NL2013990A

NL2013990A - A heat and mass exchange module and an air conditioner.

Info

Publication number: NL2013990A
Application number: NL2013990A
Authority: NL
Inventors: Theodorus Hubertus Maessen Ralph; Paul Annie Roosen Jan; Maria La Torre Federico; Wilhelmus Jacobus Hollering Robertus
Original assignee: 2Ndair B V
Priority date: 2014-12-16
Filing date: 2014-12-16
Publication date: 2016-09-20
Also published as: WO2016099254A1; NL2013990B1

Description

A heat and mass exchange module and an air conditioner Field of the invention

The invention relates to an air conditioner comprising a dehumidifier and an evaporative cooler, which dehumidifier is based on humidity absorption from an air flow into a flow of liquid desiccant, and which evaporative cooler is based on evaporation of water to reduce the temperature of the air flow.

The invention also relates to a heat and mass exchange module for use therein, comprising a plurality of air channels for air flow and a plurality of liquid channels for flow of a liquid, wherein a liquid channel is embodied as a layer of wicking material on 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.

Background of the invention A heat and mass exchange module of the above mentioned type - hereinafter also HMX module -comprises a plurality of parallel plates which are typically provided with at least one layer of wicking material. In operation, a liquid is applied onto the surface of the plates. In the context of air conditioning, the liquid may be a liquid desiccant or alternatively an evaporative liquid. Liquid desiccants are used for dehumidification, and are suitably aqueous salt solutions, typically hygroscopic and preferably concentrated. The liquid desiccants need to be regenerated after use. The HMX module can be used as a dehumidifier module and as a regenerator module. Evaporative liquids are used in evaporative coolers. These liquids may not be toxic, aggressive, corrosive and the liquid’s heat of evaporation is suitably big so as to result in significant cooling of the air. The evaporative liquid is more particularly water, such as demineralised water or tap water, which further may include an additive.

If the HMX module is a dehumidifier module, the water concentration in the liquid desiccant is typically reduced before entry, so that the liquid desiccant can take up humidity from the air. Suitably, the liquid desiccant is also cooled. If the HMX module is a regenerator module, the liquid desiccant is suitably heated prior to entry, so as to facilitate evaporation of water from the liquid desiccant to the air. The HMX module may be further used as part of an air cooling (and/or heating) system. 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, museums, sport halls, swimming pools and other buildings. The conditioning system may alternatively be used for conditioning an industrial gas flow.

One such liquid desiccant type air conditioner is known from WO2013/192397A1. The known air conditioner comprises a first stage, which is a dehumidifier, and a second stage, which is an evaporative cooler. The first and second stage are embodied as separate devices with a different construction. The first stage device is a cross-flow module between two air streams, and a flow of desiccant. The liquid desiccant is separated from the air flow that is to be conditioned by means of a membrane. The further air stream comprises a two-phase flow of water and outdoor air, which is to cool the liquid desiccant. The second stage is an indirect evaporative cooler. The air flow is cooled herein on the basis of heat transferred from an indirect channel, in which water evaporates into a separate air stream. In this manner, the air flow is cooled without being humidified. In said WO’397, the separate air stream is created as a split off portion of the outgoing air flow. This outgoing air flow has previously been dehumidified. Even though its relative humidity content (usually expressed as %RH) may have increased due to the cooling, the air flow is still dry and is therefore capable of absorbing humidity from a channel of evaporative liquid. An additional direct evaporative cooler may be added as a third stage, so as to further reduce the temperature of the outlet air flow, but at the cost of becoming less dry. This subsequent direct evaporative cooler apparently could be integrated into the second stage device.

In the known air conditioner of WO’397 an exhaust air stream is generated (in the indirect evaporative cooler and in the dehumidifier). This strongly humidified exhaust air stream that is to be removed to the outdoor, for which tubes and such elements are required. Such piping creates additional costs when introducing the technology. Moreover, no such exhaust piping is required in existing air conditioning systems. Therewith, the piping is a burden to exchanging existing and less efficient air conditioners for those based on liquid desiccant as proposed in WO’397.

Summary of the invention

It is therefore an object of the invention to provide an improved HMX module and an air conditioner therewith, which can be operated in an economically viable manner and technically straightforward manner so as to reduce the complexity of installation and maintenance, and in which the generation of an exhaust air stream is suitably avoided.

According to a first aspect, the invention provides a heat and mass exchange (HMX) module comprising a plurality of sheets in a spaced-apart arrangement and provided with a plurality of air channels for the air flow and a plurality of liquid channels, which HMX module is a cross-flow module with the air channels extending in a first flow direction between inlet and outlet, and with the liquid channels extending a second different flow direction, wherein a liquid channel is embodied as a layer of wicking material on a sheet and is arranged adjacent to an air channel with a mutual exchange surface, wherein first liquid channels for water flow and second liquid channels for flow of the liquid desiccant are present, which are arranged such that an air channel is provided between its inlet and its outlet with a first exchange surface with a first liquid channel, and with a second exchange surface with a second liquid channel.

According to a second aspect, the invention relates to an air conditioner comprising a dehumidifier and a direct evaporative cooler, wherein the HMX module of the invention is present as the dehumidifier and the evaporative cooler.

According to the invention, a direct evaporative cooler and a dehumidifier based on liquid desiccant have been integrated into a single module. More precisely, a single air channel is provided with a cooler section -the first exchange surface - and a dehumidifier section - the second exchange surface. Thereto, the module is a cross-flow module based on sheets provided with layers of wicking material, more particularly a textile material. In such cross-flow module, the liquid flows downwards and the air flows laterally through the module. The first and the second exchange surface may here be separated without a risk of mixing of the different liquids, or contamination of the wicking material in the cooling section with the salt solution that constitutes the liquid desiccant.

It has been understood by the inventors that integration of the cooler and dehumidifier sections per channel avoids generation of a separate exhaust air stream. The cooling of the liquid desiccant in the dehumidifier is no longer needed, because the design of the cooling section can be designed such that the dehumidifier is sufficiently effective also without cooling. Particularly, the total area of the exchange surface (per unit of volume) is increased. This may for instance be achieved by increasing the area of a single area of the exchange surface; in that one air channel is provided with exchange surfaces on opposite sides; by setting the thickness of the air channel. The absence of a further airstream for cooling (as present in the prior art) has the advantage that the density of air channels can be increased. A further advantage of the integration is a reduced need for pumping. The air flow is led through a module on the basis of a pressure drop. Leading an air flow out of a first device into a second device, wherein the air flow is again to be split over a plurality of air channels, overall requires a higher pressure drop, or a separate pump between each module. A higher pressure drop however tends to create higher air velocities, which constitute a risk for turbulence and a concomitant risk for carry-over. This is again important, because the integration of the sections into the channels requires omitting any membranes in the dehumidifier.

Furthermore, the invention facilitates better control of the air conditioning process. The integration of two different functions into a single module avoids intermediate connection parts, which are typically difficult to control. Such connection parts typically involve different flow behaviour and often variations in temperature. The combination of the invention avoids this. Rather, a single control for the complete module is feasible, wherein the outcome may be regulated by means of variation of a number of parameters, such as parameters of the liquid desiccant, parameters of the water, and optionally air flow rate. Preferably, a number of standard settings is pre-defined, and then one or more parameters may be tuned based upon sensing actual conditions. For instance, flow rate and flow area of the liquid desiccant and the liquid are parameters that may be varied quickly and relatively easily, and are thus suitable for the further tuning. Moreover, the presence of a plurality of air channel, which are suitably operated under the same conditions, provides an opportunity for an accurate determination of properties of the system on the basis of sensing in a single or a few individual channels. The invention thus further relates to a module that is further provided with a controller, wherein the controller controls operation of both the dehumidifier and the evaporative cooler. It also relates to a control method, and to an operation method comprising the step of controlling the operation in the combined module. It is added for sake of clarity that the controller is not necessarily located within the module. It may also be outside the module.

In one preferred embodiment, the dehumidifying section is located downstream of the cooling section within the channel. By arranging the dehumidifying section downstream of the cooling section, the humidity level of the air can be controlled in a robust manner. The reason is that the absorption of humidity in a liquid desiccant based dehumidifier can be better controlled than the release of humidity into a relatively dry air flow. In fact, the absorption of humidity by the liquid desiccant is particularly dependent on its concentration, the flow rate, the surface area of the exchange surface and the temperature. The evaporation of the evaporative liquid turns out to be primarily dependent on the humidity of the air flow. It is thus particularly with the exchange surface area that the operation of the direct evaporator can be controlled. Flence, there are more parameters in the dehumidifier for accurate control of the humidity level in the air flow. A further advantage of the present embodiment is based on the finding that the liquid desiccant acts as a disinfectant. The presence of the dehumidifier downstream therefore ensures that the resulting air is substantially free of any microorganisms such as pathogenic bacteria. Furthermore, the liquid desiccant based dehumidifier, particularly embodied as a module with a plurality of sheets between which air flow in accordance with a laminar flow profile, also releases the air flow from dust particles. For this reason, it will contribute to air with lower contamination, as typically defined in classes in the US FED STD 209E cleanroom standard and/or the ISO 14644-1 cleanroom standard.

In a specific embodiment herein, the air conditioner comprises an additional dehumidifier upstream of the cooling section. Such additional dehumidifier may be present as a separate device. Alternatively, it could be integrated within the same HMX module. Its design is anyhow suitably substantially identical as that of the HMX module with the cooling and the dehumidifying section, as further discussed with reference to the figures. Notwithstanding this option of integration, it appears beneficial that the dehumidifier is embodied on sheets separately from that of the cooling section. Furthermore, exchange of the air in at least a first subset of the air channels between the dehumidifier and the cooling section is preferred. Such merging of the air channels of a first subset simplifies assembly of the sheets. Moreover, such merging will take away any differences in humidity between different portions of the air, such as between centre portions of an air channel and portions close to the exchange surface.

This embodiment is deemed suitable for locations that have a humid and warm climate, such as locations with a tropical climate (close to the sea). The relative humidity of the air will be frequently 70% or even 80%. A cooling section is then not very effective, unless preceded by a dehumidifier. Such locations however require both a substantial cooling of air and a substantial dehumidification. It is then useful to have a first dehumidifier module, so as to arrive at sufficiently dry air, which is subsequently cooled by means of evaporation. The operation of the dehumidification section is then controlled to obtain an air flow with desired humidity content.

Such additional dehumidifier does not appear necessary for locations with lower average temperatures and/or with lower humidity levels. The HMX module may then be sufficient. Its primary task will be cooling, and the increase in humidity in the cooling section can be compensated in the dehumidification section.

In an alternative embodiment, the cooling section is arranged downstream of the dehumidifying section of the HMX module. This arrangement is deemed beneficial for situations wherein the humidity of air is to be controlled, and more particularly reduced, for instance in warehouses. It is furthermore not excluded that a heat exchanger is present for heating the air flow and/or the liquid desiccant prior to entry into the HMX module.

In one further embodiment, control of the humidity level is achieved in this configuration by variation of the surface area in a single channel at which evaporation occurs. Thereto, the module is suitably provided with means for enabling such variation. Such means are embodied, more particularly, within the manifold. As is further elaborated with respect to the Figures - which show one specific illustrative implementation - the module of the invention preferably comprises a manifold based on distance holders present between adjacent sheets. The supply of liquid into the liquid channel is herein predefined by means of the size and density of entry regions relative to closed regions. Alternatively or additionally, the overall surface area of evaporation over a duration of time may be varied by switching off the flow of evaporative liquid either in some of the first liquid channels, or by interrupting the flow for some time. The first option of variation between the channels is deemed preferred as it results in more constant properties of the conditioned air flow.

In a further implementation, the HMX module further comprises distance holders arranged between the sheets and defining entry regions for entry of liquid and closed regions wherein the wicking layer is compressed. These distance holders enable the maintenance of a uniform distance between adjacent sheets. The distance holders preferably have a strip-wise extension. This makes that the distance between adjacent sheets is substantially uniform over the length of the air channel, from its inlet to its outlet. The distance holders with such strip-wise extension suitably extend from the inlet to the outlet of the air channel. Alternatively, a plurality of strip-wise extending distance holders may be used, optionally with spaces in between of them. Moreover, by defining entry regions into the liquid channels, the distance holders are able to distribute the liquid according to any desired pattern. It is thus feasible to specify a closed region between the first and the second liquid channel, so as to prevent mixing of different liquids.

In a further embodiment, the sheets are corrugated. This enables the use of thin sheets that have nevertheless sufficient strength. Preferably, the second liquid channel is defined with a waveshape, i.e. with a pattern of ridges and valleys, the waves extending substantially parallel to the first flow direction. Such a corrugation increases the surface area of the exchange surface. In preliminary experiments, an increase of about 20% relative to a planar surface area has been achieved. Furthermore, while the liquid will follow a pattern of ridges and valleys, a single volume of air may see a straight path in the air channel. This set-up has been found to be highly advantageous for the avoidance of carry-over. This is the undesired transfer of certain components present in the liquid into the air. Carry-over is undesired when using liquid desiccants, since the salts applied as liquid desiccant are typically corrosive. It is furthermore undesired that conditioned air would contain any droplets of salt. Carry-over is further undesired in evaporative coolers. The use of water (possibly with an exception of distilled water) implies the presence of any microorganisms such as bacteria. Carry-over of such bacteria into the air is undesired from the perspective of hygiene and safety.

In one further embodiment, the evaporative liquid is an aqueous salt solution, which has a salt concentration that is lower than that of the liquid desiccant. One preferred example is sea water and/or mixtures of fresh water and sea water. The apparatus is thereto provided with supply means for salt water, including for instance a container, or a pump and the like with an inlet for sea water. Such use is particularly beneficial in coastal areas, and particularly at the coast, for instance for hotels and resorts. If the sea water would be used in a heat exchanger, a specific type of heat exchanger is needed, since copper will be prone to corrosion by sea water. However, the liquid channels are designed to be suitable for liquid desiccant and thus also for any other salt solution. Use of sea water furthermore reduces problems with hygiene and safety. Furthermore, it has been understood that the evaporation of water from sea water is not significantly less efficient than evaporation of fresh water (i.e. from the tap). It further appears that the humidity of the air flow rather than the temperature of the water is decisive for the rate of evaporation in the direct evaporative cooler.

While the first liquid channel suitably has the same shape as the second liquid channel, this is not deemed necessary. In fact, any carry-over of microorganisms occurring in the first liquid channel is likely reversed in the second liquid channel due to the release of humidity. The salty liquid desiccant solution has been found to be disinfecting, and thus will take away the microorganisms. As a result, there is significantly larger design freedom in the design of the first liquid channel, for instance to provide higher strength to the sheet. It is nonetheless deemed suitable that the air flow remains laminar, so as to avoid continued turbulence in the second liquid channel.

In a preferred embodiment, a liquid channel has a substantially uniform thickness, such that not merely the exchange surface has a specific corrugated design, but that the shape of the exchange surface corresponds to the shape of the liquid channel. Suitably, the entire sheet is corrugated, such that a valley on one side corresponds to a ridge on an opposed side of the sheet. In one preferred embodiment, the sheet has a uniform thickness. This minimizes the volume within the module used by the sheets. However, this uniform thickness is not deemed necessary, and may be dependent on the manufacturing technique of the sheets. A sheet processed by thermoforming would typically have a substantially uniform thickness when the thermoforming starts from a planar sheet. A sheet processed by a moulding technique may easily have a varying width.

Suitably, an air flow rate of the air flow and a liquid flow rate of the liquid flow are controlled. In accordance with said control, a mass flow ratio of the liquid flow rate over the air flow rate is at most 3.0, more preferably at most 2.5 or even at most 2.0. It has been found that such a mass flow ratio can be achieved with the module of the invention, and that is furthermore provided a very high drying efficiency of over 60% up to even over 90%, when the said mass flow ratio increases towards 2.0. However, good results have also been achieved with mass flow ratios in the range of 0.5 to 1.5.

More particularly, the air inlet and the air outlet may be configured to have a substantially rectangular cross-section. In fact, the non-planarity of the exchange surface when seen along the first flow direction corresponds to non-planarities along the width of the air channel.

In one suitable embodiment, an accommodation area is present between the inlet of the air channel and the exchange surface, when seen along the first flow direction. Such accommodation area is deemed beneficial to smoothen the air flow, and to provide a transition between a flow in a major pipe to flow through a plurality of air channels with limited height.

Preferably, the non-planarity of the exchange surface comprises a series of ridges and valleys. These ridges and valleys are suitably provided regularly. More particularly, the pattern of ridges and valleys along said direction suitably constitutes a wave shape, more particularly a sine wave shape.

In a preferred embodiment, the sheet further comprises at least one strengthening protrusion that is defined within an area extending substantially parallel to the liquid channel. Such strengthening protrusion is for instance arranged in the accommodation area and/or in an outlet area present between the exchange surface and the outlet of the air channel. Herewith stiffness of the sheet is further increased, therewith reducing the risk of carry over further. Such stiffness is for instance desired so as to prevent and/or suppress any vibrations that could otherwise influence the flow pattern in the air channel, and create larger carry-over from the liquid channel. The stiffness is further desired to counteract deformation of the sheets, which for instance may be due to expansion and/or contraction due to temperature differences, and more particularly differential thermal expansion between materials that are attached or bonded to each other. As a consequence of such deformation, the mutual distance between the sheets could decrease, so that droplets could bridge a first and a second liquid channel (actually separated by an air channel). Moreover, module manufacture is simplified by means of sheets of sufficient thickness. More preferably, the sheet comprises at least one strengthening portion in the accommodation area and at least one strengthening protrusion in the outlet area.

In a more particular implementation of the distance holder, it is provided with a surface of hydrophobic material. It suitably has a bottom surface that is exposed to at least one air channel, which bottom surface has a concave shape between lower edges adjacent to the first and the second sheet and an upper region between said edges. Both these implementation measures contribute to reducing the risk of carryover. In fact, with this choice of material and this shape of the bottom surface of the distance holder, a barrier is provided against flow of liquid desiccant along the surface and against the formation of droplets anywhere at the bottom surface that would otherwise drop down into the underlying air channel.

Preferably, the HMX module is designed, such that an air channel is present between a first and a second liquid channel of liquid desiccant, which liquid channels are defined by means of layers of wicking material on adjacent sheets. The number of sheets is suitably at least 10 preferably at least 30, more preferably at least 50, so as to arrive at a suitable surface area for exchange between the air channels and the liquid channels. However, this number may be changed, in dependence of climate, air volume to be conditioned, operation time, surface area of a single sheet, and other factors, such as available space. The individual sheets are preferably of uniform thickness.

Suitably, the sheets are laminates of a carrier and one, preferably two layers of wicking material, more particularly a textile material. Hence, they do not contain any channels for refrigerant. Optionally, a layer of refrigerant is present between two adjacent sheets. Such additional cooling could be useful for regeneration of the liquid desiccant, for instance.

In one embodiment of the invention, a third liquid channel may be present. The third liquid channel may be used for the provision of a further liquid. For instance, it is deemed beneficial in certain applications to provide a flow of a liquid comprising a volatile additive, such as a fragrance. The volatile additive may then evaporate and provide additional properties to the air. Other additives or additional treatments may be envisaged for specific environments, such as for instance clean rooms, low temperature (freezing) rooms for storage of food and the like, etc.

In a further embodiment, the third liquid channel may be configured for flow of liquid desiccant. The provision of more than a single liquid channel enables the definition of a flow profile along the length of the air channel. Such a flow profile enables optimization of the heat and mass transfer into the liquid desiccant. Several operation parameters of the liquid desiccant may be varied, such as the concentration, the temperature and the flow rate. Moreover, an additional channel provides options for variation of the operation of the HMX module. For instance, an additional channel is suitable for locally tuning of the operation, and therewith enabling that a first space or room is held at a different temperature than a second space. Furthermore, the third liquid channel may be used for an enhanced operation mode, while this channel is idle in normal operation mode. A third liquid channel with liquid desiccant is moreover beneficial to change the ratio between cooling and dehumidifying without downgrading operation of one of both.

It is observed that the flow profile is not merely advantageous for increase of the absorption capacity. The use of a flow profile may further be applied for keeping the dilution and concomitant heating of the liquid desiccant material within predefined limits. For instance, in the event that the air flow is highly humid after passing the first liquid channel, the heating of the second liquid channel, and particularly the first area thereof may go beyond desired operation limits. It is then preferred to have a less wide second channel, in which the flow rate can be increased without excessive consumption of regenerated liquid desiccant.

In again a further embodiment, a controller is present for controlling operation of the HMX module. Since the module comprises both an evaporative cooler and a dehumidifier on the basis of liquid desiccant, the overall operation may be controlled by means of a series of sensors and control algorithms. In addition to variation of the flow rates in the liquid channels, it is feasible to vary the air flow rate. This variation of the air flow rate is advantageous for a user so as to tune the rate at which air is refreshed. Different refreshment rates may be desired for different buildings, in dependence of the actual thermal isolation of outdoor air, and optionally for certain industrial environments wherein refreshment rates may need to be varied in dependence of the loading. The advantage of the invention, in relation thereto, is that the control is simplified as there is no need to pay attention to the operation limits of different apparatus.

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. 9 schematically shows an implementation of a sheet according to a further embodiment, and Fig. 10 schematically shows a further implementation of a module according to a further embodiment.

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 sheets 10. 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. This is an advantageous way of preventing any mixing of adjacent liquid channels that are configured for different liquids. However, it has been found that the liquid flow is sufficiently vertical, even when a layer of wicking material is wider than the area in which liquid enters the liquid channels via entry regions. Therefore, it is feasible that different liquid channels are defined within a continuous layer of wicking material. Patterning the wicking material may be carried out during or after adhesion of the layer of wicking material to an underlying sheet. Furthermore, the patterning may be carried out after that a layer of wicking material has been deposited onto a sheet, but fixing both together, for instance by means of curing an intermediate adhesive layer or by thermally bonding in a process wherein polymer chains of one material diffuses into the other one to create entanglements. There may be many ways in which a layer of wicking material, particularly a layer of textile, preferably non-woven material may be patterned. 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. Moreover, the reservoir may be used to build up static pressure, and therewith to set the flow rate (velocity) of the liquid desiccant. Alternatively, the flow rate (velocity) may be defined by means of a pump. The implementation with a pump requires, in one embodiment, the closing off of the liquid desiccant from the environment and typically the provision of overpressure. The implementation with a reservoir does not require a pump to set the flow rate. Herein, the reservoir may further be used to damp out variations in the supply of regenerated liquid desiccant, if any. Furthermore, while the present figure merely shows tube connections 18, 19 for the liquid desiccant, it will be understood that additional tube connections will be present for the liquid to be evaporated. They are for instance located on the rear side of the module. In again a further implementation, liquid flows may be coupled together in a heat exchanger. For instance, the output of the liquid desiccant may be heat exchanged to the input of the evaporative liquid, so as to transfer heat from the liquid desiccant to said liquid (water).

Clearly, this is dependent on the availability of heat and temperatures reached.

The HMX module as shown in Fig. 1 is used in accordance with the invention as a combined evaporative cooler and dehumidifier module. In the cooler section, the flow of air is cooled down by evaporation of water. In the dehumidifier section of the module a stream of air is dried, and the liquid desiccant takes up humidity. The cooling section is arranged upstream of the dehumidifier section. 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. Preferably, substantially all channels, which are arranged in parallel, comprise an evaporative cooler section and a dehumidifier section. However, if so desired, one of these sections could be left out in certain air channels. Thus more generally, at least a first of the air channels comprises both a cooler section and a dehumidifier section. As will be explained hereinafter, the air channel and a liquid channel have a mutual exchange surface. The cooler section has the first exchange surface. The dehumidifier section has the second exchange surface. Although it is well known that cooling by evaporation first results in higher efficiency, it is principally not excluded, that another section with a further exchange surface is arranged upstream of the cooling section and downstream of the air inlet. As will be understood by the skilled person, the liquid desiccant will generally be regenerated in a regeneration module after passing the module of the invention. Heat exchangers and/or heat pumps may be present between the module of the invention and the regeneration module.

As apparent from Fig. 1 the liquid channel is suitably longer than the air channel. 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. 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. The sheet shown in this Fig. 2a and also in Fig. 3 has merely a single liquid channel. However, it will be understood that the same principle applies if the sheet contains a first and a second liquid channel, or if a first and a second sheet are arranged next to each other (with the lateral sides connected).

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 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.

Fig. 2d diagrammatically shows a preferred implementation with a plurality of wave-shaped sheets 10. As shown in Fig. 2d, the distance between the sheets 10 varies somewhat due to the waveshaped 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.

The present combination of an evaporative cooler and a dehumidifier integrated into the air channels of a single module is most advantageously embodied with the corrugated sheets as shown in the Fig. 2d and following figures. Advantages are for instance a large density of sheets, the possibility to provide layers of wicking material on both sides of a single sheet, therewith doubling the exchange surface, the increase of exchange surface due to the corrugation, a very low risk of carry-over due to the laminar flow and due to the optimized design, a sheet that is suitable for assembly, because the edges of the sheet is planar. However, another configuration is not excluded. If somebody would like to use sheets with a larger thickness, internal cooling and/or higher stiffness, he could still apply the principles of the present invention.

In one implementation according to the invention - not shown - the height of a ribbon 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 ribbons 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.

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.

The sheet 10 is suitably created in a multistep process. In a first process, layers of wicking material are added to a carrier. The carrier is suitably an engineering plastic, such as PET, polycarbonate, high-density polyethylene and polypropylene. Good results have been achieved with materials have high temperature resistance, such as polypropylene or high-density polyethylene, with polypropylene being particularly preferred. For dehumidifier modules that are not subjected to operation at high temperature for a long duration, other carrier materials are very suitable as well. The wicking material typically comprises a fibrous material, such as a textile material, for instance cotton, linen, rayon or nylon fibres. Alternative hydrophilic, fibrous materials, such as starch and particularly treated starches, are not excluded. Natural rather than synthetic fibres are deemed preferred as a basis for the wicking material, since they are chemically inert and stable to LiCl and other saline desiccants. Rayon, and particularly viscose, is deemed a particularly preferred choice. Rather than a single material, a blend of materials may be applied, for instance a blend of a viscose with a carrier material, for instance an engineering plastic, such as polyethylene terephthalate, polyethylene, polypropylene, polyvinylchloride, polyester. A blend with up to 50wt% carrier material, for instance 25-40wt% carrier material is deemed very suitable. Preferably, use is made of a non-woven material that appears to be beneficial for the further step of the process. Most preferably, the non-woven material is a spunlaced material. The addition process may be achieved either by dipping (passing of a bath), coating, or laminating. The laminating process is preferred. The carrier may have been pretreated to improve adhesion, for instance by means of a surface treatment (such as a plasma treatment), or in the provision of an adhesion promoter or even a glue layer. In one advantageous embodiment, use is made of lamination under pressure, wherein an interlayer is formed between the carrier and the layer of wicking material. Good results have been obtained therewith. An advantage of this joining technique is that there is no glue needed, which could be sensitive to dissolution under the impact of the liquid desiccant that is typically very salty and corrosive. The glue may further have an impact on the porosity of the wicking material, and therewith on its wicking properties. In a further process step, the combined material is then thermoformed so as to create the corrugation of the surface, more particularly the ridges, valleys and any protrusions. Herein, the use of non-woven material is deemed beneficial, as it provides less resistance against the concomitant extension than any woven material. The thermoforming step was carried out in a manner so as to obtain an increase in surface area (‘stretch’) of 10-25%. It was found that this stretch could be made without any delamination occurring between the carrier and the layer of wicking material. The thermoformed sheet moreover turned out stable up to at least 100°C, or even up to 120°C. The thermoforming step may alternatively be carried out simultaneously with the laminating step.

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 distance holders in the form 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 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 coining from a generator, such as a diesel generator. This is further disclosed in the non-prepublished 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. Flerein 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. As shown in Fig. 5a, the manifold 40 is provided with a first section 141 and a second section 142, which provide access to the cooling section and the dehumidification section respectively. An isolation area 143 is present between the first section 141 and the second section 142. While the openings in the first and the second section 141, 142 are shown to be identical, this is not necessarily the case. The size of the cavities 38 and closing regions 39 may be different, if the section 141, 142 are to be provided with a different flow rate. It is observed that the length of the manifold 40 may correspond to the dimension (width) of a single sheet 10. Alternatively, the length of the manifold 40 may be longer than the width of a single sheet. More particularly, the cooling and the dehumidifying section may each be embodied in a separate sheet, with a means for connection in between of them. The manifold then suitably overlies both the cooling and the dehumidifying section, such that the first and the second section 141, 142 each have, substantially the length as the width of a sheet 10.

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. Flowever, 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 further embodiment of a module in accordance with the invention, in a diagrammatical cross-sectional view onto a sheet. In accordance with this embodiment, a first container 71, a second container 72, and a third container 73 are present and overlie the air channels 20 and the liquid channels 30. The three containers 71-73 are for instance 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 an implementation, each container 71, 72, 73 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. A preferred version of the manifold is shown in Fig. 9 and 10a-10b.

The module may further be provided with a plurality of containers below an exit of the liquid channels 30, i.e. at the bottom of a module 10, so as to collect the liquid that has passed the liquid channels in a specific section separately. Typically, such section corresponds to the overlying containers 71-73, and any connections to the entry regions of the liquid channels. It has been found, in experiments with a first prototype of the module of the invention, that the liquid flows downwards without broadening of flow area.

The containers 71, 72, 73 as depicted in Fig. 8 have roughly the same size and cross-sectional area. Flowever, 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.

In operation, the first, second and third containers 71-73 are typically provided with liquid that will flow into the liquid channels 30 of the module 10 from the containers 71-73. Suitably, the containers 71-73 are arranged such that each of them overlies a section of substantially all the liquid channels 30. More preferably, the intermediate manifold - which is particularly embodied in the form of strip wise extending distance holders as shown in Fig. 9, 10a and 10b - is configured such that the liquid in the first container 71 is distributed to all of the liquid channels 30. The same holds for the liquid in the second container 72 and in the third container 73. It is not excluded that the intermediate manifold distributes the liquid from any one of the containers 71-73 merely to selected (rather than to all) liquid channels.

The use of a plurality of containers 71-73 in combination with a single module 10 may be used for setting a flow profile along the width of the liquid channel 30. This is deemed beneficial to tune and optimize the flow.

The use of a plurality of containers 71-73 in combination with a single module 10 may further be used so that different liquids will flow in different sections of the liquid channels 30. In one specific example, the liquid flowing from the first container 71 into the first section is an evaporative liquid, such as water, and the liquid flowing from the third container 73 into the third section is a liquid desiccant. The second container 72 is for instance kept empty. The functions of evaporative cooler and dehumidifier are therewith integrated into a single module. This significantly simplifies the overall design, since there is no need for any connection of modules. Still, the air flow is first cooled and thereafter dehumidified.

In another specific example, the first container 71 contains an evaporative liquid, particularly water, the second container 72 contains a liquid desiccant and the third container 73 contains a diluted solution of any desired additive, for instance a disinfectant, a fragrance or parfum. It will be understood that variations are feasible. A single module may contain merely two overlying containers or even more overlying containers. Furthermore, it may be feasible that the two of the containers contain the same liquid (water, liquid desiccant), but in a different state, so as to set a flow profile along the width of the liquid channel. Options for setting flow profiles are further specified in a co-pending and simultaneously filed application of the Applicant. Generally, the term ‘state’ of the liquid refers to temperature, (static) pressure, concentration and/or composition. Fig. 9 shows a further implementation of the module of the invention, in again a very diagrammatical view onto a sheet 10. In the shown implementation, a first container 71 and a second container 72 overlie the module 10. In addition, the module comprises a first liquid channel 30A and a second liquid channel 30B. Each of the channels is provided with an exchange surface with the same air channel. The first and second liquid channels 30A, 30B are more particularly embodied as a first section 30A and a second section 30B with an intermediate isolation area 33 on a single sheet. This subdivision is suitably achieved by provision of the layer of wicking material onto the sheet according to a predefined pattern. The subdivision into a first section 30A and a second section 30B will further prevent any mixing of the liquid from the first container 71 and the second container 72. Furthermore collecting containers 91, 92 are shown for the two different liquids.

In the present configuration, the first section 30A is configured for flow of an evaporative liquid, typically water, but alternatively a diluted salt solution such as sea water. The second section 30B is configured for flow of liquid desiccant. This configuration may relate to the inlets and outlets to the containers 71, 72, 91, 92, to the openings defined in the manifold 40 defining the flow rate, to the width of the first and the second section 30A, 30B. Suitably, the second section 30B is located downstream of the first section 30A, but in one embodiment the first section 30A is located downstream of the second section 30B.

It will be understood that the subdivision into a first 30A and a second section 30B only is merely an example and that any desired number of sections may be present. Furthermore, in dependence of the overall width of the sheets, a further strengthening protrusion may be defined in the intermediate isolation area 33. Furthermore, though it is deemed beneficial for manufacturing reasons and for the avoidance of carry-over that the corrugation present in the first section 30A and the second section 30B is identical, this is not deemed strictly necessary.

Fig. 10 shows schematically a further implementation of the module of the invention, in again a very diagrammatical view. This module comprises a first sheet 10 and a second sheet 110. The first sheet 10 herein defines the cooling section, and the second sheet 110 defines the dehumidification section. Each of the sheets 10, 110 is embodied, in this example, as a sheet shown and discussed in more detail with reference to Fig. 3. The sheets 10, 110 are mutually connected by means of connection 126. These means 126 are in this example embodied in the form of spacers. Just as the spacers 26, these means 126 extend in a direction perpendicular to the sheets, so as to set the distance between the individual sheets. Preferably, the spacers 26 are embodied that the individual sheets are clamped into grooves in the spacer 26. Whereas the spacer 26 merely has grooves on one side, the means 126 are provided with grooves on opposite sides, so that the first sheets 10 and the second sheets 110 are connected. It is feasible that such means are implemented as multiple parts, i.e. with spacers and connecting parts, for instance magnets, or in the form of a mechanical connection (click-system) or a chemical connection (adhesive) as known per se. Then a first module comprising a plurality of sheets may be coupled to the second module with a plurality of sheets by connecting the spacers at the relevant sides with the connecting parts. In this example, there may be left some room between the sheets 10, 110, in which a first air channel would touch an adjacent second air channel. This is not deemed problematic.

As shown in this Fig. 10, the module is provided with a single manifold 40, suitably composed of individual strips 45 as discussed with reference to Fig. 4 and 5 above, having a first section 141, corresponding to the cooling section (in the first sheet 10), and the dehumidification section (in the second sheet 110), and an intermediate isolation area 143. It is however not excluded that the manifold comprises separate strips for the first sheet and for the second sheet. One advantage of a continuous strip in a single manifold, as shown in this Fig. 10, is however that the width of the cooling section and the width of the dehumidifying section do not need to be the same as the width of the first and the second sheet 10, 110. It is feasible that the second sheet 110 contains a first channel 30A and a second channel 30B, such as shown in Fig. 9, while the first sheet 10 is designed to contain a single channel such as shown in Fig. 3. The first sheet 10 is then for instance used for dehumidification, whereas the second sheet 110, defines a cooling section in the first channel 30A and a further dehumidifying section in the second channel 30B.

Examples

Modelling calculations were done on the combined module based on a design for the dehumidifier module as such. For the direct cooler and the dehumidifier, the calculations were carried out on the basis of a design corresponding to Fig. 10, wherein the width of the first channel (with evaporative liquid, such as water) and the width of the second channel (with liquid desiccant) were equal. The channels were designed such that the ratio of the total surface area of the exchange surface and the total volume of the air channels is 667 meter. Use was made of a module wherein the ratio of surface area of the exchange area over a unit volume was above 400 m2/m3. This contributes to effective performance and results in good convection.

The nominal air flow was set to 1500 m/h. The flow of the evaporative liquid, more particularly water, was recirculated, so that the water reached the same temperature as the air leaving the module. The evaporation rate was about 4.5 litre/hour. The liquid flow of the liquid desiccant was 15 litre per minute. The temperature of the liquid desiccant (a concentrated LiCl solution, close to its saturation concentration, around 40wt% as known) was set to be approximately 15°C (at least 5°C below the temperature of the outgoing air in a module). It was further assumed that the relative humidity of the air flow increased in the cooling section to 99% RH.

Example 1

Use was made of settings for a European summer day, wherein cooling is desired, but the relative humidity is in the good range. The conditions of the incoming air flow were assumed to be 26.7°C and 50.4%RH, which corresponds to 11.0 g water per kg of air.

It follows from this example that the combination of a cooling section and a dehumidifying section allows to cool air significantly, without change in the relative humidity. Moreover, the efficiency of the operation was improved.

Example 2

Use was made of settings for California with an average temperature of 30°C and a relative humidity of 70%RH. Here, both cooling and dehumidification are desired.

It follows from this example that air in Californian climate may be conditioned to feasible conditions (and even to temperatures below what is deemed acceptable) with the invention by combining dehumidification with subsequent cooling and further dehumidification. It is observed that these calculations provided a temperature decrease during dehumidification. The background hereof is the use of a cold liquid desiccant, and additionally a significant contribution of convection to the heat exchange. This contribution of convection is believed to be related to the - optimized -design of the liquid desiccant module, wherein the wave pattern of the sheets result therein that an air flow is on all lateral sides enclosed by liquid channels, see Fig. 2D. However, adequate air conditioning to acceptable temperatures and humidities (typically 22-25 °C and 35-50%RH) may also be achieved if the dehumidifier would lead to a temperature increase rather than a decrease. This is particularly because the calculations demonstrate that the system even cools more than needed (and ending up with a very low absolute humidity). Also the variation of the settings of the evaporative cooler and the dehumidifier allow that the conditions of the outgoing air are in the acceptable range.

Claims

A heat and mass exchange module (HMX module) comprising a plurality of sheets spaced apart and provided with a plurality of air channels for air flow and a plurality of fluid channels, the HMX module being a transverse flow module, wherein the air channels are located in a first flow direction extending between inlet and outlet, and wherein the fluid channels extend in a second, different flow direction, wherein a fluid channel is shaped as a layer of wicking material on a sheet, and arranged adjacent an air channel with an interchanging exchange surface, wherein first liquid channels for water flow and second liquid channels for the flow of liquid desiccant material are present, mutually arranged such that an air channel is provided between its inlet and outlet with a first exchange surface with a first liquid channel, and with a second exchange surface with a second fluid anal, wherein the second fluid channel is arranged downstream of the first fluid channel.

The HMX module according to claim 1, wherein the HMX module further comprises spacers arranged between the plates, shaping entrance areas, for the entrance of liquid, and closed areas where the water-ingot layer is compressed.

3. HMX module according to any of claims 1-2, wherein a first sheet is provided with a first and a second liquid channel on a first surface of the sheet.

The HMX module of claim 3, wherein the first and second fluid channels are embodied in a single water ingress layer.

The HMX module according to claim 4, wherein the water ingress layer is patterned such that an isolation zone is present between the first and the second fluid channel.

6. An HMX module according to any one of claims 1-2, wherein a first and a second sheet are arranged next to each other along the liquid channel, and each of the sheets is provided with a first surface on which a layer of water-wicking material is present, so that the first sheet carries the first fluid channel and the second sheet carries the second fluid channel.

7. HMX module as claimed in claim 6, wherein the first and the second sheets are mutually connected by connecting means which extend in a direction that is straight on the air duct, and which are provided with retaining means for keeping a predetermined distance from each other of the first sheets and of further retaining means for keeping the second sheets spaced apart at a predetermined distance.

8. HMX module according to one of the preceding claims, wherein the second fluid channels and their exchange surfaces each comprise a pattern of ridges and troughs, viewed along the second flow direction.

The HMX module of claim 8, wherein the second exchange surface is substantially flat viewed along the first flow direction.

The HMX module according to claim 8 or 9, wherein the first fluid channels and their exchange surfaces each comprise a pattern of ridges and troughs, viewed along the second flow direction.

11. HMX module as claimed in any of the foregoing claims, wherein the sheet comprises at least one stiffening protrusion that extends substantially parallel to and outside of the liquid channel.

12. HMX module according to any of the preceding claims, further comprising a first container for water and a second container for liquid desiccant material, the first and second container lying above the liquid channels.

The HMX module according to any of the preceding claims, further comprising third fluid channels, arranged downstream of the second fluid channels and upstream of the outlets of the air channels, with third exchange surfaces with the air channels.

14. HMX module according to claim 13, wherein the third liquid channels are adapted for transferring an additive to the air.

The HMX module according to claim 13, wherein the third liquid channels are arranged for flow of liquid desiccant material, and further comprise control means for driving the flow of liquid desiccant material at the second liquid channels and the third liquid channels, so that a flow profile being set up.

The HMX module according to any of the preceding claims 1-12, further comprising third fluid channels, arranged upstream of the first fluid channels, with third exchange surfaces with the air channels, wherein the third fluid channels are arranged for flow of liquid desiccant material.

An air treatment device comprising an air dryer and a direct evaporative cooler, wherein the evaporative cooler is upstream of the air dryer, and wherein the HMX module of any preceding claim is present as the dryer and the evaporative cooler.

The air treatment device of claim 17, further comprising an additional dryer arranged upstream of the HMX module.

Use of the heat and mass exchange module or the air treatment device according to one of the preceding claims for treating air.

The use of claim 19, wherein the air flow through the air ducts is set as a laminar flow.

Use according to claim 19 or 20, wherein the air flow is set to an air flow rate and wherein the fluid flow through the second fluid channels is set to a fluid flow rate, and wherein the mass flow ratio between the fluid flow rate and the air flow rate is at most 3.0 and preferably is in the range between 1.0-2.5.