Control system architecture for heat exchanger corrosion prevention

Abstract

A liquid desiccant (LD)-based dehumidification system is provided for heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems. The LD-based dehumidification system includes a tank containing LD, a contact media device including media for being disposed in an air stream to be dehumidified and a sump disposed below the media to receive the LD drained from the media, a pump and valve system for pumping the LD from the tank to the contact media device to wet the media and from the sump to the tank, a heat exchanger through which the LD pumped from the sump to the tank flows, a sensing system for sensing one or more conditions of the LD, and a controller for controlling the pump and valve system in accordance with system status and the one or more conditions of the LD.

Description

Technical Field

[0001] This disclosure relates to heating, ventilation, air conditioning and refrigeration (HVAC&R) systems, and more particularly to controls for corrosion prevention of heat exchangers used in liquid desiccant (LD) based HVAC&R systems. Background Technology

[0002] A desiccant is a substance that absorbs moisture from the environment due to its high affinity for water vapor, thus helping to keep the surrounding area dry. Desiccants typically consist of hygroscopic materials that attract and retain water vapor from the air to induce or maintain a dry state (dryness) in their vicinity. Industrially, desiccants are widely used for humidity control in packaging, pharmaceuticals, electronics, food preservation, and dehumidification systems to maintain product integrity and prevent corrosion. Summary of the Invention

[0003] According to one aspect of this disclosure, a liquid desiccant (LD)-based dehumidification system for heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems is provided. The LD-based dehumidification system includes: a tank containing the LD; a contact medium device including a medium disposed in the airflow to be dehumidified and a sump disposed below the medium to receive LD discharged from the medium; a pump and valve system for pumping the LD from the tank to the contact medium device to wet the medium and from the sump to the tank; a heat exchanger through which the LD pumped from the sump to the tank flows; a sensing system for sensing one or more conditions of the LD; and a controller for controlling the pump and valve system based on the system state and one or more conditions of the LD.

[0004] According to one or more additional and / or alternative embodiments, the LD includes at least one or more of inorganic salts and organic compounds.

[0005] According to one or more additional and / or alternative embodiments, the LD includes at least one or more of the following: aqueous solutions of inorganic salts, organic compounds, acetate and formate-based desiccants, and mixed and hybridized solutions.

[0006] According to one or more additional and / or alternative embodiments, the contact medium device is provided as at least one of an absorber and one or more desorbers, and the medium comprises a high surface area filling material.

[0007] According to one or more additional and / or alternative embodiments, the LD sump is uncovered.

[0008] According to one or more additional and / or alternative embodiments, one or more conditions of the LD are the concentration of the LD, the pH of the LD, and the temperature of the LD, and the system state is one of an operating state and a non-operating state.

[0009] According to one or more additional and / or alternative embodiments, the controller controls the pump and valve system to discharge the LD from the sump to the tank based on whether the system state is non-operating, and the controller controls the pump and valve system to cut off the flow of the LD from the sump and through the heat exchanger based on one or more conditions of the LD outside of predetermined design conditions.

[0010] According to one aspect of this disclosure, a dehumidification system based on liquid desiccant (LD) is provided, and the dehumidification system includes: a first tank containing LD; a second tank containing LD treatment agent; a contact medium device including a medium for placement in an airflow to be dehumidified and a sump disposed below the medium to receive LD discharged from the medium; a first pump and valve system for pumping LD from the first tank to the contact medium device to wet the medium and from the sump to the first tank; a second pump and valve system for pumping the LD treatment agent to the first tank to treat the LD; a heat exchanger through which LD pumped from the sump to the first tank flows; a sensing system for sensing one or more conditions of the LD; and a controller for controlling the first pump and valve system and the second pump and valve system according to the system state and one or more conditions of the LD.

[0011] According to one or more additional and / or alternative embodiments, the LD includes at least one or more of inorganic salts and organic compounds.

[0012] According to one or more additional and / or alternative embodiments, the LD includes at least one or more of the following: aqueous solutions of inorganic salts, organic compounds, acetate and formate-based desiccants, and mixed and hybridized solutions.

[0013] According to one or more additional and / or alternative embodiments, the contact medium device is provided as at least one of an absorber and one or more desorbers, and the medium comprises a high surface area filled porous material.

[0014] According to one or more additional and / or alternative embodiments, the sump is uncovered.

[0015] According to one or more additional and / or alternative embodiments, one or more conditions of the LD are the concentration of the LD, the pH of the LD, and the temperature of the LD, and the system state is one of an operating state and a non-operating state.

[0016] According to one or more additional and / or alternative embodiments, the LD treatment agent includes a pH buffer, and the controller controls a second pump and valve system to pump the LD treatment agent to the first tank for treating the LD, based on the pH of the LD outside of predetermined design conditions.

[0017] According to one or more additional and / or alternative embodiments, the controller controls the first pump and valve system to discharge the LD from the sump to the first tank based on whether the system state is non-operating, and the controller controls the first pump and valve system to cut off the flow of the LD from the sump and through the heat exchanger based on one or more conditions of the LD outside of predetermined design conditions.

[0018] According to one aspect of this disclosure, a method for operating a liquid desiccant (LD)-based dehumidification system is provided, the method comprising: pumping the LD to a contact medium device for wetting a medium by the LD, the contact medium device including a medium and a sump disposed below the medium to receive LD discharged from the medium; pumping the LD from the sump to a heat exchanger and passing it through the heat exchanger; sensing one or more conditions of the LD; and controlling the pumping according to the system state and one or more conditions of the LD.

[0019] According to one or more additional and / or alternative embodiments, the method further includes placing the medium in the airflow to be dehumidified.

[0020] According to one or more additional and / or alternative embodiments, one or more conditions of the LD are the concentration of the LD, the pH of the LD, and the temperature of the LD, and the system state is one of an operating state and a non-operating state.

[0021] According to one or more additional and / or alternative embodiments, the method further includes treating the LD based on the fact that the pH of the LD is outside the predetermined design conditions and tends toward undesirable system operating conditions or adverse atmospheric weather conditions.

[0022] According to one or more additional and / or alternative embodiments, the control includes: controlling pumping to discharge the LD from the sump based on whether the system state is non-operating; and controlling pumping to cut off the flow of the LD from the sump and through the heat exchanger based on one or more conditions of the LD outside of predetermined design conditions.

[0023] Additional features and advantages are achieved through the technology of this disclosure. Other embodiments and aspects of this disclosure are described in detail herein and are considered part of the claimed technical concept. Reference is made to the description and accompanying drawings for a better understanding of the advantages and features of this disclosure. Attached Figure Description

[0024] To gain a more complete understanding of this disclosure, reference is now made to the following description of the accompanying drawings and specific embodiments, wherein like reference numerals denote like parts: Figure 1 This is a schematic illustration of the contact medium being wetted by a liquid desiccant (LD) and by an LD with added surfactant, according to an embodiment. Figure 2 This is a schematic diagram of an LD-based dehumidification system according to an embodiment; Figure 3 This is a schematic diagram of an LD-based dehumidification system with an absorber and two desorbers according to an embodiment; Figure 4 According to the embodiments Figure 3 A schematic diagram of the controller for an LD-based dehumidification system; Figure 5 This is a flowchart illustrating a method for operating an LD-based dehumidification system according to an embodiment; Figure 6 This is a schematic diagram of an LD-based dehumidification system with flow control based on LD conditions and system status, according to an embodiment. Figure 7 This is a schematic diagram of an LD-based dehumidification system with LD processing capability and flow control based on LD conditions and system status, according to an embodiment. Figure 8 According to the embodiments Figure 7 A schematic diagram of the controller for an LD-based dehumidification system; and Figure 9 This is a flowchart illustrating a method for operating an LD-based dehumidification system with flow control based on LD conditions and system states according to an embodiment. Detailed Implementation

[0025] Traditionally, air conditioning units reduce humidity by subcooling the air and, in some cases, reheating it before it is supplied. Liquid desiccant-based HVAC systems reduce sensible and latent heat loads by absorbing moisture from the air using a liquid desiccant (LD) solution. This process helps control both temperature (sensible heat load) and humidity (latent heat load), creating a more comfortable indoor environment while improving energy efficiency. This is achieved by passing process air through a porous bed of contact medium soaked in desiccant. Such efficient and responsive dehumidification heavily relies on the instantaneous and complete wetting of the contact medium with LD at any given time. However, the inherently high surface tension of most LDs delays or significantly inhibits the achievement of a fully LD-wetted state on the contact medium. This can lead to sporadic surface coverage of the contact medium, a higher demand for LD flooding rates compared to the airflow through the contact medium (and therefore, larger pumps drawing more power), undesirable entrainment of LD droplets from the physical boundaries of the contact medium into the supply airflow, and ultimately, inefficient dehumidification.

[0026] Therefore, as described below, an advanced system for surface wettability modification is provided in liquid desiccant-based dehumidification systems for HVAC systems. This system detects, enables, and maintains continuous wetting of the contact medium by the LD. The wettability modification of the LD-medium is achieved by adding surfactants to the LD and / or surface treatment of the contact medium. For example, as... Figure 1 As shown in image A, a drop of pure LD can remain indefinitely on an untreated surface of the contact medium without wetting it, but adding only 0.1% by weight of surfactant to the LD is sufficient for superwetting, such as... Figure 1 As shown in Image B. The system may include a sensing-control system architecture that illustrates a phased approach: detecting wetting of the contact medium using computer vision-enabled optical / depth sensors; automatically adding surfactant to the LD using a metering-pumping device based on the surface tension of the LD measured in the tank; rechecking the wetting of the contact medium using sensors; and providing feedback to the system to stop surfactant addition once complete wetting is achieved.

[0027] Furthermore, heat exchangers (HX) operating in LD-based HVAC systems improve thermal efficiency by transferring heat between LD streams in the absorber and desorber, pre-cooling the desiccant for better moisture absorption, and preheating the desiccant for more efficient water desorption, thereby maximizing dehumidification performance while reducing energy consumption. HXs typically operate with 35-65% LD concentration and a pH range of 8-10. However, certain environmental and system conditions, including increases in pH and variations in LD concentration, have been found to drive LD crystallization within the HX. This drying and crystallization alters the thermophysical properties of the LD, potentially leading to accelerated corrosion and eventual loss of HX structural integrity. This results in reduced system energy efficiency due to inefficient heat transfer between hot and cold LD streams in the HX, the need for frequent repairs, and higher maintenance costs.

[0028] For example, a dedicated outdoor air system (LDDOAS) based on liquid desiccant can be configured to provide dehumidification capacity using a LD-wetting contact medium device downstream of the evaporator. During adverse weather conditions (e.g., dry winters) or in non-operating systems during unforeseen operating conditions, LD can be gravity-fed from the contact medium and crystallize near the interface between the contact medium and the LD sump below. These solidified deposits can be difficult to break down mechanically and tend to be difficult to dissolve. During cold starts, crystallized LD can cause LD pipe bursts due to blockage of the orifices in the top LD distributor assembly responsible for uniform wetting of the pad.

[0029] Therefore, as will be described below, a sensing and control system is provided, comprising ambient temperature-humidity and LD pH-conductivity sensors installed in the LD subsystem to detect adverse conditions outside the designed operating range, valves that isolate HX to ensure HX remains fully filled, and a pump control architecture for completely draining LD from the sump into a covered, isolated, and insulated LD tank, which prevents contact with ambient atmospheric conditions during non-operating system modes. When the system is not in operation, the proposed architecture can drain all LD from the absorber and / or desorber contact medium sump to a common tank by means of various pumps and valves, and can cut off flow to HX when the thermophysical properties of the LD (such as LD concentration, LD pH, LD temperature, etc.) fall outside the safe design conditions.

[0030] Reference Figure 2 A dehumidification system 201 based on an LD is provided, comprising a contact medium device 210 including a high surface area filled porous material or medium 211 (hereinafter referred to as "medium 211") for placement in the airflow to be dehumidified, a supply of surfactant 220 compatible with the LD, and a supply of LD 230 for wetting the medium 211. The contact medium device 210 may include or be provided as at least one of an absorber 2101 and a desorber 2102, and the medium 211 may include or be provided as a mesh of filter material 2110. The medium 211 and / or filter material 2110 may be contact media designed to increase the interfacial surface area between the LD and the air, and may be made of a water- and chemical-resistant durable material that provides minimal resistance to the airflow and promotes capillary action to maintain the surface film of the LD, enhancing the contact efficiency between the air and the desiccant solution, thereby improving mass transfer. Examples of media 211 and / or filter material 2110 may include asymmetric cross-flow honeycomb pads typically made of cellulose-based materials (wood-based or bamboo-based), polymer meshes made of hydrophilic materials (e.g., polypropylene, polyester, polyvinyl chloride), ceramic or porous ceramic pads, open-cell foam materials (polyurethane, melamine foam), fibrous materials (polyester, nylon), and combinations of at least one or more of the above and other suitable materials. The supply of LD 230 may be added using a supply of surfactant 220 to adjust the wettability of LD 230 to media 211. The LD-based dehumidification system 201 may also include one or more pumps 240 and one or more valves 250, one or more sensors 260, and a controller (see example...). Figure 4The controller 370. One or more pumps 240 and one or more valves 250 are configured to supply a certain amount of surfactant 220 to the supply for dosing to the LD 230, and to supply a certain amount of the LD 230 containing the amount of surfactant 220 to the contact medium device 210. One or more sensors 260 are configured to sense the wetting of the medium 211 by the amount of the supply of LD 230 containing the amount of surfactant 220. The controller is operatively coupled to one or more pumps 240, one or more valves 250 and one or more sensors 260, and configured to control one or more pumps 240 and one or more valves 260 based on the wetting of the medium by the amount of the supply of LD 230 (which contains the amount of surfactant 220) sensed by one or more sensors 260.

[0031] Potassium acetate (LD) is a salt solution, and not all surfactants are equally effective at reducing surface tension, as some may precipitate or lose their activity. According to embodiments, surfactant 220 may include at least one or more of the following categories: (i) nonionic surfactants (e.g., polyethylene glycol-based surfactants, alkyl polyglycosides such as decyl glucoside, polysorbates (i.e., the Tween series), dodecyl glucosamine, fatty alcohol ethoxylates), (ii) anionic surfactants (e.g., sodium dodecyl sulfate, sodium lauryl ether sulfate), (iii) amphoteric surfactants (e.g., cocamidopropyl betaine, lauryl betaine), and (iv) silicone-based surfactants (siloxane polyethers such as Silwet L-77). The effectiveness of a surfactant depends on the specific concentration of potassium acetate, as higher salt levels can reduce certain types of efficacy. Triton surfactants, particularly nonionic types such as Triton X-100, are effective in potassium acetate solutions due to their lack of charged groups, which provides stability in highly ionic environments. Their nonionic properties prevent interactions with ions such as potassium and acetate, thereby reducing the risk of precipitation and ensuring consistent solubility. Additionally, Triton surfactants possess an optimal hydrophilic-lipophilic balance, effectively reducing surface tension in polar salt solutions. This nonionic stability minimizes electrostatic interactions with ions, allowing Triton surfactants to function reliably under these conditions. LD 230 may comprise aqueous solutions of hygroscopic salts with high osmotic potential (affinity to water) and low volatility, which can be regenerated by heat exchange. Examples of LD 230 may include, but are not limited to, aqueous solutions of inorganic salts (such as lithium chloride, calcium chloride, lithium bromide, potassium formate, ammonium nitrate, potassium nitrate, sodium chloride, magnesium chloride, copper sulfate, aluminum chloride, barium chloride), organic compounds (such as triethylene glycol, ethylene glycol, propylene glycol, glycerol), acetate and formate-based desiccants (such as potassium acetate, potassium formate, sodium acetate, sodium formate), mixed and hybrid solutions (such as lithium chloride-magnesium chloride mixtures, calcium nitrate and magnesium nitrate blends, composite desiccants), and at least one or more of these. According to another embodiment, surfactant 220 may include at least one or more of the following categories: (i) nonionic surfactants (e.g., polyethylene glycol-based surfactants, alkyl polyglycosides such as decyl glucoside, polysorbates (i.e., Tween series), dodecyl glucosamine, fatty alcohol ethoxylates), (ii) anionic surfactants (e.g., sodium dodecyl sulfate, sodium lauryl ether sulfate), (iii) amphoteric surfactants (e.g., cocamidopropyl betaine, lauryl betaine), and (iv) organosilicon-based surfactants (siloxane polyethers such as Silwet L-77).LD 230 may include at least one or more of the following: aqueous solutions of inorganic salts (such as lithium chloride, calcium chloride, lithium bromide, potassium formate, ammonium nitrate, potassium nitrate, sodium chloride, magnesium chloride, copper sulfate, aluminum chloride, and barium chloride); organic compounds (such as triethylene glycol, ethylene glycol, propylene glycol, and glycerol); acetate and formate-based desiccants (such as potassium acetate, potassium formate, sodium acetate, and sodium formate); and mixed and hybrid solutions (such as lithium chloride-magnesium chloride mixtures, calcium nitrate and magnesium nitrate blends, and composite desiccants).

[0032] Reference Figure 3 and Figure 4 A dehumidification system 301 based on an LD is provided, comprising a first tank 310 containing an LD 311, a second tank 320 containing a surfactant 321 compatible with the LD 311, a structured contact medium device 330 incorporating a high surface area filled porous material or medium 331 (hereinafter referred to as "medium 331") for placement in the airflow to be dehumidified, a first pump and valve system 340, a sensing system 350, a second pump and valve system 360, and a controller 370 (see [link to documentation]). Figure 4 A first pump and valve system 340 is configured to pump LD 311 from a first tank 310 to a contact medium device 330 to wet the medium 331. A sensing system 350 is configured to sense the wetting of the medium 331 by the LD 311. A second pump and valve system 360 is configured to pump surfactant 321 from a second tank 320 to a first tank 310, whereby the surfactant 321 pumped to the first tank 310 can be mixed with and added to the LD 311 in the first tank 310. A controller 370 is operatively coupled to the first pump and valve system 340, the sensing system 350, and the second pump and valve system 360, and configured to control the first pump and valve system 340 and the second pump and valve system 360 based on the wetting of the medium 331 sensed by the sensing system 350, thereby controlling the addition of surfactant 321 to the LD 311 and thus regulating the wetting of the medium 331.

[0033] like Figure 4As shown, the controller 370 may include a processor 371, a memory unit 372, and an input / output (I / O) unit 373. The processor 371 communicates with the first pump and valve system 340, the sensing system 350, and the second pump and valve system 360 via the I / O unit 373. The memory unit 372 has executable instructions stored thereon that can be read and executed by the processor 371. When the processor 371 reads and executes the executable instructions, it causes the processor 371 to operate and control the operation of the first pump and valve system 340, the sensing system 350, and the second pump and valve system 360, generally as described herein. In other words, when processor 371 reads and executes the executable instructions, processor 371 and controller 370, as a whole, control the operation of the first pump and valve system 340 and the second pump and valve system 360 based on the wetting of medium 331 sensed by sensing system 350 and the measurement parameters of LD 311 in first tank 310, thereby automatically controlling the addition of surfactant 321 to LD 311 to regulate the wetting of medium 331. According to the embodiment, the measurement parameters may be, but need not be, the surface tension of LD 311 in first tank 310 and / or some other similar parameters (i.e., the wetting rate of medium 311). Furthermore, when processor 371 reads and executes the executable instructions, once complete wetting of medium 331 as sensed by sensing system 350 is achieved, processor 371 and controller 370, as a whole, automatically stop the addition of surfactant 321 to LD 311.

[0034] The contact medium device 330 may include or be provided as at least one of an absorber 332 and one or more desorbers 333. The medium 311 may include or be provided as a high surface area filled porous material 3310. Each of the absorber 332 and at least one of the desorbers 333 may include a collection pit 334 disposed below the corresponding high surface area filled porous material 3310 and fluidly connected to the first tank 310. For clarity and brevity, the following description will refer to the LD-based dehumidification system 301 comprising, as Figure 3 The example shown is of one absorber 332 and two desorbers 333, but it should be understood that this is merely exemplary, and other embodiments and configurations with different numbers of absorbers 332 and desorbers 333 may exist.

[0035] The LD-based dehumidification system 301 may also include a heat exchanger (HX) 380, which includes a hot side 381 and a cold side 382. For example... Figure 3As shown, the hot side 381 can receive relatively hot and concentrated LD 311 (with or without surfactant 321) from the collection pit 334 of each of the two desorbers 333, and the absorber 332 can receive relatively hot LD 311 (with or without surfactant 321) from the hot side 381. The cold side 382 can receive relatively cold and dilute LD 311 (with or without surfactant 321) from the collection pit 334 of the absorber 332. Each of the two desorbers 333 can receive relatively cold LD 311 (via the top LD dispenser assembly) from the cold side 382, ​​which may or may not be doped with surfactant 321.

[0036] The first pump and valve system 340 may include at least metering pumps 3411, 3412, and 3413 and at least bidirectional / solenoid or three-way metering valves 3421, 3422, 3423, 3424, 3425, 3426, 3427, and 3428, all of which are operable and controllable by the controller 370 as described above. The second pump and valve system 360 may include at least one metering pump 361 and at least one metering valve 362, which are operable and controllable by the controller 370 as described above. The sensing system 350 may include one or more sensors 351 configured to signal communicate with the controller 370 and constructed to sense the wetting of the medium 331 by the LD 311. The one or more sensors 351 may be deployed as a plurality of sensors 351 for each of the absorbers 332 and for each of the two desorbers 333. Each of the one or more sensors 351 may include or be provided at least one of a computer vision-enabled optical sensor and a computer vision-enabled depth sensor. Each of the plurality of sensors 351 may further include: a capacitive / resistive humidity sensor embedded in the medium 331 to detect dryness, which changes their electrical properties based on the moisture content; or a thermal and / or optical sensor, respectively based on infrared thermal imaging / optical reflectivity, to indicate changes in surface properties as the medium 331 dries.

[0037] According to the embodiments, surfactant 321 may include at least one or more of the following categories: (i) nonionic surfactants (e.g., polyethylene glycol-based surfactants, alkyl polyglycosides such as decyl glucoside, polysorbates (i.e., Tween series), dodecyl glucosamine, fatty alcohol ethoxylates), (ii) anionic surfactants (e.g., sodium dodecyl sulfate, sodium lauryl ether sulfate), (iii) amphoteric surfactants (e.g., cocamidopropyl betaine, lauryl betaine), and (iv) organosilicon-based surfactants (siloxane polyethers such as Silwet L-77). LD 311 may include at least one or more of the following: aqueous solutions of inorganic salts (such as lithium chloride, calcium chloride, lithium bromide, potassium formate, ammonium nitrate, potassium nitrate, sodium chloride, magnesium chloride, copper sulfate, aluminum chloride, and barium chloride); organic compounds (such as triethylene glycol, ethylene glycol, propylene glycol, and glycerol); acetate and formate-based desiccants (such as potassium acetate, potassium formate, sodium acetate, and sodium formate); and mixed and hybrid solutions (such as lithium chloride-magnesium chloride mixtures, calcium nitrate and magnesium nitrate blends, and composite desiccants). According to another embodiment, surfactant 321 may include at least one or more nonionic surfactants such as Triton, and LD 311 may include at least one or more aqueous solutions of acetate-based desiccants (such as potassium acetate).

[0038] Reference Figure 5 It provides operation of LD-based dehumidification systems (such as...) Figure 2 LD-based dehumidification system 201 and Figure 3 and Figure 4 Method 500 of an LD-based dehumidification system 301. In some cases, method 500 includes initially placing a medium in the airflow to be dehumidified (box 501). Method 500 also includes: supplying an LD to a contact medium device comprising a medium disposed in the airflow to be dehumidified for wetting the medium by the LD (box 502); and sensing the degree of wetting of the medium by the LD by at least one of computer vision-enabled optical sensing (box 5031) and computer vision-enabled depth sensing (box 5032) (box 503). Furthermore, method 500 includes: continuing the supply of the LD to the contact medium device while controlling the addition of a surfactant compatible with the LD to the LD to adjust the degree of wetting of the medium based on the sensing results of box 503 and, in some cases, parameters of the LD such as the surface tension and wetting rate of the LD (box 504). Method 500 may further include: determining whether complete wetting of the medium has been achieved (box 505); and stopping the addition of surfactant to the LD once complete wetting of the medium has been achieved (box 506).

[0039] According to embodiments, the contact medium device may include or be provided as at least one of an absorber and one or more desorbers. The medium may include a mesh of filter material such as a high surface area filled porous material, and each of the absorber and at least one of the desorbers may include a sump disposed below the corresponding medium. In these or other cases, the supply of the LD of block 502 to the contact medium device may include: supplying a relatively hot LD with or without surfactant added from the sump of each of the one or more desorbers to the hot side of the heat exchanger (block 5021); supplying a relatively hot LD with or without surfactant added from the hot side to the absorber (block 5022); supplying a relatively cold LD with or without surfactant added from the sump of the absorber to the cold side of the heat exchanger (block 5023); and supplying a relatively cold LD with or without surfactant added from the cold side to each of the one or more desorbers (block 5024).

[0040] Reference Figure 6 A dehumidification system 601 based on LD is provided, comprising a tank 610 containing LD 611 and a contact medium device 620 including a medium 621 disposed in the airflow to be dehumidified and a collection pit 622, the collection pit 622 being uncovered and disposed below the medium 621 to receive LD 611 discharged by gravity from the medium 621. The contact medium device 620 may include or be provided as at least one of an absorber 6201 and a desorber 6202, and the medium 621 may include or be provided as an asymmetric cross-flow honeycomb pad typically made of cellulose-based materials (wood-based or bamboo-based), a polymer mesh made of hydrophilic materials (e.g., polypropylene, polyester, polyvinyl chloride), a ceramic or porous ceramic pad, an open-cell foam material (polyurethane, melamine foam), and a fibrous material (polyester, nylon).

[0041] The LD-based dehumidification system 601 also includes a pump and valve system 630 and a heat exchanger 640, such as HX. The pump and valve system 630 includes one or more pumps and one or more valves, and is configured to pump LD 611 from tank 610 to contact medium device 620 to wet medium 621, and for LD 611 discharged by gravity from medium 621, pump LD 611 from sump 622 back to tank 610. LD 611 pumped from sump 622 to tank 610 flows through heat exchanger 640. The LD-based dehumidification system 601 also includes a sensing system 650 and a controller (see, for example...). Figure 8The controller 780. The sensing system 650 is configured to sense one or more conditions of the LD 611. The controller 780 is operatively coupled to the pump and valve system 630 and the sensing system 650, and is configured to control the pump and valve system 630 based on the system state and one or more conditions of the LD 611 sensed by the sensing system 650.

[0042] One or more conditions of LD 611 may include, but are not limited to, the concentration of LD 611, the pH of LD 611, and the temperature of LD 611, and the system state may be one of an operating state and a non-operating state. Controller 780 is configured to control pump and valve system 630 to discharge LD 611 from sump 622 to tank 610 based on the system state being non-operating, and is also configured to control pump and valve system 630 to cut off the flow of LD 611 from sump 622 and through heat exchanger 640 based on one or more conditions of LD 611, in addition to predetermined design conditions sensed by sensing system 650.

[0043] According to embodiments, LD 611 may comprise at least one or more of the following: aqueous solutions of inorganic salts (such as lithium chloride, calcium chloride, lithium bromide, potassium formate, ammonium nitrate, potassium nitrate, sodium chloride, magnesium chloride, copper sulfate, aluminum chloride, and barium chloride); organic compounds (such as triethylene glycol, ethylene glycol, propylene glycol, and glycerol); acetate and formate-based desiccants (such as potassium acetate, potassium formate, sodium acetate, and sodium formate); and mixed and hybrid solutions (such as lithium chloride-magnesium chloride mixtures, calcium nitrate and magnesium nitrate blends, and composite desiccants). According to further embodiments, LD 611 may comprise at least one or more of the following: aqueous solutions of acetate-based desiccants (such as potassium acetate).

[0044] Reference Figure 7 and Figure 8 A dehumidification system 701 based on LD is provided, comprising a first tank 710 containing LD 711, an optional second tank 720 containing LD treatment agent 721, a contact medium device 730 including a high surface area filled structured contact medium, a high surface area filled porous material or medium 731 (hereinafter referred to as "medium 731") for placement in the airflow to be dehumidified, and a sump 732 disposed below the medium 731 and uncovered to receive LD 711 discharged from the medium 731 by gravity. The LD-based dehumidification system 701 also includes a first pump and valve system 740, a second pump and valve system 750, an HX 760, a sensing system 770, and a controller 780 (see [link to documentation]). Figure 8 ).

[0045] For the purposes of clarity and brevity, the following description will refer to the case in which the LD-based dehumidification system 701 includes a second tank 720 containing an LD treatment agent 721.

[0046] A first pump and valve system 740 is configured to pump LD 711 from a first tank 710 to a contact medium device 730 to wet the medium 731, and for LD 711 discharged by gravity from the medium 731, pump LD 711 from a sump 732 back to the first tank 710. A second pump and valve system 750 is configured to pump LD treatment agent 721 from the second tank 720 to the first tank 710 to treat LD 711. An HX 760 is fluidly inserted between the sump 732 and the first tank 710 such that LD 711 pumped from the sump 732 to the first tank 710 flows through a heat exchanger 760. A sensing system 770 is configured to sense one or more conditions of the LD 711. The controller 780 is operatively coupled to the first pump and valve system 740, the second pump and valve system 750, and the sensing system 770, and is configured to control the first pump and valve system 740 and the second pump and valve system 750 according to the system state and one or more conditions of the LD 711.

[0047] The contact medium device 730 may include or be provided as at least one of an absorber 733 and one or more desorbers 734, the medium 731 may include or be provided as a filter material or a mesh of high surface area filled porous material 7310, and each of at least one of the absorber 733 and one or more desorbers 734 includes a sump 732. For clarity and brevity, the following description will refer to the LD-based dehumidification system 701 comprising, for example... Figure 7 The example shown is of one absorber 733 and two desorbers 734, but it should be understood that this is merely exemplary, and other embodiments and configurations with different numbers of absorbers 733 and desorbers 734 may exist.

[0048] The HX 760 may include a hot side 761 and a cold side 762. For example... Figure 7 As shown, the hot side 761 can receive relatively hot and concentrated LD 711 from the collection pit 732 of each of the two desorbers 734, the absorber 733 can receive relatively hot and concentrated LD 711 from the hot side 761, the cold side 762 can receive relatively cold and dilute LD 711 from the collection pit 732 of the absorber 733, and each of the two desorbers 734 can receive relatively cold and dilute LD 711 from the cold side 762.

[0049] like Figure 8As shown, the controller 780 may include a processor 781, a memory unit 782, and an I / O unit 783. The processor 781 communicates with the first pump and valve system 740, the second pump and valve system 750, and the sensing system 770 through the I / O unit 783. The memory unit 782 has executable instructions stored thereon that can be read and executed by the processor 781. When the processor 781 reads and executes the executable instructions, it causes the processor 781 to operate and control the operation of the first pump and valve system 740, the second pump and valve system 750, and the sensing system 770, generally as described herein. That is, when the processor 781 reads and executes the executable instructions, the processor 781 and the controller 780 as a whole can control the operation of the first pump and valve system 740 and the second pump and valve system 750 based on the system state and one or more conditions of the LD 711.

[0050] According to an embodiment, one or more conditions of LD 711 may include, but are not limited to, the concentration of LD 711, the pH of LD 711, and the temperature of LD 711, and the system state may be one of an operating state and a non-operating state. Accordingly, when the processor 781 reads and executes executable instructions, the processor 781 and the controller 780 as a whole may control the first pump and valve system 740 to discharge LD 711 from the sump 732 to the first tank 710 if the system state is non-operating, and may control the first pump and valve system 740 to cut off the flow of LD 711 from the contact medium device 730 if one or more conditions of LD 711 are outside the predetermined design conditions and tend toward undesirable system operating conditions or adverse atmospheric weather conditions, thereby preventing the crystallization of LD 711 on the contact medium device 730 and preventing damage to the heat exchanger 760.

[0051] Furthermore, in cases where the LD treatment agent 721 includes a pH buffer (such as an alkaline pH buffer), the processor 781 and controller 780, as a whole, can control the second pump and valve system 750, beyond predetermined design conditions, to pump the LD treatment agent 721 to the first tank 710 to treat the LD 711, based on the pH of the LD 711. Potassium acetate is a weakly basic salt, and its pH may become acidic over time due to the absorption of carbon dioxide from the air, forming undesirable acetic acid in LD-based HVAC systems using potassium acetate as LD 711. Examples of alkaline buffer systems that can be used for liquid desiccants such as potassium acetate include sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium carbonate, tris(hydroxymethyl)aminomethane buffer (i.e., TRIS), ammonium hydroxide, magnesium hydroxide, and boric acid with sodium tetraborate. Potassium-based buffers such as potassium carbonate are ideal for maintaining the pH of potassium acetate solutions within a desired alkaline range to preserve the integrity of potassium-based chemistry and ensure long-term pH stability. Therefore, it is possible that the processor 781 and the controller 780 as a whole prevent the pH of LD 711 from becoming too acidic or too alkaline, and thus avoid or at least delay the need to control the first pump and valve system 740 to cut off the flow of LD 711 from the contact medium device 730 outside of the predetermined design conditions according to one or more conditions of LD 711.

[0052] The first pump and valve system 740 may include at least metering pumps 7411, 7412, and 7413 and at least bidirectional / solenoid or three-way metering valves 7421, 7422, 7423, 7424, 7425, 7426, 7427, and 7428, all of which are operable and controllable by the controller 780 as described above. The second pump and valve system 750 may include at least one metering pump 751 and at least one metering valve 752, which are operable and controllable by the controller 780 as described above. The sensing system 770 may include one or more sensors T1-T4 configured to signal communicate with the controller 780 and constructed to sense one or more conditions of the LD 711.

[0053] Reference Figure 9 It provides operation of LD-based dehumidification systems (such as...) Figure 6 The LD-based dehumidification system 601 and Figure 7 and Figure 8Method 900 of a dehumidification system 701 based on an LD. Method 900 includes initially placing a medium in a contact medium device within an airflow to be dehumidified (box 901). Method 900 further includes: pumping an LD to a contact medium device comprising a medium and a sump for wetting the medium by the LD, the sump being disposed below the medium to receive the LD discharged from the medium by gravity (box 902); and pumping the LD from the sump to a heat exchanger and passing it through the heat exchanger (box 903). Method 900 further includes sensing one or more conditions of the LD (box 904) and controlling pumping based on system state and one or more conditions of the LD (box 905). The control of box 905 may include: controlling pumping to discharge the LD from the sump based on a non-operating system state (box 9051); and controlling pumping outside of predetermined design conditions based on one or more conditions of the LD to cut off the flow of the LD from the sump and through the heat exchanger (box 9052).

[0054] According to an embodiment, one or more conditions of the LD may be the concentration of the LD, the pH of the LD, and the temperature of the LD, and the system state may be one of an operating state and a non-operating state. When one or more conditions of the LD are the pH of the LD, method 900 may include treating the LD outside of predetermined design conditions based on the pH of the LD (block 906).

[0055] The technical effects and benefits of this disclosure are the provision of an advanced system for surface wettability modification in liquid desiccant-based dehumidification systems for HVAC systems. This system senses adverse operating conditions and employs a control system to ensure immediate and uniform wetting of the contact medium at low desiccant flow rates without pretreatment (i.e., water). The system is designed to protect critical components from unforeseen system disturbances while meeting target dehumidification performance and is expected to reduce the risk of LD entrainment from dry points and LD crystallization in non-operating systems. The system is also designed to protect critical LDDOAS components from seasonal and / or diurnal weather variations or unforeseen disturbances. The described method provides reduced long-term maintenance and lower maintainability costs while meeting target dehumidification performance requirements.

[0056] All means or steps plus functional elements in the following claims are intended to include corresponding structures, materials, actions, and equivalents for performing functions in combination with other claimed elements as specifically claimed. The description of this disclosure has been presented for purposes of illustration and description, but it is not intended to be exhaustive or limited to the technical concepts in the disclosed forms. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of this disclosure. The embodiments were chosen and described in order to best explain the principles and practical application of this disclosure and to enable others skilled in the art to understand this disclosure with respect to various embodiments having various modifications suitable for the particular intended use.

[0057] While preferred embodiments of this disclosure have been described, it should be understood that various modifications and enhancements falling within the scope of the appended claims can be made now and in the future by those skilled in the art. These claims should be construed as maintaining appropriate protection for this disclosure as initially described.

Claims

1. A liquid desiccant (LD)-based dehumidification system for heating, ventilation, air conditioning and refrigeration (HVAC&R) systems, comprising: The can contains LD; A contact medium device includes a medium for placement in the airflow to be dehumidified and a water collection pit disposed below the medium to receive LD discharged from the medium; A pump and valve system for pumping the LD from the tank to the contact medium device to wet the medium and from the sump to the tank; The heat exchanger is used to pump the LD from the sump to the tank; A sensing system for sensing one or more conditions of the LD; as well as A controller for controlling the pump and valve system based on the system state and one or more conditions of the LD.

2. The LD-based dehumidification system according to claim 1, wherein, The LD includes at least one or more of inorganic salts and organic compounds.

3. The LD-based dehumidification system according to any one of claims 1 or 2, wherein, The LD includes at least one or more of the following: aqueous solutions of inorganic salts, organic compounds, acetate and formate-based desiccants, and mixed and hybridized solutions.

4. The LD-based dehumidification system according to any one of claims 1 to 3, wherein, The contact medium device is provided as at least one of an absorber and one or more desorbers, and the medium comprises a high surface area filling material.

5. The LD-based dehumidification system according to any one of claims 1 to 43, wherein, The LD sump is uncovered.

6. The LD-based dehumidification system according to any one of claims 1 to 5, wherein, The one or more conditions of the LD are the concentration of the LD, the pH of the LD, and the temperature of the LD, and the system state is one of an operating state and a non-operating state.

7. The LD-based dehumidification system according to any one of claims 1 to 6, wherein: The controller controls the pump and valve system to discharge the LD from the sump into the tank based on the system state being non-operating. The controller controls the pump and valve system outside of predetermined design conditions based on one or more conditions of the LD to cut off the flow of the LD from the sump and through the heat exchanger.

8. A dehumidification system based on liquid desiccant (LD), comprising: The first can contains LD; The second container contains LD treatment agent; A contact medium device includes a medium for placement in the airflow to be dehumidified and a water collection pit disposed below the medium to receive LD discharged from the medium; A first pump and valve system is used to pump the LD from the first tank to the contact medium device to wet the medium and from the sump to the first tank; A second pump and valve system is used to pump the LD treatment agent to the first tank to treat the LD; The heat exchanger is used to pump the LD from the sump to the first tank; A sensing system for sensing one or more conditions of the LD; as well as A controller for controlling the first pump and valve system and the second pump and valve system based on the system state and one or more conditions of the LD.

9. The LD-based dehumidification system according to claim 8, wherein, The LD includes at least one or more of inorganic salts and organic compounds.

10. The LD-based dehumidification system according to any one of claims 8 or 9, wherein, The LD includes at least one or more of the following: aqueous solutions of inorganic salts, organic compounds, acetate and formate-based desiccants, and mixed and hybridized solutions.

11. The LD-based dehumidification system according to any one of claims 8 to 13, wherein, The contact medium device is provided as at least one of an absorber and one or more desorbers, and the medium comprises a high surface area filled porous material.

12. The LD-based dehumidification system according to any one of claims 8 to 11, wherein, The sump pit is uncovered.

13. The LD-based dehumidification system according to any one of claims 8 to 12, wherein, The one or more conditions of the LD are the concentration of the LD, the pH of the LD, and the temperature of the LD, and the system state is one of an operating state and a non-operating state.

14. The LD-based dehumidification system according to any one of claims 8 to 13, wherein: The LD treatment agent includes a pH buffer solution, and The controller controls the second pump and valve system to pump the LD treatment agent to the first tank to treat the LD, based on the pH of the LD outside of predetermined design conditions.

15. The LD-based dehumidification system according to any one of claims 8 to 14, wherein: The controller controls the first pump and valve system to discharge the LD from the sump into the first tank based on whether the system state is non-operating. The controller controls the first pump and valve system to cut off the flow of the LD from the sump and through the heat exchanger, based on one or more conditions of the LD that are outside the predetermined design conditions and tend toward undesirable system operating conditions or adverse atmospheric weather conditions.

16. A method of operating a dehumidification system based on liquid desiccant (LD), the method comprising: The LD is pumped to a contact medium device for wetting the medium by the LD, the contact medium device including the medium and a collection pit disposed below the medium to receive the LD discharged from the medium; The LD is pumped from the sump to the heat exchanger and passed through the heat exchanger; Sensing one or more conditions of the LD; as well as The pumping is controlled based on the system status and one or more conditions of the LD.

17. The method of claim 16, further comprising placing the medium in the airflow to be dehumidified.

18. The method according to any one of claim 16 or claim 17, wherein, The one or more conditions of the LD are the concentration of the LD, the pH of the LD, and the temperature of the LD, and the system state is one of an operating state and a non-operating state.

19. The method according to any one of claims 16 to 18, further comprising treating the LD according to the fact that the pH of the LD is outside the predetermined design conditions and tends toward undesirable system operating conditions or adverse atmospheric weather conditions.

20. The method according to any one of claims 16 to 19, wherein, The control includes: The pump is controlled to discharge the LD from the sump based on whether the system is in an inactive state. The pumping is controlled outside of predetermined design conditions according to one or more conditions of the LD to cut off the flow of the LD from the sump and through the heat exchanger.

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