is a schematic diagram of an illustrative liquid desiccant system 100 . Figure 2 is a schematic diagram of another illustrative liquid desiccant system 100 . Figure 2 The liquid desiccant system 100 illustrates adding heat removed from an absorber operation 101 to a desorber operation 102 . Figure 1The liquid desiccant system 100 is shown removing heat from the absorber operation 101 through the heat sink 145 and adding heat to the desorber operation 102 through the heat source 155. The heat sink 145 can be any useful heat sink unit operation that removes heat from the absorber operation 101, such as a refrigerant-to-air condenser coil, a cooling water coil, an evaporative cooler, etc. The heat source 155 can be any useful heat source unit operation that provides heat to the desorber operation 102 (such as electric heat, gas heat, solar heat, geothermal heat, condenser coils, etc.).

[0021] The liquid desiccant system 100 includes a liquid desiccant loop 110 having an absorber unit 112 in fluid communication with a desorber unit 114 and a liquid desiccant flowing between the absorber unit 112 and the desorber unit 114 .

[0022] The liquid desiccant system 100 includes a supply gas flow path 120 that passes through the absorber unit 112 and forms an absorber liquid / air interface within the absorber unit 112 and forms a conditioned gas flow 122 that exits the absorber unit 112. The liquid desiccant system 100 includes a regeneration gas flow path 130 that passes through the desorber unit 114 and forms a desorber liquid / air interface within the desorber unit 114 and forms an exhaust gas flow 132 that exits the desorber unit 114.

[0023] Heat exchanger 140 is thermally coupled to supply gas flow path 120 for removing heat from supply gas flow 120 upstream of absorber unit 112. Heat exchanger 150 is thermally coupled to regeneration gas flow path 130 for adding heat to regeneration gas flow 130 upstream of desorber unit 114.

[0024] The liquid desiccant has a first temperature when leaving the absorber unit 112 and a second temperature when entering the desorber unit 114, and the first temperature and the second temperature are within 5% of each other, or within 1% of each other, or are equal to each other. At least 95% or at least 99% of the total heat added to the liquid desiccant can be added at the desorber liquid / air interface.

[0025] The liquid desiccant has a first temperature when leaving the desorber unit 114 and a second temperature when entering the absorber unit 112, and the first temperature and the second temperature are within 5% of each other, or within 1% of each other, or are equal to each other. At least 95% or at least 99% of the total heat removed to the liquid desiccant can be removed at the absorber liquid / air interface.

[0026] In absorber operation 101, the heat exchanger 140 may include an evaporator coil located within the supply airflow path 120, the evaporator coil being configured to remove heat from the supply airflow. The cooled supply airflow 121 then enters the absorber unit 112 to cool the liquid desiccant (removing heat from the liquid desiccant) and transfer humidity from the cooled supply airflow to the liquid desiccant at the absorber liquid / air interface.

[0027] The absorber liquid / air interface can be formed by any vapor / liquid mass transfer unit operation. Illustrative vapor / liquid mass transfer unit operations include, for example, packed beds, tray columns, spray columns, bubbling columns, membranes, and the like.

[0028] For absorber operation 101, both heat transfer and mass transfer occur only at the liquid / air interface within the absorber unit 112. Heat is not removed from the liquid desiccant outside the absorber unit 112.

[0029] In the desorber operation 102, the heat exchanger 150 may include a condenser coil located within the regeneration gas flow path 130, the condenser coil being configured to add heat to the regeneration gas flow. The heated regeneration gas flow 131 then enters the desorber unit 114 to both heat the liquid desiccant and transfer moisture from the liquid desiccant to the heated regeneration gas flow at the desorber liquid / air interface.

[0030] The desorber liquid / air interface can be formed by any vapor / liquid mass transfer unit operation. Illustrative vapor / liquid mass transfer unit operations include, for example, packed beds, tray columns, spray columns, bubble columns, membranes, and the like.

[0031] For the desorber operation 102, both heat transfer and mass transfer occur only at the liquid / air interface within the desorber unit 114. Heat is not added from the liquid desiccant outside the desorber unit 114.

[0032] The system or liquid desiccant loop 110 does not include a refrigerant-liquid heat exchanger or a water-liquid desiccant heat exchanger. The liquid desiccant loop is a closed loop that does not include heat exchange unit operation other than heat exchange at the liquid / air interface within the absorber unit 112 and the desorber unit 114. Heat is not added or removed from the liquid desiccant outside the absorber unit 112 or the desorber unit 114. The liquid desiccant loop 110 includes one or more liquid pumps, and it is assumed that the liquid pump does not add appreciable heat to the liquid desiccant through the pumping action of the liquid pump.

[0033] The liquid desiccant loop 110 may include an absorber recirculation loop 113. The absorber recirculation loop 113 takes liquid desiccant from the absorber unit 112 and pumps it back into the absorber unit 112. The liquid desiccant loop 110 includes a transfer conduit 115 to fluidly connect the liquid desiccant from the absorber unit 112 to the desorber unit 114. The liquid desiccant loop 110 includes a transfer conduit 116 to fluidly connect the liquid desiccant from the desorber unit 114 to the absorber unit 112.

[0034] Figure 1 and Figure 2 The desorber unit 114 is shown with a single pass of liquid desiccant through the desorber unit 114. The mass flow rate of liquid desiccant through the desorber unit 114 is substantially equal to the mass flow rate of liquid desiccant entering the desorber unit 114 from the absorber unit 112 through the transfer line 115. The mass flow rate of liquid desiccant through the desorber unit 114 is substantially equal to the mass flow rate of liquid desiccant leaving the desorber unit 114 to the absorber unit 112 through the transfer line 116.

[0035] Alternatively, the liquid desiccant loop 110 may include a desorber recirculation loop (not shown). The desorber recirculation loop takes liquid desiccant from the desorber unit 114 and pumps it back into the desorber unit 114. In these embodiments, the mass flow rate of liquid desiccant passing through the desorber unit 114 is greater than either the mass flow rate of liquid desiccant entering the desorber unit 114 from the absorber unit 112 through the transfer conduit 115 or the mass flow rate of liquid desiccant leaving the desorber unit 114 to the absorber unit 112 through the transfer conduit 116.

[0036] The liquid desiccant has a first temperature when it leaves the absorber unit 112 and has a second temperature when it enters the desorber unit 114 through the conduit 115. The first temperature and the second temperature are within 5% of each other, or within 1% of each other, or are equal to each other. Heat is not added to the liquid desiccant along the conduit 115 from the absorber unit 112 to the desorber unit 114. Heat is not removed from the liquid desiccant along the conduit 115 from the absorber unit 112 to the desorber unit 114. No heat is added or removed along the recirculation conduit 113, except for a small amount of heat added by the fluid pump through pumping.

[0037] The liquid desiccant has a first temperature when it leaves the desorber unit 114 and has a second temperature when it enters the absorber unit 112 through the conduit 116. The first temperature and the second temperature are within 5% of each other, or within 1% of each other, or are equal to each other. Heat is not added to the liquid desiccant along the conduit 116 from the desorber unit 114 to the absorber unit 112. Heat is not removed from the liquid desiccant along the conduit 116 from the desorber unit 114 to the absorber unit 112. No heat is added to any desorber unit 114 recirculation conduit (if any) except for a small amount of heat added by pumping by the fluid pump.

[0038] The regeneration gas stream 130, 131 entering the desorber unit 114 has a regeneration mass gas flow value, and the liquid desiccant flowing through the desorber unit 114 has a desorber liquid desiccant mass flow value. The regeneration mass gas flow value is in the range of 40 to 80 times the desorber liquid desiccant mass flow value. The regeneration mass gas flow value is in the range of 50 to 70 times the desorber liquid desiccant mass flow value. The regeneration mass gas flow value is in the range of 55 to 65 times the desorber liquid desiccant mass flow value.

[0039] The supply gas flow 120, 121 entering the absorber unit 112 has a supply mass gas flow value, and the liquid desiccant flowing through the absorber unit 112 has an absorber liquid desiccant mass flow value. The supply mass gas flow value is in the range of 1 to 10 times the absorber liquid desiccant mass flow value. The supply mass gas flow value is in the range of 1 to 10 times the absorber liquid desiccant mass flow value. The supply mass gas flow value is in the range of 1 to 5 times the absorber liquid desiccant mass flow value. The supply mass gas flow value is in the range of 1 to 3 times the absorber liquid desiccant mass flow value.

[0040] The liquid desiccant may flow through the absorber unit 112 at an absorber liquid desiccant mass flow value, and the liquid desiccant may flow through the desorber unit 114 at a desorber liquid desiccant mass flow value. The desorber liquid desiccant mass flow value is 0.5% to 5% of the absorber liquid desiccant mass flow value. The desorber liquid desiccant mass flow value is 0.5% to 4% of the absorber liquid desiccant mass flow value. The desorber liquid desiccant mass flow value is 1% to 3% of the absorber liquid desiccant mass flow value.

[0041] The liquid desiccant can be a halide salt solution. The halide salt can be selected from sodium chloride (NaCl), potassium chloride (KCl), potassium iodide (KI), lithium chloride (LiCl), copper (II) chloride (CuCl2), silver chloride (AgCl), calcium chloride (CaCl2), chlorine fluoride (ClF), methyl bromide (CH3Br), iodoform (CHI3), hydrogen chloride (HCl), lithium bromide (LiBr), hydrogen bromide (HBr) and combinations thereof. In some embodiments, the halide salt solution is selected from LiCl, NaCl, LiBr and CaCl2. In some embodiments, the halide salt solution is LiCl. The solution can be water and is described as an aqueous solution. The halide salt can be present in the liquid desiccant in a range of 2 to 50%wt, or in a range of 10 to 40%wt, or in a range of 20 to 40%wt.

[0042] The concentration value of the liquid desiccant in the desorber unit 114 is greater than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 3% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 4% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 5% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 6% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 7% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration of the liquid desiccant in the desorber unit 114 may be 8% greater by weight than the concentration of the liquid desiccant in the absorber unit 112 .

[0043] The concentration value of the liquid desiccant in the desorber unit 114 may be 3% to 15% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 3% to 10% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 5% to 15% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112. The concentration value of the liquid desiccant in the desorber unit 114 may be 5% to 10% greater by weight than the concentration value of the liquid desiccant in the absorber unit 112.

[0044] Figure 2The liquid desiccant system 100 shows that heat removed from the absorber operation 101 is added to the desorber operation 102. The vapor compressor 157 moves refrigerant and heat from the supply gas stream 120 to the regeneration gas stream 130. The heat removed from the supply gas stream 120 is added to the regeneration gas stream 130. Additional heat from the vapor compressor 157 can also be added to the regeneration gas stream 130.

[0045] In some embodiments, a portion of the heat removed from the supply gas flow 120 is dissipated in the condenser unit 152 rather than along the regeneration gas flow path 130. In other embodiments, a portion of the regeneration gas flow is removed from the regeneration gas flow path between the heat exchanger 150 and the desorber unit 114.

[0046] The method of conditioning airflow includes circulating a liquid desiccant through a liquid desiccant loop 110, the liquid desiccant loop including an absorber unit 112 in fluid communication with a desorber unit 114. The method includes flowing supply air along a supply airflow path 120 and through the absorber unit 112 to form an absorber liquid / air interface within the absorber unit 112 and to form a conditioned airflow 122 that exits the absorber unit 112. The method includes flowing regeneration air along a regeneration airflow path 130 and through the desorber unit 114 to form a desorber liquid / air interface within the desorber unit 114 and to form an exhaust airflow 132 that exits the desorber unit 114. The method includes removing heat from the supply air 120 upstream of the absorber unit 112 and adding heat to the regeneration airflow 130 upstream of the desorber unit 114. The liquid desiccant has a first temperature when leaving the desorber unit 114 and a second temperature when entering the absorber unit 112, and the first temperature and the second temperature are within 5% of each other, or within 1% of each other, or are equal to each other. At least 95% or at least 99% of the total heat added to the liquid desiccant can be added at the desorber unit 114 liquid / air interface.

[0047] The method includes flowing regeneration air 130 through the desorber unit 114 at a regeneration mass gas flow value and flowing liquid desiccant through the desorber unit 114 at a desorber liquid desiccant mass flow value. The regeneration mass gas flow value is in the range of 40 to 80 times the desorber liquid desiccant mass flow value. The regeneration mass gas flow value is in the range of 50 to 70 times the desorber liquid desiccant mass flow value. The regeneration mass gas flow value is in the range of 55 to 65 times the desorber liquid desiccant mass flow value.

[0048] The method may include flowing supply air 120 through the absorber unit 112 at a supply mass airflow value and flowing liquid desiccant through the absorber unit 112 at an absorber liquid desiccant mass flow value. The supply mass airflow value is in a range of 1 to 10 times the absorber liquid desiccant mass flow value. The supply mass airflow value is in a range of 1 to 5 times the absorber liquid desiccant mass flow value. The supply mass airflow value is in a range of 1 to 3 times the absorber liquid desiccant mass flow value.

[0049] The method may include flowing the liquid desiccant through the absorber unit 112 at a first mass flow rate and flowing the liquid desiccant from the absorber unit 112 to the desorber 114 at a second mass flow rate. The second mass flow rate is 0.5% to 5% of the first mass flow rate. The second mass flow rate is 0.5% to 4% of the first mass flow rate. The second mass flow rate is 1% to 3% of the first mass flow rate.

[0050] The removing heat step may include flowing supply air over evaporator coils 140 within supply airflow path 120. Adding heat may include flowing regeneration air over condenser coils 150 within regeneration airflow path 130. The method does not include a refrigerant-liquid desiccant heat exchanger or a water-liquid desiccant heat exchanger.

[0051] Examples

[0052] In one embodiment, the supply gas stream has a temperature of 21 degrees Celsius (70 degrees Fahrenheit), an absolute humidity of 0.0128 kgH2O / kg air, and a flow rate of 1000 CFM. The evaporator coil removes heat from the supply gas stream to form a cooled supply gas stream, which has a temperature of 15 degrees Celsius (60 degrees Fahrenheit), an absolute humidity of 77.3, and a flow rate of 1000 CFM when entering the absorber unit. The liquid desiccant that is recycled in the absorber unit and leaves the absorber unit has a temperature of 21 degrees Celsius (70 degrees Fahrenheit) and a flow rate of 0.25 liters / minute to the desorber unit, and a recirculation flow rate of 12 liters / minute. In the absorber unit operation, the liquid desiccant is an aqueous solution containing about 25% wt desiccant (LiCl). The temperature of the conditioned gas stream leaving the absorber unit is 21 degrees Celsius (70 degrees Fahrenheit), an absolute humidity of 0.0091 kgH2O / kg air, and a flow rate of 1000 CFM. The absorber air mass flow: absorber liquid desiccant mass flow is about 2.5:1.

[0053] In this embodiment, the temperature of the regeneration gas stream is 21 degrees Celsius (70 degrees Fahrenheit), the absolute humidity is 0.0128 kg H2O / kg air, and the flow rate is 550 CFM. The condenser coil adds heat to the regeneration gas stream to form a heated regeneration gas stream, which has a temperature of 38 degrees Celsius (100 degrees Fahrenheit), an absolute humidity of 0.0127 kg H2O / kg air, and a flow rate of 550 CFM when entering the desorber unit. The temperature of the liquid desiccant circulating through the desorber unit and leaving the desorber unit is 37 degrees Celsius (98 degrees Fahrenheit) and the flow rate is 0.19 liters / minute. In the desorber unit operation, the liquid desiccant is an aqueous solution containing about 32% wt desiccant (LiCl). The temperature of the exhaust gas stream leaving the desorber unit is 28 degrees Celsius (83 degrees Fahrenheit), the absolute humidity is 113, and the flow rate is 550 CFM. The desorber air mass flow: desorber liquid desiccant mass flow is about 61:1.

[0054] In this system, heat is added to the liquid desiccant only at the liquid / air interface within the desorber unit. In this system, heat is removed to the liquid desiccant only at the liquid / air interface within the absorber unit.

[0055] This example has demonstrated a surprisingly high dehumidification efficiency (MRE) of about 4 kg / kWh. MRE is the dehumidification rate (mass / time) divided by the power input to the air conditioning or liquid desiccant system.

[0056] Unless otherwise stated, all numbers representing feature sizes, quantities, and physical properties used in the specification and claims will be understood to be modified by the term "about" in all instances. Therefore, unless otherwise indicated, the numerical parameters set forth in the foregoing specification and the appended claims are approximate values, which can vary according to the desired properties sought to be obtained by those skilled in the art using the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within the range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within the range.

[0057] The foregoing description has been presented for the purpose of illustration and description. The description is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. Any or all features of the disclosed embodiments may be applied individually or in any combination and are not meant to be limiting, but purely illustrative. The scope of the invention is not limited to this detailed description, but is determined by the appended claims.

Claims

1. A liquid desiccant system, comprising: a liquid desiccant loop comprising an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, the liquid desiccant flowing between the absorber unit and the desorber unit; a supply gas flow path that passes through the absorber unit, forms an absorber liquid / air interface within the absorber unit, and forms a conditioned gas flow that exits the absorber unit; a regeneration gas flow path that passes through the desorber unit, forms a desorber liquid / air interface within the desorber unit, and forms an exhaust gas flow that exits the desorber unit; as well as a heat exchanger thermally coupled to the supply gas flow path and removing heat from the supply gas flow upstream of the absorber unit, the heat exchanger thermally coupled to the regeneration gas flow path and adding heat to the regeneration gas flow upstream of the desorber unit; wherein at least 95% of the total heat added to the liquid desiccant is added at the desorber liquid / air interface within the desorber unit.

2. The liquid desiccant system of claim 1, wherein at least 99% of the total heat added to the liquid desiccant is added at the desorber liquid / air interface within the desorber unit.

3. The liquid desiccant system of claim 1, wherein the liquid desiccant has a first temperature when leaving the absorber unit and has a second temperature when entering the desorber unit, and the first temperature and the second temperature are substantially equal.

4. The liquid desiccant system of claim 1, wherein the heat exchanger comprises an evaporator coil located within the supply air flow path, the evaporator coil being configured to remove heat from the supply air flow.

5. The liquid desiccant system of claim 1, wherein the heat exchanger comprises a condenser coil located within the regeneration gas flow path, the condenser coil being configured to add heat from the regeneration gas flow.

6. The liquid desiccant system of claim 1, wherein the liquid desiccant loop does not include a refrigerant-to-liquid heat exchanger or a water-to-liquid desiccant heat exchanger.

7. The liquid desiccant system of claim 1, wherein the heat removed from the supply gas stream is added to the regeneration gas stream.

8. The liquid desiccant system of claim 7, wherein a portion of the heat removed from the supply airflow is dissipated in a condenser unit rather than along the regeneration airflow path.

9. The liquid desiccant system of claim 7, wherein a portion of the regeneration gas stream is removed from the regeneration gas stream path between the heat exchanger and the desorber unit.

10. The liquid desiccant system of claim 1, wherein the regeneration gas flow entering the desorber unit has a regeneration mass gas flow value, and the liquid desiccant flowing through the desorber unit has a desorber liquid desiccant mass flow value, and the regeneration mass gas flow value is in the range of 40 to 80 times the desorber liquid desiccant mass flow value.

11. The liquid desiccant system of claim 10, wherein the supply airflow entering the absorber unit has a supply mass airflow value, and the liquid desiccant flowing through the absorber unit has an absorber liquid desiccant mass flow value, and the supply mass airflow value is in the range of 1 to 10 times the absorber liquid desiccant mass flow value.

12. The liquid desiccant system of claim 10, wherein the liquid desiccant flows through the absorber unit at an absorber liquid desiccant mass flow value and the liquid desiccant flows through the desorber unit at a desorber liquid desiccant mass flow value, and the desorber liquid desiccant mass flow value is 0.5% to 5% of the absorber liquid desiccant mass flow value, and the desorber liquid desiccant mass flow value passing through the desorber unit is substantially equal to the liquid desiccant mass flow value from the absorber unit to the desorber unit.

13. The liquid desiccant system of claim 1, wherein the liquid desiccant comprises LiCl, NaCl, LiBr, or CaCl2.

14. The liquid desiccant system of claim 1, wherein the liquid desiccant comprises LiCl.

15. The liquid desiccant system of claim 10, wherein liquid desiccant flows through the absorber unit at an absorber liquid desiccant mass flow value and liquid desiccant flows through the desorber unit at a desorber liquid desiccant mass flow value, and the desorber liquid desiccant mass flow value is 0.5% to 5% of the absorber liquid desiccant mass flow value, and the desorber liquid desiccant mass flow value passing through the desorber unit is greater than the liquid desiccant mass flow value from the absorber unit to the desorber unit.

16. The liquid desiccant system of claim 1, wherein a concentration value of the liquid desiccant in the desorber unit is 3% greater by weight than a concentration value of the liquid desiccant in the absorber unit.

17. The liquid desiccant system of claim 1, wherein a concentration value of the liquid desiccant in the desorber unit is 5% greater by weight than a concentration value of the liquid desiccant in the absorber unit.

18. A method of regulating airflow, the method comprising: circulating a liquid desiccant through a liquid desiccant circuit comprising an absorber unit and liquid desiccant, the absorber unit being in fluid communication with a desorber unit; flowing supply air along a supply airflow path and through the absorber unit to form an absorber liquid / air interface within the absorber unit and to form a conditioned airflow exiting the absorber unit; flowing regeneration air along a regeneration gas flow path and through the desorber unit to form a desorber liquid / air interface within the desorber unit and to form an exhaust gas flow exiting the desorber unit; removing heat from the supply air upstream of the absorber unit; and adding heat to the regeneration air upstream of the desorber unit; Wherein the liquid desiccant has a first temperature when leaving the desorber unit and has a second temperature when entering the absorber unit, and the first temperature and the second temperature are substantially equal.

19. The method of claim 18, further comprising flowing regeneration air through the desorber unit at a regeneration mass airflow value and flowing liquid desiccant through the desorber unit at a desorber liquid desiccant mass flow value, and the regeneration mass airflow value is in the range of 40 to 80 times the desorber liquid desiccant mass flow value.

20. The method of claim 19, further comprising flowing supply air through the absorber unit at a supply mass airflow value and flowing liquid desiccant through the absorber unit at an absorber liquid desiccant mass flow value, and the supply mass airflow value is in the range of 1 to 10 times the absorber liquid desiccant mass flow value.

21. The method of claim 19, further comprising flowing liquid desiccant through the absorber unit at a first mass flow rate and flowing liquid desiccant from the absorber unit to the desorber unit at a second mass flow rate, and the second mass flow rate is 0.5% to 5% of the first mass flow rate.

22. The method of claim 18, wherein removing heat comprises flowing supply air over an evaporator coil within the supply air flow path, and adding the heat comprises flowing regeneration air over a condenser coil within the regeneration air flow path.

23. The method of claim 18, wherein the method does not include a refrigerant-liquid desiccant heat exchanger or a water-liquid desiccant heat exchanger.

24. The method of claim 18, wherein at least 95% of the total heat added to the liquid desiccant is added at the desorber liquid / air interface within the desorber unit.

25. The method of claim 18, wherein at least 99% of the total heat added to the liquid desiccant is added at the desorber liquid / air interface within the desorber unit.

26. A liquid desiccant system comprising: a liquid desiccant loop comprising an absorber unit and a liquid desiccant, the absorber unit being in fluid communication with a desorber unit, the liquid desiccant flowing between the absorber unit and the desorber unit; a supply gas flow path that passes through the absorber unit, forms an absorber liquid / air interface within the absorber unit, and forms a conditioned gas flow that exits the absorber unit; a regeneration gas flow path that passes through the desorber unit, forms a desorber liquid / air interface within the desorber unit, and forms an exhaust gas flow that exits the desorber unit; as well as a heat exchanger thermally coupled to the supply gas flow path and removing heat from the supply gas flow upstream of the absorber unit, the heat exchanger thermally coupled to the regeneration gas flow path and adding heat to the regeneration gas flow upstream of the desorber unit; The liquid desiccant loop does not include a refrigerant-liquid heat exchanger or a water-liquid desiccant heat exchanger.

27. The liquid desiccant system of claim 26, wherein at least 99% of the total heat added to the liquid desiccant is added at the desorber liquid / air interface within the desorber unit.

28. The liquid desiccant system of claim 27, wherein the liquid desiccant has a first temperature when exiting the absorber unit and has a second temperature when entering the desorber unit, and the first and second temperatures are substantially equal.

29. The liquid desiccant system of claim 26, wherein the heat exchanger comprises an evaporator coil located within the supply airflow path, the evaporator coil being configured to remove heat from the supply airflow, and the heat exchanger comprises a condenser coil located within the regeneration airflow path, the condenser coil being configured to add heat to the regeneration airflow, and the heat removed from the supply airflow is added to the regeneration airflow.

30. The liquid desiccant system of claim 29, wherein a portion of the heat removed from the supply airflow is dissipated in a condenser unit rather than along the regeneration airflow path.

31. The liquid desiccant system of claim 26, wherein the regeneration gas flow entering the desorber unit has a regeneration mass gas flow value, and the liquid desiccant flowing through the desorber unit has a desorber liquid desiccant mass flow value, and the regeneration mass gas flow value is in the range of 40 to 80 times the desorber liquid desiccant mass flow value.

32. The liquid desiccant system of claim 26, wherein the concentration of the liquid desiccant in the desorber unit is 3% greater by weight than the concentration of the liquid desiccant in the absorber unit.

33. The liquid desiccant system of claim 26, wherein the concentration of liquid desiccant in the desorber unit is 5% greater by weight than the concentration of liquid desiccant in the absorber unit.

34. A method of regulating airflow, the method comprising: circulating a liquid desiccant through a liquid desiccant circuit comprising an absorber unit and liquid desiccant, the absorber unit being in fluid communication with a desorber unit; flowing supply air along a supply airflow path and through the absorber unit to form an absorber liquid / air interface within the absorber unit and to form a conditioned airflow exiting the absorber unit; flowing regeneration air along a regeneration gas flow path and through the desorber unit to form a desorber liquid / air interface within the desorber unit and to form an exhaust gas flow exiting the desorber unit; removing heat from the supply air upstream of the absorber unit; as well as adding heat to the regeneration air upstream of the desorber unit; The liquid desiccant loop does not include a refrigerant-liquid heat exchanger or a water-liquid desiccant heat exchanger.

35. The method of claim 34, wherein at least 99% of the total heat added to the liquid desiccant is added at the desorber liquid / air interface within the desorber unit.

36. The method of claim 34, wherein the liquid desiccant has a first temperature when exiting the absorber unit and has a second temperature when entering the desorber unit, and the first temperature and the second temperature are substantially equal.

37. The method of claim 34, wherein the heat removed from the supply air is added to the regeneration air.

38. The method of claim 34, wherein the regeneration gas flow entering the desorber unit has a regeneration mass gas flow value, and the liquid desiccant flowing through the desorber unit has a desorber liquid desiccant mass flow value, and the regeneration mass gas flow value is in the range of 40 to 80 times the desorber liquid desiccant mass flow value.

39. The method of claim 34, wherein the concentration of liquid desiccant in the desorber unit is 3% greater by weight than the concentration of liquid desiccant in the absorber unit.

40. The method of claim 34, wherein the concentration of liquid desiccant in the desorber unit is 5% greater by weight than the concentration of liquid desiccant in the absorber unit.

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