Field of the invention

The invention relates to a heat and mass (HMX) exchange 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, such as liquid desiccant material, wherein a liquid channel is embodied at a surface of a plate and is arranged adjacent to an air channel with a mutual exchange surface, which liquid channel is provided with an entry and an exit and which air channel is provided with an inlet and an outlet. The invention further relates to an conditioner apparatus therewith and to the use thereof for conditioning of air and/or other gas streams.

Background of the invention

Liquid desiccant-based air conditioners are considered a promising energy-efficient alternative for existing air-conditioning systems. The liquid desiccant allows the absorption of humidity.

Moreover, the liquid desiccant may be easily transported, so that the cooling or drying of air may be carried out at different locations. The air-conditioner suitably comprises a heat and mass exchange (hereinafter also HMX) module for dehumidification and for regeneration. These HMX modules are typically used in combination with evaporators for cooling of air.

For sake of clarity, the term ΉΜΧ-module' is used within the context of the present invention to refer to any module for use in a conditioning system for air and/or another gas. Where reference is made to an air-conditioner module, this is to be understood as synonym. The conditioning system may be arranged to condition humidity and/or temperature of the air. The conditioning system is typically used for air, such as available in offices, stables, houses, theatres, musea, sporthalls, swimming pools and other buildings. The conditioning system may alternatively be used for conditioning an industrial gas flow.

A typical example of liquid desiccant is a concentrated salt solution of LiCl. Such a salt solution however have as disadvantages that LiCl may be hazardous for human health and that the concentrated LiCl solution is highly corrosive. It is therefore to be avoided that the LiCl is carried over into the air during the air-conditioning. The liquid desiccant is therefore often used in combination with a membrane, such as for instance known from WO2009/094032A1. That prior document discloses a module design wherein flow of cooling fluid, desiccant flow and air flow are integrated into a single multilevel module. As shown in Fig. 1 of WO2009/094032A1, the air flow (inlet airstream) runs in parallel to the liquid desiccant flow. This reduces the overall both heat and mass transfer efficiency relative to a counter current flow design.

Another option is the use of a porous material, more particularly a wicking material. Such modules are for instance known from WO00/55546 (Drykor), and from WO2013/094206. Herein, complex modules are shown so as to overcome apparent disadvantages of the technology. WO00/55546 discloses the use of a sponge material within a chamber, through which the liquid desiccant percolates and in which the air gets into contact with the liquid desiccant. However, this requires a high air pressure, with possible risk of carry over. WO2013/094206 discloses plates with internal channels for refrigerant so as to provide additional cooling. The plate design would overcome earlier limitations. A counterflow design is mentioned as an option to obtain sufficiently high efficiency.

There is therefore a need for a robust technology for heat and mass exchange modules, particularly based on liquid desiccant material.

Summary of the invention

In this perspective, it is a goal of the invention to provide a heat and mass exchange module that is suitable for manufacturing and of which - in operation - the dehumidification or regeneration capacity can be set.

According to a first aspect, the invention provides 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.

According to a second aspect, the invention relates to the use of the heat and mass exchange module of the invention for heat and mass exchange between a fluid in the air channel and a liquid in the liquid channel. In accordance with the invention, a module is provided that is particularly designed for cross-flow and that comprises means with which the liquid flow in the liquid channel may be set across the width of the liquid channel. It has been understood by the inventors that rather than varying the air flow rate to a large extent, it is preferred to vary the liquid flow. In fact, a major variation of the air flow has at least two disadvantages. The first is that an increase in the air flow from a predefined flow rate based on efficiency to an enhanced flow rate would easily make the air flow to become turbulent, at least in certain portions in the air channel. This increases the risk of carry-over of liquid, particularly liquid desiccant. Such carry-over is undesired, as it may not be healthy and moreover, liquid desiccants are often corrosive, thus damaging pipes and other materials in an unpredictable and undesired manner. The second disadvantage particularly relates to the integration of a module, such as a dehumidifier or an evaporator, into an air-conditioning system. It may often be the case that much more dehumidification than cooling is desired, or in the alternative that more cooling than dehumidification is desired. However, if the operation of the module is arranged by means of variation of the air flow rate, this not merely binds the module, for instance the dehumidification module, but also the other modules within an air-conditioner system.

Therefore, the inventors of the present invention have understood that it is better to vary the flow rate in the liquid channel - more precisely expressed as the volumetric flow rate (m ³ /s) or the mass flow rate (kg/s). However, the liquid in the liquid channel flows downwards under the impact of gravity. Thereto, both the linear speed (m/s) of the liquid and the surface area (m ² ) of the exchange surface between the liquid channels and the air channels may be varied. Varying the linear speed may be effected for instance by variation of a pump speed, while simultaneously closing off the circuit of liquid for the environment and suitably provided an overpressure to arrange pumping of the liquid.

According to the invention, use is made of a variation of the surfacial area of the exchange surface, and/or variation of the linear speed of the liquid along the width of the liquid channels. In other words, the flow profile is varied. This leads to efficient variation of the heat and mass transfer, and therewith to an efficient manner of setting the operation of the module, for instance

dehumidification or regeneration.

Preferably, the module of the invention is provided with at least one container for liquid overlying the module. The level of liquid in the container herein provides a static pressure, which effectively sets the linear speed of the liquid flow. One insight of the inventors is that the variation of the flow profile may be implemented so as to create a variation of the level in the at least one container, therewith creating different sections, each having a smaller surface area. It will thus be simpler to obtain a relatively high level of liquid - a high column - in one of the sections, leading to a larger linear speed in the corresponding, underlying section of the liquid channel. Such a flow profile, with a larger linear speed in a first section than in a second section, is moreover deemed beneficial, since it has been found that the efficiency of heat and mass transfer is significantly non-linear. This non-linearity may lead thereto that liquid, such as liquid desiccant, having passed a

dehumidification module close to the inlet of the air channel has a substantially higher temperature than the liquid desiccant that passed the same module at the same time close to the outlet of the air channel. Similarly, the humidity level of the air may vary from top to bottom. Also, for other types of modules, such as a regenerator module, a non-linearity of heat and mass transfer has been observed. Therefore, the efficiency of the heat and mass transfer may be improved by variation of the flow profile in accordance with the invention.

Therefore, in accordance with an embodiment of the second aspect of the invention, a control method is provided, wherein the flow profile is set on the basis of temperature sensing close to the exit of the liquid channel. Particularly temperature sensing occurs at least at a first point and at a second point along the width of a liquid channel, so as to sense a first and a second temperature. If the first temperature exceeds a predefined value and/or deviates more than a predefined threshold from the second temperature, the flow profile is to be amended. Particularly, the flow profile is controlled while using the first and the second temperature as key input parameters. It will be understood that the control may have further sensing inputs, such as the humidity level of the air at the air inlet and at the air outlet, and/or in a space to be conditioned, and a desired humidity level and/or temperature, as specified by a user or by an operation programme. Principally, another sensing parameter may be sensed at the exit of the liquid channel, such as concentration, linear speed. However, temperature is a parameter that may be sensed on-line and in a reliable manner, and with a sensor that is sufficiently small to be arranged within a liquid channel.

In one further implementation, the liquid that has passed the liquid channels may be collected in more than a single container, such subdivision of the container preferably corresponding to the subdivision into the sections of the liquid channels. More precisely, the module or the system therewith is then provided with a first and a second container - and optionally also a third and any further container - for collecting liquid that has passed the module. In such a further

implementation, the sensing, particularly of the temperature, could be carried out in the subdivisions of the container for the liquid. It will be understood that the liquid thus collected separately may thereafter be merged or be treated separately. More particularly, in one embodiment, the module design may be tuned such that in standard operation, the liquid flow in a second portion of the liquid channel is smaller than the liquid flow in a first portion of the liquid channel, wherein the second portion is located more closely to the outlet of the air channel. Particularly, the second portion is a portion adjacent to the outlet of the air channel, and the first portion may be any other portion of the liquid channel. It has been observed, in experiments with a cross-flow module of a preferred embodiment, that the liquid may be moved, under the force of the air in the air channel, from the first area to the second area, and from the second area to an edge of the liquid channel, or even to an edge of the plate. Such a lateral flow of the liquid may cause accumulation of liquid in a corner close to the outlet of the air channel. This may decrease efficiency, but could also lead to some carry-over in the long run. In order to prevent this, the inventors have understood that the flow rate in the second portion is reduced under standard operation. If however, enhanced operation is needed, the flow rate may be increased in the second area. That can be done temporarily before the accumulation starts to lead to a risk of carryover.

In one suitable embodiment of the invention, 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. It is deemed preferable that it is the entry to the liquid channel that is varied rather than portions of the liquid channel itself. In one implementation, the first and the second entry have a different cross-sectional area. In another implementation, the first and the second entry are arranged to have different length, said length being defined as a direction of liquid flow, thus typically aligned with a length of the liquid channel. Such a length difference will result in a flow difference between the first and the second entry, when the level or pressure of liquid applied to the entries is different. This embodiment is for instance implemented with distance holders having a varying height, as will be discussed hereinafter. These distance holders, arranged between adjacent plates or sheets of the module, suitably have a strip-like extension. They are arranged between two adjacent plates or sheets, but they face merely a portion of the plates. In fact, where the distance holders are located, there is no mutual exchange surface between an air channel and a liquid channel. It is an arrangement of the distance holders at the top of the module, between the container and the liquid channels, is deemed beneficial.

In an alternative or additional implementation, 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. The states of the liquid are for instance chosen from temperature, concentration, pressure and composition. Also in this embodiment, it is preferable that the first and the second container overlie the liquid channels and the plates, even though that does not appear strictly necessary. More preferably, the number of entries and corresponding containers is more than two, for instance 3 or 4. This subdivision of the container into different containers facilitates control of the flow profile. More particularly, in one further embodiment, a controller is provided for setting the state of the liquid in the various containers, therewith defining the flow profile. The pressure of the liquid herein is particularly arranged by means of setting the level of liquid in the containers.

In one preferred embodiment of the invention, the container for liquid overlies said plurality of plates, wherein said liquid channels are provided with entry regions for entry of liquid from the at least one container. The entries as defined before each thus contain a plurality of entry regions between said reservoir and the liquid channel. An entry region may be defined as a predefined channel through an element for liquid distribution, also known as a manifold. Alternatively, use may be made of distance holders between adjacent plates with a design comprising channels.

In order to set the flow profile, in this preferred embodiment, 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. Alternatively or additionally, the flow profile is set in that entry regions for the liquid channel are arranged at varying height in the at least one container.

In another embodiment, the length of the entry to the liquid channel is varied over the width thereof. This embodiment is preferably implemented with distance holders extending between adjacent plates and defining entry regions for the liquid into the liquid channel, such as a layer of wicking material. Such a distance holder is described in the non-prepublished application

NL2013565 in the name of Applicant that is included herein by reference. The entry regions are herein effectively defined as slots. Variation of the height of the distance holder thus results in variation of the height of the slots. More specifically, the variation of the height is provided at a top side, i.e. at the side of an overlying container or any channels. According to this embodiment, slots with larger height will then merely be accessible for liquid in an overlying container in some situations- that can occur under control of a controller. For instance, such slots with a larger height may be accessible, if the level in the reservoir is sufficiently high. Slots with a larger height are also feasible, if additional distribution means are present and configured for supplying liquid to predefined areas - i.e. the areas in which said slots are present. Then the slots with a higher height will be filled when supplying liquid by means of the additional distribution means. Thus, the distance holder at the entry of the liquid channel has a varying height over a width of the liquid channel. Herewith, it is achieved that the flow of liquid desiccant is varied over the width of the liquid channel, so as to set a flow profile of the liquid desiccant. Such a variation is understood to be particularly useful at the side close to the outlet of the air channel, more particularly in a preferred embodiment wherein the module is defined as a cross-flow module. In such a module, the distance holder typically defines a side wall to the air channel. The background hereof is that the air flow might result therein that the liquid desiccant is also moved with the air flow. At the side close to the outlet of the air channel, liquid desiccant would accumulate, which means in practice a thicker layer. The generation of a thicker layer may however be prevented, when the initial flow rate at the said side is reduced. This is what can be achieved with the distance holder having a varying height over the width of the liquid channel.

Suitably, the entry regions in the distance holders are mutually separated by means of closed regions. In this manner, the profile at the top of the liquid channel is interrupted to define a plurality of channels. Preferably, the width of the closed regions is chosen such that below said channels, the liquid streams through the channels merge, so as to wet the entire liquid channel. Particularly, in relation thereto, 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. In one suitable implementation hereof, 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.

The HMX module of the invention is preferably present within an air-conditioner apparatus. Such apparatus may contain a plurality of modules having different functions. More particularly, the apparatus comprises an evaporator and a dehumidifier. The dehumidifier preferably operates on the basis of liquid desiccant material, such as LiCl. Suitably, the air-conditioner apparatus further comprises a regenerator for regenerating humidified liquid desiccant material used in the dehumidifier. In accordance with a second aspect, the invention provides 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, and applying a liquid flow into at least a first portion of said liquid channels, said liquid flow flowing in a second flow direction different from the first flow direction, therewith creating cross-flow.

In accordance with the invention, the air is conditioned towards at least one predefined output parameter, in that a flow profile of the liquid is set, particularly over a width of the liquid channel. Suitably, the air flow is controlled only on a level of an air-conditioning apparatus, comprising a plurality of modules. More particularly, the air flow is held substantially constant.

More particularly, the air flow is controlled to obtain a laminar flow. This has the advantage of minimizing risk of carry-over of liquid desiccant, if any is used as the liquid in the liquid channel.

In one embodiment, the method further comprises the step of applying a second liquid flow into a second portion of the liquid channels. The second liquid flow can herein be arranged as an additional flow to enlarge the mutual exchange surface, and/or to enhance the exchange over the exchange surface. Therewith, the second flow may be used for switching the operation of the module from a normal operation mode into an enhanced operation mode, with more powerful operation, such as more powerful dehumidification. This particularly occurs without creating turbulence in the air channel. Additionally, the first and second liquid flow may be further optimized for obtaining a super effective operation mode, for instance by varying a state of the liquid in the containers. One option is for instance defining a temperature of the liquid, and more particularly lowering the temperature of the liquid in case of dehumidification or increasing the temperature of the liquid in case of regeneration.

Furthermore, it is foreseen that liquid flow may vary over time. For instance, the second flow is made to vary over time. Alternatively both the first flow and the second flow are made to vary over time. In one embodiment, at least one of the first and the second flow is varied in a repetitive manner between a 'low' and a 'high' operation. This is deemed a suitable manner so as to ensure that an air flow is not dehumidified too much (more than desired by a user). Due to the distribution of an air flow in a larger space, a resulting average air humidity will be close to an average of the humidity contents achieved with the low and the high operation. Brief introduction to the figures

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:

Fig. 1 depicts a diagrammatical view of a first embodiment of the heat and mass exchange (HMX) module;

Fig. 2a-d schematically depicts a sheet used in the HMX module;

Fig. 3 shows a diagrammatical view of an implementation of such a sheet;

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

Fig 5a shows a schematical top view of a manifold in one preferred implementation;

Fig. 5b shows a detail of Fig. 5a;

Fig. 6a-c shows side views of a plate and manifold according to another implementation;

Fig. 7 shows a schematical side view of a HMX module including a reservoir of liquid desiccant; Fig. 8 schematically depicts a module with three containers overlaying the plates;

Fig. 9a depicts a side view of an embodiment of a distance holder configured to create a certain liquid flow profile;

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

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

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 Figure 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.

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 module - also referred to as a drier module - a 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.

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 entry - also referred to as inlet - 31 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 exit - also referred to as outlet - 32. 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).

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 Figure 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 Figure 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.

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. In one implementation according to the invention - not shown - the 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.

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.

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. Fig. 3 furthermore shows the presence of spacers 26, which preferably have a strip wise 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.

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. 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 and - in at least one embodiment - creating entry regions and closed regions, as will be explained with reference to Fig 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 ard 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.

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.

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.

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.

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.

In the Figures 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).

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.

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.

Fig. 6a-c discloses again an alternative implementation of the distribution system in accordance with the invention. Herein the sheets 10 comprise slits 16. Figure 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. 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.

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.

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.

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 KC1 in addition to LiCl (more precisely other alkali cations, such as potassium or sodium, in addition to the litium 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, and - typically related thereto - the liquid pressure exerted by said volume onto an underlying entry into the liquid channel.

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.

Although not shown in Figure 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. 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.

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. 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.

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.

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. 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.

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.

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.

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. 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. 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. 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.

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.

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 figure 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. 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. In fig. 10a, a different design for a distance holder configured to generate a liquid flow profile is depicted.

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 figure 4) into the layer 11 of wicking material.

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. 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.

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. 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.

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. 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.

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. lOa-c 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.

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. 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. 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.

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 manner - for 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.

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. 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.

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.

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.