Patent Publication Number: US-2022212140-A1

Title: Humidity control device

Description:
TECHNICAL FIELD 
     The present invention relates to a humidity control device. The present application claims priority to Japanese Patent Application No. 2019-082170, filed on Apr. 23, 2019, the contents of which are incorporated herein by reference in its entirety. 
     BACKGROUND ART 
     Conventional humidity control devices known in the art adjust room humidity. A humidity control device disclosed in Patent Document 1 uses, for example, a liquid hygroscopic material to dehumidify a room. 
     The humidity control device cited in Patent Document 1 is capable of removing moisture absorbed into the hygroscopic material, such that the hygroscopic material is rendered reusable. The hygroscopic material cited in Patent Document 1 is a solution containing a solvent such as water and a hygroscopic substance dissolved in the solvent. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: WO 2018/235773 
     SUMMARY OF INVENTION 
     Technical Problem 
     The above humidity control device absorbs humidity with the hygroscopic material and removes water from the hygroscopic material to adjust humidity in a room environment. The humidity control device still has room for improvement in achieving stable humidity control performance. 
     In view of the above problem, an aspect of the present invention is intended to provide a humidity control device capable of stably absorbing and desorbing moisture. 
     Solution to Problem 
     In order to solve the above problem, an aspect of the present invention provides a humidity control device including: a moisture absorber causing a hygroscopic material to come into contact with air so that the hygroscopic material absorbs portion of moisture contained in the air, the hygroscopic material being in liquid and containing water, polyalcohol having hygroscopicity, and metal salt having hygroscopicity; and a composition controller controlling composition of the hygroscopic material. The composition controller controls the composition of the hygroscopic material to be within a range in which the hygroscopic material is capable of absorbing the moisture while the metal salt is kept from being deposited. 
     In an aspect of the present invention, the composition controller may include: a measurer measuring a concentration of the hygroscopic material; an adjuster adjusting the concentration of the hygroscopic material; and a controller controlling an operation of the adjuster in accordance with a result of the measurement by the measurer. 
     In an aspect of the present invention, the adjuster may include an atomizing separator separating, from the hygroscopic material, portion of moisture contained in the hygroscopic material. The portion of the water may be separated in a form of atomized droplets. 
     In an aspect of the present invention, the atomizing separator may include an ejection outlet ejecting a mixture, containing the atomized droplets, out of the atomizing separator. The atomized droplets may include large droplets, and fine droplets smaller in diameter than the large droplets. The ejection outlet may be provided with a separator separating the large droplets from the mixture. 
     In an aspect of the present invention, the separator may be a cyclone separator. 
     In an aspect of the present invention, the adjuster may include a diluter adding water to the hygroscopic material. 
     In an aspect of the present invention, the polyalcohol may include glycerin. 
     In an aspect of the present invention, the metal salt may include lithium chloride. 
     In an aspect of the present invention, the metal salt may include calcium chloride. 
     Advantageous Effects of Invention 
     The present invention can provide a humidity control device capable of stably absorbing and desorbing moisture. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a humidity control device  1 . 
         FIG. 2  is a phase diagram illustrating a hygroscopic material of a three-component system, the hygroscopic substance containing water, hygroscopic polyalcohol, and hygroscopic metal salt. 
         FIG. 3  is a block diagram illustrating a controller  60 . 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Described below is a humidity control device  1  according to this embodiment, with reference to  FIGS. 1 to 3 . Note that, in all the drawings below, the constituent features are illustrated in different dimensions and proportions as appropriate in view of viewability of the drawings. 
       FIG. 1  is a schematic diagram illustrating the humidity control device  1 . In the drawings below, some constituent features can be illustrated in different scales of dimension in view of viewability of these constituent features. 
     Humidity Control Device 
     As illustrated in  FIG. 1 , the humidity control device  1  according to this embodiment includes: a moisture absorber  10 ; an atomizing separator  20 ; a circulator  30 ; a measurer  40 ; a diluter  50 ; and a controller  60 . The humidity control device  1  of this embodiment includes a casing  100 . The moisture absorber  10 , the atomizing separator  20 , the circulator  30 , the measurer  40 , and the diluter  50  are housed in an internal space  100   c  of the casing  100 . 
     The atomizing separator  20 , the measurer  40 , the diluter  50 , and the controller  60  correspond to a “composition controller” of the present invention. Moreover, the atomizing separator  20  corresponds to an “adjuster” of the present invention. 
     Moisture Absorber 
     The moisture absorber  10  includes: a first reservoir  11 ; a nozzle  13 ; a porous member  15 ; an intake passage  18 ; and an ejection passage  19 . 
     The moisture absorber  10  causes a hygroscopic material W, containing a hygroscopic substance, to come into contact with air A 1  found in an external space so that the hygroscopic material W absorbs at least portion of moisture contained in the air A 1 . The moisture absorber  10  desirably causes the hygroscopic material W to absorb as much moisture as possible. However, the moisture absorber  10  may cause the hygroscopic material W to absorb at least portion of the moisture contained in the air A 1 . 
     First Reservoir, Intake Passage, Ejection Passage 
     The first reservoir  11  reserves the hygroscopic material W. The hygroscopic material W will be described later. 
     The intake passage  18  and the ejection passage  19  are connected to the first reservoir  11 . Moreover, pipes  31  and  32  are also connected to the first reservoir  11 . The pipes  31  and  32  are included in the circulator  30  to be described later. 
     Along the intake passage  18 , a blower  181  is provided. The blower  181  takes the air A 1  from the external space of the casing  100 , and sends the air A 1  to the inside of the first reservoir  11  through the intake passage  18 . Moreover, the blower  181  creates an air current to flow from the inside of the first reservoir  11  through the ejection passage  19  out of the casing  100 . 
     The first reservoir  11  includes an ejection port  11   b  to which the pipe  31  is connected. Moreover, the pipe  32  is connected to the nozzle  13  to be described later. The first reservoir  11  is supplied with a hygroscopic material W 1  from a second reservoir  21  through the pipe  32 . 
     In the second reservoir  21 , at least portion of moisture is removed from a hygroscopic material W 2  utilizing a device configuration to be described later, so that the hygroscopic material W 1  is generated. The generated hygroscopic material W 1  is ejected from an ejection port  21   b.    
     Nozzle 
     The nozzle  13  is disposed in an upper portion of an internal space in the first reservoir  11 . Through the pipe  32 , the hygroscopic material W 1  returns from the atomizing separator  20  to the moisture absorber  10 . The hygroscopic material W 1  then flows down from the nozzle  13  into the internal space of the first reservoir  11 . When flowing down, the hygroscopic material W 1  comes into contact with the air A 1 . This contact technique between the hygroscopic material W 1  and the air A 1  is commonly referred to as the “flow-down technique.” 
     Note that the hygroscopic material W 1  and the air A 1  may come into contact with each other not only with the flow-down technique, but also with any given technique. For example, the air A 1  is foamed and supplied into the hygroscopic material W reserved in the first reservoir  11 . Such a technique is referred to as the “bubbling” technique. 
     Porous Member 
     The porous member  15  is formed into a rectangular plate having a mesh-like structure. The porous member  15  is provided approximately perpendicularly to a bottom plate  11   f  of the first reservoir  11 . 
     At least one porous member  15  is provided inside the first reservoir  11 . The porous member  15  preferably includes two or more porous members  15 . The porous member  15  guides the hygroscopic material W, flowing out of the nozzle  13 , toward the bottom plate  11   f  of the first reservoir  11 . The hygroscopic material W flowing down from the nozzle  13  flows downward through the mesh of the porous member  15 . 
     The air A 1  found in the external space creates an air current flowing from the blower  181  toward an ejection port  11   a  of the first reservoir  11 . The air current comes into contact with the hygroscopic material W flowing down from the nozzle  13  and the hygroscopic material W flowing down through the porous member  15 . 
     Here, at least portion of the moisture contained in the air A 1  is absorbed into the hygroscopic material W and removed from the air A 1 . That is, air A 2  to be ejected from the ejection port  11   a  is drier than the air A 1  in the external space. 
     The air A 2  created in the moisture absorber  10  is ejected out of the casing  100  through the ejection passage  19 . 
     Hygroscopic Material 
     The hygroscopic material W is a liquid exhibiting a property to absorb moisture (hygroscopicity). After absorbing moisture, the hygroscopic material W shows a decrease in hygroscopicity. However, using the atomizing separator  20  to be described later, at least portion of the absorbed moisture can be removed from the hygroscopic material W. Such a feature makes it possible to render the hygroscopic material W reusable. 
     Preferably, the hygroscopic material W exhibits the hygroscopicity under such a condition as, for example, a temperature of 25° C. and a relative humidity of 50% at atmospheric pressure. 
     The hygroscopic material W of this embodiment contains water serving as a solvent, polyalcohol having hygroscopicity, and metal salt having hygroscopicity. The hygroscopic polyalcohol and the hygroscopic metal salt are hygroscopic substances contained in the hygroscopic material W. 
     Examples of the polyalcohol include glycerin, propanediol, butanediol, pentanediol, trimethylolpropane, butanetriol, ethylene glycol, diethylene glycol, and triethylene glycol. Moreover, the polyalcohol may be a dimer or a polymer of polyalcohol. In particular, the polyalcohol preferably includes glycerin, diglycerin, and polyglycerin. 
     The polyalcohol to be used may be of either one kind alone, or two or more kinds combined. 
     Examples of the metal salt include calcium chloride, lithium chloride, magnesium chloride, potassium chloride, sodium chloride, zinc chloride, aluminium chloride, lithium bromide, calcium bromide, potassium bromide, sodium hydroxide, and sodium pyrrolidone carboxylate. In particular, the metal salt preferably includes lithium chloride and calcium chloride. 
     The metal salt to be used may be of either one kind alone or two or more kinds combined. 
     That is, the hygroscopic material W to be used in the humidity control device  1  is preferably: a hygroscopic material containing water, glycerin, and lithium chloride; a hygroscopic material containing water, glycerin, and calcium chloride; a hygroscopic material containing water, diglycerin, and lithium chloride; a hygroscopic material containing water, diglycerin, and calcium chloride; a hygroscopic material containing water, polyglycerin, and lithium chloride; or a hygroscopic material containing water, polyglycerin, and calcium chloride. 
     Other than the above materials, the hygroscopic material W may include an organic solvent having an amide group, sugars, and publicly known materials to be used as ingredients of, for example, moisturizing cosmetics. 
     Examples of the organic solvent having an amide group include formamide and acetamide. 
     Examples of the sugars include sucrose, pullulan, glucose, xylene, fructose, mannitol, and sorbitol. 
     Examples of the publicly known materials to be used as ingredients of moisturizing cosmetics include 2-methacryloyloxyethyl phosphorylcholine (MPC), betaine, hyaluronic acid, and collagen. 
     The hygroscopic material W has a viscosity of 25 mPa·s or below. Thanks to this viscosity, the atomizing separator  20  to be described later is easily create a plume C of the hygroscopic material W on the surface of the hygroscopic material W. Such a feature makes it possible to efficiently separate moisture from the hygroscopic material W. 
     The inventors have conducted studies to find out that, if polyalcohol alone is used as the hygroscopic substance to be dissolved into water in order to prepare the hygroscopic material W, the hygroscopicity of the hygroscopic material W increases as a concentration of the hygroscopic material W increases. However, the studies show that the atomizing separator  20  suffers a decrease in efficiency of removing moisture. 
     Moreover, if metal salt alone is used as the hygroscopic substance, the hygroscopic material W is high in hygroscopicity, and the hygroscopicity increases as a concentration of the hygroscopic material W increases. However, the studies show a drawback of the hygroscopic material W containing metal salt alone as the hygroscopic substance. When the atomizing separator  20  separates moisture from the hygroscopic material W, the separating moisture is likely to contain the metal salt. 
     Hence, the studies of the hygroscopic material W prepared in conventional manners show a trade-off between the hygroscopicity and the efficiency in separating moisture by atomization. Such a hygroscopic material W has required improvements. 
     In contrast, the hygroscopic material W to be used for the humidity control device  1  of the present application contains both polyalcohol and metal salt. Such a feature makes it possible to improve the efficiency in separating moisture by atomization and to enhance hygroscopicity, compared with a hygroscopic material containing either polyalcohol or metal salt alone as a hygroscopic substance. 
     The hygroscopic material W contains both polyalcohol and metal salt, such that the polyalcohol and the metal salt are believed to form a coordination complex. Hence, the metal salt dissolved into the hygroscopic material W is bound by the polyalcohol, and is less likely to move. Thanks to such a feature, the metal salt contained in the hygroscopic material W is less likely to mix with atomized droplets W 3  generated by the atomizing separator  20  to be described later, making it possible to improve efficiency in separating water by atomization. 
     Composition Controller 
     The atomizing separator  20  includes: the second reservoir  21 ; an ultrasonic transducer  22 ; a separator  25 ; an intake passage  28 ; and an ejection passage  29 . The atomizing separator  20  atomizes at least portion of moisture contained in the hygroscopic material W 2  supplied from the moisture absorber  10  through the pipe  31 , and removes at least portion of the moisture from the hygroscopic material W 2 . Such a feature enhances the hygroscopicity of the hygroscopic material W 2  again, so that the hygroscopic material W 1  can be returned to the moisture absorber  10  and reused. The ejection passage  29  corresponds to an ejection outlet of the present invention. 
     Second Reservoir, Intake Passage, Ejection Passage 
     The intake passage  28 , the ejection passage  29 , and the pipes  31  and  32  are connected to the second reservoir  21 . Along the intake passage  28 , a blower  281  is provided. The blower  281  supplies the air A 1  to an internal space of the second reservoir  21  through the intake passage  28 . 
     The blower  281  takes the air A 1  from the external space of the casing  100  and sends the air A 1  to the inside of the second reservoir  21  through the intake passage  28 . Moreover, the blower  281  creates an air current to flow from the inside of the second reservoir  21  through the ejection passage  29  out of the casing  100 . 
     The second reservoir  21  includes: a fill port  21   a  to which the pipe  31  is connected; and the ejection port  21   b  to which the pipe  31  is connected. The second reservoir  21  is supplied with the hygroscopic material W 2  from the first reservoir  11  through the pipe  31 . 
     In the second reservoir  21 , at least portion of moisture is removed from the hygroscopic material W 2  utilizing a device configuration to be described later, so that the hygroscopic material W 1  is generated. The generated hygroscopic material W 1  is ejected from the ejection port  21   b.    
     Ultrasonic Transducer 
     The ultrasonic transducer  22  is provided to a bottom plate  21   f  of the second reservoir  21 , and emits an ultrasonic wave toward the surface of the hygroscopic material W 2  reserved in the second reservoir  21 . 
     When emitting the ultrasonic wave to the hygroscopic material W 2 , the ultrasonic transducer  22  adjusts a condition for generating the ultrasonic wave so that the plume C of the hygroscopic material W 2  can be formed on the surface of the hygroscopic material W 2 . From the plume C of the hygroscopic material W 2 , at least portion of moisture contained in the hygroscopic material W 2  is atomized and separated. Hence, many atomized droplets W 3  are produced. 
     Here, the “atomized droplets” are a group of fine airborne water droplets in the second reservoir  21 . The atomized droplets W 3  include large droplets WL, and fine droplets WS smaller in diameter than the large droplets WL. 
     The ultrasonic transducer  22  is provided at an angle to the bottom plate  21   f  of the second reservoir  21 . Here, a radiation axis J is defined as an axis of the ultrasonic wave. The radiation axis J extends orthogonally from a center of an ultrasonic wave emission face  22   a  of the ultrasonic transducer  22 . 
     The ultrasonic transducer  22  is angled with respect to the bottom plate  21   f  of the second reservoir  21 . Hence, the ultrasonic wave is propagated from the ultrasonic wave emission face  22   a  toward the surface of the hygroscopic material W 2  so that the radiation axis J is angled with respect to the surface of the hygroscopic material W 2 . Portion of the ultrasonic wave reaching the surface of the hygroscopic material W 2  is reflected regularly on the surface. Here, an incident angle of the ultrasonic wave with respect to the surface of the hygroscopic material W 2 ; that is, an angle between the surface and the radiation axis J, is not a right angle. That is why the ultrasonic wave reflected on the surface is less likely to return to the ultrasonic transducer  22 . Hence, the ultrasonic transducer  22  is less likely to suffer damage by the ultrasonic wave emitted from the ultrasonic transducer  22  itself. 
     Moreover, since the radiation axis J is angled, the plume C is formed to be angled with respect to the surface of the hygroscopic material W 2 . That is, the ultrasonic transducer  22  is provided to the bottom plate  21   f  of the second reservoir  21 , so that the plume C to be formed is angled with respect to the surface of the hygroscopic material W 2 . 
     The ultrasonic transducer  22  is angled so that an end, of the ultrasonic wave emission face  22   a , toward the fill port  21   a  is positioned high, and another end, of the ultrasonic wave emission face  22   a , toward the ejection port  21   b  is positioned low. That is, the ultrasonic transducer  22  is provided such that the plume C, to be formed on the surface of the hygroscopic material W 2 , is angled toward the ejection port  21   b.    
     The ultrasonic transducer  22  is preferably angled in a direction as described above so that the plume C is less likely to be deformed, compared with the case where the ultrasonic transducer  22  is angled against the above direction. 
     A mixture A 3 , which contains the atomized droplets W 3  generated from the plume C, is released from the ejection passage  29  out of the second reservoir  21 . 
     In order to confirm advantageous effects of a combined use of polyalcohol and metal salt as the hygroscopic material W, hygroscopic materials (1) to (3) were prepared. After the hygroscopic materials (1) to (3) had absorbed moisture, a device model having the same configuration as the atomizing separator  20  had was operated to check how moisture was separated from the hygroscopic materials (1) to (3) by atomization: 
     (1) a glycerin aqueous solution at 80 mass percent; 
     (2) a lithium chloride aqueous solution exhibiting the same hygroscopicity as the aqueous solution (1) did; and 
     (3) an aqueous solution of lithium chloride and glycerin exhibiting the same hygroscopicity as the aqueous solution (1) did. 
     In order to control concentrations of the aqueous solutions (2) and (3), a three-phase diagram of lithium chloride, glycerin, and water was used to identify composition, of the aqueous solutions (2) and (3), that expresses the hygroscopicity equivalent to the hygroscopicity of the aqueous solution (1). Moreover, viscosities of the aqueous solutions were higher in the order of (1), (3), and (2). As to the viscosity, the aqueous solution (1) was the highest and the aqueous solution (2) was the lowest. 
     The measurement result showed that the aqueous solution (3) was higher in efficiency of separating moisture by atomization (a rate of an amount of separated water to supplied electric power) than the aqueous solution (1). Moreover, the measurement confirmed that the moisture separated from the aqueous solution (3) did not contain lithium chloride, and the aqueous solution (3) allowed moisture to be separated more precisely than the aqueous solution (2) did. 
     Furthermore, similar to the hygroscopic materials (1) to (3), hygroscopic materials (4) to (9) were prepared. After the hygroscopic materials (4) to (9) had absorbed moisture, a device model having the same configuration as the atomizing separator  20  had was operated to check how moisture was separated from the hygroscopic materials (4) to (9) by atomization: 
     (4) an aqueous solution of lithium chloride and glycerin exhibiting the same hygroscopicity as the aqueous solution (3) did; 
     (5) an aqueous solution of lithium chloride and diglycerin exhibiting the same hygroscopicity as the aqueous solution (3) did; 
     (6) an aqueous solution of lithium chloride and polyglycerin (polyglycerin #300) exhibiting the same hygroscopicity as the aqueous solution (3) did; 
     (7) an aqueous solution of lithium chloride and polyglycerin (polyglycerin #300) exhibiting the same hygroscopicity as the aqueous solution (3) did; 
     (8) an aqueous solution of lithium chloride and polyglycerin (polyglycerin #500) exhibiting the same hygroscopicity as the aqueous solution (3) did; and 
     (9) an aqueous solution of lithium chloride and polyglycerin (polyglycerin #500) exhibiting the same hygroscopicity as the aqueous solution (3) did. 
     Note that, the hygroscopic materials (4), (6), and (8) were the hygroscopic material (3) with glycerin replaced with diglycerin or polyglycerin, and a percentage of the water decreased. Hence, the hygroscopic materials (4), (6), and (8) were prepared to exhibit the same hygroscopicity as the hygroscopic material (3) did. Furthermore, the hygroscopic materials (5), (7), and (9) were the hygroscopic material (3) with the glycerin replaced with diglycerin or polyglycerin, and a percentage of the lithium chloride increased. Hence, the hygroscopic materials (5), (7), and (9) were prepared to exhibit the same hygroscopicity as the hygroscopic material (3) did. 
     When the efficiency of separating moisture from the aqueous solution (3) by atomization (a ratio of the amount of separated moisture with respect to supplied electric power) is denoted as 1, the measurement results below showed relative values of the efficiency in separating moisture from the aqueous solutions (4) to (9) by atomization. 
     Efficiency in separating moisture from the aqueous solution (4) by atomization: 1.18 
     Efficiency in separating moisture from the aqueous solution (5) by atomization: 1.10 
     Efficiency in separating moisture from the aqueous solution (6) by atomization: 1.20 
     Efficiency in separating moisture from the aqueous solution (7) by atomization: 1.28 
     Efficiency in separating moisture from the aqueous solution (8) by atomization: 1.32 
     Efficiency in separating moisture from the aqueous solution (9) by atomization: 1.18 
     As can be seen, the obtained relative values confirmed that the aqueous solutions (4) to (9) allowed moisture to be separated more precisely than the aqueous solution (3) did. 
     Separator 
     A separator  25  is provided in a path of the ejection passage  29 . The separator  25  of this embodiment is referred to as a cyclone separator. 
     The separator  25  includes: a separation tank  251 ; and a guide pipe  252 . 
     The separation tank  251  includes: a cylinder  251   a ; and a cone  251   b  connected to a lower portion of the cylinder  251   a  and communicating with the cylinder  251   a . The cylinder  251   a  has an upper portion closed with a top. The cone  251   b  protrudes downward. 
     The guide pipe  252  penetrates the top of the cylinder  251   a  to be inserted in the cylinder  251   a.    
     The ejection passage  29  is connected to a side face of the cylinder  251   a  and the guide pipe  252 . 
     The separator  25  creates a downward spiral flow of the mixture A 3  inside the separation tank  251 , and separates the atomized droplets W 3  contained in the mixture A 3  into the fine droplets WS and the large droplets WL. 
     The separated fine droplets WS are transported to the guide pipe  252  by an air current flowing from the cone  251   b  toward the cylinder  251   a  of the separation tank  251 . The fine droplets WS are released out of the casing  100  through the ejection passage  29  connected to the guide pipe  252 . 
     Air A 4 , obtained by the separator  25 , contains the separated fine droplets WS, and thus is wetter than the air (the air A 1 ) outside the casing  100 . 
     Meanwhile, the large droplets WL cannot move with the air current flowing from the cone  251   b  toward the cylinder  251   a , and fall down to the bottom of the cone  251   b . The large droplets WL falling down to the cone  251   b  may return to the second reservoir  21  through a not-shown pipe. 
     Circulator 
     A circulator  30  circulates the hygroscopic material W between the moisture absorber  10  and the atomizing separator  20 . 
     The circulator  30  includes the pipes  31  and  32  connected to the moisture absorber  10  and the atomizing separator  20 , and forming a circular passage of the hygroscopic material W. Moreover, the circular  30  includes a pump  33  provided in a path of the pipe  32 . 
     From the moisture absorber  10  to the atomizing separator  20 , the pipe  31  transports the hygroscopic material W 2  absorbing at least portion of the moisture. The pipe  31  has an end connected to the ejection port  11   b  provided below the surface of the hygroscopic material W 1  in the first reservoir  11 . 
     Meanwhile, the pipe  31  has another end connected to the fill port  21   a  provided below the surface of the hygroscopic material W 2  in the second reservoir  21 . 
     From the atomizing separator  20  to the moisture absorber  10 , the pipe  32  transports the hygroscopic material W 1  whose moisture is removed (the hygroscopic material W). The pipe  32  has an end connected to the ejection port  21   b  provided below the surface of the hygroscopic material W 2  in the second reservoir  21 . 
     Meanwhile, the pipe  32  has another end connected to the nozzle  13  provided above the surface of the hygroscopic material W 1  in the first reservoir  11 . 
     The pump  33  is provided in the path of the pipe  32  to render the hygroscopic material W flow. The pump  33  may be provided also to the pipe  31 . Furthermore, a pump may be provided to each of the pipes  31  and  32  to independently control a flow of the hygroscopic material W from the moisture absorber  10  to the atomizing separator  20  and a flow of the hygroscopic material W from the atomizing separator  20  to the moisture absorber  10 . 
     Measurer 
     The measurer  40  is provided to the second reservoir  21  to measure a concentration of the hygroscopic material W 2  in the second reservoir  21 . The measurer  40  includes: a sensor  41 ; and a pipe  42  connected to the sensor  41 . In the measurer  40 , portion of the hygroscopic material W 2  in the second reservoir  21  is supplied to the sensor  41  through the pipe  42 . The sensor  41  measures the concentration of the hygroscopic material W 2 . 
     Here, the concentration of the hygroscopic material W 2  to be measured by the sensor  41  is a percentage of all the substances (a sum of the polyalcohol and the metal salt) dissolved and contained in the hygroscopic material W 2 . Moreover, the sensor  41  may measure percentages of the polyalcohol and the metal salt contained in the hygroscopic material W 2 . 
     In such a case, an electric conductivity may be previously measured for each of hygroscopic materials containing polyalcohol and metal salt at different percentages. The electric conductivities may be used as numerical values corresponding to the concentrations of the polyalcohol and the metal salt. For example, a table can be prepared to indicate corresponding relationships between the proportions of the composition of the hygroscopic material W 2  and the electric conductivities of the hygroscopic material W 2 , so that the table may be used as reference data for controlling the composition of the hygroscopic material W 2 . In this case, the sensor  41  measures an electric conductivity of the hygroscopic material W 2 , so that, on the basis of the obtained electric conductivity, the percentages of the polyalcohol and the metal salt contained in the hygroscopic material W 2  can be controlled with reference to the table. 
     The sensor  41  may have any given configuration as long as the sensor  41  can measure a concentration of the hygroscopic material W 2 . For example, the sensor  41  may be a sensor to measure a refractive index of the hygroscopic material W 2  and to obtain the concentration of the hygroscopic material W 2  in accordance with the obtained refractive index. In such a case, refractive indexes may be previously measured of multiple samples having different proportions and concentrations of the substances dissolved in the hygroscopic material W 2 , and corresponding relationships may be previously prepared between the reflective indexes and the concentrations of the hygroscopic materials W 2 . 
     Diluter 
     The diluter  50  includes: a water storage tank  51 ; a connector  52 ; and a pipe  53  connecting the water storage tank  51  and the connector  52  together. 
     The water storage tank  51  stores water for adjusting the composition of the hygroscopic material W. 
     The connector  52  may be, for example, a three-way solenoid valve to be opened and closed by the controller  60 . 
     The diluter  50  is connected to the pipe  32 . The diluter  50  adds water to, and dilutes, the hygroscopic material W 2  flowing in the pipe  32 . 
     Controller 
     The controller  60  controls an operation of the humidity control device  1 . 
     As can be seen, the hygroscopic material W to be used for the humidity control device  1  is of a three-component system. The hygroscopic material W contains water, hygroscopic polyalcohol, and hygroscopic salt. If, for example, the percentage of the water content is low in the composition of the hygroscopic material W, the metal salt might be deposited on, and clog, the nozzle  13  and the circulator  30 . Moreover, if the percentage of the hygroscopic substance content is low in the composition of the hygroscopic material W, the hygroscopic material W might not absorb moisture, and could fail to dehumidify the air. 
       FIG. 2  is a phase diagram illustrating a hygroscopic material of a three-component system. The hygroscopic material contains water, hygroscopic polyalcohol, and hygroscopic metal salt. The phase diagram schematically illustrates the composition and the physical properties of the hygroscopic material. 
     The hygroscopic material whose composition is represented in a region A illustrated in  FIG. 2  can exhibit excellent hygroscopicity and excellent separation of moisture in the atomizing separator  20 . Meanwhile, the hygroscopic material whose composition is represented in a region B contains excessive water and cannot absorb moisture. Moreover, the hygroscopic material whose composition is represented in a region C inevitably causes deposition of the metal salt. 
     Meanwhile, the humidity control device  1  alternately absorbs moisture using the hygroscopic material W and removes moisture contained in the hygroscopic material W. Hence, the humidity control device  1  controls the composition of the hygroscopic material W to be within the region A of the phase diagram in  FIG. 2 , making it possible to stably absorb and desorb moisture. 
     The controller  60  included in the humidity control device  1  of this embodiment controls the constituent features as described below in order to control the concentration of the hygroscopic material W to be within a range represented with the region A in  FIG. 2 . Such control keeps from deposition of the metal salt while maintaining the physical properties of the hygroscopic material W to allow for absorption of moisture. 
       FIG. 3  is a block diagram illustrating the controller  60 . As illustrated in  FIG. 3 , the controller  60  includes: a data receiver  61 ; an arithmetic processor  62 ; a memory  63 ; a determiner  64 ; and an instructor  65 . 
     The data receiver  61  receives a result detected by the sensor  41 . For example, if the sensor  41  is a refractometer, the data receiver  61  receives, as the detection result, data on a refractive index of the hygroscopic material W 2  to be measured by the sensor  41 . 
     The arithmetic processor  62  calculates a concentration of the hygroscopic material W 2  in accordance with the detection result received from the data receiver  61 . 
     The memory  63  stores a threshold corresponding to an upper limit of the concentration of the hygroscopic material W in an allowable range. Hereinafter, the threshold is referred to as an upper limit threshold. 
     Moreover, the memory  63  stores a threshold corresponding to a lower limit of the concentration of the hygroscopic material W in an allowable range. Hereinafter, the threshold is referred to as a lower limit threshold. 
     Note that the “threshold corresponding” to the upper limit in the allowable range may be the upper limit per se, or a value smaller than the upper limit. For example, if the threshold is set as the upper limit per se, the hygroscopic material W might further condenses while the concentration of the hygroscopic material W is controlled as described below. The condensation could start deposition of the metal salt contained in the hygroscopic material W. Hence, the threshold can be set smaller than the above upper limit not to start the deposition of the metal salt even if a time period required for adjustment of the concentration elapses. 
     Likewise, the “threshold corresponding” to the lower limit in the allowable range may be the lower limit per se, or a value larger than the lower limit. For example, if the threshold is set as the lower limit per se, the hygroscopic material W might further be diluted while the concentration of the hygroscopic material W is controlled as described below. Consequently, the concentration of the hygroscopic material W might fall so low that the hygroscopic material W could not absorb moisture in the moisture absorber  10 . Hence, the threshold can be set larger than the above lower limit so that the hygroscopic material W can absorb moisture in the moisture absorber  10  during adjustment of the concentration of the hygroscopic material W. 
     In accordance with the concentration of the hygroscopic material W 2  obtained by the arithmetic processor  62  and the threshold of the concentration of the hygroscopic material W stored in the memory  63 , the determiner  64  determines whether the concentration of the current hygroscopic material W 2  is within a range in which the hygroscopic material W is capable of absorbing moisture while the metal salt is kept from being deposited. 
     In accordance with the result of the determination by the determiner  64 , the instructor  65  instructs the atomizing separator or the diluter to control the concentration of the hygroscopic material W. 
     Specifically, if the concentration of the hygroscopic material W is higher than the threshold corresponding to the upper limit in the allowable range, the instructor  65  instructs the connector  52  connecting to the water storage tank  51  to open so that hygroscopic material W 2  flowing in the pipe  32  is diluted. 
     If the concentration of the hygroscopic material W is lower than the threshold corresponding to the lower limit in the allowable range, the instructor  65  instructs the ultrasonic transducer  22  to drive, so that moisture is separated from the hygroscopic material W in the atomizing separator  20 . Here, the instructor  65  may stop the blower  181  to suspend absorption of moisture in the moisture absorber  10 . 
     Furthermore, the instructor  65  finishes the above control of the concentration under a previously set condition. 
     In diluting the hygroscopic material W 2 , the instructor  65  may, for example, instruct the connector  52  connecting to the water storage tank  51  to close after a designated amount of water has been supplied from the water storage tank  51  to the interior of the pipe  42 . 
     In separating moisture from, and condensing, the hygroscopic material W 2 , the instructor  65  may drive the ultrasonic transducer  22  for a certain time period, and then suspend the ultrasonic transducer  22 . 
     Moreover, the instructor  65  may measure the concentration, of the hygroscopic material W 2 , varying by the control of the concentration, and finish the control of the concentration (diluting or condensing the hygroscopic material W) in accordance with the result of the measurement. 
     The humidity control device  1  in the above configuration can stably absorb and desorb moisture. 
     Note that, in this embodiment, the separator  25  is, but not limited to, a cyclone separator. Alternatively, the separator  25  may be a mist separator in another configuration, such as an impactor. 
     Furthermore, in this embodiment, the control of the composition of the hygroscopic material W 2  involves, but not limited to, adjusting the amount of water contained in the hygroscopic material W 2 . 
     For example, in response to the result of the measurement by the measurer  40 , the control may involve adding polyalcohol to the hygroscopic material W 2 , so that the composition of the hygroscopic material W 2  is within the region A in the  FIG. 2 . In such a case, the humidity control device  1  may be similar in configuration to the diluter  50  to add polyalcohol. Here, the polyalcohol to be added may be previously diluted with water so that the concentration of the diluted polyalcohol is lower than that of stock polyalcohol and higher than that of a target concentration of the polyalcohol in the hygroscopic material W 2 . 
     Moreover, an agitation mechanism may be provided to accelerate agitation of the polyalcohol and the hygroscopic material W 2 . Examples of the agitation mechanism include an agitation blade provided to the pipe  32  and positioned where the polyalcohol is added, and a static agitator provided inside the pipe  32 . In addition, the pump  33  may be disposed downstream of the position, in the pipe  32 , where the polyalcohol is added. Hence, the pump  33  may act as the agitating mechanism. 
     The humidity control device  1  of this embodiment ejects the air A 2 , which is dehumidified, from the moisture absorber  10  through the ejection passage  19 . Moreover, the air A 4  humidified is ejected from the atomizing separator  20  through the ejection passage  29 . Using such mechanisms, the humidity control device  1  can adopt a configuration below. 
     If the humidity control device  1  of this embodiment can be used only for dehumidifying a space in which the humidity control device  1  is installed, the ejection passage  19  may, for example, have an air ejection port facing inside the room; whereas, the ejection passage  29  may, for example, have an air ejection port facing outside the room. 
     If the humidity control device  1  of this embodiment can be used only for humidifying a space in which the humidity control device  1  is installed, the ejection passage  29  may, for example, have an air ejection port facing inside the room; whereas, the ejection passage  19  may, for example, have an air ejection port facing outside the room. 
     If the humidity control device  1  of this embodiment can be used for both dehumidifying and humidifying a space in which the humidity control device  1  is installed, the air ejection ports of both of the ejection passages  19  and  29  may face inside the room, and the controller  60  may cause the air to be ejected from either air ejection port. 
     In the humidity control device  1  of this embodiment, the moisture absorber  10  and the atomizing separator  20  are housed in, but not limited to, the interior space  100   c  of the same casing  100 . For example, the moisture absorber  10  and the atomizing separator  20  may separately be housed in individual casings as long as the moisture absorber  10  and the atomizing separator  20  are connected together with the circulator  30 . 
     Described above is a preferable embodiment of the present invention, with reference to the drawings. As a matter of course, the present invention shall not be limited to the embodiment. The shapes and combinations of the constituent features described in the above embodiment are examples, and can be modified in various manners in accordance with, for example, a design requirement unless otherwise departing from the technical scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to an air conditioner to be used for conditioning indoor air.