Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
  • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
  • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
  • F24F3/1411—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification by absorbing or adsorbing water, e.g. using an hygroscopic desiccant
  • F24F3/1417—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification by absorbing or adsorbing water, e.g. using an hygroscopic desiccant with liquid hygroscopic desiccants
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
  • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
  • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
  • F24F2003/144—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification by dehumidification only
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F6/00—Air-humidification, e.g. cooling by humidification
  • F24F6/02—Air-humidification, e.g. cooling by humidification by evaporation of water in the air
  • F24F6/04—Air-humidification, e.g. cooling by humidification by evaporation of water in the air using stationary unheated wet elements
  • F24F6/043—Air-humidification, e.g. cooling by humidification by evaporation of water in the air using stationary unheated wet elements with self-sucking action, e.g. wicks

Definitions

• the invention relates to systems for conditioning air utilizing a liquid desiccant. BACKGROUND OF THE INVENTION The use of liquid desiccants in dehumidifier systems, both with and without associated heat pumps is well known.
• liquid dehumidifier systems comprise a dehumidifying section, in which air to be dehumidified contacts a liquid desiccant having a relatively low level of moisture and a regenerating section in which outside air contacts a liquid desiccant having a relatively high level of liquid desiccant.
• moisture is removed from the air and adsorbed by the liquid desiccant.
• moisture is transferred from the moisture- rich liquid desiccant to the outside air.
• Means are generally provided for transferring at least moisture from the dehumidifying section to the regenerating section.
• a heat pump is used to pump heat from the dehumidifying section to the regenerating section. This can result in the conditioned air being cooled as well as dehumidified.
• an additional radiator (additional to those present in the regenerating and dehumidifying sections) is provided for the heat pump to remove additional heat from the refrigerant in the heat pump. This radiator can be placed at the entrance of the outside air to the regenerating section to thereby pre-heat this air utilizing an additional radiator. This preheating improves the efficiency of the system.
• the additional radiator can be placed at the outlet of the dehumidifying section to heat the conditioned air.
• the conditioned air is heated as well as dehumidified.
• means are provided for switching the system between a cooling/dehumidifying function and a heating/dehumidifying function. Additionally, in some embodiments, means are provided for converting the system into a heating/humidifying system.
• each of the dehumidifying and regenerating sections is provided with a reservoir from which liquid desiccant is taken to be used in the respective dehumidification or regeneration process. After the process, the desiccant is returned to the same respective reservoir.
• a small aperture or apertures connects the two reservoirs.
• the aperture is designed such that only moisture passes from the dehumidifier reservoir to the regenerator reservoir. In the steady state, there is no net transfer of desiccant ions between the reservoirs, via the aperture. Furthermore, such systems can be produced so that liquid transfer is only via the aperture and no pumps are used to transfer liquid between the reservoirs.
• pumps are used to pump liquid from the reservoirs to a higher position from which the liquid is dripped or sprayed into a regenerating or a dehumidifying chamber.
• Fans are generally used to introduce air into the dehumidifying and regenerating chambers.
• the prior art systems include pumps that pump liquid from the reservoirs to the regenerating or dehumidifying chambers.
• pump- less transfer is provided.
• transfer of moisture from a region where it is removed from the air to be dehumidified to the region where it is transferred to ambient (outside) air is substantially only by diffusion and gravity.
• the excess moisture travels, by diffusion, under the influence of a concentration gradient, from the location at which the moisture is removed (dehumidifying section) to a first reservoir in which the concentration of desiccant is higher than that in said location.
• This difference of concentration is generated by the absorption of moisture from the air to be conditioned.
• the moisture is then transferred to a second reservoir in the regenerator, for example, via a hole that is designed so that there is only a net flow of moisture ions and no net flow of desiccant ions.
• the increased volume of liquid in the first reservoir causes the flow of low concentration desiccant from the first to the second reservoir.
• concentration of desiccant in the second reservoir is higher than in the first reservoir, there is a reverse flow of desiccant ions, to provide substantially zero net flow of desiccant ions.
• the second reservoir is heated to increase the evaporation of the moisture, and this heated liquid is further concentrated at a second location at which this moisture is transferred to "outside' air. This concentration causes a further diffusion of the moisture to the second location from the second reservoir.
• the liquid desiccant can be maintained in the first and second locations by a wicking system which also serves as the medium for transferring the moisture from regions of low concentration liquid desiccant to high concentration liquid desiccant (between the locations and the reservoirs).
• wicking action is used to draw the liquid desiccant from the reservoirs to regions in which that are in contact with the air used in the dehumidifying/regenerating processes.
• the wicking material also allows for the transfer of moisture in either an upward or downward direction, by diffusion, in response to gradients of concentration in the liquid desiccant.
• the wicking action is provided by sheets of material, through which air to be dehumidified or ambient air passes. In other embodiments the air flows along the surface of the material.
• the wicking material is mounted on a heat conducting structure, to efficiently transfer heat between the reservoir and the liquid desiccant in the wicking material.
• a heat pump is used to transfer heat from the dehumidifying section to the regenerating section.
• the heat pump may have its respective heat exchangers in the reservoirs of the two sections.
• the heat pump is dispensed with, and the liquid in the regenerator reservoir is heated by an external heating source. While this is less efficient than using a heat-pump, in some embodiments as, for example, in cold areas, where overall heating of the air is not objectionable, this reduced efficiency is acceptable, given the lower cost of such a system. In some cases, the heat used for the regeneration is available without additional cost as waste heat from various sources, resulting in a high overall efficiency.
• the heated dried air is cooled by heat exchange with ambient air, to provide air at a temperature somewhat hotter than the temperature of the ambient air, but at a much lower humidity. If this air is cooled by evaporation cooling, as known in the art, the air temperature can be reduced below the ambient air temperature, optionally at a lower temperature. While cooling based on dehumidifying, heat exchange and evaporation cooling is generally known in the art, it is especially attractive when waste heat is available, using a system according to exemplary embodiments of the present invention, since such a system will give "free" cooling, since no pumps are necessary and there is only a need for fans to move the air. The only major energy source is the waste heat that is used to power the system.
• the aperture method of transferring moisture between the reservoirs is used.
• a moisture transfer element for a system for conditioning air comprising: a reservoir containing liquid desiccant; a housing defining a chamber and having an air inlet and an air outlet; and a wicking structure comprising wicking material that that wicks liquid desiccant or components thereof between the reservoir and the chamber, such that air that enters the chamber via the inlet contacts liquid desiccant transported to the chamber from the reservoir, prior to leaving the chamber.
• the wicking material comprises at least one sheet of said wicking material having one end in the liquid desiccant in the reservoir, at least a portion of the wicking material being in the chamber.
• the wicking structure comprises a heat conducting structure that contacts the liquid desiccant in the reservoir and the wicking material in the chamber.
• the heat conducting structure blocks air.
• the heat conducting structure comprises a heat conducting metal.
• the heat conducting structure is formed with apertures through which air can pass.
• the heat conducting structure comprises a heat conducting metal.
• the wicking structure is oriented such that air passing through the chamber passes along a surface of the wicking material.
• wicking structure is oriented such that air passing through the chamber passes through the wicking material.
• no pumps are used to transport the liquid desiccant between the reservoir and the chamber.
• transportation of liquid desiccant or its components between the reservoir and the chamber is by wicking or by diffusion only.
• a system for conditioning air comprising: a dehumidifying section and a regenerating section, at least one of which comprises a moisture transfer element according to the invention, as defined above.
• both the dehumidifying and regenerating sections comprise a moisture transfer element according of the invention, as defined herein.
• liquid desiccant reservoirs in the dehumidifying and regenerating sections are connected by at least one aperture, the size of said aperture being such that, in a steady state condition, no net amount of desiccant ions are transported between the reservoirs.
• transport of liquid desiccant or its components between the reservoirs is only via said at least one aperture.
• liquid desiccant between the dehumidifying and regenerating sections.
• transfer of liquid desiccant or its components is by diffusion or gravity fed flow only.
• the system includes a heater that heats liquid desiccant in said regenerator.
• the system includes a liquid heat pump that transfers heat from liquid desiccant in the dehumidifying section to liquid desiccant in the regenerating section, said heater comprising a condenser of said heat pump.
• a method for conditioning air comprising: providing a liquid desiccant at a first location; removing moisture from the liquid desiccant at the first location to a first source of air; providing liquid desiccant at a second location, said liquid desiccant at said second location being in fluid communication with the liquid desiccant at the first location; absorbing moisture by the liquid desiccant at the second location from a second source of air; and transferring moisture from the first location to the second location substantially only by diffusion and gravity.
• the method includes heating the liquid desiccant in the first location.
• the first location is in a regenerator for liquid desiccant and the second location is in a dehumidifier and including transferring heat, via a heat pump, from the dehumidifier to the regenerator.
• Fig. 1 is a schematic representation of a dehumidifying system in accordance with an exemplary embodiment of the invention
• Fig. 2 is a schematic representation of an alternative dehumidifying system, in accordance with an exemplary embodiment of the invention.
• Fig. 3 is a schematic representation of a wicking system, useful in the embodiments of Figs 1 and 2, in accordance with an embodiment of the invention
• Fig. 4 is a schematic representation of a cooling system in which the embodiment of
• Fig. 1 is utilized, in accordance with an embodiment of the invention.
• Fig. 5 is a flow diagram of the operation of a cooling system, in accordance with an embodiment of the invention.
• Fig. 1 shows a schematic representation of an exemplary dehumidifier 10 in accordance with an embodiment of the invention.
• wicking in accordance with an aspect of the invention, can be applied to substantially any liquid dehumidifying system.
• a simple dehumidifier system is used to illustrate this aspect of the invention.
• the principles described herein can be used with a variety of different liquid desiccant, dehumidifier systems.
• Dehumidifier 10 comprises a dehumidifying section 12 and a regenerating section 14.
• Dehumidifying section 12 comprises a reservoir 18, in which a liquid desiccant 20 is held. This desiccant may comprise water together with a desiccant salt, or may comprise any other liquid desiccant as known in the art.
• Dehumidifying section 12 comprises a housing 13 formed with an inlet 22 for introduction of air to be dehumidified and an outlet 24 for dehumidified air. Generally, the air is fan driven into the opening.
• inlet 22 is shown at the bottom of the housing and outlet 24 is shown at its top. However, in general, since the flow is from side to side, the inlet and outlet can be in the middle of the side walls of the housing.
• a wick fed dehumidifying structure 26 is held within housing 13.
• a series of sheets 28 of wicking material are attached to a barrier 30.
• the lower end of sheets 28 sit within liquid desiccant 20, such that liquid desiccant is wicked up on sheets 28 and moistens them.
• sheets 28 form a partial barrier to flow between inlet 22 and outlet 24 such that air, entering inlet 22, passes through the sheets and interacts with the liquid desiccant contained in them.
• Means, such as weights or a bracket, may be provided at the bottoms of sheets 28 to keep them from moving under the influence of the air passing through them.
• Regenerating section 14 is constructed in a manner similar to that of dehumidifying section 12.
• regenerating section 14 comprises a reservoir 18', in which a liquid desiccant 20' is held.
• This desiccant is of the same basic type as desiccant 20 in reservoir 18, except that the concentration and temperature of the desiccant is different.
• Regenerating section 14 comprises a housing 13' formed with an inlet 22' for introduction of ambient air, which is to carry away moisture from the regenerator. After humidification of the ambient air, the air exits from an outlet 24' for dehumidified air. Generally, the air is fan driven into the opening.
• a wick fed dehumidifying structure 26' is held within housing 13'.
• a series of sheets 28' of wicking material are attached to a barrier 30'.
• the lower end of sheets 28 sit within liquid desiccant 20', such that liquid desiccant is wicked up on sheets 28' and moistens them.
• sheets 28' form a partial barrier to flow between inlet 22' and outlet 24' such that air, entering inlet 22', passes through the sheets and interacts with the liquid desiccant contained in them.
• Means, such as weights or a bracket, may be provided at the bottoms of sheets 28' to keep them from moving under the influence of the air passing through them.
• a concentration differential is formed between liquid desiccants 20 and 20'.
• the more concentrated desiccant 20 in dehumidifying section 12 absorbs moisture from the air being conditioned and the ambient air removes moisture from the desiccant 20'.
• a heater shown schematically at 36 heats liquid desiccant 20'. This hotter liquid desiccant, when it contacts the air flowing through sheets 28', gives up some moisture and heat.
• a concentration differential then forms between the liquid desiccant in the sheets and the liquid desiccant in reservoir 18'. This concentration differential causes a net flow of water ions from the reservoir to the sheets.
• the liquid desiccant in the sheets also is cooled by the evaporation of the water.
• This flow of water causes an increased concentration and reduced amount of desiccant in reservoir 18'.
• the drop in level of liquid desiccant cause a height equalizing flow of liquid desiccant from reservoir 18 to reservoir 18' via aperture 34.
• the flow includes both water and desiccant ions.
• the higher concentration of desiccant ions in reservoir 18' causes a diffusion of desiccant from reservoir 18' to reservoir 18.
• the net effect at steady state is no net flow of desiccant ions between the two reservoirs.
• the concentration of desiccant ions in reservoir 18 is lower than that in reservoir 18'.
• Liquid desiccant is wicked up by sheets 28 in the same manner as it is wicked up by sheets 28'.
• liquid desiccant in reservoir 18 is at a lower temperature than that in reservoir 18', the desiccant in dehumidifying section 12 absorbs moisture from the air being conditioned.
• the liquid desiccant is also heated (and heats the air) in the dehumidifying process.
• the steady state there is a net flow of water down the sheet into the reservoir.
• moisture is absorbed in the desiccant in sheets 28 in dehumidifying section 12 from the "room” air. By diffusion (and perhaps, to some extent, by gravity), this moisture travels down the sheets to reservoir 18. From reservoir 18 the moisture travels, again by gravity and to some extent by diffusion, to reservoir 18'. From reservoir 18' the moisture travels up sheet 28' (by diffusion) in regenerating section 14. Moisture is removed from the liquid desiccant by the outside air.
• the concentration at the desiccant concentration at the top of sheets 28 is (for example) 20%; the concentration in reservoir 18 is (for example) 25%; the concentration in reservoir 18' is 30% and the concentration in sheets 28' is 35%.
• a sheet of wicking material may not conduct heat well and the heat carrier by the water may not be sufficient to provide desiccant in the sheets at a desired temperature, it may be desirable to increase the conduction of heat between the respective reservoirs and the liquid desiccant in the sheets.
• One way of doing this is to provide an apertured metal support to which the sheets are attached. This support provides both heat conduction and physical support for the sheets.
• the lower portions of the sheets should also be situated in the desiccant liquid in the reservoir.
• a large number of threadlike wicks supported by long wires are used. Further alternatively, the structure described below with reference to Fig. 3 is used.
• Fig. 2 shows an alternative dehumidifier system 10', in accordance with another embodiment of the invention.
• Dehumidifier system 10' differs from dehumidifier 10 of Fig. 1 in that dehumidifier system 10' includes a heat pump generally denoted by reference number 16.
• dehumidifier system 10' includes a heat pump generally denoted by reference number 16.
• the operation of dehumidifying section 12 and regenerating section 14 in dehumidifier 10' is similar in operation to the corresponding sections in dehumidifier 10 (Fig. 1).
• Heat pump 16 includes a compressor 38, a condenser 40 situated in liquid desiccant 20' in reservoir 18', an evaporator 42 situated in liquid desiccant 20 in reservoir 18 and an expansion valve 44 between the condenser and the evaporator.
• Heat pump 16 by transferring heat from desiccant 20 to desiccant 20', provides two desirable effects, namely the removal of heat generated during the dehumidifying process and the heating of desiccant 20' to aid in the removal of moisture therefrom.
• an additional heat exchanger 46 (a secondary condenser) is preferably provided which removes additional heat from refrigerant in heat pump 16, following the removal of heat at condenser 40.
• the air entering at inlet 22' is also heated by heat exchange from compressor 38. As described, this system dehumidifies and cools the conditioned air.
• the additional heat exchanger can be placed at outlet 24 to heat the conditioned air.
• Such a system dehumidifies and heats the conditioned air.
• a secondary evaporator (in a manner similar to the use of the secondary condenser 46 ) is placed at the air outlet of the regenerator , to condense water, so that hot and wet air is not emitted. This process can be used as a desalination process, with moisture removed from the exiting air being collected.
• the dehumidifying system includes two additional heat exchangers and a switching arrangement to switch between them to provide dehumidified conditioned air that is either heated or cooled.
• This embodiment parallels the embodiment shown in Fig. 4C of the above referenced concurrently filed PCT application.
• the liquid desiccant is cooled by the regeneration process (i.e., evaporation of part of its moisture cools the liquid desiccant) and heated by the dehumidifying process (condensation of the moisture heats the desiccant).
• the heating and cooling is counteracted by the action of heat pump 16 and (as to the heating) by heater 36 (Fig. 1).
• the thermal impedance between the condenser/evaporator/heating element should be as low as possible.
• Fig. 3 shows a cross sectional view of an embodiment of a wicking system 50 in accordance with an embodiment of the invention, looking down on the structure from the top.
• the wicking system comprises a plurality of heat conducting (e.g., metal) plates 52, optionally in the form of corrugated sheets. At least one side, and optionally both sides of the sheets are covered with a wicking material 54, which can be either cotton fabric or felt or a synthetic material or any material that will wick the liquid desiccant. Plates 52 are optionally spaced slightly apart, by a space 56. The lower ends of the metal plates are optionally attached to the respective condenser/evaporator/heating element (Figs.
• wicking system 50 is oriented such that air must travel along the corrugations, in space 56, as shown by anows 58.
• the corrugations (or other similar structure) are provided to increase the path of the air and its surface contact with the desiccant.
• plates 52 may also be flat. The spacing between the plates may be determined based on calculations of air resistance and dehumidification, or an optimal value may be determined experimentally.
• plates 52 may be formed with apertures and covered with the wicking material, such that air passes through the apertures.
• Other structures and configurations for supporting the wicking material in the chambers and configuring the wicking material will occur to persons of skill in the art.
• the support of the wicking material are optionally made of a material, such as, for example, a metal , which will provide good heat transfer from the heat exchanger in the liquid to the liquid on the wicking material and to the air. Different material may make differences in the sensible/latent heat ratio.
• This unit can replace air conditioning in some cases where enough sensible heat is removed by the liquid and the supports. This unit can be used for desalination, while heat could be provided from sun or any other free heating source, and cooling is from the outside air.
• Fig. 4 shows a system 60 (in block form) and
• Fig. 5 shows a flow chart 200 for an air- conditioning and/or dehumidifying system based dehumidifier 10 of Fig. 1, in accordance with an embodiment of the invention.
• the exiting air is optionally heated to high temperature, to increase the system efficiency and reduce the number of times the air has to be treated.
• the heated dehumidified air is then cooled (103) by transfer of heat in a heat exchanger 62 with outside air, to provide cooler dehumidified air.
• the cooled dehumidified air is not as cool as the conditioned air, but depending on the structure of the heat exchanger, it can be reasonably close to the temperature of the outside air used in the regenerator. In particular, if heat is exchanged between the heated dehumidified air and the air entering the regenerator, the amount of heat required from heater 36 (Fig. 1) can be reduced.
• heat can be transferred from the heated dehumidified air to water in a heat exchanger.
• the cooler dehumidified air is then evaporation cooled (104) (for example, by contacting it with water, as is well known in the art, in an evaporation cooler 64), resulting in air that has a lower enthalpy than the air that input the dehumidifier in the first place.
• This lower enthalpy can manifest itself as air that only dehumidified, by air that is cooled or by air that is both cooled and dehumidified.
• Figs. 4 While a single cycle is shown in Figs. 4 the cycle can be repeated (105) (utilizing all or part of the conditioned air) in order to provide a desired temperature/humidity. Eventually, the conditioned air exits (106) the system. It should be noted that if waste heat is available (as for example in an industrial facility), this heat can be used to heat desiccant 20' in reservoir 18'. Thus, the heating/dehumidification system would have relatively no cost, other than for fans for moving the air.
• the invention may include, for one of the reservoirs, a pumping system to pump the desiccant into the chamber, as is known in the art.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Drying Of Gases (AREA)
• Central Air Conditioning (AREA)

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• 2001
  • 2001-04-23 MX MXPA03009675A patent/MXPA03009675A/es unknown
  • 2001-04-23 CN CNB018233473A patent/CN1283958C/zh not_active Expired - Lifetime
  • 2001-04-23 JP JP2002583880A patent/JP4986372B2/ja not_active Expired - Fee Related
  • 2001-04-23 NZ NZ529698A patent/NZ529698A/en unknown
  • 2001-04-23 US US10/475,819 patent/US20040211207A1/en not_active Abandoned
  • 2001-04-23 IL IL15853601A patent/IL158536A0/xx unknown
  • 2001-04-23 EP EP01925842A patent/EP1384034A1/en not_active Withdrawn
  • 2001-04-23 WO PCT/IL2001/000374 patent/WO2002086391A1/en not_active Application Discontinuation
• 2002
  • 2002-10-25 TW TW091125086A patent/TW559651B/zh active

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