US20150047382A1

US20150047382A1 - Fully regenerative liquid desiccant system for residential applications

Info

Publication number: US20150047382A1
Application number: US14/462,051
Authority: US
Inventors: Owen P. Jappen; Daniel Munt; Victoria K. Baldwin; John Wright; Samuel Cochran; Ronald S. Besser
Original assignee: Stevens Institute of Technology
Current assignee: Stevens Institute of Technology
Priority date: 2013-08-19
Filing date: 2014-08-18
Publication date: 2015-02-19

Abstract

An air dehumidification system includes a modified packed column air stripper for contacting humid air with a liquid desiccant. The dehumidification system also includes a solar distiller for regenerating the liquid desiccant through evaporation of water. The liquid desiccant may be a salt solution, more specifically, an aqueous solution of calcium chloride. The dehumidification system may also include an evaporative cooler for cooling dehumidified air exiting the air stripper. Condensate from the solar distiller may be directed to the evaporative cooler.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Patent Application No. 61/867,530, having a filing date of Aug. 19, 2013, the disclosure of which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to absorptive and evaporative technologies for humidity and temperature control in residential buildings, and, more particularly, to such technologies as operate using alternative energy sources, such as solar energy.

BACKGROUND OF THE INVENTION

Conventional air conditioning systems rely primarily on energy-intensive refrigeration technologies in which electrical energy is used to compress and decompress a refrigerant through successive refrigeration cycles. New design philosophies promote the use of technologies that have low energy demands compared to conventional processes. Desiccant air conditioning systems are able to utilize alternative energy sources for cooling and dehumidification of indoor air, thereby reducing electric power consumption and reliance upon conventional power sources.

SUMMARY OF THE INVENTION

In an aspect of the present invention, an air dehumification system comprises a dehumidification unit and a desiccant regenerating unit. In an embodiment, the dehumidification systems including means for contacting humid air with a liquid desiccant solution, thereby humidifying the desiccant solution and dehumidifying the air. In an embodiment, the desiccant regeneration system includes means for removing water from the humidified desiccant solution as water vapor, thereby regenerating the desiccant solution. In an embodiment, the liquid desiccant and humid are contacted with each other in a packed column air stripper. In an embodiment, the desiccant regeneration unit includes a solar distiller for removing the water vapor from the humidified desiccant solution. In an embodiment, the dehumidification system further includes an evaporative cooling unit for cooling the dehumidified air. In an embodiment, the water from the regenerative unit is condensed and the resulting condensate is directed to the evaporative cooling unit.

BRIEF DESCRIPTION OF THE FIGURES

For a more complete understanding of the present invention, reference is made to the following detailed description of exemplary embodiments considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a conceptual system for dehumidification of ambient indoor air according to a first embodiment of the present invention;

FIG. 2 is a plot of the relative humidity of air in equilibrium with a range of concentrations of a desiccant solution suitable for use in some embodiments of the present invention;

FIG. 3 is a plot of the relative humidity of air over time through contact with a desiccant solution suitable for use in some embodiments of the present invention;

FIG. 4 is a schematic diagram of a dehumidification system for the implementation of the conceptual approach illustrated in FIG. 1;

FIG. 5 is a schematic flow sheet for a dehumidification subsystem according to a second embodiment of the present invention;

FIG. 6 is a schematic flow sheet for a water management subsystem according to a third embodiment of the present invention;

FIG. 7 is a schematic flow sheet for an air conditioning system according to a fourth embodiment of the present invention;

FIG. 8 is a schematic cross-sectional elevation of a partial dehumidification unit according to a fifth embodiment of the present invention;

FIG. 9 is a schematic cross-sectional elevation of a partial dehumidification unit according to a sixth embodiment of the present invention; and

FIG. 10 is a schematic cross-sectional elevation of an evaporative cooling unit according to a seventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic diagram of a conceptual system 10 for dehumidification of ambient indoor air according to a first embodiment of the present invention. A dehumidification unit 12 is provided with means to efficiently contact a stream of humid air 14 with a liquid desiccant (not shown) such that water vapor is transferred from the humid ambient air 14 to the liquid desiccant, thereby humidifying the liquid desiccant. The dehumidified air 16 is discharged from the dehumidification unit 12 into the indoor space. The humidified liquid desiccant, carrying the water transferred from the humid indoor air 14, is transferred as liquid desiccant stream 18 to a regeneration unit 20, where water is removed from the liquid desiccant using radiant energy 22 (e.g., solar radiation, or radiative heating from an electrical source or heated fluid) to heat the liquid desiccant, increasing the vapor pressure of the water over the desiccant solution. The water vapor is thus transferred from the liquid desiccant to a stream of ambient outdoor air 24, which is discharged to the outdoor environment as a stream of humidified outdoor air 26. The regenerated liquid desiccant is returned to the dehumidification unit 12 as liquid desiccant stream 28. In an embodiment, the regeneration unit 20 includes means to condense the water vapor, thereby forming a condensate which may be processed further or disposed of.
The dehumidification and regeneration processes of system 10 are driven by the relationships between the partial pressure of atmospheric water vapor and the water content of a liquid desiccant. In an embodiment of the present invention, the liquid desiccant is a salt solution, although other liquid desiccant systems may be used. In the exemplary embodiments discussed herein, the liquid desiccant is an aqueous solution of calcium chloride (CaCl₂).
FIG. 2 is a plot of the relative humidity of air in equilibrium with a range of concentrations of calcium chloride in water. The reference temperature for this relative humidity curve is 25° C. As temperature increases, the partial pressure of water vapor (e.g., the amount of water carried in air) over a salt solution of a given concentration also increases, allowing a greater rate of mass transfer of water from the solution to the air. The relationships among temperature, partial pressure of water vapor, relative humidity, and solution concentrations are well-understood for a wide variety of salts and other materials.
FIG. 3 is a plot of relative humidity over time for humid indoor air contacted with a solution of 41% (w/w) calcium chloride in water. Humidified room air was contacted with the calcium chloride solution in a pilot-scale packed column modified to include horizontal perforated trays within the packing material to form a descending series of stages. The trays were arranged horizontally to increase the length of the flow path for the air as it moved from the bottom of the packing to the top of the packing. The calcium chloride solution was cycled through the packed column from top to bottom, flowing downward through the perforations in the trays. The dimensions of the packed volume were about 1.5 feet in length, 1 foot in height and 2 inches in depth. A 2-inch deep reservoir was maintained at the bottom of the column.
The pilot-scale dehumidifier was placed in a closed room having dimensions of 8 feet by 8 feet with a height of 10 feet, which was then humidified with hot water and steam to a relative humidity of about 82% at a temperature of 77° F. (25° C.). Humid room air was then forced through the packed column at a rate of 35 cubic feet per minute (cfm). The calcium chloride solution was pumped to the top of the packed column at a rate of 30 gal/hr and evenly distributed along the top stage of the packed column. The dehumidified air was returned to the interior of the room. After 18 minutes, the relative humidity in the room had stabilized at about 60% at a temperature of 73° F. (23° C.).
What follows are descriptions of various exemplary embodiments of the present invention. While these embodiments are described in various degrees of detail, the practical details related to the selection, design, operating parameters, and implementation of the various units, means, and systems disclosed herein will be understood by those having ordinary skill in chemical engineering or mechanical engineering given such disclosures. Such practical details include measures that may be taken to improve or optimize the implementation or performance of the various units, means, and systems disclosed herein.
FIG. 4 is a schematic diagram of a dehumidification system 30 according to an embodiment of the present invention. In an embodiment, a dehumidification unit 32 of the dehumidification system 30 includes a contacting means 34 for contacting the desiccant solution (not shown) with indoor air (not shown). The contacting means 34 may include any known means for enhancing mass transfer between a gas-phase stream and a liquid-phase stream. Such contacting means include, without limitation, packed columns, tray towers, spray towers, and water curtains. The dehumidification unit 32 is provided with a desiccant solution distribution means (e.g., a pump 36 hydraulically connected to spray heads 38) for distributing desiccant solution within the contacting means 34. The dehumidification unit 32 is also provided with a room air intake means (shown in FIG. 4 as an intake fan 40) to transfer indoor air into the contacting means 34, and a room air discharge means (shown in FIG. 4 as a discharge fan 42) to draw dehumidified air from the dehumidification unit 32. In an embodiment, a discharge pump 44 is hydraulically connected to a desiccant collection conduit 46, such that the discharge pump 44 conveys desiccant solution from the dehumidification unit 32 (hereinafter, “humidified desiccant solution”) through a discharge conduit 48 to a desiccant regeneration unit 50.
In an embodiment, the dehumidification unit 32 is inside of the room (or enclosed space) which is to be dehumidified. In an embodiment, the dehumidification unit 32 is outside of the room which is to be dehumidified, but air intake ports (not shown) and air discharge ports (not shown) are provided in the room which is to be dehumidified. The air intake ports and air discharge ports are pneumatically connected to, or are part of, the room air intake means and room air discharge means, respectively. In an embodiment, the air intake means is pneumatically connected to the outdoors, so as to take in outdoor air, rather than room air.
The desiccant regeneration unit 50 of the dehumidification system 30 is provided to remove water from the humidified desiccant solution. In the embodiment of FIG. 4, the desiccant regeneration unit 50 comprises a solar distiller 52 having a basin 54 and sloped cover 56. At least a portion of the sloped cover 56 is transparent, so as to allow the desiccant solution within the basin 54 to be heated by solar radiation (e.g., by the “greenhouse effect”), causing water to evaporate from the desiccant solution. At least two air vents 58, 60 are provided between the sloped cover 56 and the basin 54 to allow a natural flow of ambient outdoor air through the solar distiller 52 and over the humidified desiccant solution so as to carry away the water vapor. In an embodiment, outdoor ambient air may be forced through the solar distiller 52 by fans (not shown), or other air moving means. In an embodiment, the regeneration unit 50 is provided with means to condense the water vapor and collect the resulting condensate. In an embodiment, the desiccant regeneration unit 52 is provided with an auxiliary heat source 62 (e.g., an electrical heater) to heat the humidified desiccant solution when the ambient solar radiation is insufficient to evaporate water at the desired rate.
The desiccant regeneration unit 50 is further provided with a drain 64 at a low point in the basin 54, a drainage conduit 66 hydraulically connected to a transfer tank 68, and a solenoid flow control valve 70 in the drainage conduit 66. In the embodiment of FIG. 4, the desiccant solution returned from the desiccant regeneration unit 50 (hereinafter, the “regenerated desiccant solution”) drains from the desiccant regeneration unit 50 to the transfer tank 68 by gravity flow. In other embodiments, the regenerated desiccant solution may be transferred from the desiccant regeneration unit 50 to the transfer tank 68 (or to the dehumidification unit 32, or to some other location) by mechanical means (e.g., by a pump).
In the embodiment of FIG. 4, the desiccant regeneration unit 50 is located outdoors. It may be positioned so as to maximize the amount of solar energy entering the solar distiller 52. In an embodiment, the desiccant regeneration unit 50 may be located indoors, and air intake means and air discharge means (not shown) provided to pass outdoor air through the solar distiller 52, with the air then being discharged outdoors. An auxiliary heater could be required to heat the desiccant solution.
The dehumidification system 30 also includes a transfer tank 68. The transfer tank 68 facilitates control of the flow rate of the regenerated desiccant solution from the regeneration unit 50 to the dehumidification unit 32, and permits passive cooling of the regenerated desiccant solution through the walls of the transfer tank 68. In other embodiments, an additional passive cooling device (e.g., an evaporative cooler) may be provided to increase the rate at which the regenerated desiccant solution cools. In yet other embodiments, an active cooling device (e.g., forced air, refrigerated coolant, a thermoelectric cooling device, or an evaporative cooler) may be used to cool the regenerated desiccant solution. The transfer tank 68 is provided with a drain 70 at the low point of the transfer tank 68, a drainage conduit 72 hydraulically connected to the dehumidification unit 32, and a solenoid flow control valve 74 in the drainage conduit 66. In the embodiment of FIG. 4, the regenerated desiccant solution drains from the transfer tank 68 by gravity flow. In other embodiments, the regenerated desiccant solution may be transferred from the transfer tank 68 to the dehumidification unit 32 (or to some other location) by mechanical means (e.g., by a pump).
In an embodiment, the operation of the dehumidification system 30 may be controlled electronically by sensors placed in the various units 32, 50, 68 and actuators, using a centralized or distributed computer system. In an exemplary embodiment of the present invention, the dehumidification system 30 operates in a semibatch mode, as described herein below.
The humidity and temperature of the indoor air is continuously monitored by humidity sensor 76 and a temperature sensor 78, which transfer data to a control unit (not shown). When the relative humidity of the air, as calculated at the control unit from the humidity and temperature data, reaches a preset level, dehumidification system 30 begins operation.
During operation, a desiccant solution is continually circulated within the dehumidification unit 32 via the desiccant circulation means (e.g., the pump 36 and spray heads 38) while humid air from the room is forced through the dehumidification system 32 by the room air intake means and room air discharge means (e.g., fans 40 and 42), thereby humidifying the desiccant solution. A salinity sensor 80 within the dehumidification system 32 is used to monitor the concentration of salt (e.g., CaCl₂) in the humidified desiccant solution. When the concentration of salt in the humidified desiccant solution decreases below a preset concentration, the transfer pump 44 is activated to transfer humidified desiccant solution to the regeneration unit 50. Solenoid valve 74 is opened to transfer regenerated desiccant solution from the transfer tank 68 to the dehumidification unit 32, increasing the salinity of the desiccant solution within the dehumidification unit 32. When the salinity of the desiccant solution within the dehumidification unit 32 is restored to a target value, as sensed by the salinity sensor 80, the solenoid valve 70 closes and the transfer pump 44 is stopped.
A salinity sensor 82 and temperature sensor 84 are provided in the basin 54 of the regeneration unit 50. The temperature sensor 84 monitors the temperature of the desiccant solution within the basin 54 as a proxy value for the evaporation rate of water from the desiccant solution. If the temperature is too low, the auxiliary heat source 62 is activated. The salinity sensor 82 monitors the concentration of salt within the desiccant solution. When the salt concentration reaches a preset level, as sensed by the salinity sensor 82, the control valve 78 opens to allow the regenerated desiccant solution to flow to the transfer tank 68.
It will be understood by persons having ordinary skill in chemical or mechanical engineering that additional components, such as power supplies, sensors, control elements, pumps, or additional hydraulic valves of various types, may be required for the implementation of the dehumidification system 30. Proper selection and placement of such components can be made by those having ordinary skill in such engineering fields.
FIG. 5 is a schematic flow sheet for a dehumidification subsystem 86 according to a second embodiment of the present invention. The dehumidification subsystem 86 comprises a dehumidification unit 88 of a type similar to the dehumidification unit 32 discussed with respect to FIG. 4, a flow equalization tank 90, and a discharge pump 92, which is hydraulically connected to the flow equalization tank 90 and a solar distiller 94, having a sloped cover 100, by a desiccant collection conduit 96 and a discharge conduit 98. In an embodiment, the flow equalization tank 90 is beneath the dehumidification unit 88. In an embodiment, the flow equalization tank 90 is remote from the dehumidification unit 88. In an embodiment, humidified desiccant solution is transferred from the dehumidification unit 88 to the flow equalization tank 90 under gravity flow. In an embodiment, humidified desiccant solution is transferred to the flow equalization tank 90 by mechanical means (e.g., by a pump).
In the embodiment of FIG. 5, the dehumidification subsystem 86 is provided with two transfer tanks 102, 104 in series between the solar distiller 94 and the dehumidification unit 88. More or fewer transfer tanks may be used as needed for implementation of the dehumidification subsystem 86. Providing multiple transfer tanks improves flow control and temperature management of the desiccant solution, as will be understood by those having ordinary skill in chemical or mechanical engineering.
Continuing to refer to FIG. 5, a control valve 106 is provided between the final transfer tank 104 and the dehumidification unit 88 to control the transfer of regenerated desiccant solution to the dehumidification unit 88. In the embodiment of FIG. 5, the flow of regenerated desiccant solution from the solar distiller 94 to the transfer tanks 102, 104 and the dehumidification unit 88 is by gravity flow. In other embodiments, such a transfer may be achieved by mechanical devices, such as pumps (not shown). A room air intake means 110 and room air discharge means 112 are also provided to force room air through the dehumidification unit 88.
It will be understood by persons having ordinary skill in chemical or mechanical engineering that additional components, such as power supplies, sensors, control elements, pumps, or additional hydraulic valves of various types, may be required for the implementation of the dehumidification subsystem 86. Proper selection and placement of such components can be made by those having ordinary skill in such engineering fields.
FIG. 6 is a schematic flow sheet for a water management subsystem 114 according to a third embodiment of the present invention. The water management subsystem 114 includes the solar distiller 94 discussed with respect to the dehumidification subsystem 86 of FIG. 5. During the regeneration of the desiccant solution in the solar distiller 94, water vapor condenses on the underside of the sloped cover 100, and droplets of condensate flow along the sloped roof 100 to a condensate collection pipe 116 at the lower edge 118 of the sloped cover 100. The collected condensate is transferred from the collection pipe 116 to a transfer tank 120. A control valve 122 controls the flow of condensate from the transfer tank 120 to an evaporative cooling unit 124. Excess condensate is transferred from the transfer tank 120 to a storage tank 126 (also referred to as a “grey water” tank) for further treatment or disposal. Other means of condensing the water vapor and handling the resulting condensate may be used in other embodiments of the water management subsystem of the present invention.
The evaporative cooling unit 124 of the water management subsystem 114 is provided to cool dehumidified air 112 discharged from the dehumidification unit 88 (see FIG. 5). Inside the evaporative cooling unit 124, condensate is evaporated to cool the dehumidified air before it is discharged to the environment as discharged air stream 128. A cooling air stream of indoor air 130 is supplied to the evaporative cooling unit 124 to assist the evaporation of condensate, and carry the vapor out of the evaporative cooling unit 124 in an air stream 132, which may be further treated or discharged outdoors. In an embodiment, cooling air stream 130 is outdoor air, rather than room air. Excess condensate drains from the evaporative cooling unit 124 to a transfer tank 134, and is recycled by a recycle pump 136, which is hydraulically connected to the transfer tank 134 and evaporative cooling unit 124 by condensate conduit 138 and condensate recycle conduit 140. Thus, the condensate is recycled through the evaporative cooling unit 124, with occasional make-up condensate added to the evaporative cooling unit 124 to replace condensate that has been removed from the water management subsystem 114 as water vapor. The evaporative cooling unit 124 is designed and operated so that the dehumidified air stream 112 and the cooling air stream 130 do not mix. An exemplary evaporative cooler according to an embodiment of the present invention is described in more detail hereinbelow.
It will be understood by persons having ordinary skill in chemical or mechanical engineering that additional components, such as power supplies, sensors, control elements, pumps, or additional hydraulic valves of various types, may be required for the implementation of the water management subsystem 112. Proper selection and placement of such components can be made by those having ordinary skill in such engineering fields.
FIG. 7 is a schematic flow sheet for an air conditioning system 142 according to a fourth embodiment of the present invention. The air conditioning system of FIG. 7 combines the dehumidification and water management subsystems 86, 114 of FIGS. 5 and 6 with a conventional HVAC system 144 to manage the humidity, temperature, and ventilation of indoor air. Components of the air conditioning system that are described with respect to FIGS. 5 and 6 are identified in FIG. 7 by the same reference numbers that are used in FIGS. 5 and 6.
Continuing to refer to FIG. 7, outside air 146 is drawn through a ventilation unit 148, from which is used as a humid air stream 150 to the dehumidification subsystem 86. In an embodiment, indoor air from within the building is used as a humid air stream, rather than outdoor air stream 150, or the humid air stream may be a combination of outdoor air and indoor air. In an embodiment, the ventilation unit 148 includes an energy recovery ventilator (ERV) or a heat recovery ventilator (HRV). The humid air stream 150 is dehumidified in the dehumidification subsystem 86, as discussed with respect to FIG. 5.
Continuing to refer to FIG. 7, dehumidified air 112 from the dehumidification subsystem 86 is passed through the evaporative cooling unit 124 and the cooled air 128 exits the evaporative cooling unit 124, and is discharged into an air distribution system 152, which is described in more detail hereinbelow. A stream of indoor room air 130 is passed through the evaporative cooling unit 124 and exits as air stream 132 for eventual discharge to the outdoors. In an embodiment, a stream of outdoor air is used in place of the stream of indoor air 130, or a combined stream of indoor air and outdoor air may be used.
Continuing to refer to FIG. 7, air distribution system 152 includes mechanical components (represented by box 154) and a system 156 of conduits and vents to distribute air throughout the interior spaces of a building (not shown). The air distribution system 152 includes air discharge vents 158 to discharge dehumidified and cooled air (e.g., air supplied as air stream 128) into the interior spaces of the building, and intake vents 160 to withdraw indoor air for eventual discharge to the outdoors. In an embodiment, the indoor air collected by the intake vents 160 may be recycled to the dehumidification unit 88. In an embodiment, the indoor air collected by the intake vents 160 may be recycled to the evaporative cooling unit 124. The air distribution system 152 discharges air withdrawn through the intake vents 160 to an exhaust conduit 162 which leads to the ventilation unit 148, which, in turn, discharges the exhaust air 164 to the outdoors.
Continuing to refer to FIG. 7, the air conditioning system 142 includes a conventional HVAC system 144, referred to above, which operates separately from the combination of dehumidification subsystem 86, water management system 114, and air distribution system 152. In some embodiments, components of the HVAC system may be integrated with, or may interact with, the dehumidification subsystem 86, water management system 114, and/or air distribution system 152 discussed above. The HVAC system 144 includes a compressor 166, an HVAC unit 168 interacting with the compressor 168, and a system 170 of conduits and vents pneumatically connected to the HVAC unit 168 to distribute air throughout the interior spaces of the building. In some embodiments, the HVAC system 144 may be omitted, depending on the air treatment and ventilation desired in the indoor spaces of the building.
The air conditioning unit 142 is scalable over a range of air volumes that may require dehumidification and cooling. For example, the individual components may be designed to handle selected ranges of air flow rates and humidity reduction. Desiccant solutions may be devised to provide the most efficient uptake rates and capacities with respect to water vapor, to fulfill health, safety, and environmental requirements, and for economic operation of the system.
It will be understood by persons having ordinary skill in chemical or mechanical engineering that additional components, such as power supplies, sensors, control elements, pumps, or additional hydraulic valves of various types, may be required for the implementation of the air conditioning system 142. It will also be understood that the various air and liquid streams discussed above are conveyed within pipes and conduits suitable for such purposes. Proper selection and placement of such components, pipes, and conduits can be made by those having ordinary skill in such engineering fields.
FIGS. 8-10 are schematic illustrations of exemplary units suitable for residential air conditioning systems according to embodiments of the present invention. While the actual units may include components not described hereinbelow, practical details of the selection, design, operating parameters, and implementation of the these units will be understood by those having ordinary skill in chemical engineering or mechanical engineering given the disclosures made herein. Such practical details include measures that may be taken to improve or optimize the implementation or performance of the various units disclosed herein.
FIG. 8 is a schematic cross-sectional elevation of a partial dehumidification unit 172 based on a modified packed column air stripper, according to a fifth embodiment of the present invention, wherein water vapor is scrubbed from the air stream by the desiccant solution. Components such as, but not limited to, supply and drainage means for the desiccant solution, air intake and discharge means, air and liquid distribution means, and air stripper packing are omitted, but will be understood by those persons having ordinary knowledge of air stripper design and operation.
Continuing to refer to FIG. 8, the partial dehumidification unit 172 includes a shell 174 for containing air stripper packing and other internal components (not shown) of the dehumidification system. A perforated drainage plate 176 is provided to allow drainage of desiccant solution into a reservoir 178. A desiccant solution inlet 180 is provided near the top of the shell 174, and a desiccant solution outlet 182 is provided near a low point of the reservoir 178. An air inlet 184 is provided at a low point of the shell 174, but above the perforated drainage plate 176. An air outlet 186 is provided at a high point of the shell 174.
FIG. 9 is a schematic cross-sectional elevation of a second partial dehumidification unit 188 based on a modified packed column air stripper, according to a sixth embodiment of the present invention. Components such as, but not limited to, supply and drainage means for the desiccant solution, air intake and discharge means, air and liquid distribution means, and air stripper packing are omitted, but will be understood by those persons having ordinary knowledge of air stripper design and operation.
Continuing to refer to FIG. 9, the partial dehumidification unit 188 includes a shell 190 for containing air stripper packing and other internal components (not shown) of the dehumidification system. A perforated drainage plate 192 is provided to allow drainage of desiccant solution into a reservoir 194. A desiccant solution inlet 196 is provided near the top of the shell 188, and a desiccant solution outlet 198 is provided near a low point of the reservoir 194. An air inlet 200 is provided at a low point of the shell 188, but above the perforated drainage plate 192. An air outlet 202 is provided at a high point of the shell 180. All of the aforesaid inlets and outlets of the partial dehumidification unit 188 penetrate the shell 190.
The partial dehumidification unit 188 is also provided with a series of perforated trays 204, 206, 208, 210 within the shell 190. The trays 204, 206, 208, 210 are arranged such that there are gaps 212, 214, 216, 218 between the ends 220, 222, 224, 226 of the trays 204, 206, 208, 210 and the shell 190. Air stripper packing (not shown) is provided to fill at least the spaces between the trays 204, 206, 208, 210 and the gaps 212, 214, 216, 218. The trays 204, 206, 208, 210 are further arranged such that air entering the partial dehumidification unit 188 at the air inlet 200 moves along a winding path (not shown) through the packing and the successive open spaces 212, 214, 216, 218 to reach the air outlet 202. The foregoing arrangement provides a longer air flow path relative to the height of the shell 190 than in a conventional packed column (see, e.g., partial dehumidification unit 172 of FIG. 8), allowing the use of shorter, wider columns to achieve a given degree of dehumidification.
FIG. 10 is a schematic cross-sectional elevation of an evaporative cooling unit 228 according to a seventh embodiment of the present invention. The evaporative cooling unit 228 comprises a shell 230 having a conduit 232 therein, and a perforated drainage plate 234 between the conduit 232 and a reservoir 236 at the bottom of the shell 230. An upper end 238 of the conduit 232 is in pneumatic communication with a first air inlet 240 and a lower end 242 of the conduit 232 is in pneumatic communication with a first air outlet 244. The evaporative cooling unit is further provided with a second air inlet 246 near, but not connecting with, the upper end 238 of the conduit 232, and a second air outlet 248 near, but not connecting with, the lower end 242 of the conduit 232. A drainage outlet 250 is provided near a low point in the reservoir 236. All of the aforesaid inlets and outlets of the evaporative cooling unit 228 penetrate the shell 230.
Continuing to refer to FIG. 10, the evaporative cooling unit 228 is provided with evaporation pads 252, 254, 256. In an embodiment, the evaporation pads 252, 254, 256 are proximate the conduit 232. In an embodiment, the evaporation pads 252, 254, 256 are in contact with the conduit 232. In an embodiment, the evaporation pads 252, 254, 256 are installed so as to minimize the air flow around the evaporative pads 252, 254, 256 relative to the air flow through the evaporative pads 252, 254, 256. In the embodiment of FIG. 10, three evaporation pads are shown. More or fewer evaporation pads may be used in other embodiments of the invention, depending on the operating parameters of the evaporative cooling unit 232 and the media selected for the evaporative pads. In an embodiment of the invention, the evaporative pads 252, 254, 256 comprise a medium that is water absorptive, but creates a minimal pneumatic pressure drop across the evaporative pads 252, 254, 256. In an embodiment, the medium comprises a corrugated paper block. In an embodiment, the medium comprises a water-absorbent fiber mesh.
In an embodiment, the evaporative cooler 228 is provided with a water distribution system (not shown) for providing water to the evaporative pads 252, 254, 256. In an embodiment, the water is condensate from a solar distiller, such as the solar distiller 94 discussed above with respect to FIG. 6. In an embodiment, water that is not absorbed by the evaporative pads 252, 254, 256 drains through the perforated drainage plate 234 to the reservoir 236, from which it is disposed or recycled to the water distribution system. Persons having ordinary skill in chemical or mechanical engineering, and possession of the present disclosure, will recognize how to design, install, and operate water distribution systems suitable for use with the evaporative cooling unit 228.
In operation, dehumidified air, such as dehumidified air stream 112 discussed in relation to FIGS. 5 and 7, is supplied to the evaporative cooler 228 at the first air inlet 240. The dehumidified air stream 112 passes through the conduit 232, and is discharged at the first air outlet 244 as air stream 128, discussed above with respect to FIGS. 6 and 7. While passing through the conduit 232, the dehumidified air stream 112 is cooled by the evaporation of water from the evaporative pads 252, 254, 256. Air is also supplied at the second air inlet 246 to assist the evaporation of water from the evaporative pads 252, 254, 256, and to carry the evaporated water out of the shell 230 through the second air outlet 248.
In an embodiment, the evaporative cooling unit 228 is suitable for installation in a cabinet (not shown) adjacent a dehumidification unit of the same general type as the dehumidification unit 172 discussed with respect to FIG. 8. In an embodiment, the first air inlet 240 of the evaporative cooling unit 228 may be aligned with the air outlet 186 of the dehumidification unit 172. In an embodiment, the first air inlet 240 of the evaporative cooling unit 228 may be continuous with the air outlet 186 of the dehumidification unit 172. In an embodiment, the shell 230 of the evaporative cooling unit 228 may be continuous with the shell 174 of the dehumidification unit 172, and a single opening or device may serve as both the first air inlet 240 of the evaporative cooling unit 228 and the air outlet 186 of the dehumidification unit 172.
It will be understood that the embodiments of the invention described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. For instance, below a critical value of relative humidity, which varies according to the composition of the desiccant solution, the desiccant solution humidifies the air above it. In such circumstances, the systems disclosed herein may be readily adapted for humidification of indoor air without eliminating the units described. Such variations and modifications, as well as others not described above, are intended to be included within the scope of the invention, as embodied in the claims appended hereto.

Claims

We claim:

1. An air conditioning system, comprising:

a dehumidification unit including contacting means for contacting humid air with a desiccant solution, thereby humidifying the desiccant solution and dehumidifying the air by moving a first water vapor from the humid air into the desiccant solution;

a desiccant regeneration unit for removing water from the humidified desiccant solution as a second water vapor, thereby regenerating the desiccant solution;

first transferring means for transferring the humidified desiccant solution into said desiccant regeneration unit; and

second transferring means for transferring the regenerated desiccant solution into said dehumidification unit.

2. The air conditioning system of claim 1, wherein said desiccant regeneration unit includes a solar distiller that uses solar radiation to heat the humidified desiccant solution, whereby the second water vapor is removable from the humidified desiccant solution.

3. The air conditioning system of claim 1, further comprising an evaporative cooling unit for cooling the dehumidified air and conveying means for conveying the dehumidified air from said dehumidification unit into and through said evaporative cooling unit.

4. The air conditioning system of claim 3, further comprising condensing means for condensing the second water vapor to thereby form a condensate, and third transferring means for transferring the condensate to said evaporative cooling unit.

5. The air conditioning system of claim 1, wherein said contacting means includes a packed column air stripper, transporting means for transporting the air through said packed column air stripper, and third transferring means for transferring the desiccant solution into said packed column air stripper.

6. The air conditioning system of claim 5, wherein said packed column air stripper includes internal trays arranged to direct the flow of the air within the packed column air stripper.

7. The air conditioning system of claim 1, wherein said contacting means includes circulating means for circulating the desiccant solution within said contacting means.

8. The air conditioning system of claim 1, further comprising a cooling means for cooling the regenerated desiccant solution, said cooling means located between said dehumidification unit and said desiccant regeneration unit.

9. The air conditioning system of claim 1, wherein said cooling means includes a transfer tank hydraulically connected to said dehumidification unit and said desiccant regeneration unit.

10. The air conditioning system of claim 1, further including at least one transfer tank between said dehumidification unit and said desiccant regeneration unit.