HEAT AND MASS EXCHANGE MODULE AND USE THEREOF

Abstract

A heat and mass exchange (HMX) module comprising a plurality of plates in a spaced-apart arrangement and provided with a plurality of air channels for air flow and a plurality of liquid channels for flow of liquid, wherein a liquid channel is present on a surface of a plate and is arranged adjacent to an air channel with a mutual exchange surface, wherein the liquid channel is provided with a width extending substantially perpendicular to a flow direction in the liquid channel, further comprising means for setting a flow profile over the width of the liquid channel.

Claims

1. A heat and mass exchange (HMX) module comprising a plurality of plates in a spaced-apart arrangement and provided with a plurality of air channels for air flow and a plurality of liquid channels for flow of liquid, wherein a liquid channel is present on a surface of a plate and is arranged adjacent to an air channel with a mutual exchange surface, wherein the liquid channel is provided with a width extending substantially perpendicular to a flow direction in the liquid channel, further comprising means for setting a flow profile over the width of the liquid channel.

2. The HMX module as claimed in claim 1, wherein the means for setting a flow profile are configured such that flow of liquid in a second area is reduced relative to flow in a first area, which second area is located more closely to an outlet of the air channel than the first area.

3. The HMX module as claimed in claim 1, wherein the means for setting a flow profile comprise a first entry and a second entry to the liquid channel, wherein the first entry differs from the second entry.

4. The HMX module as claimed in claim 3, wherein the first and the second entry have a different cross-sectional area.

5. The HMX module as claimed in claim 3, wherein the first entry is coupled to a first container for liquid and the second entry is coupled to a second container for liquid, and wherein the containers are configured for containing liquid in different states.

6. The HMX module as claimed in claim 5, wherein the states of the liquid are chosen from different temperature, different concentration, different pressure, different composition.

7. The HMX module as claimed in claim 1, comprising at least one container for liquid overlying said plurality of plates, wherein said liquid channels are provided with entry regions for entry of liquid from the at least one container.

8. The HMX module as claimed in claim 7, wherein the flow profile is set in that a density of the entry regions along the width of the liquid channel and/or cross-sectional area of an entry region varies along the width of the liquid channel.

9. The HMX module as claimed in claim 7, wherein the flow profile is set in that entry regions for the liquid channel are arranged at varying height in the at least one container.

10. The HMX module as claimed in claim 7, wherein the entry regions are mutually separated by means of closed regions.

11. The HMX module as claimed in claim 10, wherein the liquid channels are defined as layers of a wicking material onto the plates, wherein said a top side of the layer of wicking material is at least partially closed for liquid entry in the closed regions.

12. The HMX module as claimed in claim 11, wherein the wicking material is locally compressed in the closed regions.

13. The HMX module as claimed in claim 12, wherein a spacer is present between a first and a second adjacent plate, said spacer locally compressing the wicking material in the closed regions, without compression of the wicking material in the entry regions.

14. The HMX module as claimed in claim 1, wherein the air channel is provided with an inlet and an outlet, such that the air flows in a flow direction extending substantially parallel to the width of the liquid channel.

15. An air-conditioner comprising the heat and mass exchange module of claim 1.

16. Use of the heat and mass exchange module of claim 1 for heat exchange between a fluid in the air channel and a liquid in the liquid channel.

17. (canceled)

18. A method of conditioning air using a heat and exchange module comprising a plurality of air channels and a plurality of liquid channels, wherein a first air channel and a first liquid channel have a mutual exchange surface, comprising the steps of: Applying an air flow into the plurality of air channels, said air flow flowing in a first flow direction; Applying a liquid flow into at least a first section of said liquid channels, said liquid flow flowing in a second flow direction different from the first flow direction, therewith creating cross-flow; Wherein the air is conditioned towards at least one predefined output parameter, in that a flow profile of the liquid is set.

19. The method as claimed in claim 18, wherein the air flow is applied so as to provide a laminar flow.

20. The method as claimed in claim 18, further comprising the step of applying a second liquid flow into a second section of the liquid channels.

21. (canceled)

22. The method as claimed in claim 18, further comprising the step of sensing input parameters and/or output parameters of the air flow to obtain sensing results, and using the sensing results for controlling the first and/or the second liquid flow.

23. (canceled)

24. (canceled)

Description

BRIEF INTRODUCTION TO THE FIGURES

[0035] These and other aspects of the air-conditioner module and the method of air conditioning are further elucidated with reference to following figures, which are not drawn to scale and are merely diagrammatical in nature. Equal reference numerals in different figures refer to identical or corresponding elements. Herein:

[0036] FIG. 1 depicts a diagrammatical view of a first embodiment of the heat and mass exchange (HMX) module;

[0037] FIG. 2a-d schematically depicts a sheet used in the HMX module;

[0038] FIG. 3 shows a diagrammatical view of an implementation of such a sheet;

[0039] FIG. 4 show schematical side views of the module with a plurality of plates and distance holders according to one embodiment of the invention;

[0040] FIG. 5a shows a schematical top view of a manifold in one preferred implementation;

[0041] FIG. 5b shows a detail of FIG. 5a;

[0042] FIG. 6a-c shows side views of a plate and manifold according to another implementation;

[0043] FIG. 7 shows a schematical side view of a HMX module including a reservoir of liquid desiccant;

[0044] FIG. 8 schematically depicts a module with three containers overlaying the plates;

[0045] FIG. 9a depicts a side view of an embodiment of a distance holder configured to create a certain liquid flow profile;

[0046] FIG. 9b depicts a side view of a different embodiment of a distance holder configured to create a certain liquid flow profile, and

[0047] FIG. 10a-10c depict a top view of different embodiments of a distance holder configured to create a certain liquid flow profile.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0048] FIG. 1 shows in a diagrammatical view an HMX module 100 according to a first embodiment of the invention. The HMX module 100 comprises a plurality of plates. Most preferably, the plates are sheets 10, which comprise a carrier layer between a first and a second layer of wicking material. The wicking material is more suitably a non-woven textile material, such as cotton or rayon. The first and second layer may further contain another material mixed therewith, such as an engineering plastic. More details on the sheet are specified in the non-prepublished application NL2013566 in the name of Applicant. However, alternative options are not excluded in the context of the present invention. The sheets are suitably substantially identical, so that the corrugation in the sheets is repetitive and the distance between the sheets does not change. The sheets are corrugated, as will be discussed with reference to following figures. Due to the corrugation and its orientation, the sheets, which are inherently flexible, are sufficiently stiffened so that they can be arranged at a relative short and uniform distance of each other without touching each other. If the sheets touched each at a contact point, liquid would get collected at the contact point. With air flowing along the contact point, there would be a high risk carry-over. Each of the sheets 10 is in the preferred implementation provided with layers of wicking material 11 of both the front and the rear side of the sheet. As shown in this FIG. 1, the layer of wicking material 11 may be subdivided into two lateral portions. However, this is not deemed particularly beneficial or preferred. The HMX module 100 is designed as a cross-flow module, such that the air and the liquid desiccant run in mutually perpendicular directions through the HMX module 100. It will be clear that an entirely perpendicular design is deemed advantageous and most straightforward for manufacturing, since the sheets can be of rectangular shape. However, this is not deemed necessary. Alternative shapes, such as that of a parallelogram, are not excluded. Preferably, the module is configured such that the air channel extends laterally and that the liquid channel of the liquid desiccant extends vertically. In this manner, the liquid desiccant will flow within the HMX module 100 under the impact of gravity. The module as shown in FIG. 1 comprises tube connections 18, 19 for the provision and removal of liquid desiccant. Their location is not deemed critical. Though not shown explicitly, it is furthermore deemed beneficial that a reservoir of liquid desiccant is present so as to overlie the sheets 10 of the HMX module. The advantage thereof is that the liquid desiccant may be distributed into and onto the layers 11 of wicking material through apertures in a bottom of such reservoir, and typically spread over the entire surface thereof. Therewith, it is prevented that an initial flow of the liquid desiccant in a lateral direction needs to be converted into flow in a vertical direction.

[0049] The HMX module as shown in FIG. 1 may be used both as a dehumidifier and as a regenerator module, but also as any other module for use in an air-conditioning system, such as a cooling module. In a dehumidifier modulealso referred to as a drier modulea stream of air is dried, and the liquid desiccant takes up humidity. In a regenerator module, a flow of liquid desiccant is dried and the air in the adjacent air channel is humidified. There is no need that exactly the same design of a module is used for the dehumidifier as for the regenerator module. By means of temperature control, the dehumidifier module may further be arranged to operate as a cooler. The shown module as shown in FIG. 1 comprises a plurality of sheets. The number of sheets can be chosen as desired in dependence of climate, air volume to be conditioned and space. As apparent from FIG. 1 the liquid channel is suitably longer than the air channel, particularly in a drier module. With a well regenerated liquid desiccant, for instance an aqueous LiCl solution of sufficient concentration (i.e. typically close to the maximum loading concentration), drying turns out more effective in the first portion of the air channel. However, the liquid desiccant material does not need to be an aqueous LiCl solution, but could alternatively be a salt solution comprising various soluble salts.

[0050] FIG. 2a shows in a schematical view a sheet 10 for use in the module of the invention. An air channel 20 is defined between two sheets 10 and is indicated for sake of reference. It is configured in a lateral direction. The air channel 20 is provided with an inlet 21 and an outlet 22. Air in the air channel 20 will first pass an accommodation area 23 then an active area 25 and finally an outlet area 24. The active area 25 is configured to enable exchange with the liquid channel 30 that is defined at the surface of the layer of wicking material (on the sheet 10). It is observed for clarity that the layer of wicking material may extend beyond the active area 25. However, the active area 25 is further defined by means of the entry regions of the liquid desiccant, which are defined at the entryalso referred to as inlet31 of the liquid channel 30. These entry regions are typically defined by means of a manifold (shown in FIG. 4). The liquid channel 30 ends at the exitalso referred to as outlet32. This outlet 32 is suitably embodied as a container for the liquid of several parallel liquid channels 30. It can be seen that the liquid channel 30 thus has a width (i.e. substantially as defined by the active area 25) which is smaller than the length of the air channel 20 (i.e. the distance between the inlet 21 and the outlet 22 thereof).

[0051] FIG. 2b shows schematically the generation of a module from a plurality of sheets 10 and the air channels 20 in between of the sheets 10. FIG. 2c shows a representative corrugation when seen from the entry of the air channel 20. The arrow indicates the direction of the liquid channel 30. The view of FIG. 2c is in fact a cross-sectional view of the air channel. FIG. 2d shows a detail from FIG. 2c. It is apparent from this FIG. 2c that in order to prevent carry-over, the liquid desiccant needs to have sufficient adhesion to the underlying surface. It preferably flows in a steady state. Most suitably, the film onto the surface of the layer 11 of wicking material (not shown in this FIG. 2c) is sufficiently thin. The film thickness is thinned, in one preferred embodiment in accordance with the invention, by using a specific manifold, wherein the liquid desiccant first flows through a series of slots and is thereafter laterally distributed to cover the area of the liquid channel between the slots.

[0052] As shown in FIG. 2d, the distance between the sheets 10 varies somewhat due to the wave-shaped pattern of the sheets 10. This variation in the distance is an important reason for arranging the wave along the length of the liquid channel rather than along the length of the air channel. If arranged along the length of the air channel, the variation in distance would result in a temporary narrowing of the air channel, resulting in an increase in flow rate (followed by a reduction in flow rate). Such variations in air flow rate would increase the risk of carry-over. By arranging the waves along the length of the liquid channel, the air flows substantially parallel to the waves. This turns out to be beneficial. In fact, one may consider an air channel to be divided in a large number of parallel portions, extending laterally and each having the same length, The lateral portions will have slightly varying height (i.e. distance between the sheet). However, the height of a single lateral portion is substantially constant along its length, at least within the active area, where exchange with the liquid channel occurs. As a result, a single air drop travelling in a single lateral portion will not experience any changes in height within the active area. This therefore reduces a chance that the air drop starts to move in a turbulent manner, and therewith may interfere with the liquid channel to result in droplet formation of liquid desiccant, i.e. carry over. Additionally, it was found that this configuration has a lower pressure drop, as compared to an alternative configuration.

[0053] In one implementation according to the inventionnot shownthe height of a ridges and a valley is higher in the middle part of the air channel than close to the outlet area 24. Herewith, it may be prevented that carry-over occurs at the end of the air channel due to a sudden change in direction of the air channel. In one further or additional implementation according to the invention, the ribbons and valleys extend from the active area 25 into the outlet area 24. Therewith, it is achieved that the end of said ribbons and valleys, corresponding to a change in orientation of the air channel is at least substantially outside the exchange surface between air and liquid desiccant material.

[0054] In again one further implementation, the height of ridges and valleys may be lower in a bottom part of the air channel than in a top part. The liquid desiccant may gain velocity in the course of flowing downwards. In a dehumidifier module, it additionally may warm up. Therefore, the lower part is more sensitive to carry over. This may be compensated by less steep ribbons and valleys, to prevent any ejection of single droplets of liquid desiccant.

[0055] FIG. 3 shows in a diagrammatical view the sheet 10 more specifically. Herein, it is indicated that the sheet 10 is provided with ridges 12 and valleys 13, in alternating arrangement. The sheet 10 suitably has a shape of a wave, wherein the ridges 12 extend into a first direction and the valleys 13 extend into the opposite direction. With these ridges 12 and valleys 13 a corrugated surface is created that is deemed positive for the necessary strength of the sheet 10, without increasing risk for carry-over. More particularly, the wave may be a sine wave. Moreover, the edges of the sheet 10 are at least substantially planar. This facilitates assembly of the sheet 10 into the module, particularly by means of a distance holder as will be explained with reference to further figures. In the shown embodiment, the ridges 12 and valleys 13 extend parallel to the width of the liquid channel 30, such that the liquid channel 30 in fact includes a curved trajectory. However, the air channel 20 is substantially planar over the width of the liquid channel, i.e. in the area where the liquid channel and the air channel have an interface. This has the advantage of minimum disturbance of air flow. As a consequence, carry over can be prevented, at least substantially, while the sheets are very thin. In this manner, a large packing density of sheets per unit volume is achieved, resulting in a large exchange area between the air channels and the liquid channels. In tests with a preliminary version of the heat and mass exchange module according to the invention, wherein the air flow was laminar and a liquid channel wave-shaped, no carry-over was found to occur. The sheet 10 is suitably created in a multistep process, comprising the provision of the carrier and one or more layers of wicking material into a provisional laminate and thereafter thermoforming of the laminate. In the course of the thermoforming, the provisional laminate is suitably bond to form the final laminate. However, the lamination process may also preceed the thermoforming process.

[0056] FIG. 3 furthermore shows the presence of spacers 26, which preferably have a stripwise extension and are assembled to a plurality of sheets 10. The spacers 26 are arranged within the accommodation area 23 and the outlet area 24, which are most preferably substantially or completely planar.

[0057] The sheet 10 shown in FIG. 3 furthermore comprises stiffening protrusions. These are arranged outside the active area 25, in which the pattern of ridges 12 and valleys 13 is arranged, and effectively within the accommodation area 23 and the outlet area 24. In the present configuration, a first and a second stiffening protrusion 15 are defined, both extending in this configuration along the width of the air channel (i.e. along the width of the active area 25 as shown in FIG. 2). While a longer stiffening protrusion is deemed beneficial, it is not excluded that this long protrusion is subdivided into two or more shorter protrusions. Moreover, more protrusions could be present, particularly in the accommodation area and in the outlet area. This is however neither deemed necessary nor deemed advantageous. Both protrusions 15 have the same dimensions in this configuration. Again, this may be useful, so as to obtain a design that is most symmetrical, but it does not appear necessary.

[0058] FIG. 4 shows the HMX module 10 more detail, and particularly the connection to an overlying reservoir 50. The sheets 10 are herein kept together by means of strips 45 that are provided with a plurality of clamps 57, present at side faces of the sheets 10. The strips 45 are designed so as to create entry channels, through which liquid desiccant material can flow in and onto a surface of the layer of wicking material 11. The strips 45 are more particularly embodiments of distance holders defining and holding a distance between adjacent sheets 10 andin at least one embodimentcreating entry regions and closed regions, as will be explained with reference to FIGS. 5a and 5b. Side walls 61 are present at the outside, so that the assembly of sheets and strips may be fixed and contained, particularly by means of a pressing operation. O-rings 62 may be present to avoid leakage of liquid desiccant along the walls 61. Although not shown, it would be perfectly possible to insert a bottom of the reservoir in the form of a sheet with apertures. The clamps 57 and particularly defined for holding a first and an adjacent second distance holder and an intermediate plate together. Such clamping means are deemed advantageous in the assembly of the holders and the plates. Furthermore, such means may further stabilize the assembly during use. The clamping means may be a monolithic portion of the distance holder. Alternatively, the clamping means may be connected to the distance holder, for instance in that a clamping means further comprises a pin or other protruding element for insertion into a corresponding hole in the distance holder, or vice versa, or another lock & key combination.

[0059] The reservoir 50 is suitable for use as a first container in accordance with the invention. As shown in this FIG. 4, the reservoir 50 is provided with a first inlet 51, with a second inlet 52 and with a stirrer 53. According to one embodiment of the invention, the first inlet 51 is used for liquid desiccant material that has been regenerated directly. The second inlet 52 is used for liquid desiccant material that has been regenerated separately and is provided from a second container (not shown in this Figure). The first and the second inlet 51, 52 may be provided with switchable valves so as to vary the mutual ratio of the first flow through the first inlet 51 and the second flow through the second inlet 52. In the shown embodiment, the second inlet 52 is configured for a solution, dispersion or suspension. In one further implementation (not shown), the second inlet may be configured as a plurality of inlets across the side wall 61 or a top side of the reservoir 50. This may contribute to distribution. The stirrer 53 is one implementation of mixing means. Rather than using a stirrer (for instance mechanical or magnetic), mixing may further be achieved by designing the reservoir such that the flows are mixed together. In one further embodiment, the first flow and the second flow originate from different sources. For instance, in an example wherein the liquid is liquid desiccant and the module is a dehumidifier, the first flow may originate from a local regenerator module, and the second flow may originate from a central regenerator module and/or a liquid desiccant storage, that is for instance obtained by regenerating liquid desiccant with rest heat coming from a generator, such as a diesel generator. This is further disclosed in the non-pre-published Dutch application NL2013586 in the name of applicant, which is included herein by reference.

[0060] FIG. 5a and FIG. 5b show a top view of the manifold 40 as shown in FIG. 4. Herein the strip 45 is provided with a plurality of contact surfaces 47 that are in contact with the sheet 10, and particularly the layer 11 of wicking material present thereon. The contact surfaces 47 are mutually separated by means of cavities 48. It will be apparent that the number of contact surfaces 47 may be varied. Preferably, the contact surfaces 47 and the cavities 48 are present in alternating and repetitive order. The contact surface and the cavity each have a size for instance in the range of 0.3-3.0 cm. However, where the wicking material should be closed, i.e. outside the liquid channel, there will not be any cavity 48. More preferably, the contact surfaces 47 on opposite sides of the strip-shaped manifold are aligned. This is beneficial to obtain an assembly that is sufficiently pressed together. A very advantageous feature of such an assembly is that the layer 11 of wicking material that is present between the contact surface 47 and the carrier 10 is able to absorb manufacturing tolerances and also variations in dimensions of the other materials due to decrease and increase in temperature.

[0061] Furthermore, the distance holder may be provided with a surface of a hydrophobic material. The advantage of a distance holder with such a surface is that the polar liquid desiccant comprising a salt solution (i.e. a ionic solution) is not attracted by but rather repulsed from the distance holder. As a consequence, the surface of the distance holder will normally not be wetted by the liquid desiccant, and undesired distribution of liquid desiccant is prevented. Such a hydrophobic material may be a coating of a specific material, for instance a polymer material such as a polyolefin, a halogenated material, but it may be alternatively a surface layer of a material that is made hydrophobic. Silica for instance, can be hydrophobic or hydrophilic depending on its surface. The material of the surface may be equal or different to the base material of the distance holder. Preferably, the distance holder is based on one or more polymer materials, and is for instance prepared by a moulding technique, even though alternative manufacturing techniques known in the field of polymer engineering are not excluded. It is deemed suitable that the distance material is based on the same polymer material as the plates are, for instance a polyolefin. This is deemed preferable in order to avoid as much as possible issues with respect to thermal cycling, i.e. differential thermal expansion leading to stress and strain with the risk of deformation and/or crack formation.

[0062] The operation of this strip for the distribution of liquid desiccant is more specifically and still schematically shown in FIG. 5b. In fact, due to the pressing action onto the assembly of strips 45 and sheets 10 as shown in FIG. 4, the layer 11 of wicking material will be compressed opposite the contact surfaces 47. However, the layer 11 will not be compressed at the location of a cavity 48. This compression can be arranged that the layer of wicking material is effectively closed opposite a contact surface 47, thus forming a closed region 39. At the location of a cavity 48, the layer 11 of wicking material is not closed. This region thus constitutes an entry region 38, where liquid desiccant can enter from the reservoir 50 (as shown in FIG. 4) into the layer 11 of wicking material.

[0063] In the FIGS. 5(a) and 5(b), the distribution of the entry regions 38 is uniform over the length of the sheets 10. However, it is observed that this distribution may be varied so as to obtain a most efficient operation of the module, while minimizing risk of carry over. For instance, it would be preferable that no entry regions 38 are present in an area not overlying the liquid channel 30, more particularly neither the portion overlying the accommodation area 23 nor the portion overlying the outlet area 24 (shown in FIG. 2a).

[0064] Furthermore, in the shown Figures, the cavities 48 all have substantially the same size. However, these cavities 48 may differ in size. For instance, the depth may vary, resulting in variations in the extent of compression of the layer 11 of wicking material. Clearly, a larger degree of compression results in less open pores and thus a lower flow rate of liquid desiccant at such location.

[0065] Moreover, the height of the strip 45 may be varied, and/or the size of the contact surfaces 47 and depth of the cavities 48 can be varied. With such variations an aspect ratio of the entry region 38 can be specified. Effectively, an entry region 38 is to be considered as an entry channel. The flow of liquid desiccant will not be merely in the vertical direction but also sidewise. In fact, the area of wicking material below a closed region 39 is to be filled with liquid desiccant entering through the entry region 38.

[0066] FIG. 6a-c discloses again an alternative implementation of the distribution system in accordance with the invention. Herein the sheets 10 comprise slits 16. FIG. 6a shows a schematical side view of a sheet 10. FIG. 6b shows a schematical front view of the sheet 10. FIG. 6c shows an assembly of a plurality of sheets 10 with strips 45. In accordance with the present implementation, the strips 45 extend along the sheets 10 and suitably have a uniform width. The sheets 10 are provided with slits 16. The slits 16 in this figure are closed. That seems beneficial for the stability of the sheet, but is not strictly necessary. Extensions 14 are present between the slits 16.

[0067] As shown in FIG. 6(b), and corresponding to the situation shown in FIG. 5(b), where the strip 45 is in contact with the sheet, i.e. at an extension 14, a contact surface is present. This results in closing off the layer 11 of wicking material, and a closed region 39. At the location of a slit 16, no contact is present, resulting in an entry region 38.

[0068] FIG. 7 is similar to the view of FIG. 6c. The figure additionally shows the presence of a reservoir 50 of liquid desiccant, present between the walls 61 that also press the strips 45 and the sheets 10 together. Although not shown, it will be apparent to the skilled person that further tools and means may be present to maintain this assembly together.

[0069] FIG. 8 shows a module according to the present invention overlaid with a first container 71, a second container 72, and a third container 73. In the image, the three containers are embodied as a vessel subdivided into three sub-containers, with partitions in between. Alternatively, individual containers attached to one another or simple arranged adjacent to one another can also be employed. In the embodiment with one partitioned vessel, the partitions are preferably impermeable to the liquid desiccant. Fewer or more containers may also be used.

[0070] In operation, the first, second and third container 71-73 are typically provided with liquid, such as liquid desiccant that will flow into the liquid channels 30 of the module 10 from the containers 71-73. One advantage of the embodiment with a plurality of containers 33-35 is that a liquid in the first container 71 may be in a different state than a liquid in the second or third container 72, 73, or vice versa. The term state of a liquid refers in the context of the present application to at least one physical or chemical property of the liquid that is relevant for the behaviour of the liquid, particularly the liquid desiccant, during dehumidification of air or during regeneration of the liquid desiccant. By definition, a liquid desiccant material, which is a solution of liquid desiccant into one or more solvents, and usually an aqueous solution, has a concentration, and is held at a temperature, a pressure. Moreover the composition of the material may be varied, for instance with respect to the salt composition of the material. For instance, the material may contain LiBr in addition to LiCl (more precisely bromide and chloride anions in addition to the lithium cations). The material could also contain KCl in addition to LiCl (more precisely other alkali cations, such as potassium or sodium, in addition to the lithium cation and the chloride anion). It will be understood that the ratio of potassium and lithium cations may have an impact on the dehumidifying potential of the liquid desiccant material. The term state furthermore refers to flow properties of the liquid desiccant material, such as the volume of liquid in a container 71-73, andtypically related theretothe liquid pressure exerted by said volume onto an underlying entry into the liquid channel.

[0071] The various properties may be either similar or different. In an embodiment, the liquid in the first, second and third container may have the same temperature, concentration, volume and composition but a different pressure. In another embodiment, the first, second and third containers may be configured to set different temperatures and volumes for the liquid they contain, while the other properties are kept similar. Many other configurations are possible, where any combination of one or more properties can be varied across the containers.

[0072] Although not shown in FIG. 8, means for define the state of the liquid in a container 71-73 may be present. Such means are for instance arranged upstream of the container 71-73, so as to ensure that liquid entering a container 71-73 is in a predefined state. Such an arrangement upstream and optionally external to a module is for instance deemed beneficial to provide a mixture with a first composition to the container via an inlet.

[0073] Alternatively or additionally, such means may be arranged in or to a container 71-73, such that a desired state of the liquid is achieved in such container 71-73. Such an internal arrangement is for instance deemed beneficial to apply a certain pressure.

[0074] For instance, a container 71-73 may have a plurality of inlets for the provision of liquid desiccant material at different concentrations. By setting an inflow ratio for the plurality of inlets, the concentration of the liquid desiccant material may be varied. One implementation hereof for a dehumidifier module is for instance described in the non-prepublished application NL2013586 in the name of application, that is herein included by reference. According to said implementation, regeneration of liquid desiccant material occurs not merely by means of a closed circuit through a regenerator module, but also by means of adding liquid desiccant material from a storage container. The said added liquid desiccant material may be present in a higher concentration (lower humidity content) than the liquid desiccant material regenerated in a regeneration module. Hence by setting the inflows of liquid desiccant material from the storage container and from the regenerator module the concentration of the liquid desiccant material in the containers may be tuned. The concentration of the liquid desiccant material in the first, the second and/or the third container 71-73 may therefore be mutually different. It could alternatively be equal, if so desired.

[0075] In the configuration shown in FIG. 8, the first container 71 is closer to the inlet 23 of the air channel than the second container 72. In one advantageous operation mode, the pressure is configured such that the liquid pressure at the level of the entry region is higher in the first container as compared to the liquid pressure at the level of the entry region below the second container. This may ensure that the thickness of the liquid layer in a first section of the module below the first container is more significant than the thickness of the liquid layer in a second section of the module below the second container. As the air flow 20 may displace some of the liquid laterally along the direction of air flow, providing more liquid in a first section may compensate for a disparity that would otherwise have been created. Furthermore, in this operation mode, due to the higher pressure at the entry region, the velocity of liquid flow in the first section of the model may also be higher than the velocity of liquid flow in the second section, which may lead to the liquid flow being less sensitive to displacement by the air flow.

[0076] Alternatively or additionally, the first container 71 closer to the inlet 23 of the air channel than the second container may also contain a higher volume of liquid desiccant relative to the second container. This may be either to provide a higher pressure and/or to provide a higher supply of liquid.

[0077] In an implementation, each container 71, 72, 53 is provided with a separate entry 81, 82, 83 to the liquid channel. These entries may take the form of a manifold, of which different types are feasible. The manifold may comprise a porous material, through which the liquid desiccant may flow downwards. The manifold may alternately comprise a body of for instance rigid material with apertures. The manifold may also comprise a combination of a rigid body and a layer of porous material.

[0078] In general, the separate entries from the separate containers to the liquid channel may be entries of a similar type; however, this is not necessarily so. Furthermore, the entries may be configured to be suitable for the properties (pressure, temperature, concentration, composition, etc.) of the liquid desiccant in the associated container.

[0079] The containers 71, 72, 73 as depicted in FIG. 8 have roughly the same size and cross-sectional area. However, this is not strictly necessary. Rather, it may be advantageous to use containers that differ in size. For instance, the first container may have a larger cross-sectional area than the second container, which may in turn have a larger cross-sectional area than the third container. Conversely, the first container may have a smaller cross-sectional area than the second container, which may in turn have a smaller cross-sectional area than the third container. The skilled person will be able to determine which set-up is most appropriate to yield a certain desired liquid flow profile.

[0080] FIG. 9a depicts a specific and advantageous implementation of elements at the entry of the liquid channels that can be employed to create a liquid flow profile. In this implementation, the particular element is a distance holder that extends along a width of the liquid channel between a first and a second sheet (or plate). This distance holder can be used both with a set-up with several containers or with a set-up with only one container. It can furthermore be used also if the liquid supply is achieved in other ways than with a container overlaying the module.

[0081] Distance holders may create a liquid flow profile in several ways. The embodiment depicted in FIG. 9a is a distance holder with a different height 93 in a first portion 90 than the height 94 of a second portion 91 of the distance holder, with a slope 92 in between. The particular slope in the figure is merely an example, and slopes of various widths and angles may be used according to the desired flow profile.

[0082] Depending on the material, structure, configuration and/or shape of the distance holder, the higher portion 90 of the distance holder may lead to a higher flow rate (usually defined in units of kg/s) of liquid desiccant. Accordingly, the higher portion of the distance holder may be arranged at the side of the module corresponding to the air inlet 23.

[0083] Typically, a distance holder with a variation in height along the width of the liquid channel fixes a predefined flow profile, so that it is not need to provide active control of a volume in at least one of a plurality of overlying containers. Rather the flow profile is obtained inherently. Clearly, it is also feasible with such built-in flow profile to adjust the settings in the one or more overlying containers to compensate the built-in flow profile and obtain again a rather flat flow profile.

[0084] In a further implementation, a single module contains a first type and a second type of distance holders. For instance, the first type has a varying height along the width of the liquid channel, whereas the second type has a flat height (substantially no variation in height) along the width of the liquid channel. In this manner, the overall flow profile may be adjusted, i.e. the effect of the varying height of distance holders may be reduced, or by using various types with different variations, a more specific flow profile (on average through the module) may be created.

[0085] The depicted distance holder has one step from a high portion 90 to a low portion 91. However, other embodiments may also have three or more different levels with steps in between. In a first embodiment, these portions get lower monotonically. In a second embodiment, these portions may get higher monotonically. In further embodiments, the heights of the portions may go up and down along the width of the distance holder, where the width is defined as the size in the direction parallel to the air flow.

[0086] A different embodiment of a distance holder configured to occasion a liquid flow profile is depicted in FIG. 9b. In this embodiment, the distance holder has a slope over its entire width. As with the embodiment depicted in FIG. 9a, the higher end 93 may either by at the side of the module corresponding to the air inlet 23 or at the side of the module corresponding to the air outlet 24, according to the material, structure, configuration and/or shape of the distance holder, generally to assure that there is more liquid throughput at the side of the module corresponding to the air inlet 23, to compensate for any lateral movement occasioned by the air flow 20 and thus prevent accumulation of liquid desiccant material at the side closest to the air outlet.

[0087] While the depicted distance holder is shown to have a constant slope, this need not be the case, and varying slopes may be used. Neither the height or the slope need necessarily change monotonically, though in many cases they will.

[0088] In FIG. 10a, a different design for a distance holder configured to generate a liquid flow profile is depicted.

[0089] These types of distance holders function in the following manner. A plurality of contact surfaces 47 is brought into contact with the sheet 10, and particularly with the layer 11 of wicking material present thereon. The contact surfaces 47 are mutually separated by means of cavities 48. Due to the pressing of the distance holder on the sheets 10, the layer 11 of wicking material will be compressed opposite the contact surfaces 47. However, the layer 11 will not be compressed at the location of a cavity 48. This compression can be arranged that the layer of wicking material is effectively closed opposite a contact surface 47, thus forming a closed region. At the location of a cavity 48, the layer 11 of wicking material is not closed. This region thus constitutes an entry region, where liquid desiccant can enter from the reservoir 50 (as shown in FIG. 4) into the layer 11 of wicking material.

[0090] In FIG. 10a, in a first region of the distance holder the cavities 48 are spaced at a certain first distance 54, while in another region of the distance holder the cavities are spaced at a second distance 55, where the distance 55 is larger than the distance 54. The distance between two subsequent cavities 48 may also vary gradually along the length of the distance holder, in most cases monotonically increasing or decreasing. The spacing may also go from a first spacing to a second bigger spacing to a third even bigger spacing, etc.

[0091] In an advantageous implementation the cavities 48 are spaced closer together at a side of the distance holder closest to the air inlet 23 than they are at a side of the distance holder closest to the air outlet 24. In this manner, the number of entries will be higher on the side closest to the air inlet than on the side closest to the air outlet. This compensates a possible lateral displacement of the liquid flow 30 due to the air flow 20 so that any accumulation of liquid desiccant material at the side closest to the air outlet is prevented.

[0092] In FIG. 10b, the cavities 48 are equally spaced. However, their depth varies, from a first depth 56 in a first portion to a second depth 58 in a second portion which is larger than the first depth 56, and to a third depth 59 in a third portion which is larger than the second depth 58. A different embodiment may employ two different depths, or more than three different depths. The depths will in most cases vary monotonically, but this need not be the case.

[0093] In a portion in which the depth is bigger, the entries may be bigger as well, and more liquid may pass through the entry per unit time. It may therefore be advantageous to position the portion with deeper cavities 48 closest to the air inlet 23, such that possible lateral displacement of the liquid flow 30 due to the air flow 20 is compensated for so as to prevent accumulation of liquid desiccant material at the side closest to the air outlet.

[0094] FIG. 10c shows another embodiment of a distance holder. In a first portion of the distance holder, at least one cavity may have a first width 84. In a second portion of the distance holder, at least one cavity may have a second width 85 larger than the first width 84. In a third portion of the distance holder, at least one cavity may have a third width 86 larger than the second width 85.

[0095] While in the depicted embodiment the widths of the cavities increases monotonically, this need not be the case. A wider cavity will occasion a wider entry to the liquid channel, and more liquid desiccant may pass though. Therefore it may be advantageous to position the portion of the distance holder with the widest cavities toward the side of the module where the air inlet can be found, so as to compensate for possible lateral motion of the liquid flow 30 which may be occasioned by the air flow 20, and thus prevent accumulation of liquid desiccant material at the side closest to the air outlet.

[0096] The module in accordance with the invention may be operated in various operation modes. This will now be elucidated for the implementation shown in FIG. 9. However, it equally applies to other implementations, such as the embodiment shown in FIG. 8 and in FIG. 10a-c

[0097] In a first operation mode, a lower flow rate of liquid desiccant is provided at the side of the module corresponding to the air inlet, so as to compensate for the possible lateral movement of liquid desiccant occasioned by the air flow 20.

[0098] In a further operation mode, that may be used in situations for enhanced operation, the flow rate along the width of a liquid channel may be substantially equal. This may give a somewhat higher risk for carry-over. However, it has been found in preliminary investigations that a temporary increase in liquid flow close to the outlet of the air channel does not result in substantial increase of carry-over risk. It is believed that the carry-over risk occurs due to accumulation of liquid desiccant in close to the outlet of the air channel. However, it requires some time before such accumulation occurs.

[0099] In again a further operation mode for enhanced operation, it may be that the liquid flow in the second and third part of the liquid channel is substantially identical, while the liquid flow in the first part is even higher.

[0100] In a further operation mode, the supply of liquid desiccant into the container is varied over time, and particularly in a repetitive pattern. This creates variation in the flow over time, and in view of the built-in height difference in the distance holder also a flow profile along the width of the liquid channel. For instance the volume in the container can be specified to be at a maximum every second minute and at a minimum every other minute. Such variations over time appear beneficial to ensure that the liquid flow not merely on the surface of the layer of wicking material but also sufficiently through the layer. Moreover, such a variation in time of the liquid flow is deemed advantageous for a limited reduction of the humidity content of the air. While the maximum liquid flow will create a relatively dry air, the minimum air flow will result in air with a higher humidity content. However, these air flows may be mixed subsequently, for instance in a separate mixing vessel. Alternatively, an air-conditioning apparatus may contain both a first and a second dehumidifier module, each with liquid flow varying in time. Preferably, the liquid flows of the first and second dehumidifier module are provided with a mutually different phase, i.e. when the liquid flow through the first module is at a maximum, the liquid flow through the second module is at a minimum, or at least not at a maximum, and vice versa.

[0101] The liquid flow profile may also be varied according to changing circumstances. The air flow may change in time, in an either discrete or continuous mannerfor instance, an air conditioner in which the module is arranged may have several strength settings. At a lower setting, for which the air flow is relatively modest, a mostly flat liquid flow profile (i.e. a liquid flow profile that is substantially even either constantly or more than half the time) may be adequate, while at a higher setting, for which the air flow is more substantial, a more varied liquid flow profile may be more advantageous in order to compensate for possible lateral displacement of the liquid flow 30 due to the air flow 20, so that any accumulation of liquid desiccant material at the side closest to the air outlet is prevented.

[0102] In other embodiments, the liquid flow profile may be such that the liquid flow is substantially absent over a portion of the module, for instance if the humidity is detected to be low or if the air flow is relatively modest. This may conserve resources and contribute to the efficiency of the device.

[0103] The liquid flow may furthermore be varied both according to changing circumstances as well as periodically, combining the advantages of the two embodiments described above.

[0104] For sake of clarity, the term portion of liquid channel(s) in which liquid flow is varied, is understood to refer to a portion of a single channel. If the module comprises a plurality of liquid channels, the variation suitably occurs in all or at least a first subset of the liquid channels. Where reference is made to liquid, this relates more particularly to liquid desiccant material, such as an aqueous salt solution, for instance containing a Li-salt, for instance LiCl.

[0105] It will be clear to the skilled person that the techniques illustrated by the figures can be combined. A certain distance holder may have varying heights, varying distances between cavities, varying depths of cavities, and/or varying cavity widths. Furthermore, other alternative means of setting a flow profile, such as for instance variation in the shape of the cavities or in the thickness of the distance holder, are not excluded. Finally, all these possible distance holders can be used both in embodiments where one container is present and in embodiments where several containers are present. They may also be used in embodiments where the liquid supply does not employ containers overlaying the module.