U.S. patent application number 14/901399 was filed with the patent office on 2017-07-20 for heat and mass exchange module and use thereof.
The applicant listed for this patent is 2NDAIR B.V.. Invention is credited to Robertus Wilhelmus Jacobus HOLLERING, Ralph Theodorus Hubertus MAESSEN, Jan Paul Annie ROOSEN.
Application Number | 20170205155 14/901399 |
Document ID | / |
Family ID | 52706242 |
Filed Date | 2017-07-20 |
United States Patent
Application |
20170205155 |
Kind Code |
A1 |
HOLLERING; Robertus Wilhelmus
Jacobus ; et al. |
July 20, 2017 |
HEAT AND MASS EXCHANGE MODULE AND USE THEREOF
Abstract
A heat and mass exchange (HMX) module comprising a plurality of
plates in a spaced-apart arrangement and provided with a plurality
of air channels for air flow and a plurality of liquid channels for
flow of liquid, wherein a liquid channel is present on a surface of
a plate and is arranged adjacent to an air channel with a mutual
exchange surface, wherein the liquid channel is provided with a
width extending substantially perpendicular to a flow direction in
the liquid channel, further comprising means for setting a flow
profile over the width of the liquid channel.
Inventors: |
HOLLERING; Robertus Wilhelmus
Jacobus; (Voorburg, NL) ; MAESSEN; Ralph Theodorus
Hubertus; (Eindhoven, NL) ; ROOSEN; Jan Paul
Annie; (Eindhoven, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
2NDAIR B.V. |
Voorburg |
|
NL |
|
|
Family ID: |
52706242 |
Appl. No.: |
14/901399 |
Filed: |
September 30, 2015 |
PCT Filed: |
September 30, 2015 |
PCT NO: |
PCT/NL2015/050682 |
371 Date: |
December 28, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 13/06 20130101;
F28F 1/006 20130101; F28F 2240/00 20130101; F28D 5/00 20130101;
F24F 3/1417 20130101; F28F 2250/106 20130101; F28F 13/08 20130101;
F28D 2021/0038 20130101; F24F 5/0035 20130101; F28D 9/0025
20130101; F28F 2225/04 20130101; F28D 9/0062 20130101; F24F
2003/1458 20130101; F28F 27/00 20130101; F28F 9/0075 20130101; F28D
21/0015 20130101 |
International
Class: |
F28D 21/00 20060101
F28D021/00; F28D 9/00 20060101 F28D009/00; F28F 13/08 20060101
F28F013/08; F24F 3/14 20060101 F24F003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2014 |
NL |
2013563 |
Dec 16, 2014 |
NL |
2013988 |
Claims
1. A heat and mass exchange (HMX) module comprising a plurality of
plates in a spaced-apart arrangement and provided with a plurality
of air channels for air flow and a plurality of liquid channels for
flow of liquid, wherein a liquid channel is present on a surface of
a plate and is arranged adjacent to an air channel with a mutual
exchange surface, wherein the liquid channel is provided with a
width extending substantially perpendicular to a flow direction in
the liquid channel, further comprising means for setting a flow
profile over the width of the liquid channel.
2. The HMX module as claimed in claim 1, wherein the means for
setting a flow profile are configured such that flow of liquid in a
second area is reduced relative to flow in a first area, which
second area is located more closely to an outlet of the air channel
than the first area.
3. The HMX module as claimed in claim 1, wherein the means for
setting a flow profile comprise a first entry and a second entry to
the liquid channel, wherein the first entry differs from the second
entry.
4. The HMX module as claimed in claim 3, wherein the first and the
second entry have a different cross-sectional area.
5. The HMX module as claimed in claim 3, wherein the first entry is
coupled to a first container for liquid and the second entry is
coupled to a second container for liquid, and wherein the
containers are configured for containing liquid in different
states.
6. The HMX module as claimed in claim 5, wherein the states of the
liquid are chosen from different temperature, different
concentration, different pressure, different composition.
7. The HMX module as claimed in claim 1, comprising at least one
container for liquid overlying said plurality of plates, wherein
said liquid channels are provided with entry regions for entry of
liquid from the at least one container.
8. The HMX module as claimed in claim 7, wherein the flow profile
is set in that a density of the entry regions along the width of
the liquid channel and/or cross-sectional area of an entry region
varies along the width of the liquid channel.
9. The HMX module as claimed in claim 7, wherein the flow profile
is set in that entry regions for the liquid channel are arranged at
varying height in the at least one container.
10. The HMX module as claimed in claim 7, wherein the entry regions
are mutually separated by means of closed regions.
11. The HMX module as claimed in claim 10, wherein the liquid
channels are defined as layers of a wicking material onto the
plates, wherein said a top side of the layer of wicking material is
at least partially closed for liquid entry in the closed
regions.
12. The HMX module as claimed in claim 11, wherein the wicking
material is locally compressed in the closed regions.
13. The HMX module as claimed in claim 12, wherein a spacer is
present between a first and a second adjacent plate, said spacer
locally compressing the wicking material in the closed regions,
without compression of the wicking material in the entry
regions.
14. The HMX module as claimed in claim 1, wherein the air channel
is provided with an inlet and an outlet, such that the air flows in
a flow direction extending substantially parallel to the width of
the liquid channel.
15. An air-conditioner comprising the heat and mass exchange module
of claim 1.
16. Use of the heat and mass exchange module of claim 1 for heat
exchange between a fluid in the air channel and a liquid in the
liquid channel.
17. (canceled)
18. A method of conditioning air using a heat and exchange module
comprising a plurality of air channels and a plurality of liquid
channels, wherein a first air channel and a first liquid channel
have a mutual exchange surface, comprising the steps of: Applying
an air flow into the plurality of air channels, said air flow
flowing in a first flow direction; Applying a liquid flow into at
least a first section of said liquid channels, said liquid flow
flowing in a second flow direction different from the first flow
direction, therewith creating cross-flow; Wherein the air is
conditioned towards at least one predefined output parameter, in
that a flow profile of the liquid is set.
19. The method as claimed in claim 18, wherein the air flow is
applied so as to provide a laminar flow.
20. The method as claimed in claim 18, further comprising the step
of applying a second liquid flow into a second section of the
liquid channels.
21. (canceled)
22. The method as claimed in claim 18, further comprising the step
of sensing input parameters and/or output parameters of the air
flow to obtain sensing results, and using the sensing results for
controlling the first and/or the second liquid flow.
23. (canceled)
24. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 371 national stage application of PCT
Patent Application No. PCT/NL2015/050682, entitled "Heat and mass
exchange module and use thereof," filed on Sep. 30, 2015, which
claims priority to Dutch Patent Application No. 2013563 filed on
Oct. 2, 2014 and Dutch Patent Application No. 2013988 filed on Dec.
16, 2014, the entire contents of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] 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.
[0003] 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
[0004] 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.
[0005] For sake of clarity, the term `HMX-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.
[0006] 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.
[0007] 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.
[0008] 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
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.sup.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.sup.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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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 carry-over.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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: [0028]
applying an air flow into the plurality of air channels, said air
flow flowing in a first flow direction, and [0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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
[0035] These and other aspects of the air-conditioner module and
the method of air conditioning are further elucidated with
reference to following figures, which are not drawn to scale and
are merely diagrammatical in nature. Equal reference numerals in
different figures refer to identical or corresponding elements.
Herein:
[0036] FIG. 1 depicts a diagrammatical view of a first embodiment
of the heat and mass exchange (HMX) module;
[0037] FIG. 2a-d schematically depicts a sheet used in the HMX
module;
[0038] FIG. 3 shows a diagrammatical view of an implementation of
such a sheet;
[0039] FIG. 4 show schematical side views of the module with a
plurality of plates and distance holders according to one
embodiment of the invention;
[0040] FIG. 5a shows a schematical top view of a manifold in one
preferred implementation;
[0041] FIG. 5b shows a detail of FIG. 5a;
[0042] FIG. 6a-c shows side views of a plate and manifold according
to another implementation;
[0043] FIG. 7 shows a schematical side view of a HMX module
including a reservoir of liquid desiccant;
[0044] FIG. 8 schematically depicts a module with three containers
overlaying the plates;
[0045] FIG. 9a depicts a side view of an embodiment of a distance
holder configured to create a certain liquid flow profile;
[0046] FIG. 9b depicts a side view of a different embodiment of a
distance holder configured to create a certain liquid flow profile,
and
[0047] FIG. 10a-10c depict a top view of different embodiments of a
distance holder configured to create a certain liquid flow
profile.
DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS
[0048] FIG. 1 shows in a diagrammatical view an HMX module 100
according to a first embodiment of the invention. The HMX module
100 comprises a plurality of plates. Most preferably, the plates
are sheets 10, which comprise a carrier layer between a first and a
second layer of wicking material. The wicking material is more
suitably a non-woven textile material, such as cotton or rayon. The
first and second layer may further contain another material mixed
therewith, such as an engineering plastic. More details on the
sheet are specified in the non-prepublished application NL2013566
in the name of Applicant. However, alternative options are not
excluded in the context of the present invention. The sheets are
suitably substantially identical, so that the corrugation in the
sheets is repetitive and the distance between the sheets does not
change. The sheets are corrugated, as will be discussed with
reference to following figures. Due to the corrugation and its
orientation, the sheets, which are inherently flexible, are
sufficiently stiffened so that they can be arranged at a relative
short and uniform distance of each other without touching each
other. If the sheets touched each at a contact point, liquid would
get collected at the contact point. With air flowing along the
contact point, there would be a high risk carry-over. Each of the
sheets 10 is in the preferred implementation provided with layers
of wicking material 11 of both the front and the rear side of the
sheet. As shown in this FIG. 1, the layer of wicking material 11
may be subdivided into two lateral portions. However, this is not
deemed particularly beneficial or preferred. The HMX module 100 is
designed as a cross-flow module, such that the air and the liquid
desiccant run in mutually perpendicular directions through the HMX
module 100. It will be clear that an entirely perpendicular design
is deemed advantageous and most straightforward for manufacturing,
since the sheets can be of rectangular shape. However, this is not
deemed necessary. Alternative shapes, such as that of a
parallelogram, are not excluded. Preferably, the module is
configured such that the air channel extends laterally and that the
liquid channel of the liquid desiccant extends vertically. In this
manner, the liquid desiccant will flow within the HMX module 100
under the impact of gravity. The module as shown in FIG. 1
comprises tube connections 18, 19 for the provision and removal of
liquid desiccant. Their location is not deemed critical. Though not
shown explicitly, it is furthermore deemed beneficial that a
reservoir of liquid desiccant is present so as to overlie the
sheets 10 of the HMX module. The advantage thereof is that the
liquid desiccant may be distributed into and onto the layers 11 of
wicking material through apertures in a bottom of such reservoir,
and typically spread over the entire surface thereof. Therewith, it
is prevented that an initial flow of the liquid desiccant in a
lateral direction needs to be converted into flow in a vertical
direction.
[0049] The HMX module as shown in FIG. 1 may be used both as a
dehumidifier and as a regenerator module, but also as any other
module for use in an air-conditioning system, such as a cooling
module. In a dehumidifier 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.
[0050] FIG. 2a shows in a schematical view a sheet 10 for use in
the module of the invention. An air channel 20 is defined between
two sheets 10 and is indicated for sake of reference. It is
configured in a lateral direction. The air channel 20 is provided
with an inlet 21 and an outlet 22. Air in the air channel 20 will
first pass an accommodation area 23 then an active area 25 and
finally an outlet area 24. The active area 25 is configured to
enable exchange with the liquid channel 30 that is defined at the
surface of the layer of wicking material (on the sheet 10). It is
observed for clarity that the layer of wicking material may extend
beyond the active area 25. However, the active area 25 is further
defined by means of the entry regions of the liquid desiccant,
which are defined at the 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).
[0051] FIG. 2b shows schematically the generation of a module from
a plurality of sheets 10 and the air channels 20 in between of the
sheets 10. FIG. 2c shows a representative corrugation when seen
from the entry of the air channel 20. The arrow indicates the
direction of the liquid channel 30. The view of FIG. 2c is in fact
a cross-sectional view of the air channel. FIG. 2d shows a detail
from FIG. 2c. It is apparent from this FIG. 2c that in order to
prevent carry-over, the liquid desiccant needs to have sufficient
adhesion to the underlying surface. It preferably flows in a steady
state. Most suitably, the film onto the surface of the layer 11 of
wicking material (not shown in this FIG. 2c) is sufficiently thin.
The film thickness is thinned, in one preferred embodiment in
accordance with the invention, by using a specific manifold,
wherein the liquid desiccant first flows through a series of slots
and is thereafter laterally distributed to cover the area of the
liquid channel between the slots.
[0052] As shown in FIG. 2d, the distance between the sheets 10
varies somewhat due to the wave-shaped pattern of the sheets 10.
This variation in the distance is an important reason for arranging
the wave along the length of the liquid channel rather than along
the length of the air channel. If arranged along the length of the
air channel, the variation in distance would result in a temporary
narrowing of the air channel, resulting in an increase in flow rate
(followed by a reduction in flow rate). Such variations in air flow
rate would increase the risk of carry-over. By arranging the waves
along the length of the liquid channel, the air flows substantially
parallel to the waves. This turns out to be beneficial. In fact,
one may consider an air channel to be divided in a large number of
parallel portions, extending laterally and each having the same
length, The lateral portions will have slightly varying height
(i.e. distance between the sheet). However, the height of a single
lateral portion is substantially constant along its length, at
least within the active area, where exchange with the liquid
channel occurs. As a result, a single air drop travelling in a
single lateral portion will not experience any changes in height
within the active area. This therefore reduces a chance that the
air drop starts to move in a turbulent manner, and therewith may
interfere with the liquid channel to result in droplet formation of
liquid desiccant, i.e. carry over. Additionally, it was found that
this configuration has a lower pressure drop, as compared to an
alternative configuration.
[0053] In one implementation according to the 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.
[0054] In again one further implementation, the height of ridges
and valleys may be lower in a bottom part of the air channel than
in a top part. The liquid desiccant may gain velocity in the course
of flowing downwards. In a dehumidifier module, it additionally may
warm up. Therefore, the lower part is more sensitive to carry over.
This may be compensated by less steep ribbons and valleys, to
prevent any ejection of single droplets of liquid desiccant.
[0055] FIG. 3 shows in a diagrammatical view the sheet 10 more
specifically. Herein, it is indicated that the sheet 10 is provided
with ridges 12 and valleys 13, in alternating arrangement. The
sheet 10 suitably has a shape of a wave, wherein the ridges 12
extend into a first direction and the valleys 13 extend into the
opposite direction. With these ridges 12 and valleys 13 a
corrugated surface is created that is deemed positive for the
necessary strength of the sheet 10, without increasing risk for
carry-over. More particularly, the wave may be a sine wave.
Moreover, the edges of the sheet 10 are at least substantially
planar. This facilitates assembly of the sheet 10 into the module,
particularly by means of a distance holder as will be explained
with reference to further figures. In the shown embodiment, the
ridges 12 and valleys 13 extend parallel to the width of the liquid
channel 30, such that the liquid channel 30 in fact includes a
curved trajectory. However, the air channel 20 is substantially
planar over the width of the liquid channel, i.e. in the area where
the liquid channel and the air channel have an interface. This has
the advantage of minimum disturbance of air flow. As a consequence,
carry over can be prevented, at least substantially, while the
sheets are very thin. In this manner, a large packing density of
sheets per unit volume is achieved, resulting in a large exchange
area between the air channels and the liquid channels. In tests
with a preliminary version of the heat and mass exchange module
according to the invention, wherein the air flow was laminar and a
liquid channel wave-shaped, no carry-over was found to occur. The
sheet 10 is suitably created in a multistep process, comprising the
provision of the carrier and one or more layers of wicking material
into a provisional laminate and thereafter thermoforming of the
laminate. In the course of the thermoforming, the provisional
laminate is suitably bond to form the final laminate. However, the
lamination process may also preceed the thermoforming process.
[0056] FIG. 3 furthermore shows the presence of spacers 26, which
preferably have a stripwise extension and are assembled to a
plurality of sheets 10. The spacers 26 are arranged within the
accommodation area 23 and the outlet area 24, which are most
preferably substantially or completely planar.
[0057] The sheet 10 shown in FIG. 3 furthermore comprises
stiffening protrusions. These are arranged outside the active area
25, in which the pattern of ridges 12 and valleys 13 is arranged,
and effectively within the accommodation area 23 and the outlet
area 24. In the present configuration, a first and a second
stiffening protrusion 15 are defined, both extending in this
configuration along the width of the air channel (i.e. along the
width of the active area 25 as shown in FIG. 2). While a longer
stiffening protrusion is deemed beneficial, it is not excluded that
this long protrusion is subdivided into two or more shorter
protrusions. Moreover, more protrusions could be present,
particularly in the accommodation area and in the outlet area. This
is however neither deemed necessary nor deemed advantageous. Both
protrusions 15 have the same dimensions in this configuration.
Again, this may be useful, so as to obtain a design that is most
symmetrical, but it does not appear necessary.
[0058] FIG. 4 shows the HMX module 10 more detail, and particularly
the connection to an overlying reservoir 50. The sheets 10 are
herein kept together by means of strips 45 that are provided with a
plurality of clamps 57, present at side faces of the sheets 10. The
strips 45 are designed so as to create entry channels, through
which liquid desiccant material can flow in and onto a surface of
the layer of wicking material 11. The strips 45 are more
particularly embodiments of distance holders defining and holding a
distance between adjacent sheets 10 and--in at least one
embodiment--creating entry regions and closed regions, as will be
explained with reference to FIGS. 5a and 5b. Side walls 61 are
present at the outside, so that the assembly of sheets and strips
may be fixed and contained, particularly by means of a pressing
operation. O-rings 62 may be present to avoid leakage of liquid
desiccant along the walls 61. Although not shown, it would be
perfectly possible to insert a bottom of the reservoir in the form
of a sheet with apertures. The clamps 57 and particularly defined
for holding a first and an adjacent second distance holder and an
intermediate plate together. Such clamping means are deemed
advantageous in the assembly of the holders and the plates.
Furthermore, such means may further stabilize the assembly during
use. The clamping means may be a monolithic portion of the distance
holder. Alternatively, the clamping means may be connected to the
distance holder, for instance in that a clamping means further
comprises a pin or other protruding element for insertion into a
corresponding hole in the distance holder, or vice versa, or
another lock & key combination.
[0059] The reservoir 50 is suitable for use as a first container in
accordance with the invention. As shown in this FIG. 4, the
reservoir 50 is provided with a first inlet 51, with a second inlet
52 and with a stirrer 53. According to one embodiment of the
invention, the first inlet 51 is used for liquid desiccant material
that has been regenerated directly. The second inlet 52 is used for
liquid desiccant material that has been regenerated separately and
is provided from a second container (not shown in this Figure). The
first and the second inlet 51, 52 may be provided with switchable
valves so as to vary the mutual ratio of the first flow through the
first inlet 51 and the second flow through the second inlet 52. In
the shown embodiment, the second inlet 52 is configured for a
solution, dispersion or suspension. In one further implementation
(not shown), the second inlet may be configured as a plurality of
inlets across the side wall 61 or a top side of the reservoir 50.
This may contribute to distribution. The stirrer 53 is one
implementation of mixing means. Rather than using a stirrer (for
instance mechanical or magnetic), mixing may further be achieved by
designing the reservoir such that the flows are mixed together. In
one further embodiment, the first flow and the second flow
originate from different sources. For instance, in an example
wherein the liquid is liquid desiccant and the module is a
dehumidifier, the first flow may originate from a local regenerator
module, and the second flow may originate from a central
regenerator module and/or a liquid desiccant storage, that is for
instance obtained by regenerating liquid desiccant with rest heat
coming from a generator, such as a diesel generator. This is
further disclosed in the non-pre-published Dutch application
NL2013586 in the name of applicant, which is included herein by
reference.
[0060] FIG. 5a and FIG. 5b show a top view of the manifold 40 as
shown in FIG. 4. Herein the strip 45 is provided with a plurality
of contact surfaces 47 that are in contact with the sheet 10, and
particularly the layer 11 of wicking material present thereon. The
contact surfaces 47 are mutually separated by means of cavities 48.
It will be apparent that the number of contact surfaces 47 may be
varied. Preferably, the contact surfaces 47 and the cavities 48 are
present in alternating and repetitive order. The contact surface
and the cavity each have a size for instance in the range of
0.3-3.0 cm. However, where the wicking material should be closed,
i.e. outside the liquid channel, there will not be any cavity 48.
More preferably, the contact surfaces 47 on opposite sides of the
strip-shaped manifold are aligned. This is beneficial to obtain an
assembly that is sufficiently pressed together. A very advantageous
feature of such an assembly is that the layer 11 of wicking
material that is present between the contact surface 47 and the
carrier 10 is able to absorb manufacturing tolerances and also
variations in dimensions of the other materials due to decrease and
increase in temperature.
[0061] Furthermore, the distance holder may be provided with a
surface of a hydrophobic material. The advantage of a distance
holder with such a surface is that the polar liquid desiccant
comprising a salt solution (i.e. a ionic solution) is not attracted
by but rather repulsed from the distance holder. As a consequence,
the surface of the distance holder will normally not be wetted by
the liquid desiccant, and undesired distribution of liquid
desiccant is prevented. Such a hydrophobic material may be a
coating of a specific material, for instance a polymer material
such as a polyolefin, a halogenated material, but it may be
alternatively a surface layer of a material that is made
hydrophobic. Silica for instance, can be hydrophobic or hydrophilic
depending on its surface. The material of the surface may be equal
or different to the base material of the distance holder.
Preferably, the distance holder is based on one or more polymer
materials, and is for instance prepared by a moulding technique,
even though alternative manufacturing techniques known in the field
of polymer engineering are not excluded. It is deemed suitable that
the distance material is based on the same polymer material as the
plates are, for instance a polyolefin. This is deemed preferable in
order to avoid as much as possible issues with respect to thermal
cycling, i.e. differential thermal expansion leading to stress and
strain with the risk of deformation and/or crack formation.
[0062] The operation of this strip for the distribution of liquid
desiccant is more specifically and still schematically shown in
FIG. 5b. In fact, due to the pressing action onto the assembly of
strips 45 and sheets 10 as shown in FIG. 4, the layer 11 of wicking
material will be compressed opposite the contact surfaces 47.
However, the layer 11 will not be compressed at the location of a
cavity 48. This compression can be arranged that the layer of
wicking material is effectively closed opposite a contact surface
47, thus forming a closed region 39. At the location of a cavity
48, the layer 11 of wicking material is not closed. This region
thus constitutes an entry region 38, where liquid desiccant can
enter from the reservoir 50 (as shown in FIG. 4) into the layer 11
of wicking material.
[0063] In the FIGS. 5(a) and 5(b), the distribution of the entry
regions 38 is uniform over the length of the sheets 10. However, it
is observed that this distribution may be varied so as to obtain a
most efficient operation of the module, while minimizing risk of
carry over. For instance, it would be preferable that no entry
regions 38 are present in an area not overlying the liquid channel
30, more particularly neither the portion overlying the
accommodation area 23 nor the portion overlying the outlet area 24
(shown in FIG. 2a).
[0064] Furthermore, in the shown Figures, the cavities 48 all have
substantially the same size. However, these cavities 48 may differ
in size. For instance, the depth may vary, resulting in variations
in the extent of compression of the layer 11 of wicking material.
Clearly, a larger degree of compression results in less open pores
and thus a lower flow rate of liquid desiccant at such
location.
[0065] Moreover, the height of the strip 45 may be varied, and/or
the size of the contact surfaces 47 and depth of the cavities 48
can be varied. With such variations an aspect ratio of the entry
region 38 can be specified. Effectively, an entry region 38 is to
be considered as an entry channel. The flow of liquid desiccant
will not be merely in the vertical direction but also sidewise. In
fact, the area of wicking material below a closed region 39 is to
be filled with liquid desiccant entering through the entry region
38.
[0066] FIG. 6a-c discloses again an alternative implementation of
the distribution system in accordance with the invention. Herein
the sheets 10 comprise slits 16. FIG. 6a shows a schematical side
view of a sheet 10. FIG. 6b shows a schematical front view of the
sheet 10. FIG. 6c shows an assembly of a plurality of sheets 10
with strips 45. In accordance with the present implementation, the
strips 45 extend along the sheets 10 and suitably have a uniform
width. The sheets 10 are provided with slits 16. The slits 16 in
this figure are closed. That seems beneficial for the stability of
the sheet, but is not strictly necessary. Extensions 14 are present
between the slits 16.
[0067] As shown in FIG. 6(b), and corresponding to the situation
shown in FIG. 5(b), where the strip 45 is in contact with the
sheet, i.e. at an extension 14, a contact surface is present. This
results in closing off the layer 11 of wicking material, and a
closed region 39. At the location of a slit 16, no contact is
present, resulting in an entry region 38.
[0068] FIG. 7 is similar to the view of FIG. 6c. The figure
additionally shows the presence of a reservoir 50 of liquid
desiccant, present between the walls 61 that also press the strips
45 and the sheets 10 together. Although not shown, it will be
apparent to the skilled person that further tools and means may be
present to maintain this assembly together.
[0069] FIG. 8 shows a module according to the present invention
overlaid with a first container 71, a second container 72, and a
third container 73. In the image, the three containers are embodied
as a vessel subdivided into three sub-containers, with partitions
in between. Alternatively, individual containers attached to one
another or simple arranged adjacent to one another can also be
employed. In the embodiment with one partitioned vessel, the
partitions are preferably impermeable to the liquid desiccant.
Fewer or more containers may also be used.
[0070] In operation, the first, second and third container 71-73
are typically provided with liquid, such as liquid desiccant that
will flow into the liquid channels 30 of the module 10 from the
containers 71-73. One advantage of the embodiment with a plurality
of containers 33-35 is that a liquid in the first container 71 may
be in a different state than a liquid in the second or third
container 72, 73, or vice versa. The term `state` of a liquid
refers in the context of the present application to at least one
physical or chemical property of the liquid that is relevant for
the behaviour of the liquid, particularly the liquid desiccant,
during dehumidification of air or during regeneration of the liquid
desiccant. By definition, a liquid desiccant material, which is a
solution of liquid desiccant into one or more solvents, and usually
an aqueous solution, has a concentration, and is held at a
temperature, a pressure. Moreover the composition of the material
may be varied, for instance with respect to the salt composition of
the material. For instance, the material may contain LiBr in
addition to LiCl (more precisely bromide and chloride anions in
addition to the lithium cations). The material could also contain
KCl in addition to LiCl (more precisely other alkali cations, such
as potassium or sodium, in addition to the lithium cation and the
chloride anion). It will be understood that the ratio of potassium
and lithium cations may have an impact on the dehumidifying
potential of the liquid desiccant material. The term `state`
furthermore refers to flow properties of the liquid desiccant
material, such as the volume of liquid in a container 71-73,
and--typically related thereto--the liquid pressure exerted by said
volume onto an underlying entry into the liquid channel.
[0071] The various properties may be either similar or different.
In an embodiment, the liquid in the first, second and third
container may have the same temperature, concentration, volume and
composition but a different pressure. In another embodiment, the
first, second and third containers may be configured to set
different temperatures and volumes for the liquid they contain,
while the other properties are kept similar. Many other
configurations are possible, where any combination of one or more
properties can be varied across the containers.
[0072] Although not shown in FIG. 8, means for define the state of
the liquid in a container 71-73 may be present. Such means are for
instance arranged upstream of the container 71-73, so as to ensure
that liquid entering a container 71-73 is in a predefined state.
Such an arrangement upstream and optionally external to a module is
for instance deemed beneficial to provide a mixture with a first
composition to the container via an inlet.
[0073] Alternatively or additionally, such means may be arranged in
or to a container 71-73, such that a desired state of the liquid is
achieved in such container 71-73. Such an internal arrangement is
for instance deemed beneficial to apply a certain pressure.
[0074] For instance, a container 71-73 may have a plurality of
inlets for the provision of liquid desiccant material at different
concentrations. By setting an inflow ratio for the plurality of
inlets, the concentration of the liquid desiccant material may be
varied. One implementation hereof for a dehumidifier module is for
instance described in the non-prepublished application NL2013586 in
the name of application, that is herein included by reference.
According to said implementation, regeneration of liquid desiccant
material occurs not merely by means of a closed circuit through a
regenerator module, but also by means of adding liquid desiccant
material from a storage container. The said added liquid desiccant
material may be present in a higher concentration (lower humidity
content) than the liquid desiccant material regenerated in a
regeneration module. Hence by setting the inflows of liquid
desiccant material from the storage container and from the
regenerator module the concentration of the liquid desiccant
material in the containers may be tuned. The concentration of the
liquid desiccant material in the first, the second and/or the third
container 71-73 may therefore be mutually different. It could
alternatively be equal, if so desired.
[0075] In the configuration shown in FIG. 8, the first container 71
is closer to the inlet 23 of the air channel than the second
container 72. In one advantageous operation mode, the pressure is
configured such that the liquid pressure at the level of the entry
region is higher in the first container as compared to the liquid
pressure at the level of the entry region below the second
container. This may ensure that the thickness of the liquid layer
in a first section of the module below the first container is more
significant than the thickness of the liquid layer in a second
section of the module below the second container. As the air flow
20 may displace some of the liquid laterally along the direction of
air flow, providing more liquid in a first section may compensate
for a disparity that would otherwise have been created.
Furthermore, in this operation mode, due to the higher pressure at
the entry region, the velocity of liquid flow in the first section
of the model may also be higher than the velocity of liquid flow in
the second section, which may lead to the liquid flow being less
sensitive to displacement by the air flow.
[0076] Alternatively or additionally, the first container 71 closer
to the inlet 23 of the air channel than the second container may
also contain a higher volume of liquid desiccant relative to the
second container. This may be either to provide a higher pressure
and/or to provide a higher supply of liquid.
[0077] In an implementation, each container 71, 72, 53 is provided
with a separate entry 81, 82, 83 to the liquid channel. These
entries may take the form of a manifold, of which different types
are feasible. The manifold may comprise a porous material, through
which the liquid desiccant may flow downwards. The manifold may
alternately comprise a body of for instance rigid material with
apertures. The manifold may also comprise a combination of a rigid
body and a layer of porous material.
[0078] In general, the separate entries from the separate
containers to the liquid channel may be entries of a similar type;
however, this is not necessarily so. Furthermore, the entries may
be configured to be suitable for the properties (pressure,
temperature, concentration, composition, etc.) of the liquid
desiccant in the associated container.
[0079] The containers 71, 72, 73 as depicted in FIG. 8 have roughly
the same size and cross-sectional area. However, this is not
strictly necessary. Rather, it may be advantageous to use
containers that differ in size. For instance, the first container
may have a larger cross-sectional area than the second container,
which may in turn have a larger cross-sectional area than the third
container. Conversely, the first container may have a smaller
cross-sectional area than the second container, which may in turn
have a smaller cross-sectional area than the third container. The
skilled person will be able to determine which set-up is most
appropriate to yield a certain desired liquid flow profile.
[0080] FIG. 9a depicts a specific and advantageous implementation
of elements at the entry of the liquid channels that can be
employed to create a liquid flow profile. In this implementation,
the particular element is a distance holder that extends along a
width of the liquid channel between a first and a second sheet (or
plate). This distance holder can be used both with a set-up with
several containers or with a set-up with only one container. It can
furthermore be used also if the liquid supply is achieved in other
ways than with a container overlaying the module.
[0081] Distance holders may create a liquid flow profile in several
ways. The embodiment depicted in FIG. 9a is a distance holder with
a different height 93 in a first portion 90 than the height 94 of a
second portion 91 of the distance holder, with a slope 92 in
between. The particular slope in the figure is merely an example,
and slopes of various widths and angles may be used according to
the desired flow profile.
[0082] Depending on the material, structure, configuration and/or
shape of the distance holder, the higher portion 90 of the distance
holder may lead to a higher flow rate (usually defined in units of
kg/s) of liquid desiccant. Accordingly, the higher portion of the
distance holder may be arranged at the side of the module
corresponding to the air inlet 23.
[0083] Typically, a distance holder with a variation in height
along the width of the liquid channel fixes a predefined flow
profile, so that it is not need to provide active control of a
volume in at least one of a plurality of overlying containers.
Rather the flow profile is obtained inherently. Clearly, it is also
feasible with such built-in flow profile to adjust the settings in
the one or more overlying containers to compensate the built-in
flow profile and obtain again a rather flat flow profile.
[0084] In a further implementation, a single module contains a
first type and a second type of distance holders. For instance, the
first type has a varying height along the width of the liquid
channel, whereas the second type has a flat height (substantially
no variation in height) along the width of the liquid channel. In
this manner, the overall flow profile may be adjusted, i.e. the
effect of the varying height of distance holders may be reduced, or
by using various types with different variations, a more specific
flow profile (on average through the module) may be created.
[0085] The depicted distance holder has one step from a high
portion 90 to a low portion 91. However, other embodiments may also
have three or more different levels with steps in between. In a
first embodiment, these portions get lower monotonically. In a
second embodiment, these portions may get higher monotonically. In
further embodiments, the heights of the portions may go up and down
along the width of the distance holder, where the width is defined
as the size in the direction parallel to the air flow.
[0086] A different embodiment of a distance holder configured to
occasion a liquid flow profile is depicted in FIG. 9b. In this
embodiment, the distance holder has a slope over its entire width.
As with the embodiment depicted in FIG. 9a, the higher end 93 may
either by at the side of the module corresponding to the air inlet
23 or at the side of the module corresponding to the air outlet 24,
according to the material, structure, configuration and/or shape of
the distance holder, generally to assure that there is more liquid
throughput at the side of the module corresponding to the air inlet
23, to compensate for any lateral movement occasioned by the air
flow 20 and thus prevent accumulation of liquid desiccant material
at the side closest to the air outlet.
[0087] While the depicted distance holder is shown to have a
constant slope, this need not be the case, and varying slopes may
be used. Neither the height or the slope need necessarily change
monotonically, though in many cases they will.
[0088] In FIG. 10a, a different design for a distance holder
configured to generate a liquid flow profile is depicted.
[0089] These types of distance holders function in the following
manner. A plurality of contact surfaces 47 is brought into contact
with the sheet 10, and particularly with the layer 11 of wicking
material present thereon. The contact surfaces 47 are mutually
separated by means of cavities 48. Due to the pressing of the
distance holder on the sheets 10, the layer 11 of wicking material
will be compressed opposite the contact surfaces 47. However, the
layer 11 will not be compressed at the location of a cavity 48.
This compression can be arranged that the layer of wicking material
is effectively closed opposite a contact surface 47, thus forming a
closed region. At the location of a cavity 48, the layer 11 of
wicking material is not closed. This region thus constitutes an
entry region, where liquid desiccant can enter from the reservoir
50 (as shown in FIG. 4) into the layer 11 of wicking material.
[0090] In FIG. 10a, in a first region of the distance holder the
cavities 48 are spaced at a certain first distance 54, while in
another region of the distance holder the cavities are spaced at a
second distance 55, where the distance 55 is larger than the
distance 54. The distance between two subsequent cavities 48 may
also vary gradually along the length of the distance holder, in
most cases monotonically increasing or decreasing. The spacing may
also go from a first spacing to a second bigger spacing to a third
even bigger spacing, etc.
[0091] In an advantageous implementation the cavities 48 are spaced
closer together at a side of the distance holder closest to the air
inlet 23 than they are at a side of the distance holder closest to
the air outlet 24. In this manner, the number of entries will be
higher on the side closest to the air inlet than on the side
closest to the air outlet. This compensates a possible lateral
displacement of the liquid flow 30 due to the air flow 20 so that
any accumulation of liquid desiccant material at the side closest
to the air outlet is prevented.
[0092] In FIG. 10b, the cavities 48 are equally spaced. However,
their depth varies, from a first depth 56 in a first portion to a
second depth 58 in a second portion which is larger than the first
depth 56, and to a third depth 59 in a third portion which is
larger than the second depth 58. A different embodiment may employ
two different depths, or more than three different depths. The
depths will in most cases vary monotonically, but this need not be
the case.
[0093] In a portion in which the depth is bigger, the entries may
be bigger as well, and more liquid may pass through the entry per
unit time. It may therefore be advantageous to position the portion
with deeper cavities 48 closest to the air inlet 23, such that
possible lateral displacement of the liquid flow 30 due to the air
flow 20 is compensated for so as to prevent accumulation of liquid
desiccant material at the side closest to the air outlet.
[0094] FIG. 10c shows another embodiment of a distance holder. In a
first portion of the distance holder, at least one cavity may have
a first width 84. In a second portion of the distance holder, at
least one cavity may have a second width 85 larger than the first
width 84. In a third portion of the distance holder, at least one
cavity may have a third width 86 larger than the second width
85.
[0095] While in the depicted embodiment the widths of the cavities
increases monotonically, this need not be the case. A wider cavity
will occasion a wider entry to the liquid channel, and more liquid
desiccant may pass though. Therefore it may be advantageous to
position the portion of the distance holder with the widest
cavities toward the side of the module where the air inlet can be
found, so as to compensate for possible lateral motion of the
liquid flow 30 which may be occasioned by the air flow 20, and thus
prevent accumulation of liquid desiccant material at the side
closest to the air outlet.
[0096] The module in accordance with the invention may be operated
in various operation modes. This will now be elucidated for the
implementation shown in FIG. 9. However, it equally applies to
other implementations, such as the embodiment shown in FIG. 8 and
in FIG. 10a-c
[0097] In a first operation mode, a lower flow rate of liquid
desiccant is provided at the side of the module corresponding to
the air inlet, so as to compensate for the possible lateral
movement of liquid desiccant occasioned by the air flow 20.
[0098] In a further operation mode, that may be used in situations
for enhanced operation, the flow rate along the width of a liquid
channel may be substantially equal. This may give a somewhat higher
risk for carry-over. However, it has been found in preliminary
investigations that a temporary increase in liquid flow close to
the outlet of the air channel does not result in substantial
increase of carry-over risk. It is believed that the carry-over
risk occurs due to accumulation of liquid desiccant in close to the
outlet of the air channel. However, it requires some time before
such accumulation occurs.
[0099] In again a further operation mode for enhanced operation, it
may be that the liquid flow in the second and third part of the
liquid channel is substantially identical, while the liquid flow in
the first part is even higher.
[0100] In a further operation mode, the supply of liquid desiccant
into the container is varied over time, and particularly in a
repetitive pattern. This creates variation in the flow over time,
and in view of the built-in height difference in the distance
holder also a flow profile along the width of the liquid channel.
For instance the volume in the container can be specified to be at
a maximum every second minute and at a minimum every other minute.
Such variations over time appear beneficial to ensure that the
liquid flow not merely on the surface of the layer of wicking
material but also sufficiently through the layer. Moreover, such a
variation in time of the liquid flow is deemed advantageous for a
limited reduction of the humidity content of the air. While the
maximum liquid flow will create a relatively dry air, the minimum
air flow will result in air with a higher humidity content.
However, these air flows may be mixed subsequently, for instance in
a separate mixing vessel. Alternatively, an air-conditioning
apparatus may contain both a first and a second dehumidifier
module, each with liquid flow varying in time. Preferably, the
liquid flows of the first and second dehumidifier module are
provided with a mutually different phase, i.e. when the liquid flow
through the first module is at a maximum, the liquid flow through
the second module is at a minimum, or at least not at a maximum,
and vice versa.
[0101] The liquid flow profile may also be varied according to
changing circumstances. The air flow may change in time, in an
either discrete or continuous 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.
[0102] In other embodiments, the liquid flow profile may be such
that the liquid flow is substantially absent over a portion of the
module, for instance if the humidity is detected to be low or if
the air flow is relatively modest. This may conserve resources and
contribute to the efficiency of the device.
[0103] The liquid flow may furthermore be varied both according to
changing circumstances as well as periodically, combining the
advantages of the two embodiments described above.
[0104] For sake of clarity, the term `portion of liquid channel(s)`
in which liquid flow is varied, is understood to refer to a portion
of a single channel. If the module comprises a plurality of liquid
channels, the variation suitably occurs in all or at least a first
subset of the liquid channels. Where reference is made to liquid,
this relates more particularly to liquid desiccant material, such
as an aqueous salt solution, for instance containing a Li-salt, for
instance LiCl.
[0105] It will be clear to the skilled person that the techniques
illustrated by the figures can be combined. A certain distance
holder may have varying heights, varying distances between
cavities, varying depths of cavities, and/or varying cavity widths.
Furthermore, other alternative means of setting a flow profile,
such as for instance variation in the shape of the cavities or in
the thickness of the distance holder, are not excluded. Finally,
all these possible distance holders can be used both in embodiments
where one container is present and in embodiments where several
containers are present. They may also be used in embodiments where
the liquid supply does not employ containers overlaying the
module.
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