GB2503191A

GB2503191A - Refrigeration apparatus comprising fluid reservoirs

Info

Publication number: GB2503191A
Application number: GB1201437.9A
Authority: GB
Inventors: Ian Tansley
Original assignee: True Energy Ltd
Current assignee: True Energy Ltd
Priority date: 2012-01-27
Filing date: 2012-01-27
Publication date: 2013-12-25
Also published as: GB201201437D0; CO7101213A2

Abstract

An apparatus 1 for cooling objects such as food items, beverages or vaccines, comprises first and second fluid reservoirs 20a, 20b, cooling means 28 for cooling fluid contained in the first fluid reservoir, and a thermal transfer region 26 arranged between respective upper regions of the first and second fluid reservoirs. The thermal transfer region permits thermal transfer between the fluid contained in the reservoirs such that cooling of the fluid in the first reservoir causes cooling of the fluid in the second reservoir. In further aspects of the invention, a refrigeration apparatus comprises a casing 10 with a payload compartment 12 located within the casing, and a fluid volume situated within the casing and comprising either weirs (22a, 22b, fig.6) dividing the fluid volume into a central fluid reservoir and outer fluid reservoirs, or a cylindrical weir (22, fig.8) dividing the fluid volume into inner and outer fluid reservoirs. In another aspect of the invention, a method comprises fluid within a first fluid reservoir, at a temperature below a critical temperature, rising and mixing in a thermal transfer region with fluid at a temperature above the critical temperature, from a second fluid reservoir, with critical temperature fluid then sinking.

Description

REFRIGERATION APPARATUS

FIELD OF THE INVENTION

The present invention relates to a refrigeration apparatus. In particularly, but not exclusively, the invention relates to a refrigeration apparatus for use in storing and transporting vaccines, perishable food items, packaged beverages or the like, and for the cooling or temperature control of equipment such as batteries, in the absence of a reliable supply of electricity. Aspects of the invention relate to an apparatus and to a method.

BACKGROUND

A large proportion of the world's population do not have access to a consistent and reliable supply of mains electricity. Underdeveloped countries, or regions remote from populated areas, frequently suffer from rationing of electrical power, often implemented by means of "load shedding", being the creation of intentional power outages, or failures of the distribution network.

The storage of vaccines, food items and beverages at appropriate temperatures is difficult in such areas where this absence of a constant and/or reliable supply of electrical power restricts the widespread use of conventional refrigeration equipment. Vaccines, for example, are required to be stored within a narrow temperature range between approximately 2 -8CC, outside of which their viability can be compromised or destroyed. Similar problems arise in connection with the storage of food, particularly perishable food items, and packaged beverages such as canned or bottled drinks.

In response to this problem, the present applicants have previously proposed a form of refrigeration apparatus, disclosed in co-pending patent application no. PCT/GB2O1O/051129, which permits a refrigerated storage space to be maintained within a temperature range of 4 -8CC for up to 30 days following a loss of electrical power. This prior art apparatus comprises a payload space for vaccines, food items, drinks container or any other item to be cooled, the payload space being disposed at a lower region of a thermally insulated reservoir of water. Above the reservoir, and in fluid communication therewith, a water-filled head space containing a cooling element or low-temperature thermal mass, provides a supply of cold water to the reservoir.

This prior art apparatus relies upon the known property that water is at its maximum density at approximately 4°C. Thus, water cooled to this temperature by the cooling element or thermal niass in the head space tends to sink down into the reservoir, settling at the lower region surrounding the payload space which, through thermal transfer, is cooled to a temperature at or close to 4°C.

The applicants have identified a need to improve on the above mentioned apparatus to facilitate packaging, transportation and efficiency. It is against this background that the present invention has been conceived. Other aims and advantages of the invention will become apparent from the following description, claims and drawings.

STATEMENT CF INVENTION

Aspects of the invention therefore provide an apparatus and a method as claimed in the appended claims.

According to another aspect of the invention for which protection is sought, there is provided an apparatus comprising at least first and second fluid reservoirs, cooling means for cooling fluid contained in the first fluid reservoir, and a thermal transfer region disposed between respective upper regions of the first and second fluid reservoirs for permitting thermal transfer between the fluid contained in the first fluid reservoir and fluid contained in the second fluid reservoir.

In an embodiment, the first and second fluid reservoirs are disposed in a side by side configuration.

In an embodiment, one or both of the first and second fluid reservoirs is arranged, in use, to contain a fluid having a negative temperature coefficient of thermal expansion below a critical temperature and a positive temperature coefficient of thermal expansion above the critical temperature. In other words, the density of the fluid increases as its temperature rises towards the critical temperature and then decreases as the temperature rises above the critical temperature, meaning that its density is at its maximum at the critical temperature. The fluids contained in the first and second fluid reservoirs may be the same or different and may have the same or different critical temperatures. The fluid may comprise water or a fluid having similar thermal properties to water.

In an embodiment, the first and second fluid reservoirs are defined, at least in part, by a container having weir means dividing the container into said first and second fluid reservoirs.

The weir means may take the form of a wall or other structure extending into the volume of the container with the first and second fluid reservoirs being defined by the respective volumes on either side thereof. The weir means may be formed from a material having a low thermal conductivity or an insulating material.

In an embodiment, the weir means extends upwardly from a lower wall of the container towards an upper wall of the container. In an embodiment, a free end of the weir means is spaced from the upper wall of the container. The region above or adjacent to the free end of the weir means may define said thermal transfer region.

Alternatively, the weir means may extend between upper and lower walls of the container and include one or more apertures or slots in an upper region thereof. The region at or adjacent to the one or more apertures or slots in the weir means may define said thermal transfer region.

The thermal transfer region may define a mixing region for permitting mixing of fluids from the first and second fluid reservoirs. Alternatively, or in addition, the thermal transfer region may define a thermal flow path for permitting the flow of heat between fluids contained in the respective first and second fluid reservoirs.

In an embodiment, the first and second fluid reservoirs are in fluid communication via said thermal transfer region. The thermal transfer region may thus be arranged to permit fluid to be transferred between the first and second fluid reservoirs.

In an embodiment, the apparatus is arranged to cool the fluid in the first fluid reservoir to a temperature below its critical temperature thereby to cool fluid in the second fluid reservoir via the thermal transfer region.

Alternatively, the fluid reservoirs are in fluid isolation from one another. In this embodiment, a fluid-tight, thermally conducting barrier may be disposed between the upper regions of the fluid reservoirs. The region at or adjacent to the thermally conducting barrier may thus define said thermal transfer region.

The cooling means may be arranged to cool fluid in a region of the first fluid reservoir that is below the upper region thereof to a temperature below the critical temperature such that fluid in the first fluid reservoir that is cooled below the critical temperature rises in the first fluid reservoir towards the upper region. Alternatively, or in addition, fluid at a temperature on either side of the critical temperature may be displaced towards the upper region by water at the critical temperature.

In an embodiment, fluid at a temperature below the critical temperature displaced to the upper region of the first fluid reservoir in use mixes with fluid at a temperature above the critical temperature. In an embodiment, fluid at the upper region of the second fluid reservoir is cooled towards the critical temperature. Fluid in this mixing region at the critical temperature may therefore sink into a lower region of the second fluid reservoir.

The arrangement may be such that fluid in the second fluid reservoir may be maintained at a substantially constant temperature, at or around the critical temperature, for extended periods of time.

The cooling means may include a refrigeration unit that can cool water within the first fluid reservoir, and a power supply unit that can act as a source of power for the refrigeration unit. The power supply may comprise a solar power supply, such as a plurality of photovoltaic cells, for converting sunlight into electrical power. Alternatively, or in addition, a mains power supply may be used.

In typical embodiments, the refrigeration unit includes an electrically-powered compressor.

However, refrigeration units using other refrigeration technology might be used to increase the electrical efficiency of the refrigerator. One example of such alternative technology is a Stirling engine cooler, which may be operated in solar direct drive mode.

The apparatus may comprise a sensor disposed to detect the formation of ice in the first fluid reservoir.

The sensor may be operative to cause operation of the refrigeration unit to be interrupted upon detection of the formation of ice.

In alternative embodiments of the invention, the cooling means includes a thermal mass that, for use and at least initially, is at a temperature below a target temperature of the payload space. This can provide a refrigerator that is simple in construction and that has no moving parts in operation. For example, the thermal mass may be a body of water ice. Such an arrangement may be used on its own (i.e. without a refrigeration unit) or in combination with a refrigeration unit. Cooling means having a combination of a thermal mass supplied from a source external to the refrigerator and in addition a refrigeration unit can cool the refrigerator to its working temperature more quickly than can the refrigeration unit alone.

Such embodiments may include a compartment for receiving the thermal mass in thermal communication with water in the first fluid reservoir. For example, the compartment may be suitable for receiving ice. Alternatively, the thermal mass may be immersed in fluid within the first fluid reservoir. In this latter case, the thermal mass may be an ice pack.

According to another aspect of the present invention for which protection is sought, there is provided a refrigeration apparatus comprising an apparatus according to the previous aspect and a payload volume for containing an object or item to be cooled disposed in thermal communication with the second fluid reservoir.

In an embodiment, the payload volume may comprise one or more shelves for supporting items or objects to be cooled. The payload volume may be open fronted. Alternatively, the payload volume may comprise a closure such as a door for thermal insulation thereof.

The payload volume may comprise one or more bottle coolers. The payload volume may comprise one or more fluid pipelines through which a fluid to be cooled flows, in use. For example, the payload volume may comprise a pipeline for a beverage dispensing apparatus.

In an embodiment, the payload volume may be arranged to contain one or more batteries.

In an embodiment, the apparatus is configured to be disposed within a conventional refrigerator or the like. In this embodiment, the cooling means may comprise the existing cooling element of the refrigerator. The apparatus may be arranged to be positioned within the refrigerator such that the first fluid reservoir is in thermal communication with the existing cooling element so as to cool the fluid therein.

The apparatus may for example be in the form of a structure formed to fit within a conventional refrigerator. The apparatus may be moulded or otherwise formed to fit within a conventional refrigerator.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples, features and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings may be taken independently or in any combination thereof. For example, features described in connection with one embodiment are applicable to all embodiments, unless there is incompatibility of features.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a graph of the density of water against temperature; Figure 2 is a section through an apparatus embodying one form of the invention; Figure 3 is a perspective view of an apparatus embodying another form of the invention; Figure 4 is a section through an apparatus embodying another form of the invention; Figure 5 is a section through a variation to the apparatus of Figure 4; Figure 6 is a section through an apparatus embodying a further form of the invention; Figure 7 is a section through a variation to the apparatus of Figure 6; Figure 8 is a section, in plan view, through an apparatus embodying a still further form of the invention; Figures 9a and 9b illustrate a section through an apparatus embodying another form of the invention; and Figure 10 is a section through an apparatus embodying yet another form of the invention.

Within the following description, as far as possible, like reference numerals indicate like parts.

It will be understood from the foregoing that operation of the present invention relies upon one of the well-known anomalous properties of water: namely, that its density is maximum at approximately 4°C, as shown in Figure 1. That is to say, water has a negative temperature coefficient of thermal expansion below approximately 4°C and a positive temperature coefficient of thermal expansion above approximately 4°C. Hereinafter, the term "critical temperature" will be used to refer to the temperature, being approximately 4°C, at which the density of water is at its maximum.

In the apparatus disclosed in co-pending POT application no. PCT/0B2010/051 129, a headspace is disposed above the payload space. This arrangement is functionally advantageous but may be compromised in terms of packaging for certain applications. More particularly, the applicants have identified that the disposition of the headspace above the payload space limits the retail frontage available for use. That is to say, the head space occupies a portion of the apparatus volume at the front of the apparatus which may be the most valuable or useful refrigerated storage space.

The applicants have discovered that it is possible to position the headspace, i.e. the reservoir containing the cooling means, behind the storage compartment (as opposed to above it) and yet still achieve sufficient cooling of the storage compartment using a similar thermal principle to that of the earlier application.

Referring firstly to Figure 2, a refrigeration apparatus embodying a first form of the invention is shown generally at 1.

The apparatus 1 comprises a casing 10, which is, in this embodiment, shaped generally as an upright cuboid. The casing 10 is formed from a thermally insulative material to reduce heat transfer into or out of the apparatus 1. For example, the casing 10 may be formed as a one-piece rotational moulding of a plastic material. The volume within the casing 10 is divided into adjacent compartments, a payload compartment 12 and a fluid volume 14, by means of a separator comprising a thermally conductive wall 16 extending between the upper, lower and side walls of the casing 10.

The payload compartment 12 is arranged to store one or more objects or items to be cooled, such as vaccines, food items or packaged drinks. As shown in Figure 3, the payload compartment 12 may comprise a closure such as a door 18 which can be opened to gain access to the compartment through the open face of the casing 10. Insulating material is carried on the door 18 so that, when it is closed, heat transfer therethrough is reduced. In an alternative embodiment (not shown) the payload compartment 12 may be open-faced, permitting easy access to objects or items stored therein. For example, the payload compartment may comprise a shelving unit for use in retail outlets or shops.

The fluid volume 14 is itself partially divided into respective first and second fluid reservoirs 20a, 20b by weir means in the form of a thermal barrier or wall 22 extending upwardly from the lower wall of the fluid volume 14, and fully between the side walls thereof. The wall 22 may be formed of substantially any material having suitable thermal insulative properties. In particular, it is advantageous for the wall 22 to be formed from a material having a low thermal conductivity so as to reduce thermal transfer therethrough between the first and second fluid reservoirs.

In the illustrated embodiment, the wall 22 terminates a distance from the upper wall such that a slot or opening 24 is defined therebetween. The slot or opening 24 thereby provides a fluid and/or thermal flowpath between upper regions of the respective first and second fluid reservoirs 20a, 20b. The first and second fluid reservoirs 20a, 20b are thus in fluid communication at their upper regions which together define a fluid mixing region, shown approximately by the dashed line 26 and described below.

Cooling means, in the form of an electrically powered cooling element 28, is disposed within the first fluid reservoir 20a so as to be immersed in the fluid. The cooling element 28 is disposed in a lower region of the first fluid reservoir 20a and is spaced from the side, end, upper and lower walls of the reservoir by a layer of fluid. The apparatus has an external power supply (not shown) to supply electrical power to the cooling element 28. The power supply can operate from a supply of mains power in the absence of bright sunlight. The power supply can also operate from photovoltaic panels (not shown) whereby the apparatus 1 can be run without the need of a mains supply during sunny daytime conditions.

In some embodiments the cooling element 28 may be arranged to cool fluid in the first fluid reservoir 20a by means of a refrigerant pumped therethrough by means of a pump external to the fluid volume 14. In some embodiments the cooling element 28 is pumped by refrigerant that has been cooled by expansion of compressed refrigerant in the manner of a conventional vapour-compression refrigeration cycle.

The first and second fluid reservoirs 20, 20b each contain a volume of a fluid having a negative temperature coefficient of thermal expansion below a critical temperature and a positive temperature coefficient of thermal expansion above the critical temperature. In the illustrated embodiments, the fluid is water, the critical temperature for which is approximately 4°C. The water largely fills both fluid reservoirs 20a, 20b, but a small volume may be left unfilled in each to allow for expansion. Liquids other than water are also useful.

Operation of the apparatus 1 will now be described.

It can be assumed that all of the water in the first and second fluid reservoirs 20a, 20b is initially at or around the ambient temperature. The apparatus 1 is activated such that electrical power is supplied to the cooling element 28, which thereby cools to a temperature that is typically well below the freezing point of water, for example, as low as -30°C. This, in turn, causes water in the immediate surroundings of the cooling element 28 within the first fluid reservoir 20a to cool. As the water cools, its density increases. The cooled water thus sinks towards the bottom of the first fluid reservoir 20a displacing warmer water which rises towards the upper region of the first fluid reservoir 20a.

It will be appreciated that, over time, most or all of the waler contained in the first fluid reservoir 20a is cooled to a temperature of 4°C or less. Because the density of water is at its maximum at the critical temperature, water at this temperature tends to pool at the bottom of the first fluid reservoir 20a displacing lower temperature water towards the upper region of the first fluid reservoir 20a. This leads to a generally positive temperature gradient being generated within the first fluid reservoir 20a with water at the critical temperature lying in the lower region of the first fluid reservoir 20a and less dense, more buoyant water at temperatures below the critical temperature lying in the upper region adjacent the opening 24 at the junction between the first and second fluid reservoirs 20a, 20b.

At this junction, hereafter referred to as the fluid mixing region 26, water at temperatures below the critical temperature displaced upwardly by the sinking of water at the critical temperature within the first fluid reservoir 20a meets and mixes with warmer water, for example at approximately lOt, disposed in the upper region of the second fluid reservoir 20b. A transfer of heat from the warmer water to the colder water thus occurs within the mixing region 26, causing the cold water from the first fluid reservoir 20a and the warmer water from the second fluid reservoir 20b to increase and decrease in temperature, respectively, towards the critical temperature. The fluid mixing region 26 thus defines a thermal transfer region of the apparatus 1 wherein transfer of heat between fluid from the first and second fluid reservoirs occurs.

As the cold water from the first fluid reservoir 20a rises in temperature towards the critical temperature, its density increases, as shown in Figure 1, and thus it sinks back down towards the cooling element 28, displacing cooler water below. Similarly, as the warmer water from the second fluid reservoir 20b reduces in temperature towards the critical temperature, its density increases and thus it, too, sinks down towards the lower region of the second fluid reservoir 20b displacing warmer water below.

The water in the second fluid reservoir 20b cooled following mixing within the mixing region 26 pools at the bottom of the second fluid reservoir 20b which, as described above, is disposed in thermal communication with the payload compartment 12. Heat from the payload compartment 12 is thus absorbed by the cooled volume of water in the second fluid reservoir 20b and the temperature of the payload compartment 12, and hence the objects or items stored therein, begins to decrease.

To reiterate, water within the first fluid reservoir 20a cooled to temperatures below the critical temperature by the cooling element 28 is displaced upwardly towards the mixing region 26 by water at the critical temperature. Conversely, within the second fluid reservoir 20b, water above the critical temperature is displaced upwardly towards the mixing region 26 by water at the critical temperature. Thus, water on either side of the thermal barrier 22, and at temperatures on either side of the critical temperature, merge and mix within the mixing region 26 causing the average temperature of the water in the mixing region 26 to approach the critical temperature and thus to cascade or sink back into the lower regions of the respective fluid reservoirs 20a, 20b.

Over time, this process reaches something approaching a steady state through the dynamic transfer of heat between water at temperatures below the critical temperature rising to the upper region of the first fluid reservoir 20a and water at temperatures above the critical temperature rising to the upper region of the second fluid reservoir 20b.

The applicants have discovered the surprising technical effect that, over time, despite the cooling element 28 being disposed in a lower region of the first fluid reservoir 20a, the temperature of the water in the second fluid reservoir 2Db reaches a steady state temperature approximately at the critical temperature. That is to say, much or all of the water in the second fluid reservoir 2Db, particularly at the lower region thereof, becomes comparatively stagnant, with a temperature of around 4°C. Water heated above the critical temperature by absorption of heat from the payload compartment 12 is displaced towards the mixing region 26 by water at the critical temperature descending from the mixing region 26 having been cooled by the below-critical temperature water in the upper region of the first fluid reservoir 20a.

Through absorption of heat from the payload compartment 12 by the water in the second fluid reservoir 20b, the payload compartment 12 is maintained at a desired temperature of approximately 4°C which is ideal for storing many products including vaccines, food items and beverages.

It is to be understood that fluid in contact with the cooling element 28 will typically freeze, and a solid mass of frozen fluid or ice will form in the first fluid reservoir. An ice detector may be provided for detecting the formation of ice once the ice has grown to a critical size.

Once the detector detects the formation of ice of the critical size the apparatus may be arranged to switch off the cooling element 28 to prevent further ice formation. Once the mass of frozen fluid has subsequently shrunk to a size below the critical size, the cooling element may be reactivated. The detector may be in the form of a thermal probe in thermal contact with fluid a given distance from the cooling element 28. Fluid in thermal contact with the detector will fall to a temperature at or close to that of the frozen fluid once the frozen fluid comes into contact with the detector. It is to be understood that a relatively abrupt temperature change typically takes place between the mass of frozen ice and fluid in contact with the ice within a very short distance from the frozen mass.

In the event that the power supply to the cooling element 28 is interrupted or disconnected, the displacement process imparted upon the water within the first and second fluid reservoirs 20a, 20b continues whilst the mass of frozen fluid remains in the first fluid reservoir 20a. Once the mass of frozen fluid is exhausted, the displacement process will begin to slow but is maintained by the continued absorption of heat from the payload space by the water in the second fluid reservoir 20b. Due to the high specific heat capacity of water and the significant volume of water at temperatures below the critical temperature within the fluid volume, the temperature in the lower region of the second fluid reservoir 20b remains at or close to 4°C for a considerable length of time.

That is to say, even without a supply of electrical power to the cooling element 28, the natural tendency of water at the critical temperature to sink and displace water above or below the critical temperature results in the first and second fluid reservoirs 20a, 20b, or at least the lower regions thereof, holding water at or around the critical temperature for some time after loss of power, enabling the payload compartment 12 to be maintained within an acceptable temperature range for extended periods of time. Embodiments of the present invention are capable of maintaining fluid in the second reservoir 20b at a target temperature for a period of up to several weeks.

Figures 4 and 5 illustrate a variation of the embodiment of Figure 2 adapted to be retrofitted to an existing refrigeration device. In the embodiment of Figure 4, the external shape of the casing 10 is configured to complement, and sit within, the internal volume of a conventional refrigerator (not shown). In particular, a lower region of the rear face of the casing 10 is stepped inwardly to accommodate the housing for the condenser and motor of the refrigerator which is often disposed at the lower rear portion of the refrigerator.

In the embodiment of Figure 5, in addition to the revised external shape of the casing 10, the cooling element 28 is disposed outside of the first fluid reservoir 20a and is instead integrated into the rear wall of the casing 10 and in thermal communication with the water contained in the first fluid reservoir 20a.

Operation of the embodiments of Figures 4 and 5 is substantially identical to that of the embodiment of Figure 2. It will also be appreciated that the positioning of the cooling element 28 outside of the first fluid reservoir 20a can be implemented independently of the external shape of the casing 10, for example in the embodiment of Figure 2.

In a further variation of the embodiments of Figures 4 and 5 (not shown), the cooling element 28 is eliminated and the rear wall of the casing 10 is replaced by a thermally conductive membrane. In this arrangement, the cooling means comprises the existing refrigeration device itself, the cooling element of the refrigeration device being used to perform the function of the cooling element 28. The operation of such an embodiment is substantially identical to that of Figure 2 in that the water in the first fluid reservoir 20a is cooled, in this case by the cooling apparatus of the refrigeration device in thermal communication therewith, through the conductive membrane thereby establishing the thermally-induced fluid displacement process described above.

Referring next to the embodiments of Figures 6 and 7, a dual payload space arrangement is shown. In this embodiment, a fluid-filled cooling chamber 50 is provided within the casing 10 with payload compartments 1 2a, 1 2b defined on either side thereof. The cooling chamber is at least partially divided into three chambers defining respectively, a central fluid reservoir 20a and two outer fluid reservoirs 20b1, 20b2, by weir means in the form of two upright, generally parallel walls 22a, 22b. In the illustrated embodiment, the walls 22a, 22b do not extend fully to the upper wall of the cooling chamber 50 and thereby define a fluid mixing region 26 disposed across the upper regions of the respective fluid reservoirs 20a, 20b1, 20b2.

In this embodiment, the central fluid reservoir 20a contains the cooling means in the form of an electrically powered cooling element 26 and thus is functionally equivalent to the first fluid reservoir 20a of the embodiment of Figure 2. Similarly, each of the outer fluid reservoirs 20b1, 20b2 is in thermal communication with a respective payload compartment 1 2b1, 1 2b2 and thus is functionally equivalent to the second fluid reservoir 20b of the embodiment of Figure 2.

Operation of the embodiment of Figure 6 is similar to that of the embodiment of Figure 2.

Specifically, water cooled to below the critical temperature within the central fluid reservoir 20a is displaced towards the fluid mixing region 26 by water at the critical temperature sinking to the bottom of the reservoir. The below-critical-temperature water mixes with warmer water from the outer fluid reservoirs 20b1, 20b2 in the fluid mixing region 26, which warmer water is thereby cooled towards the critical temperature in a process of thermal transfer and thus sinks down into the outer fluid reservoirs, displacing warmer water upwardly into the fluid mixing region 26. The below-critical-temperature water from the central fluid reservoir 20a is warmed by this thermal transfer process towards the critical temperature and, due to the corresponding increase in density, sinks into the central fluid reservoir 20a thereby displacing colder water upwardly into the fluid mixing region 26, whereupon the process is repeated. It is to be understood that in some embodiments fluid that rises within one fluid reservoir may subsequently fall within a different fluid reservoir.

This process continues until the water in the outer fluid reservoirs 20b1, 20b2 reaches a substantially steady state of at or around 4°C and is maintained at or near this temperature by the continuing thermally induced displacement of water within the reservoirs and the subsequent mixing within the fluid mixing region 26.

The embodiment of Figure 7 is structurally similar to that of Figure 6. In this embodiment, however, the cooling element 28 is replaced by a body of cold material 52 at a temperature that is below the intended operating temperature of the payload compartment. It will typically be below 0°C. A temperature of around -18°C can be obtained by placing the body 52 in a conventional food freezer before use, and -30°C or less would emulate the effect of a refrigeration unit. The body of cold material 52 can be anything with a suitable thermal mass. However, water ice is particularly suitable because it is readily available and has an advantageously high latent heat of fusion.

The ice may be in the form of standard 0.6 litre, plastic coated ice packs that are used in transport and storage of medical supplies. Other sizes of ice pack are also useful. Other arrangements may be used. In one embodiment, one or more blocks of ice, or a mass of ice cubes, is introduced into the central fluid reservoir 20a. In this case, since the displacement volume of the ice is greater than the equivalent volume when melted, the overall volume of water in the reservoir decreases as the ice melts. A sufficient draft of water above the thermal barriers 22a, 22b should be maintained within the cooling chamber 50 to enable fluid mixing when the volume of ice reduces during melting. A liquid drain arrangement may be provided in addition or instead in some arrangements.

Figure 8 illustrates, in plan view, a still further embodiment of the invention. In this embodiment, a cylindrical fluid-filled cooling chamber 50 is disposed generally centrally within the casing 10 with the payload compartment 12 defined by the space outside of the cooling chamber 50. Other locations of the chamber 50 are also useful.

The cooling chamber 50 is divided into inner and outer fluid reservoirs 20a, 20b by weir means in the form of a generally upright, cylindrical or tubular wall 22 extending upwardly from a lower surface of the cooling chamber. The cylindrical volume bounded by the wall 22 comprises the inner fluid reservoir 20a while the annular volume outside of the wall 22 comprises the outer fluid reservoir 20b. In the illustrated embodiment, the wall 22 does not extend fully to the upper wall of the cooling chamber 50 and thereby defines a fluid mixing region (not shown) disposed across the upper regions of the respective fluid reservoirs 20a, 20b.

In this embodiment, the inner fluid reservoir 20a contains the cooling means in the form of an electrically powered cooling element 28 and thus is functionally equivalent to the first fluid reservoir 20a of the embodiment of Figure 2. Similarly, the outer fluid reservoir 20b is in thermal communication with the payload compartment 12 and thus is functionally equivalent to the second fluid reservoir 20b of the embodiment of Figure 2.

Operation of the embodiment of Figure 8 is similar to that of the embodiment of Figure 2.

Specifically, water cooled to below the critical temperature within the inner fluid reservoir 20a is displaced towards the fluid mixing region 26 by water at the critical temperature sinking to the bottom of the reservoir. The below-critical-temperature water mixes with warmer water from the outer fluid reservoir 20b in the fluid mixing region 26, which warmer water is thereby cooled towards the critical temperature in a process of thermal transfer and thus sinks down into the outer fluid reservoir 20b, displacing warmer water upwardly into the fluid mixing region 26. The below-critical-temperature water from the inner fluid reservoir 20a is warmed by this thermal transfer process towards the critical temperature and, due to the corresponding increase in density, sinks into the central fluid reservoir 20a thereby displacing colder water upwardly into the fluid mixing region 26, whereupon the process is repeated.

This process continues until the water in the outer fluid reservoir 20b reaches a substantially steady state of at or around 4°C and is maintained at or near this temperature by the continuing thermally induced displacement of water within the fluid reservoirs and the subsequent mixing within the fluid mixing region 26.

It will be appreciated that the embodiments of Figures 6 -8 may find advantageous application in retail shelving such as that found in supermarkets. By disposing the cooling chamber 50 between oppositely accessible payload compartments 1 2a, 1 2b, or centrally within the casing so that a 360° payload compartment 12 is provided, the apparatus 1 can be positioned between adjacent aisles within the supermarket, or as a centrally positioned, standalone unit, providing increased retail frontage and improved flexibility for product placement.

Referring next to Figures 9a and 9b, a variation to the embodiment of Figure 8 is shown. In this embodiment, the cooling chamber 50 extends fully between the upper and lower walls of the casing 10 (although this is not essential) and the thermal barrier 22 is surrounded by a cylinder or sleeve 60 formed from a material having low thermal conductivity. The length of the cylinder 60 is variable such that at its minimum length, it extends approximately to the end of the annular wall 22, thereby retaining the thermal flowpath between the inner and outer fluid reservoirs 20a, 20b, while at its maximum length it extends into abutment with the upper wall of the cooling chamber 50 or casing 10. In this extended-length configuration, the outer fluid reservoir 20b is in fluid isolation and thermally insulated (or isolated) from the inner fluid reservoir 20a.

In one embodiment, it is envisaged that the sleeve may take the form of a bellows arrangement 60 whose natural length is comparable to the height of the walls 22 but which can be stretched or expanded such that it can close and/or seal off the inner fluid reservoir 20a. The bellows 60 may comprise a bi-metallic structure configured in such a way that when cold, the bellows expands towards the closed position.

Such an arrangement may be beneficial for mobile applications wherein the refrigeration apparatus is required to be moved or re-located on a frequent or regular basis. Movement of the apparatus, and hence the fluid volume tends to stir up the water upsetting the normal thermally-induced fluid displacement process.

In the present embodiment, however, when stirred up through movement of the apparatus, colder water in the central fluid reservoir 20a may be caused to spill over into the outer fluid reservoir 2Db thereby lowering the temperature therein. This drop in temperature "activates" the bellows arrangement 60 to close the slot or aperture 24 and hence substantially isolate the central fluid reservoir 20a, as shown in Figure 9b.

Once the apparatus is relocated and the temperature of the water in the outer fluid reservoir 2Db rises, the bellows arrangement 60 contracts to its natural length to permit the desired fluid displacement process to be re-established.

The inner surface of the bellows arrangement 60 may be insulated to prevent significant conduction of heat therethrough.

It will be appreciated from the foregoing that the bellows arrangement functions as a form of valve which can selectively close in order to disrupt the thermal conduction process within the apparatus and open when the process is to be re-established. It is also envisaged that the provision of such valve means may enable the temperature of the fluid in the outer fluid reservoir 20b to be varied. In particular, by reducing the depth of the gap 24 between the end of the wall 22 and the upper wall of the cooling chamber 50, such as by partially extending the bellows arrangement 60, the thermal conduction between the water in the central fluid reservoir 20a and the water in the outer fluid reservoir 2Db can be selectively adjusted, for example decreased. This permits the temperature of the water in the outer fluid reservoir 2Db to be increased above the critical temperature which may be beneficial depending on the nature of the objects or items contained in the payload compartment 12.

It is envisaged that the bellows arrangement 60 can be configured to operate, that is to say open and/or close, at any desired temperature, depending on the application. For example, in a battery cooler the bellows 60 may be arranged to close at a temperature of approximately 25°C and to release colder water when the temperature of the water in the outer fluid reservoir 20b exceeds this level.

In another embodiment (not shown) the bellows arrangement 60 is connected through the upper wall of the casing 10 to a retractable carrying handle attached thereto. The carrying handle is movable between a retracted position and a deployed, use position, the latter enabling the apparatus to be carried by a user. The bellows arrangement 60 is connected to the handle in such a way that, in the deployed position of the handle, the bellows is extended into abutment with the upper wall, thereby substantially sealing off the central reservoir 20a from the outer fluid reservoir 20b. Such an arrangement ensures that, during movement of the apparatus 1 requiring deployment of the handle, the reservoirs are mutually isolated so as to limit mixing of fluid, and consequent thermal disruption, during transportation. Once the apparatus is relocated, the handle is lowered or retracted causing the bellows arrangement 60 to retract to its natural, open position.

It is envisaged that the handle may also be connected to a door or closure of the apparatus such that deploying the handle not only raises the bellows and substantially seals off the fluid reservoirs but additionally locks the closure. Releasing the handle after relocation of the apparatus lowers the bellows arrangement 60 and unlocks the closure.

It will be appreciated that the above-described bellows arrangement 60 is not limited to the embodiment of Figures 9a and 9b and can be readily adapted or re-configured for use in the embodiments of Figures 2-6.

It is to be further understood that the retractable handle described above may be connected to a valve not comprising a bellows arrangement. With the handle in a retracted position the valve may be arranged to open; with the handle in a deployed condition (such as when the apparatus is being carried) the valve may be arranged to close.

The above description assumes that the maximum density of water occurs at 4°C, which is the case for pure water. The temperature at which the maximum density occurs can be altered by introduction of impurities into the water. For example, if salt is added to the waler to a concentration of 3.5% (approximately that of sea water) then the maximum density occurs at nearer 2°C. This can be used to adjust the temperature of the payload space for specific applications. Other additives may be employed to raise or lower the critical temperature, as required.

Figure 10 illustrates a further embodiment in which the position of the wall 22 within the fluid volume 14 is adjustable. As with the above mentioned bellows arrangement 60, adjusting the position of the wall 22 allows the fluid displacement process to be modified, for example slowed or reduced. In the illustrated embodiment, wall 22 is pivotable about its lower end so as to vary the area of the upper openings of the first and second fluid reservoirs 20a, 20b.

This can be used to affect the flow of fluid between the first and second fluid reservoirs and hence control the thermal transfer therebetween. For example, by tilting the wall 22 towards the payload compartment, the area of the upper opening of the second fluid reservoir 20b is reduced, thereby reducing the rate at which fluid is displaced therefrom. This, in turn, allows the temperature of the fluid in the second fluid reservoir 20b to be maintained at temperatures above 4°C if required. It will be appreciated from the foregoing that the movable wall 22 in this embodiment also functions as a valve means.

Another beneficial effect provided by the wall 22 being tilted towards the payload compartment is that ice formation within the first fluid reservoir may be facilitated without blocking the upward flow of cooler water into the mixing region 26. This beneficial effect is equally applicable where the wall 22 is substantially permanently fixed at an angle inclined or tilted towards the payload compartment, an arrangement also envisaged within this application.

It will be appreciated that the present invention provides a novel and inventive device for storing and cooling items such as vaccines, perishable food items as well as a plurality of beverage containers such as bottles or drinks cans, providing a temperature controlled storage means which can be maintained within a desirable temperature range following loss of power to the device for many hours. Embodiments of the invention are arranged to passively regulate the flow of heat energy inside the device, to enable long-term storage of temperature sensitive products.

Of particular benefit is the feature that, in embodiments of the invention, the fluid reservoirs 20a, 20b are disposed in a side-by-side configuration with the payload compartment 12. By avoiding the use of a head-space above the payload compartment, greater versatility is provided for setting the size, shape and position of the payload compartment.

Other embodiments of the invention provide a battery cooler for cooling batteries used as back-up power supplies. In this case, the battery may be housed in the payload compartment 12 or in another area in thermal communication with the second or outer fluid reservoirs 2Db, 20b1, 20b2.

Embodiments of the invention effect a relatively slow and/or gentle heat transfer process primarily by thermal conduction through the fluid but which, at start up of the system, may be effected more rapidly so as to cause the second or outer fluid reservoirs 2Db, 20b1, 20b2 to reach a working temperature more quickly, by means of thermally-induced fluid displacement within the fluid volume.

The above described embodiments represent advantageous forms of the invention but are provided by way of example only and are not intended to be limiting. In this respect, it is envisaged that various modifications and/or improvements may be made to the invention within the scope of the appended claims.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example comprising" and comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Claims

CLAIMS1. An apparatus comprising: first and second fluid reservoirs; cooling means for cooling fluid contained in the first fluid reservoir; and a thermal transfer region disposed between respective upper regions of the first and second fluid reservoirs for permitting thermal transfer between the fluid contained in the first fluid reservoir and fluid contained in the second fluid reservoir.
2. An apparatus as claimed in claim 1, wherein the first and second fluid reservoirs are defined, at least in part, by a container having weir means dividing the container into said first and second fluid reservoirs.
3. An apparatus as claimed in claim 2, wherein the weir means comprises a wall or other structure extending into the volume of the container with the first and second fluid reservoirs being defined by the respective volumes on either side thereof.
4. An apparatus as claimed in claim 2 or claim 3, wherein the weir means is formed from a material having a low thermal conductivity or an insulating material.
5. An apparatus as claimed in any of claims 2 to 4, wherein the weir means extends from a lower wall of the container towards an upper wall of the container.
6. An apparatus as claimed in claim 5, wherein an upper end of the weir means is spaced from the upper wall of the container so as to define a gap, aperture or slot therebetween.
7. An apparatus as claimed in any of claims 2 to 5, wherein the weir means extends between upper and lower walls of the container and includes one or more apertures or slots provided in an upper region thereof.
8. An apparatus as claimed in any preceding claim wherein the first and second fluid reservoirs are in fluid communication via said thermal transfer region.
9. An apparatus as claimed in any of claims 1 to 7 wherein the first and second fluid reservoirs are in fluid isolation from one another.
10. An apparatus as claimed in claim 9 comprising a fluid-tight, thermally conductive barrier disposed between the upper regions of the first and second fluid reservoirs.
11. An apparatus as claimed in any of claims 6 to 10, wherein the thermal transfer region is defined, at least in part, by one or more of: a region at or adjacent the upper end of the weir means; a region at or adjacent the one or more apertures or slots in the weir means; and a region at or adjacent the thermally conducting barrier.
12. An apparatus as claimed in any preceding claim wherein the thermal transfer region is arranged to permit limited mixing of fluids from the first and second fluid reservoirs.
13. An apparatus as claimed in any preceding claim, wherein one or both of the first and second fluid reservoirs is arranged, in use, to contain a fluid having a negative temperature coefficient of thermal expansion below a critical temperature and a positive temperature coefficient of thermal expansion above the critical temperature.
14. An apparatus as claimed in any preceding claim wherein the first and second fluid reservoirs contain the same fluid.
15. An apparatus as claimed in any preceding claim wherein the first and second fluid reservoirs contain different fluids.
16. An apparatus as claimed in claim 15, wherein the fluids contained in the first and second fluid reservoirs have different critical temperatures.
17. An apparatus as claimed in any preceding claim, wherein the fluid comprises water or a fluid having similar thermal properties to water.
18. An apparatus as claimed in any preceding claim wherein the cooling means is arranged to cool fluid in the first fluid reservoir to a temperature below a critical temperature thereof.
19. An apparatus as claimed in any preceding claim wherein the cooling means is arranged to cool fluid in a region of the first fluid reservoir disposed below said upper region to a temperature below a critical temperature thereof such that fluid in the first fluid reservoir that is cooled below the critical temperature rises in the first fluid reservoir towards said upper region.
20. An apparatus as claimed in claim 18 or claim 19 wherein fluid within the first fluid reservoir at a temperature above or below the critical temperature is displaced towards the upper region of the first fluid reservoir by water at the critical temperature.
21. An apparatus as claimed in any of claims 18 to 20, wherein fluid within the first fluid reservoir at a temperature below the critical temperature and displaced to the upper region of the first fluid reservoir in use mixes in the thermal transfer region with fluid from the second fluid reservoir at a temperature above the critical temperature.
22. An apparatus as claimed in any preceding claim, wherein fluid at the upper region of the second fluid reservoir is cooled towards a critical temperature through mixing in the thermal transfer region with fluid from the first fluid reservoir.
23. An apparatus as claimed in claim 22, wherein fluid at the critical temperature disposed in the thermal transfer region sinks into the a lower region of the second fluid reservoir.
24. An apparatus as claimed in any preceding claim wherein the cooling means comprises a refrigeration unit or element arranged to cool water within the first fluid reservoir, and a power supply unit for providing power to the refrigeration unit.
25. An apparatus as claimed in claim 24, wherein the power supply comprises at least one of: a solar power supply; and a mains power supply.
26. An apparatus as claimed in any preceding claim, wherein the cooling means comprises a thermal mass that, in use, and at least initially, is at a temperature below a critical temperature of the fluid.
27. An apparatus as claimed in claim 26, wherein the thermal mass comprises a body of water ice.
28. An apparatus as claimed in claim 2 or any claim dependent on claim 2, wherein the weir means comprises at least one of: a cylindrical wall, with the first fluid reservoir being defined within the wall and the second fluid reservoir being defined outside the wall; and a generally planar wall, with the first and second fluid reservoirs being disposed, respectively, on opposite sides of the wall in a side by side arrangement.
29. An apparatus as claimed in any preceding claim comprising valve means for hindering or preventing thermal transfer between fluid contained in the first fluid reservoir and fluid contained in the second fluid reservoir.
30. An apparatus as claimed in claim 29, wherein the valve means is selectively operable to thermally and/or fluidly isolate the fluid contained in the first fluid reservoir and the fluid contained in the second fluid reservoir.
31. An apparatus as claimed in claim 29 or claim 30 wherein the valve means comprises an expandable sleeve at least partially surrounding the weir means.
32. An apparatus as claimed in claim 29 or claim 30 wherein the valve means comprises the weir means being movable so as to alter the volume and/or shape of the upper region of the first and/or second fluid volume so as to restrict movement of water therethrough.
33. An apparatus as claimed in any preceding claim further comprising a third fluid reservoir, the first fluid reservoir including the cooling means and being disposed between the second and third fluid reservoirs, wherein the thermal transfer region is disposed between respective upper regions of the first, second and third fluid reservoirs for permitting thermal transfer between the fluid contained therein.
34. A refrigerator comprising an apparatus as claimed in any preceding claim and a payload volume for containing one or more objects or items to be cooled, the payload volume being disposed in thermal communication with the second fluid reservoir.
35. A refrigerator as claimed in claim 34 comprising one or more of: A bottle cooler; A fluid pipeline for dispensing beverages; and A battery cooler.
36. A refrigerator as claimed in claim 34 or claim 35 and arranged to be disposed within a conventional refrigerator or the like, wherein the cooling means comprises an existing cooling element or cooling system of the refrigerator, and wherein the apparatus is configured to be positioned within the refrigerator such that the first fluid reservoir is in thermal communication with the existing cooling element or cooling system so as to cool the fluid therein.
37. A refrigeration apparatus comprising: a casing; a fluid volume disposed within the casing and comprising weir means dividing the fluid volume into a first, central fluid reservoir, and second and third, outer fluid reservoirs; cooling means disposed in the first fluid reservoir for cooling fluid contained in the first fluid reservoir; a thermal transfer region defined, at least in part, by respective upper regions of the fluid reservoirs for permitting heat transfer between fluid contained in the first fluid reservoir and fluid contained in the second and third fluid reservoirs; and first and second payload compartments disposed within the casing and in thermal communication with the second and third fluid reservoirs.
38. A refrigeration apparatus comprising: a casing; a fluid volume disposed within the casing and comprising a cylindrical weir means dividing the fluid volume into a first, inner fluid reservoir, and a second, outer fluid reservoir; cooling means disposed in the first fluid reservoir for cooling fluid contained in the first fluid reservoir; a thermal transfer region defined, at least in part, by respective upper regions of the fluid reservoirs for permitting heat transfer between fluid contained in the first fluid reservoir and fluid contained in the second fluid reservoir; and a payload compartment disposed within the casing, at least partially surrounding the fluid volume and in thermal communication with the second fluid reservoir.
39. A method comprising: cooling a fluid in a lower region of a first fluid reservoir; permitting fluid within the first fluid reservoir at a temperature below a critical temperature of the fluid to rise to an upper region of the first fluid reservoir; mixing the fluid at a temperature below the critical temperature with fluid at a temperature above the critical temperature from a second fluid reservoir in a thermal transfer region disposed between respective upper regions of the first and second fluid reservoirs; and permitting fluid at the critical temperature in the thermal transfer region to sink into at least the second fluid reservoir so as to cool a payload compartment in thermal communication therewith.
40. An apparatus, a refrigerator or a method constructed and/or arranged substantially as described herein with reference to the accompanying drawings.