This invention relates to heat transfer devices. In particular, but not
exclusively, this invention relates to heat transfer devices for heating or
cooling edible or drinkable materials.
The development of efficient and "environmentally-friendly" technologies
for cooling drink and food products has been sought after. The trend
towards more leisure time being spent in locations away from home is on
the increase as the range and availability of outdoor entertainments and
pastimes increases.
Advances have been made in developing cooling devices, including cold
boxes, thermoelectric picnic coolers and portable chilling units.
However, these units have the disadvantages of being bulky and
expensive. One device, known as the "chill can" has been subjected to
International restrictions owing to environmental concerns over its use.
Furthermore, little attention has been paid to the development of heating
devices for heating drinks and food products.
A lot of work has already been done in the area of self-cooling cans/self-heating
cans (or other containers). In order to understand fully the
remainder of this application the reader is now directed to read
PCT/GB99/00255 (the contents of which are hereby incorporated into this
application by reference), and to read: US 4 978 495, US 5 168 708,
US 736 599, WO 9 202 770, US 4 771 607, US 4 752 310, EP 0 726 433,
US 4 126 016, US 5 088 302, US 5 083 607, and US 5 054 544, and our
own earlier patent applications GB 2 329 461, GB 2 329 392, GB 2 329
459 and GB 2 333 586. Reading these documents, especially our own
patent applications and PCT/GB99/00255, will assist in determining the
full disclosure of the text and drawings that follow.
According to one aspect of the invention there is provided a heat transfer
device containing a refrigerant, and said device further including
operative means for allowing transfer of the refrigerant from a first region
of the device to a second region of the device and means to drive said
transfer of the refrigerant, thereby transferring heat from said first region
to said second region, such that heat can be transferred to or from a
material to be heated or cooled.
Preferably, the transfer of said refrigerant occurs by evaporation of the
refrigerant. However, any other change of phase of a material may be
used. For example sublimation of a solid to a gas may be used. The use
of a phase change is advantageous because of the heat that must be
absorbed to achieve this phase change.
Desirably, the means to drive said transfer of the refrigerant comprises a
refrigerant take up agent to take up said refrigerant. Thus, heat can be
extracted from the material by transfer of the refrigerant and heat is given
out by the take up agent when the refrigerant is taken up thereby. The
take up agent may be in the form of an adsorbent or absorbent.
According to another aspect of this invention there is provided a heat
transfer device containing a refrigerant and a refrigerant take up agent,
and said device further including operative means for allowing
evaporation of the refrigerant, whereby the take up agent takes up said
evaporated refrigerant such that heat absorbed on evaporation of the
refrigerant is evolved at the take up agent to enable heat to be transferred
to or from a material to be heated or cooled.
Advantageously, the device is of a suitable size to be inserted in, or
arranged in, or installed, or arranged around, a vessel suitable for holding
a beverage or a foodstuff. Examples of such a vessel include beverage
cans, bottles, cups, kegs, casks, and the like.
Preferably, the taking up of the refrigerant occurs at a first region of the
device and evaporation of the refrigerant by the take up agent occurs at a
second region.
The take up agent may be an adsorbent or an absorbent. Thus, heat of
adsorption or absorption is given out when the evaporated refrigerant is
adsorbed onto the adsorbent or absorbed by the absorbent and the heating
or cooling of the material is enhanced.
Desirably, the device comprises a first part for the take up agent and a
second part for the refrigerant. The first part is preferably at a lower
pressure than the second part before the operative means is operated. An
advantage of having the lower pressure in the first part is that evaporation
of the refrigerant is enhanced once the pressures have been allowed to
equalise.
In one embodiment, the second part may be at ambient pressure and the
first part may be evacuated. In another embodiment, the second portion
may be at above ambient pressure and the first part may be at ambient
pressure. Alternatively, both the first and second parts are evacuated.
The skilled person will appreciate that the rate of evaporation is affected
by the physical conditions surrounding the system in which evaporation is
occurring. That is the pressure, temperature, temperature gradients. etc.
will all affect the evaporation rate. Providing a low pressure environment
may be advantageous because of a consequent reduction in the temperature
at which evaporation of the refrigerant occurs.
In one embodiment the refrigerant may be water and the pressures in the
first and second parts (once the operative means has allowed evaporation
of the refrigerant) may be such that the water boils at substantially room
temperature. Such a structure is clearly advantageous because boiling of
the water will increase the rate of evaporation of the refrigerant which
will speed the rate of cooling or heating of the material.
The first and second parts are advantageously isolated from each other,
providing a structure in which the pressures can be maintained before
activation of the operative means.
The operative means may be adapted to provide communication between
the first and second parts on operation thereof. The first and second parts
may be permanently attached to each other, for example they may be
integral with each other. Alternatively, the first and second parts may be
initially separate from each other to be attached together to allow
communication therebetween on operation of the operative means.
The device may comprise a first element, which may be in the form of a
first wall, on which the take up agent can be arranged, and a second
element, which may be in the form of a second wall, to provide dispersion
of the refrigerant.
The first element may be substantially cylindrical in shape, but it may be
of any other suitable shape. The second element may be cylindrical in
shape and dispersal means may be provided on said second element to
disperse the refrigerant around the second element.
The dispersal means may comprise wicking means. The first and second
elements are desirably spaced from each other to allow heat transfer from
one to the other.
In one embodiment, the first part includes the second element and the
second part may be in the form of a container adapted to release
refrigerant into the second element on operation of the operative means.
In another embodiment, the second part may comprise the second element.
The operative means may comprise a release member adapted to provide
an aperture in the second part to release said refrigerant or it may
comprise an elongate rod having at one end thereof a substantially
cylindrical member (the elongate rod and the cylindrical member may be
thought of as a release means).
A membrane may be provided between the first and second parts to isolate
the first part from the second part. The membrane may be formed of a
metallic foil, for example aluminium foil. Alternatively, the membrane
may be formed from a plastics material. Indeed, the membrane may be
formed from any material which is compatible with the materials of the
device.
A membrane compromising means (which may be the same as the release
member) may be provided, adapted to pierce, rupture, cut or otherwise
compromise said membrane so connecting said first and second parts.
The operative means may comprise the membrane compromising means.
The skilled person will appreciate that the membrane compromising means
should be adapted to allow communication between the first and second
parts and that should the membrane compromising means simply pierce
the membrane the membrane may still substantially provide a seal between
the first and second parts i.e. perhaps sealing to the membrane
compromising means. Therefore, the membrane piercing means may be
adapted, in use, to retract slightly after compromising the membrane.
This retraction may be provided by way of a cam or other similar
structure. Alternatively, or additionally, the membrane compromising
means may comprise a vent means, which may be duct, or hole, etc. to
allow communication between the first and second parts once the
membrane has been compromised.
The cylindrical member preferably has an open end arranged adjacent the
membrane, whereby operation of the operative means pushes the open end
of the cylindrical member into engagement with the membrane and pierces
the membrane.
The release member may be in the form of a spike or pin to pierce the
second part.
The second part may be formed of a suitable plastics material, and may be
in the form of a bubble.
Where the device is to be used to cool the material, the second element is
advantageously adapted to be arranged adjacent, or in contact with, said
material, and the first element is arranged such that heat transfer thereto
can be dissipated to the atmosphere.
Where the device is to be used to heat the material, the first element is
advantageously adapted to be arranged adjacent, or in contact with, said
material and the second element is arranged such that heat can be
extracted from the atmosphere to be transferred to the first element
thereby heating said material.
Preferably, at least the first part is in the form of a tube or pipe, although
both first and second parts may be generally in the form generally of a
tube or pipe. The first part or both first and second parts may be in the
form of an elongate tube, wherein the first part constitutes a first portion
of the tube and the second part constitutes a second portion of the tube.
The skilled person will appreciate that the tube or pipe is intended to
cover embodiments wherein the cross section is not circular and is for
example square, triangular, elliptical, etc.
In one embodiment, the first part constitutes a double skin of a vessel
holding the material to be heated or cooled, the double skin comprising
inner and outer walls.
In another embodiment, the device is in the form of a sleeve having said
inner and outer walls, the said sleeve being adapted to receive a vessel,
for example a bottle or a can to be heated or cooled. Preferably, where
the material is to be heated, the inner wall comprises said first element
and the outer wall comprises said second element. Preferably, where the
material is to be cooled, the outer wall comprises the first element and the
inner wall comprises the second element.
In a further embodiment, the device is configured to be arranged inside a
vessel for heating or cooling the material therein. The device may be
manufactured separately to be inserted in the vessel when desired, or may
be arranged in the vessel during manufacture.
A wicking means may be provided to assist the evaporation or movement
of said refrigerant. A wicking means is advantageous because it increases
the surface area from which the refrigerant can evaporate thus speeding
the heat transfer process. Preferably the wicking means is pre-wetted
with refrigerant prior to the operation of the operative means. Pre-wetting
is advantageous because it increases the rate at which evaporation
initially occurs, thus again increasing the heat transfer rate.
Pre-wetting (wetting of the wick prior to actuation of the device) is
further advantageous because it should evenly distribute the refrigerant on
the wick and removes the need for the refrigerant to wet the wick. Such
wetting of refrigerant through the wick may slow the cooling process.
Preferably the material from which the wicking means is fabricated
readily gives up the vapour phase of the refrigerant whilst maintaining the
liquid phase within. This is advantageous because it allows the
refrigerant to remain in the wicking means (if it is pre-wetted) before
operation of the operative means but allows the refrigerant to evaporate
readily. Using a material which holds onto the liquid phase is
advantageous in circumstances wherein the device is tipped before
operation which is clearly a possibility during transport of the device.
The wicking means can be made, for example, of metallic mesh (e.g.
copper mesh or stainless steel mesh), or of a sintered powder (e.g.
sintered copper or P.T.F.E.), tissue paper, plastic foam, or paper fibre.
Alternatively, the wicking means may be formed of a porous fabric, for
example cloths sold under the trade mark JCloth or similar. The fabric is
preferably perforated to define at least one aperture, and desirably a
plurality of apertures therethrough which may serve to prevent or reduce
the formation of ice on the fabric/wick.
In yet further embodiments, the wicking means may be provided from
materials such a shammy (which may be real or synthetic), hyrophillic
gels or granules (which may be such as water retaining gels used in
horticulture), micro-fibre type materials, or Pertex™.
Localised freezing may occur which is caused by the cooling process
being too efficient at localised points in the device. Freezing of the
refrigerant is disadvantageous because it restricts further evaporation of
the refrigerant and means that additional energy is required to melt the ice
which reduces the efficiency. Pre-wetting of the wick may be
advantageous because it increases the surface area over which the
refrigerant evaporates which may prevent such localised freezing from
occurring (if the evaporation occurs over a larger area the localised rates
of cooling may be less). Further, the pre-wetting may ensure that
evaporation occurs over the whole surface area of the wick. If the
refrigerant is left to wet up the wick, initially evaporation will only occur
from portions of the wick.
The wicking means may be corrugated, or other wise contoured. Such a
structure is advantageous because it maximises the surface area of the
wicking means and increases the advantageous effects.
In another embodiment, the second part constitutes a double skin of a
vessel holding the material to be cooled, the double skin comprising inner
and outer walls.
Preferably, the inner wall is provided with the wicking means which
preferably substantially covers the inner wall. Again, the wicking means
is advantageously wetted prior to use of the device.
In a further embodiment, the first part is arranged on the second part.
The first part may be in the form of a first tube and the second part may
be in the form of a second tube.
The first or second part may be receivable in the material and may further
include one or more heat exchange members adapted to extend into the
material to enhance the transfer of heat. Enhancing the heat transfer is
advantageous because it speeds the heating or cooling process.
The heat exchange member(s) may comprise a plurality of fins which are
preferably in the form of wire loops. Both of these structures providing
simple yet efficient heat transfer.
Further heat exchange members may extend in the second part, which may
comprise a plurality of fins preferably in the form of wire loops.
Heat absorption means may be provided in association with the take up
agent. Such an absorption means is advantageous because it may promote
further take up of the refrigerant because the take up agent may be
maintained at a lower temperature. A lower temperature of the take up
agent may not only increase the rate of heating or cooling of the material
but may also reduce make the device more pleasant to hold and perhaps
safer as well.
The heat absorption means may be a heat sink provided in the take up
agent. The heat sink may comprise fins (which may be metal), coils/loops
(which may be of wire) or portions of a heat absorbing material (which
may be a metal). Each of these structures is beneficial because it will
help to remove heat from the take up agent thereby increasing the rate of
heating or cooling of the material. The heat absorption means may
comprise a powder of a heat absorbing material, may be a metal powder.
The heat take up means may comprise powder, particles, or granules
distributed through the body of adsorbent material, preferably
substantially uniformly distributed, and preferably distributed throughout
substantially the whole of the body of adsorbent.
The heat absorbing means may be moulded into the take up agent. Indeed
a mixture of heat take up material and adsorbent may be formed (e.g.
moulded) into a cake or body.
The heat absorption means may also comprise pockets of a material which
is adapted to change phase (a phase change material) as heat is absorbed.
The skilled person will appreciate that a phase change requires an
enthalpy change which in turn requires a heat input. Such a phase change
is therefore advantageous because of the increased amount of heat
absorbed from the take up agent. The phase change material may change
from solid to liquid, from liquid to vapour or possibly from solid to
vapour. The heat absorption means may comprise capsules or
micro-capsules. The capsules may contain a phase change material or may
contain a material with a high heat capacity, perhaps water, oil, or air.
They may have a wall of a first material and a centre of a different
material, which may change phase with temperature over the operating
temperature of the device (e.g. plastics, or other material, capsules may
surround a wax centre which may melt, absorbing energy, in use). The
capsule may have a high thermal conductivity wall, for example a metal
wall, or metal foil. Alternatively, there may be no containment wall for
the melted phase change material, which when melted may be permitted to
contact the adsorbent directly.
The heat absorption means may comprise pockets of air.
The heat adsorption means may also comprise a tube or other container
extending through the take up agent. The tube may contain a fluid, which
may be a liquid. Filling the tube with a liquid is advantageous because of
the high heat capacity of the liquids which will increase the amount of
heat which can be absorbed from the take up agent, thereby increasing the
rate of heating or cooling of the material.
Water may be used to fill the tube, providing a cheap material with a high
thermal mass.
The tube may be formed into a convoluted shape, such as a spiral, thereby
increasing the length of tube (and therefore the heat capacity) which can
be fitted within the take up agent. The skilled person will appreciate that
it is important for the heat absorption means to have a large surface area
to increase the rate at which heat can be absorbed.
Conveniently the tube is fabricated from a material with a high heat
conductivity. The tube may be fabricated from a metal. This structure is
advantageous because it increases the amount of heat that can be absorbed
by the tube.
Insulation means may be provided. The insulation means may insulate the
first part, or the second part or perhaps both of the first and second parts.
The skilled person will appreciate that insulation on the first part (around
the take up agent) may be adapted to prevent heat given off from the take
up agent from heating any of the refrigerant, the atmosphere or the
material. If the device is adapted to cool the material then it is clearly
disadvantageous for heat from the take up agent to reach the material.
Further, it is clearly disadvantageous for the device to become too hot and
it is desirable to provide insulation to prevent this from occurring. The
insulation may be required to prevent significant, rapid, heat transfer,
rather than completely block heat transfer. For example, it is envisaged
that a can of self-chilled beverage would be drunk by the consumer in,
say, 15 minutes after opening, or 20 minutes (or perhaps 30 minutes).
After, next say 10 minutes or 15 minutes (a period) it may not matter to
the consumer too much if the beverage begins to warm up due to heat
transfer from the adsorbent - they have by then had a first cold draught
from the can, and the can is in any event absorbing heat from the external
environment. Thus a "firewall" delay of heat transfer from the adsorbent
may be enough.
Further, it will be appreciated that insulation on the second part (around
the refrigerant) may be adapted to prevent heat from reaching the
refrigerant from the atmosphere, the material or the take up agent. If the
device is adapted to heat the material then it is clearly disadvantageous for
heat to be absorbed by the refrigerant from the material. Insulation may
be provided around the second part to ensure that heat is not absorbed
from the atmosphere by the refrigerant: if the material is to be cooled
then it is advantageous that heat is absorbed from the material rather than
from the surroundings.
One of said first and second elements may surround the other of said first
and second elements. The other of said first and second element can
preferably be arranged in a material to be heated or cooled.
In one embodiment, the first element is in the form of a first tube
surrounding the second element, which is preferably in the form of a
second tube. The second element is desirably adapted to be arranged in a
material to be cooled.
A conduit arrangement may extend between the first and second elements
to conduct the evaporated refrigerant, thereby transferring heat from the
second element to the first element. When the device is to be used to cool
the material, the first element surrounds the second element and, when the
device is to be used to heat the material, the second element surrounds the
first element.
Heat exchange members may extend from the first or second element into
the material to be heated or cooled.
The first and second elements may comprise first and second tubes
initially separate from each other and adapted to be connected in
communication for heating or cooling. The first and second elements may
be connected by the operative means.
The second part may comprise a container connected to the first part.
The operative means may comprise a valve between the first and second
parts. The valve is preferably movable to an open position to allow the
first and second parts to communicate with each other.
Heat absorption means may be arranged adjacent one of the first or second
elements. Where the device is to be used to cool the material, the heat
absorption means may be arranged in thermal contact with the first
element to absorb heat given out by the take up agent. The heat so
absorbed by the heat absorption means may be given off to the
atmosphere.
Where the device is to be used to heat the material, the heat absorption
means may be arranged in thermal contact with the second element,
whereby heat absorbed by the heat absorption means can be desorbed via
the second element to evaporate refrigerant in the first part.
In one embodiment, the heat absorption means is provided in a chamber
which may be defined at least partially by the first or second element.
Preferably, the chamber surrounds, or is surrounded by, said first part.
In one embodiment, the chamber is in the form of a substantially
cylindrical tube defined substantially wholly by said first or second
element internally of the first part. The skilled person will appreciate that
the chamber could have any other cross section and is not necessarily
cylindrical.
In another embodiment, the chamber is in the form of a sleeve defined
partially by the first or second element externally of said first part. The
sleeve is conveniently defined between said first or second element and an
external wall.
In one embodiment, the heat absorption means comprises a refrigerant
adapted to evaporate when heat is absorbed thereby. Valve means may
also be provided to release to the atmosphere evaporated refrigerant from
the heat absorption means. The valve means is particularly suitable where
the device is to be used for cooling the material.
In another embodiment, the heat absorption means may be a phase change
material adapted to change phase from solid to liquid or from solid to
vapour on absorption of heat. Where the phase change material changes
from solid to vapour, valve means may be provided to release the vapour
to the atmosphere. The use of valve means is particularly suitable where
the device is to be used in cooling the material.
In a further embodiment, the heat absorption means may be a heat pipe
preferably having one end region in thermal contact with the first part and
the opposite end region outside the first part. The end region of the heat
pipe external of said first part may be provided with fin means to assist in
heat transfer to or from the heat pipe. In this embodiment, said one end
region is preferably surrounded by the first part.
In another embodiment, the device may comprise at least one heat pipe,
and preferably a plurality of heat pipes extending from the second part
into the material. The, or each, heat pipe is preferably in the form of a
needle heat pipe. In this embodiment, a valve is provided between the
second part and the first part, whereby when the valve is opened,
refrigerant in the second part is evaporated to be taken up by the take up
agent in the first part, and the evaporation of the refrigerant causes heat
to be transferred from the material along the heat pipes to an end region
of the or each heat pipe in the first part, thereby cooling the material. In
this embodiment, the first part is arranged outside the vessel containing
the material, and the second part is arranged inside the vessel.
Alternatively, where heating is required, the second part may be arranged
outside the vessel, and heat pipes may extend from the first part inside the
vessel whereby when the valve is opened, evaporating refrigerant is taken
up by the take up agent and heat dissipated by the, or each, heat pipe into
the material.
The above embodiments are particularly suitable for use with a take up
agent in the form of an adsorbent.
In a further embodiment, where the take up agent comprises an absorbent,
the device may be provided with a third part initially containing the
absorbent. The third part may be provided with release means, whereby
when the release means is activated, absorbent is released into the second
portion. In this embodiment, when the operative means for the second
part is operated, the refrigerant is released into the first part to be
evaporated therein and absorbed by the absorbent thereby releasing heat.
The third part may be a further bubble, and the operative means may be
suitable for piercing the bubble, or otherwise forming an aperture in said
further bubble.
A material mixing means may be provided adapted to ensure that the
material is mixed. The skilled person will appreciate that the
cooling/heating process relies on temperature differences. Unless the
material is mixed temperature gradients may occur in the material which
slows the cooling or heating process. Therefore, mixing the material is
advantageous because it can help to prevent the occurrence of such
gradients and can help to increase the rate at which the material is heated
or cooled. The skilled person will appreciate that the rate of
heating/cooling should be higher if there is more of a temperature
difference. Therefore, if temperature gradients exist within the material
(for instance cooler toward an outside region and hotter toward a central
region) then the rate of cooling/heating may be reduced because the
temperature difference between the material and the first or second part is
reduced. Therefore, removing temperature gradients within the material
is beneficial because it may increase the rate of cooling or heating.
The material mixing means may comprise a disk or other body provided
within the material. This is especially advantageous when the material is
a liquid.
Preferably the disk/body is perforated. The disk/body may be adapted, in
use, to move through the material, thus providing a mixing action. The
device may be adapted to be inverted to cause the disk/body to move
through the material under the influence of gravity. Such a structure is
simple yet effective in providing a mixing action. Alternatively a
manually operated mixing/circulating mechanism may be provided, for
example a finger-operated pump or paddle.
Of course, the skilled person will appreciate that any means that mixes the
material will prevent temperature gradients from forming. Pumps, vanes,
stirring means may all be provided to prevent temperature gradients from
occurring.
In one embodiment, the device may comprise a pipe (or a linked plurality
of pipes).
Preferably, a device according to this embodiment comprises an elongate
pipe having a first portion to containing the adsorbent or absorbent, a
second portion initially separated from said first portion and adapted to
contain the refrigerant, and communication means between said first and
second portions, whereby operation of said communication means causes
the refrigerant to be adsorbed or absorbed by the adsorbent or absorbent,
with evolution of heat from the first portion of the device and
corresponding absorption of heat at the second portion of the device.
The second portion (to contain the refrigerant) is generally integral with
the elongate pipe. The second portion may be adapted to contain the
refrigerant either under sub-ambient or under super-ambient pressure, I.e.
under vacuum or under pressure respectively, relative to ambient
pressure.
The second portion may contain the refrigerant under permanent sub-ambient
or super-ambient pressure.
Alternatively, means, such as a pump, may be provided to produce a sub-ambient
or super-ambient pressure in the first portion when required.
Means may also be provided to purge air from the first portion, thereby
increasing the efficiency of the device.
The first portion (to contain the adsorbent or absorbent) may likewise be
integral with the elongate pipe.
Alternatively, the first portion may be initially discrete relative to the
second portion and adapted to be connected thereto. Such connection may
preferably include operating means for causing communication between
the first and second portions of the elongate pipe.
The communication means may, for example, comprise one or more
valves (such as one-way or throttle valves). Alternatively, the
communication means may comprise a three-way (or ejector) valve.
In another embodiment, the heat-transfer device may comprise a pipe (or
a linked plurality of pipes).
In a further embodiment, the device comprises an elongate pipe in which
the refrigerant and the adsorbent or absorbent are combined and under
super ambient pressure within the pipe. In this embodiment, the
adsorption or absorption of the refrigerant by the adsorbent or absorbent,
with consequent cooling and heating respectively, is achieved by the
release of the super-ambient pressure by means of a valve or the like
provided in operative association with the elongate pipe.
In yet another embodiment, the refrigerant is contained, under sub-ambient
pressure, in an outer skin of a vessel containing a liquid such as a
soft drink) to be cooled. A valve is provided in the skin for the release of
the vacuum and the valve is operable by means including a container for
the adsorbent.
The device according to the present invention, may be permanently fixed
inside a vessel to contain a liquid to be cooled or heated.
Alternatively, such a device may be provided as a "portable" or "pocket"
device, to be placed in an opened container (such as a can of beer to be
cooled or a can of soup to be heated) when required.
Devices according to the present invention may be operated by producing
communication between the refrigerant and the adsorbent or absorbent
(generally by actuating a valve). The provision of the communication
causes the refrigerant to volatilise and to interact with the adsorbent or
absorbent. As a result of that interaction, heat is evolved from the
adsorbent or absorbent and heat is correspondingly absorbed from the
surroundings of the refrigerant.
In one instance, where a device according to the present invention is
placed in, say, a can of beer, with the portion containing the adsorbent or
absorbent being outside the can and the portion containing the refrigerant
material being inside the can, interaction between the refrigerant and the
adsorbent or absorbent causes the evolution of heat to the atmosphere and
absorption of heat from the beer within the can leading to cooling.
In a second instance, where the device is placed in, say, a can of soup,
with the portion containing the adsorbent or absorbent being inside the
can, interaction between the refrigerant and the adsorbent or absorbent
again causes evolution of heat from the adsorbent, but the heat evolved is
used to heat the soup within the can instead of being vented to the
atmosphere.
Operation of the valve may be achieved by means external to the device
(as, for example, where a pump or the like is operatively associated with
the elongate pipe or the adsorbent material is contained in a discrete
"plug-in" member). Alternatively, the valve may be actuated by means of
the internal pressure of the contents of a vessel (as, for example, a can of
drinkable liquid to be cooled or heated by means of a device according to
the present invention).
Refrigerants suitable for use with a present invention preferably include
the following:-
Water, alcohols (e.g. methanol, ethanol), haloalcohols (e.g. trifler-ethanol),
haloalkanes (e.g. trifluoro-ethane), alkanes (e.g. C3 to C6),
ammonia, carbon dioxide, aromatic hydrocarbons (e.g. benzene, toluene,
aniline), acetophenone, butyl acetate, butyric acid, cellulose acetate,
cresol, cumene, cyclohexanol, cyclohexanone, dibutylphtalate,
diethanolamine, diethylsulphate, dimethylformamide, dimethylhydrazine,
dimethylphtalate, ethylene glycol, hydrazine, methylhydrazine,
methylpyrrolidinone, naphthalene, styrene, sulfolane, tetrachloroethylene,
trichloroethylene, undecane.
In the preferred embodiment the refrigerant may be water. Water is
advantageous because it is cheap and readily available and is also non-toxic.
Clearly, when the device is being used in conjunction with
foodstuffs it is desirable that there is no chance of contamination of the
foodstuff occurring.
The skilled person will appreciate that a mixture of a first substance and a
second substance will have a different boiling point to a sample of
substantially pure first substance. In some embodiments the refrigerant
may be a mixture adapted to reduce the boiling point of the refrigerant.
For instance, the refrigerant may be a mixture of water and alcohol.
Take up agents suitable for use with the present invention preferably
include the following:
silica gel, activated alumina, zeolites (molecular sieves), activated
charcoal, alkanes (e.g. C3 to C6), alcohols (e.g. methanol, ethanol),
amides (e.g. N, N-dimethyl acetamide), ketones/lactams (e.g. N-methyl
pyrrolidone), carboxylic acid salts (e.g. potassium formate), esters, alkali
metal salts (e.g. lithium bromide, lithium nitrate).
Thus, the refrigerant may be a volatile liquid or a gas, and the take up
agent may be a solid or a liquid.
Suitable combinations of refrigerant/take up agent for use with the present
invention preferably include the following:
water/zeolites-activated carbon, ethyl alcohol/silica gel, water/silica gel,
water/activated alumina, carbon dioxide/activated alumina, water/zeolites
4A, 5A, 13X, ammonia/zeolites 4A, 5A, 13X, carbon dioxide/zeolites
4A, 5A, 13X, ethene/activated carbon, ammonia/activated carbon,
water/activated carbon, methyl alcohol/activated carbon, water/polymers,
ammonia or water/metal in organic salts (e.g. water/ CaCl2, ammonia
CaCl2 hydrogen/LaNi4, hydrogen/FeTi, water/potassium formate),
hydrofluorocarbons (HFC) refrigerant/adsorbent combinations (e.g.
R134a/activated carbon), fluid mixtures (e.g. water, methanol/activated
carbon, water/ammonia, ammonia (or carbon dioxide/potassium formate,
water/lithium bromide, N-methylpyrrolidinone/trifluorethanol,
dithioglycol (DTG)/tetrafluorethane, water/ammonia-lithium nitrate,
carbon, dioxide/N, N-dimethylacetamide, H20/CaO.
It is desirable to increase the surface area of the adsorbent/absorbent as
much as possible to increase the rate at which the adsorbent/absorbent can
take up the refrigerant. This can be achieved by the following means, for
example coating the surface with the adsorbent/absorbent (e.g. by using a
binder or growing adsorbent/absorbent on the surface) using
adsorbent/absorbent membranes (e.g. growing zeolites on a mesh) using
an adsorbent/absorbent cloth (e.g. activated carbon), providing channels
within the adsorbent/absorbent (or take up agent), providing the take up
agent as a powder or as pellets.
Suitable phase change materials that can be used with the present
invention preferably include the following: Glycerol, oils, coconut/butter,
paraffin wax, glauber salt (Na2 S04.10H20, butyl phenol, methanol,
pentane, ethane.
In most circumstances, the take up agent can be regenerated once
adsorption has occurred. Regeneration may be achieved by heating the
adsorbent (for example by means of a Peltier or like device) or by means
of an integral compressor provided in association with the device.
The present invention further provides a method for heating or cooling the
contents of an enclosed vessel, in which one or more heat transfer devices
of the type hereinbefore described are placed in contact with the contents
of the vessel and each said device is caused to transfer heat by means of
an adsorption-based process between a refrigerant material and an
adsorbent material, whereby heat is respectively liberated into or absorbed
from the contents of the vessel.
Thus, a method according to the present invention can be applied to the
heating of soup, tea or the like in an enclosed vessel
Alternatively, the method can be applied to the cooling of beer, soft
drinks or the like in an enclosed vessel.
According to another aspect of the present invention there is provided a
heat-transfer device comprising an elongate, generally tubular member
adapted to contain a refrigerant and an adsorbent or absorbent, together
with means to cause the refrigerant to be adsorbed by the adsorbent,
whereby heat is evolved from the adsorbent or absorbent and absorbed by
the refrigerant material.
According to another aspect of this invention there is provided an
assembly comprising a vessel for holding a material to be cooled or
heated and a heat transfer device as described above arranged in thermal
contact with the material.
According to another aspect of the invention comprises a self cooling
beverage container having a beverage chamber adapted to hold a
beverage, an adsorbent, an evaporative refrigerant, an isolator isolating
the refrigerant from the adsorbent, and an actuator adapted in use to
communicate the adsorbent with the refrigerant so that, in use, the
evaporative refrigerant evaporates and is adsorbed by the adsorbent,
evaporation causing cooling of the beverage in use.
Preferably the adsorbent comprises activated carbon and the refrigerant
comprises water. The heat take up material may be provided associated
with the adsorbent, the heat take up material comprising at least one of i)
phase change material or ii) heat exchange members comprising wire
loops or wire bushes; or iii) liquid-cooled surfaces provided in a body of
the adsorbent.
A pre-wetted wick, wetted before activation of the device, may be
provided, the wick being wetted with the refrigerant and the relationship
between the refrigerant and wick being such that when activated the
refrigerant evaporates from the wick but before activation the wick holds
the refrigerant such that the liquid refrigerant does not seep under gravity
to leave a wick having dry areas, irrespective of the orientation of the
container during storage or prior to use. The relationship between the
wick and refrigerant is preferably such that the wick is substantially
saturated with refrigerant, and remains so over substantially the whole
evaporative surface prior to use of the device, irrespective of the
orientation of the container during pre-use storage. A refrigerant
reservoir may be provided, refrigerant in the reservoir replacing
refrigerant in the wick as refrigerant in the wick evaporates in use.
Beverage mixing means may be provided adapted to ensure that the
beverage to be cooled is mixed or made turbulent during cooling of the
beverage. Said beverage mixing means may comprise a gravity moved
member adapted to move through the beverage under the influence of
gravity. The member may comprise a sliding body provided with
through-holes. The beverage mixing means may comprise a so-called
"widget", adapted to generate a head on the beverage.
The heat take up material comprises a tube, capsule or other closure
provided within a body of adsorbent. The closure may comprise a
spiralled or curved tube. The closure may contain at least one of i) water;
or ii) phase change material.
The adsorbent may be provided as a body of adsorbent material and the
body may be provided with surface area maximising means which may
comprise any one of the of following: i) channels provided on or within
the body; ii) the adsorbent being provided in granular form or in powder
form.
A membrane may be provided to separate the adsorbent and refrigerant
prior to the actuator allowing the refrigerant to be adsorbed.
The wick may be provided with apertures, which may assist in the
prevention of ice. The adsorbent may be provided as a body and there are
distributed in the adsorbent body of a plurality of microcapsules
comprising water or a waxy phase change material. The microcapsules
may contain phase change material which melts, in use, and wherein the
microcapsules have a sheath to retain the melted phase change material.
The adsorbent may be provided as a body, and wherein the adsorbent
body has provided in it a plurality of channels adapted to take refrigerant
vapour to different regions of said body.
The self cooling beverage container may have a beverage chamber, a
beverage in the beverage chamber, a body of adsorbent material, an
evaporative refrigerant held on wick, an isolator isolating the wick from
the adsorbent body, an actuator adapted in use to communicate the
adsorbent with the wick so that said evaporative refrigerant evaporates
and is adsorbed by the adsorbent, with the evaporation cooling the
beverage; and wherein the adsorbent is activated carbon, the evaporature
refrigerant is water, and the evaporative process occurs at sub
atmospheric pressure; and wherein a mixer is provided in said beverage
chamber, said mixer being gravity operated by inversion of the container
to cause said mixer to move and thereby mix the beverage to assist
cooling of the beverage; and wherein said adsorbent body has heat take up
means provided in it, said heat take up means comprising at least one of;
i) microcapsules of phase change material or heat capacity material
distributed in said body; ii) liquid cooled surfaces provided on said
adsorbent body; and wherein said wick is thermally coupled with at least
one of: i) heat exchange fins extending into said beverage; ii) extensions
or loops of wire in thermal contact with said beverage.
A method of cooling a beverage may comprise providing a container
having a gravity powered beverage mixer and actuating said actuator, and
then periodically inverting said container to cause said gravity moved
member to move repeatedly through said beverage, in opposite directions
relative to said conductor, and repeatedly moving said beverage prior to
opening said beverage container.
Embodiments of the invention will now be described by way of example
only, with reference to the accompanying drawings in which:
Figure 1 shows a self-cooling can of beverage in accordance with
the invention; Figure 2 shows a modification of the device shown in Figure 1; Figure 3 is a further embodiment of the heat transfer device
showing the use of heat exchange means to enhance a transfer; Figures 4A to C show the sequence of events for using the
embodiment shown in Figure 3; Figure 5 is a modification of the device shown in Figure 3; Figure 6 is a further embodiment of the heat transfer device, in
which the adsorbent is arranged around the material, and a conduit
arrangement is used to deliver evaporated refrigerant to the
adsorbent; Figure 7 is a further embodiment of the heat transfer device; Figure 8 is a further embodiment of the heat transfer device using
an enlarged chamber for the adsorbent; Figure 9 shows schematic representations of further possible
enhancements of the system; Figures 10A to 10D show heat take up mechanisms which may be
provided associated with the evaporant take up medium; Figures 11A to 11B show heat sink material distributed in
adsorbent/evaporant take up material; Figures 12A to 12DC show further heat sink structures; Figures 13A to 13D show ways of getting the evaporated coolant to
deeper parts of a body of evaporant take up material; Figure 14 shows a way of cooling the adsorbent/take up agent; and Figure 15 shows a self-cooling beverage container with a
temperature gradient over the volume of adsorbent.
Referring to Figure 1 there is shown a can 300 having a heat transfer
device 410 comprising a first part 416 having a cylindrical chamber 419
for an adsorbent 418 (e.g. activated charcoal), and a second part 420
which cools a beverage 422 (e.g. beer, lager, soft drinks or the like) to be
cooled, and comprises a double skin in the form of a pair of
concentrically arranged outer and inner walls 424, 426. Wicking means
428 is provided on and surrounds the inner wall 426. The wicking means
428 is soaked in a suitable refrigerant, for example water, and can be a
porous fabric material capable of dispersing the refrigerant throughout the
fabric by capillary action. One example of a suitable fabric is that sold
under the Trade Mark J-Cloth. The space between the outer and inner
walls 424, 426 is evacuated to a low pressure. Mixing means in the form
of a disc or body 430 provided with a plurality of perforations is provided
in the beverage 422, the purpose of which is explained below.
Operative means in the form of a plunger 432 is provided in the first part
416 and comprises an elongate rod 434 extending between a button 436 to
be pressed to operate the operative means 432, and piercing means 438 at
the opposite end region of the rod 434 to pierce a membrane 440
separating and isolating the first and second parts from each other. The
operative means extends through an elongate hole 435 through the
cylindrical chamber 417.
The piercing means 438 is in the form of a substantially cylindrical
member, the lower end 439 being open. The edge of the cylinder
surrounding the open end is sharp and can readily pierce the membrane
440 which is in the form of a suitable plastics or metal foil, for example
aluminium foil.
In operation, the button 436 is depressed which causes the piercing means
438 to pierce the membrane 440. Upon piercing of the membrane, the
water in the space between the outer and inner walls 424, 426 is adsorbed
by the adsorbent 418, and evaporates from the wicking means 428 thereby
extracting heat from the beverage 422. In order to ensure that heat is
extracted from all parts of the beverage 422, the device 410 is inverted to
enable the mixing disc 430 to descend under gravity thereby creating eddy
currents in the beverage 422 and stirring the beverage.
As the water evaporates from the wicking means, it is absorbed by the
adsorbent 418 until all the water has been so adsorbed or until the
adsorbent is substantially exhausted and there is no further significant
driver to the evaporative process.
A ring pull 442 is provided to open an aperture in the can and allow the
beverage to be consumed.
Referring to Figure 2, there is shown a modification of the device shown
in Figure 36 in which the first part 416 is surrounded by heat absorption
means, or a heat sink 444. The heat sink 444 absorbs heat from the
adsorbent 418.
The heat sink 444 could, for example, be further wicking means, soaked
in a suitable refrigerant e.g. water, whereby as the adsorbent releases heat
of adsorption, the refrigerant evaporates thereby removing the heat of
adsorption from the device. Again, the further wicking means could be a
porous cloth, for example a cloth sold under the Trade mark J-Cloth.
Alternatively, in an embodiment not shown, the further wicking means
could be provided around the inside walls of the elongate hole 435.
Micro capsules containing water may be provided in the further wicking
means to enhance the removal of heat of adsorption. The micro capsules
may contain water (or other high heat capacity material) or they may
contain phase change material. It is envisaged that of the order of tens,
several tens, hundreds, several hundred, or even thousands of
microcapsules would be used. The microcapsules may not have an outer
skin and a core of different material; they could be of a single material
(e.g. wax pellets) or metal powder or granules.
Both the first part and the second part of both embodiments, shown in
Figures 1 and 2 are placed under vacuum.
The adsorbent is placed in a cylinder made from stainless steel or copper
mesh. The operative means extends through the hole 435 through the
centre of the cylinder.
Referring to Figures 3 to 5, there is shown a heat transfer device 510
which comprises a first part 512 which holds an adsorbent 514 (e.g.
activated carbon) arranged in a cylinder of stainless steels or copper mesh
516. A second part 518 is provided on the first part 512 and extends into
a beverage to be cooled 520. The second part 518 consists of a
cylindrical tube 522 having provided on the inner surface thereof wicking
means 524 which is saturated with a suitable refrigerant, for example,
water. Heat exchange means in the form of wire filaments, loops,
protrusions, or fins 526 extend outwardly from the tube 522. Both the
first and second parts 512, 518 are under vacuum/low pressure.
Operative means 528 is provided in the first part 512 and extends through
a bore in the cylinder holding the adsorbent 514. The operative means
528 comprises a button 530 and piercer 532 adapted to pierce a membrane
534 separating and isolating the first and second parts from each other. A
rigid rod 536 extends between the button 530 and the piercing means 532
such that depression of the button 530 causes the piercing means 532 to
pierce the membrane 534.
Referring to Figures 4A to 4C, there is shown the sequence of events for
using the device shown in Figure 3.
Figure 4A shows the device as it appears in Figure 3 i.e. before
operation. Referring to 4B, when it is desired to consume the beverage
520, the button 530 is pushed down. This causes the piercing means 532
to be pushed through the membrane 534 by the rod 536 and ruptures the
membrane 534.
Immediately this is done, the water on the, pre-wet, wicking means 524
evaporates and is adsorbed by the absorbent 516. This extracts heat from
the beverage 520 and this heat extraction is enhanced by the fins 526.
The fins 526 could be bushes of wire strands, for example like wire wool.
This would have a large surface area and good thermal conductivity, and
would allow the beverage 520 to flow through the bushes.
When the heat transfer has been completed, and the beverage 520 is
cooled, a ring pull 538 can be pulled to allow the beverage 520 to be
poured into a glass 540 for consumption.
Referring to Figure 39, there is shown a modification to the device shown
in Figure 37 in which the inside of the tube 522 forming the second part
518 is provided with an internal arrangement 542 of looped wire, similar
to that provided outside.
A filter may be provided to prevent any parts of the heat exchange
mechanism that have broken off in transport, storage, or use, of the
container from being dispensed from the can via the aperture by the ring
pull. The heat exchanger or cooling unit may be provided in a
porous/permeable bag/shroud.
Referring to Figure 6, there is shown a further embodiment 610 in which
a first part 612 comprises a vessel having a double skin inner and outer
wall 616, 618, the adsorbent 614 being arranged circumferentially around
the outer wall 618. An inner tube 620 extends into the beverage 622 and
comprises wicking means 624 arranged internally of the tube 620, and fins
626 extending outwardly from the tubes 620 into the beverage 622. The
second part 628 is provided separate from the vessel, and comprises a
copper container 630 holding a refrigerant 632, for example water. A
conduit 636 extends from the container 628 to a region adjacent the
bottom of the tube 620. A valve 638 is provided in the pipe 636 which is
initially set to its closed position and, upon opening, allows water in the
container 630 to flow into the tube 620. An arrangement of conduits 640
extends from the tube 620 into the first part 612 for the purpose of
delivering evaporated refrigerant to the first part 612. A water trap 642
is provided at the top of the tube 620 to connect the tube 620 to the
conduit arrangement 640, whereby any water condensing prior to entering
the conduit arrangement 640 is returned back to the tube 620 to undergo
evaporation again.
In operation, the valve 638 is opened and water from the container 630 is
emptied into the tube 620. The water is then dispersed by the wicking
means around the inside of the tube 620 and is evaporated by the transfer
of heat from the beverage via the fins 626. The evaporated water thereby
extracts heat from the beverage to cool it down. Water vapour passes
through the tube via the conduit arrangement 640 into the first part 612 to
be adsorbed by the adsorbent 614 arranged on the outer wall 618. A
covering of insulating material 644 is provided around the inner wall 616
to ensure that, once cooled, the beverage 622 is kept cool. When the
cooling process is completed, the ring pull 646 can be pulled to allow the
beverage to be consumed. The ring pull 646 could be a closable closure,
to enable the beverage chamber to be sealed closed after opening, and
possibly re-filled with beverage.
A lid 648 is provided which can be removed to allow the water in the
adsorbent 614 to be discharged thereby allowing the device to be used
again.
Referring to Figure 7, there is shown a modified device 710 which
comprises an inner cylinder 712 holding a beverage 714. Wicking means
716 is provided on the wall of the cylinder 712. An outer wall 718 is
provided on the inside thereof with an adsorbent 720 which extends
substantially wholly around the inside of the wall 718.
A container 722 is provided separate from the vessel and contains a
suitable refrigerant, for example water. The container 722 is connected to
the wicking means 716 via a conduit 724 and a valve 726. The space
between the inner and outer walls 712, 718 is under vacuum.
On operation, the valve 726 is opened to allow the water in the container
722 to empty into the space between the two walls 718, 712 whereupon
the water is dispersed around the outside of the cylinder holding the
beverage 714. In evaporation the water therefrom extracts heat from the
beverage 714. The evaporated refrigerant is then adsorbed by the
adsorbent 720 surrounding the inside of the outer wall 718. In this way,
the beverage 714 is cooled
A lid 728 (e.g. plastic) is provided to cover the space between the inner
and outer wall 718, 712 and the conduits 724 is formed in the lid 728.
An evacuation point 730 is provided on the lid, to allow the water
adsorbed onto the adsorbent 720 to be discharged therefrom to allow the
device to be used again. The container 722 can be refilled with water
through a suitable fill point 732. The container 722 is suitably formed
from copper.
Referring to Figure 8, there is shown a further embodiment 710 and is
formed in two separate but connected elements 712. The first element
712 comprises a large cylinder the adsorbent 718 extends substantially
wholly around the inside of the wall of the cylinder 716. A lid 720 is
provided on the cylinder to allow water adsorbed onto the adsorbent 718
to be reused.
The second element 714 comprises a tubular member 722 having provided
on the outside thereof a plurality of fins 724. Wicking means 726 extends
around the inside of the wall of the tube 722. A container 728, initially
charged with a refrigerant, for example water is provided separately from.
the tube 722 and is connected thereto by pipes 730 and a valve 732. A
flange 734 is provided to connect the two elements 712, 714 together.
On operation, the first element 712 is connected to the second element
714 by the flange 734 The tube 722 is then inserted in a material to be
cooled, and a valve 732 is opened to allow the water to enter the tube 722
to be dispersed around the inside wall of the tube. Heat is transferred to
the inside of the tube via the fins 724 to evaporate the water thereby
cooling the material. The evaporated water is then passed into the first
element 712 to be adsorbed by the adsorbent 718. When the process is
completed, the cooled material can be consumed, and the first clement can
be used again by removing the water from the adsorbent 718 by, for
example, heating.
Figure 9 is based upon Figure 3 but shows enhancements which may be
provided. The skilled person will appreciate that the enhancements shown
in relation to Figure 9 could equally well be applied to any other of the
embodiments shown in the various Figures of this description.
Figure 9a shows pockets 800 of a phase change material provided within
the within the take up agent (e.g. adsorbent) 514. As the device is used
the temperature of the take up agent 514 rises and eventually the material
provided within the pockets either melts, vaporises, or sublimates. This
change of phase of the material within the pocket 800 requires a heat
input which is absorbed from the take up agent 514. This absorption of
heat reduces the temperature of the take up agent thus improving the rate
of cooling of the beverage 520. The absorbing/take up reaction of the
take up agent/evaporant is an equilibrium reaction and operates faster the
further away from equilibrium - it is therefore helpful to cool the take up
agent to maintain the speed of reaction and hence speed of cooling of the
beverage.
Figure 9b shows a tube 802, provided as a spiral within the take up
agent 514. The tube is fabricated from a metal, in this case aluminium,
so that it conducts heat rapidly. The tube is filled with water which
absorbs heat from the take up agent 514 again increasing the rate of
cooling of the beverage 520. The tube and its water is a heat sink.
Figure 9c shows cooling fins 804 extending into the take up agent 514.
As with the embodiments shown in Figures 9a and 9b the fins are adapted
to remove heat from the take up agent 514 so that its rate of change of
temperature is reduced which promotes cooling of the beverage 520.
Figure 9d shows the provision of insulation around the heat transfer
device 510. A portion of insulation 806 is provided between the first
part 512 (containing the take up agent) and the beverage container 808
which is adapted to prevent heat from the take up agent 517 from reaching
the beverage 520. It will be appreciated that in this embodiment the heat
transfer device is adapted to cool the beverage 520 and that therefore it is
not desirable for heat to reach the beverage 520.
A portion of insulation 810 is provided around the beverage container 808
and is adapted to prevent heat reaching the beverage 520 from the
atmosphere.
A further portion of insulation 812 is provided around the first part 512
and is adapted to prevent the outside of the heat transfer device 510 from
becoming too hot. It will be appreciated that the take up agent is
absorbing heat and will therefore experience a temperature rise. This may
become dangerous or uncomfortable for a user. Indeed, this may cause a
psychological effect wherein the user knows that the heat transfer
device 510 is adapted to cool the beverage 520 but is somewhat surprised
by the device 510 becoming hot and may not perceive the cooled beverage
as really being as cold as it is.
Figure 9e shows channels 814 provided within the take up agent 517.
These channels are adapted to maximise the surface area of the take up
agent and improve efficiency of the cooling process of the beverage 520.
They take the water vapour (evaporant) to different regions of the take up
agent, preventing localised saturation of the take up agent (and localised
heating) which would serve to stop/retard the equilibrium drive of the
process: ensuring that substantially the whole body of the take up agent is
exposed to water vapour makes for a further cooling process for the
beverage.
The skilled person will appreciate that the features shown in Figure 9 are
applicable to any of the embodiments shown herein, including those
adapted to heat a beverage or food stuff. Indeed, some embodiments may
have a combination of the features shown in Figure 9. With respect to
Figure 9d only some of the portions of insulation may be provided, and
the purpose of the insulation may be different (although readily apparent)
if it is provided on devices adapted to heat a beverage or foodstuff.
Where "heat-pipe" is referred to in the foregoing description, it is to be
understood as including any one or more of needle heat-pipes, loop heat-pipes
or micro heat-pipes.
Various modifications can be made without departing from the scope of
the invention. For example, each of the embodiments shown above
comprises one adsorber or absorber unit. The devices may comprise two
or more absorber or adsorber units to enhance the cooling/heating
programme. Also, a device may comprise a combination of solid/gas
adsorption and liquid/gas absorption. In the pocket/portable
coolers/heaters (or, indeed any of the embodiments shown in the
drawings) the refrigerant may be desorbed from the adsorbent to allow the
adsorbent to be re-used.
Figures 10a to 10d show heat sink devices which in some embodiments
may be provided distributed in the evaporant take up agent/adsorbent. A
spiral shape, such as that of Figure 10a, or a convoluted shape, as in
Figure 10d (which need not be planar) are space-efficient. Smaller,
simpler shapes such as shown in Figures 10b and 10c may be used. The
heat sink devices may simply be of a material with high heat capacity
(e.g. metal), or they may be of a phase change material, e.g. wax. They
may have an outer skin or sheath of one material and a core of another
(e.g. metal, or cloth, or plastics skin with a phase change core). They
may be distributed through the body if adsorbent.
Figures 11a shows a cake of adsorbent (e.g. carbon) 900 having heat sink,
particles 902 randomly distributed in it. The heat sink particles 902 are
made of metal in this example. Figure 11b shows a cake of adsorbent
(e.g. carbon or zeolite) with both metal particles 902, and phase-change
heat sink particles 904 distributed within it. The phase change particles
are preferably non-toxic to humans, as are preferably all materials in the
container/can. That is why carbon/water is preferred as the
adsorbent/evaporant, and why wax is preferred as heat sink/phase change
material.
Figure 12a shows a heat sink/sphere 910 having a stem 912 containing a
core 914. The core 914 is of high heat capacity material, e.g. water. The
stem 912 is a good thermal conductor, e.g. a metal foil/metalised
membrane. Figure 12b shows a capsule 916 having an outer wall 918 of
retaining material, e.g. wax, cloth, metal or plastic, and a core 920 of
phase change material.
Figure 12c shows a capsule 920 having an outer skin 922, an inner core
924, and an intermediate layer 926. The intermediate layer 926 could be
of a phase change material or high heat capacity material and could be
solid or liquid. The core could be of phase change material or high heat
capacity material and would be solid or liquid. In one version the core is
water and the intermediate layer is a phase change material, such as wax.
The outer stem may itself be of wax and may or may not melt in use (e.g.
the wax of the skin could have a higher melting point that that of the
intermediate layer or core).
Figure 13a shows a body 930 of adsorbent (or other evaporant take up
agent) having a number of channels 932a, 932b, 932c, 932d, provided in
it. Each channel 932 has its own entrance 934 and water vapour (or other
evaporant vapour) enters via the entrances 934. This ensures (and the aim
of the improvement is to ensure) that not all of the water vapour is
adsorbed at the end, referral 936, of the body of adsorbent near the
vapour entrance to the body. If no channels/guide/splitter for the vapour
was not provided the vapour may tend to condense on the lower parts of
the body first, and the adsorption reaction would be greatly unequal over
the height of the body 930. The separate channels 932a to 932d ensure
that "fresh" vapour reaches the further/remote parts of the adsorbent.
The right hand half of Figure 13a shows another modification in which the
passages/channels 932 are not simply straight, but are convoluted (938) in
order to have a larger surface area/have less of the body of adsorbent so
far away from the nearest channel portion/place where water can be
adsorbed. Of course, the channels can have an arcuate extent around the
can/container, and may have both a circumferential extent and an axial
extent. The body 930 may be made of sections which define the channels
between them, as shown in Figure 13d. The sections may be circular and
may stack one above the other, possibly with protrusions to hold them
apart so as to define the channels.
Figure 13b shows another body of adsorbent/take up material 940 which
has a channel 942 into which vapour enters at entry 944. The channel 942
is shaped so that at its entry the vapour is flowing relatively quickly, and
such that further downstream in the channel, for example at point 946, the
flow is slower. This means that vapour reaches the downstream regions
of the channel since at least some of it rushes past the upstream surfaces
of adsorbent before it can be adsorbed, thereby spreading out the
adsorption over a larger volume of the body, or makes the adsorption
more even over the volume of the body. This may be achieved in part by
having the channel 942 have an increased cross-sectional area at a region
downstream of the entry 944, and it may have a progressively, or stepped,
widening of cross-section.
Figure 13c shows another way of spreading out the adsorption of reaction
over a larger volume of body of adsorbent.
Figure 14 shows a body 950 of adsorbent (or other take up material) 951
with a liquid cooling system. Water cooling channels 952 are provided
and movable circulation drivers 954 are provided in the channels 952, as
is water 955. Access to the adsorbent 951 for the evaporated water
vapour (or other vapour) is not shown, but does exist. In this example the
circulation drivers 954 are bodies with a through bores 956. When the
body 950 is inverted the drivers 954 slide down the channels 952, with
the water 955 flowing through the bores 956 as they move under gravity.
This causes turbulent mixing of the water 955, which aids heat transfer
from the body 950 to the water 955. The drivers 954 may be parts of a
common member, e.g. a plate. They may not be of the same cross-section
as the channels, allowing water to slide past them. They may not then
need bores 956.
The coolant liquid circulation achieved by drivers 954 is, of course,
similar to that achieved by plate 430 for the beverage itself. The plate
430 and driver 954 may be different components, or they may be provided
by a common gravity driven component. In a modification instead of
being gravity driven the beverage mixer and/or coolant fluid mixer may
be manually driven. They may be gravity driven as they fall, and
manually returnable to an elevated position. Alternatively the user may
be directed to turn the container upside down periodically whilst it cools,
so as to enable the plate 430 and/or drivers 954 to operate repeatedly.
Figure 15 shows a temperature gradient over a block of adsorbent. This
may encourage the reaction to use the cooler parts of the block. The
usage of the block may therefore be in part self-regulating. However, for
maximum speed of cooling of the beverage large temperature gradients
over the adsorbent are to be avoided since they demonstrate that some
parts of the adsorbent are not taking up as much vapour as they could be
(and indeed as other parts of the adsorbent are taking up).
The performance of the self-cooling can/container is intended to cool a
can at an initial temperature of 20-25°C to a final temperature of around
8°C ± a few °C in a time of 2 minutes or less.
It will be appreciated that the self-cooling container of main interest is
likely to be a can, or other container having about 300-500ml or so of
beverage. Typical cans and bottles have 275ml, 330ml, 440ml, 500ml of
beverage, and the temperature reduction performance envisaged is for
such containers.
Whilst endeavouring in the foregoing specification to draw attention to
those features of the invention believed to be of particular importance it
should be understood that the Applicant claims protection in respect of
any patentable feature or combination of features hereinbefore referred to
and/or shown in the drawings whether or not particular emphasis has been
placed thereon.