WO2017153405A1

WO2017153405A1 - Vapor producing device

Info

Publication number: WO2017153405A1
Application number: PCT/EP2017/055318
Authority: WO
Inventors: Guangming Su; Weimin Xiao; Yafang JIN; Qiao HUA
Original assignee: Koninklijke Philips N.V.
Priority date: 2016-03-07
Filing date: 2017-03-07
Publication date: 2017-09-14

Abstract

A device for producing a vapor from a liquid is provided together with a method of operating the device and a food storage container comprising the device. The device comprises a container, an expansion mechanism, an inlet and an outlet. The container defines, at least in part, a volume for containing the liquid to be vaporized in fluid communication with gas inside the volume. The expansion mechanism enables the volume to be expanded from a first size to a second size. The inlet enables gas to enter the volume when the volume is expanded to the second size. The outlet enables gas comprising the vapor produced from the liquid to exit the volume. Both the inlet and the outlet are configured to restrict the entry of gas into the volume during expansion of the volume from the first size to the second size.

Description

VAPOR PRODUCING DEVICE

FIELD OF THE INVENTION

The present invention relates to the vaporization of liquid. In particular, it relates to a humidifier device for producing water vapor from liquid water, as well a method for operating the device and a food storage container comprising the device.

BACKGROUND OF THE INVENTION

Humidifiers are widely used in both domestic and industrial appliances and applications to control the relative humidity of an environment. As an example, humidifiers are commonly used to increase the relative humidity in interior spaces of buildings.

Humidifiers are particular useful for those purpose for buildings in arid climates, or for those in cold climates during the heating season (e.g. winter), since the relative humidity in the interior spaces of such buildings is typically at a lower level than is desirable.

There are three different types of humidification technologies used by current humidifiers. The first type, evaporative humidification, typically achieves humidification by passing an air flow across the surface of heated water, or across a wet membrane, to absorb water vapor. The second type, steam humidification, produces water vapor through the production of steam by heating or boiling the water using a heating element such as an electrode or an infrared element. Finally, the third type, water spray humidification, produces a mist (as opposed to vapor) by breaking the water into fine droplets that are suspended in the air. These droplets may subsequent evaporate into water vapor if they are able to absorb enough heat energy from the air.

Evaporation of a liquid occurs from the surface of a liquid (e.g. water), into a gaseous phase that is not saturated with the evaporating substance (e.g. water vapor). In essence, on average, a fraction of the molecules in the liquid will have enough heat energy to escape from the liquid to enter the gaseous phase, so long as the relative humidity of the gaseous phase is less than 100%. If the evaporation takes place in an enclosed area, the escaping molecules accumulate as a vapor above the liquid raising the relative humidity of the gaseous phase. The correlation between W₀ the evaporation rate of water (k mol/h) and pressure may be expressed by the following equation:

W₀ = 140 x S x (P, ,s - Pw) x Λ/MW ÷ (2 x π x R x T in which: S is the area (m ²) of the water's surface; P_WiS is the saturated vapor pressure (bar) at a temperature T; P_w is the partial pressure of the vapor in the chamber (bar); M_w is the molar mass of water; R is the universal gas constant; and T is the temperature of the water

(K).

SUMMARY OF THE INVENTION

The known humidification technologies have complicated structures and/or consume a significant amount of energy, in particular for heating. This heating also increases the dry-bulb air temperature. There is therefore a need for a simple and efficient design for a device for producing vapor and which avoids at least some of these drawbacks.

The invention is defined by the claims.

According to examples in accordance with a first aspect of the invention, there is provided a device for producing a vapor from a liquid. The device has a container defining, at least in part, a volume for containing the liquid to be vaporized. The liquid to be vaporized is in fluid communication with gas inside the volume. The device has an expansion mechanism for expanding the volume from a first size to a second size. The device has an inlet for enabling gas to enter the volume when the volume is expanded to the second size. The device has an outlet for enabling gas comprising the vapor produced from the liquid to exit the volume. The inlet and the outlet are configured to restrict the entry of gas into the volume during expansion of the volume from the first size to the second size.

The aforementioned equation can be simplified, for a particular predetermined system, to the following equation:

in which A is a constant. Therefore, if the system temperature and the water surface area remain constant, lowering the vapor partial pressure (i.e. increasing the degree of vacuum) will result in a higher rate of evaporation of the water. Indeed, in general, the rate of evaporation of a liquid occurs faster if the gaseous phase exerts less pressure on the surface of the liquid as this pressure keeps the molecules from launching into the gaseous phase.

As a result of the restriction of the entry of gas into the volume by the inlet and the outlet during expansion of the volume from the first size to the second size, the expansion of the volume results in the pressure of the gas inside the volume being reduced. This reduction in gas pressure leads to the vaporization of at least part of the liquid inside the volume. After the volume has been fully expanded to the second size, gas may enter the volume via the inlet and the gas inside the volume, which comprises the vapor produced during the expansion of the volume, may exit the volume via the outlet. Through this use of pressure to vaporize the liquid, the device provides an efficient way of humidifying an environment that can avoid significantly altering the dry bulb air temperature. Also, because the device does not rely on heating the liquid to vaporize it, any safety concerns based on the liquid drying up in the container can be abated. Furthermore, the device produces vapor from the liquid without generating water droplets or mist that can cause significant amounts of condensation within the environment to be humidified. Because the device does not generate water droplets or mist, the device can have more relaxed requirements for water quality as any impurities in the water will not be present in the water vapor that is produced.

The expansion mechanism for expanding the volume from the first size to the second size may comprise an expansion mechanism for expanding the volume from the first size to the second size and subsequently contracting the volume from the second size to the first size and wherein the outlet is further configured to enable the gas comprising the vapor to exit the volume during the contraction of the volume. The use of an expansion mechanism which is also configured to contract the volume from the second size to the first size allows the volume to be contracted (or collapsed or shrunk or reduced) which helps to reconfigure the device for another vapor-producing expansion cycle thereby enabling the continuous (or recurrent or repeated or cyclical) operation of the device. The pressure of the gas in the volume does not substantially change during the contraction of the volume because the outlet allows the gas to escape while the size of the volume is being reduced. Therefore, the contraction of the volume also helps to expel the vapor from the volume through the outlet.

The expansion mechanism may comprise a movable structure which at least partly defines the volume.

The expansion mechanism may comprise a piston which at least partly defines the volume. The piston is movable between a first position, which defines the first size of the volume, and a second position, which defines the second size of the volume. The use of a piston provides a convenient and cost effective way of enabling the container's volume to be expanded. The use of a piston to contract the volume allows the device to provide precise control over the humidification by controlling the speed and distance of the movement of the piston. The device may comprise a motor which is configured to move the piston between the first position and the second position to expand and contract the volume. The inlet may be located between the first position of the piston and the second position of the piston in proximity to the second position. This position of the inlet means that the inlet is only in fluid communication with the volume when the piston is substantially in the second position. This arrangement provides a convenient way of ensuring that gas may only enter the volume via the inlet when the volume is substantially expanded to the second size and not during expansion of the volume from the first size to the second size. Preferably, the proximity of the inlet to the second position is less than 20% of the distance between the second and first positions. Yet more preferably, the proximity of the inlet to the second position is less than 10% of the distance between the second and first positions. Yet more preferably still, the top of the inlet is positioned so that it is aligned with the bottom of the piston when the piston is in the second position. This alignment of the top of the inlet with the bottom of the piston means that the inlet is only fully in fluid communication with the volume once the piston has reached the second position.

The outlet may be lower than the inlet.

The container may comprise a detachable reservoir portion for containing the liquid. The use of a detachable reservoir portion enables easy cleaning and maintenance of the container and the reservoir portion, as well as allowing the liquid within the container to be easily replenished. The detachable reservoir portion may be connected to the container via a screw joint.

The inlet may comprise a valve. Preferably the inlet valve comprises a nonreturn valve configured to prevent gas from exiting the volume via the inlet.

The outlet may comprise a valve. Preferably the outlet valve comprises a nonreturn valve configured to prevent gas from entering the volume via the outlet.

The liquid to be vaporized may be water and/or the gas may be air.

According to examples in accordance with a second aspect of the invention, there is provided a food storage container which comprises a device according to the first aspect. The device according to the first aspect of the invention is particularly suitable for use in humidifying a food storage container (where a higher level of relative humidity is desired to prolong the life of the food). This is because, it avoids increasing the dry bulb air temperature or increasing amounts of condensation both of which can cause damage to the food (especially fruits and vegetables) being stored.

The food storage container may further comprise a refrigeration unit. For example, the food storage container may be a refrigerator, a refrigerating house or a refrigerating container. The device according the first aspect of the invention is particularly suitable for use in a food storage container comprising a refrigeration unit, because there is no need for the air temperature to rise, either as part of the humidifying process, or as a result of it. This means that the operation of the device according to the first aspect of the invention does not conflict with the operation of the refrigeration unit which functions to cool the air temperature. Therefore, the refrigerated food storage container can function more efficiently and maintain a better environment for the storage of food.

The food storage container may further comprise a heating element for cooking food contained in the food storage container. For example, the food storage container may be a cooker, an oven, a grill, a microwave or an air-frying cooker. The use of the device according to the first aspect of the invention in a food storage container comprising a heating element allows the humidity to be controlled during the cooking of food contained in the food storage container.

According to examples in accordance with a third aspect of the invention, there is provided a method of operating a device according to the first aspect of the invention to humidify an enclosed space. The method comprises the steps of: expanding the volume from a first size to a second size while the entry of gas into the volume is restricted by the inlet and the outlet; allowing gas to enter the volume via the inlet while the volume is expanded to the second size; contracting the volume from the second size to the first size; and allowing gas comprising the vapor to exit the volume via the outlet during the contraction of the volume. The method may further comprise the steps of: receiving a feedback signal indicating a relative humidity in the enclosed space; calculating a target position for the piston based on the feedback signal and a target humidity level; and stopping the movement of the piston when the piston reaches the target position. By stopping the piston when the piston reaches an appropriate position, the humidification of the environment can be precisely controlled to reach a target humidity level.

Therefore, embodiments of the present invention can overcome various drawbacks that may be present in current humidifiers.

For example, whilst the use of evaporative humidification generates water vapor which is not easy to condense, it can cause an increase in the dry-bulb temperature as measured. This unwanted temperature change may occur as air is forced across the warmed liquid (or membrane) in such a humidifier. Increasing the dry-bulb temperature can cause damage to items (such as, for example, fruit and vegetables) in the environment being humidified. Furthermore, evaporative humidification systems which use a membrane may require more regular cleaning and or replacement of parts, due to the depositing of impurities from the liquid (i.e. "liming-up" in humidifiers using hard water).

Similarly, steam humidification will also tend to generate vapor which has a much higher temperature than the vapor produced by embodiments of the present invention. Additionally, the use of steam humidification incurs a high running cost due to the requirement to heat the liquid, which is not incurred required by embodiments of the present invention.

Finally, water spray humidification produces a mist (as opposed to vapor) which can easily condense resulting in various issues. Firstly, the condensation of the mist result in the relative humidity of the environment being humidified decreasing. Secondly, the formation of liquid water can result in microbial contamination of the environment being humidified. This is particularly undesirable when the environment being humidified is used for storing food. The problems associated with water spray humidification can be

exacerbated when it is used in conjunction with a refrigerator. This is because the mist that is produced needs heat from the environment to evaporate into water vapor, whilst a refrigerator generally functions to reduce the heat that is available within it storage chamber. Therefore, even more of the mist will tend to condense in a refrigerated environment.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 A schematically illustrates an exemplary device for producing a vapor from a liquid in a first configuration according to an embodiment of the invention;

Fig. IB schematically illustrates the exemplary device of Fig. 1 A in an intermediate configuration during an expansion of the device according to an embodiment of the invention;

Fig. 1C schematically illustrates the exemplary device of Figs. 1A and IB in a second configuration following the expansion of the device according to an embodiment of the invention; Fig. ID schematically illustrates the exemplary device of Figs. 1A, IB and 1C in an intermediate configuration during contraction of the device according to an embodiment of the invention;

Fig. 2 schematically illustrates an exemplary method of operating the device illustrated in Figs. 1A, IB, 1C and ID; and

Fig. 3 schematically illustrates an exemplary food storage container comprising the device illustrated in Figs. 1A, IB, 1 C and ID.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the description that follows and in the figures, certain embodiments of the invention are described. However, it will be appreciated that the invention is not limited to the embodiments that are described and that some embodiments may not include all the features that are described below. It will be evident, however, that various modifications and changes may be made herein without departing from the broader spirit and scope of the invention as set forth in the appended claims.

Figs. 1A, IB, 1C and ID of the accompanying drawings schematically illustrate an exemplary device 100 for producing a vapor 105 from a liquid 1 10 according to an embodiment of the invention. Typically the liquid 1 10 is water. However, the device 100 may be used to produce vapor 105 from any liquid 1 10.

The device 100 comprises a container 120, an expansion mechanism, an inlet

140 and an outlet 150.

The container 120 defines, at least in part, a volume for containing the liquid 1 10 to be vaporized. The liquid 1 10 is contained in fluid communication with gas that is also contained inside the volume. Typically the gas is air. However, the device 100 may be used to produce vapor 105 mixed with any other gas. The container 120 may comprise a detachable reservoir portion 160 for containing the liquid 1 10. The detachable reservoir portion 160 may be connected to the container 120 via a screw thread 170 or any other detaching mechanism (such as clips) which allows the detachable reservoir portion 160 to be removed from container 120. The detachment of the detachable reservoir portion 160 may allow for easy refilling of the liquid 1 10 within the device 100, as well as cleaning of the inside of the detachable reservoir portion 160 and the container 120. The container 120 may comprise a liquid inlet (not shown) which may be used to maintain a certain level of liquid within the container 120. As an example, a float switch may be used to open the liquid inlet when the level of the liquid drops below a certain level allowing the container 120 to fill with liquid. Once the container 120 has filled with sufficient liquid to allow the level of the liquid to reach the desired level, the float switch may close the liquid inlet preventing any further entry of liquid into the container 120. The container 120 may be any shape. For example, the container 120 may be cylindrical or cuboid. The container 120 may be made of any material, such as metal, which prevents the passage of liquid and gas through it.

The expansion mechanism enables the volume to be expanded from a first size when the device 100 is in a first configuration, as illustrated in Fig. 1 A, to a second size when the device 100 is in a second configuration, as illustrated in Fig. 1C. During expansion of the volume from the first size to the second size, the device 100 may enter one or more intermediate configurations, such as that illustrated in Fig. IB in which the volume is larger than the first size, but smaller than second size.

The expansion mechanism may be configured to contract the volume from the second size to the first size following the expansion of the volume to the second size. During contraction of the volume from the second size to the first size, the device 100 may enter one or more intermediate configurations, such as that illustrated in Fig. ID. However, in some embodiments of the invention which may relate to a single-use type of device 100, the expansion mechanism need not allow the volume to be contracted back to the first size. The expansion mechanism may comprise a piston 130 which at least partly defines the volume, as illustrated in Figs. 1 A, IB, 1C and ID. The piston 130 is movable between a first position, in which the device 100 is in the first configuration (as illustrated in Fig. 1 A) and a second position, in which the device 100 is in the second configuration (as illustrated in Fig. 1C). The first position of the piston 130 defines the first size of the volume, whilst the second position of the piston 130 defines the second size of the volume. The piston 130 may be coupled with a seal (such as a plastic seal) to help create a better seal between the piston 130 and the container 120 and ensure that the pressure inside the volume is unaffected by gas from the environment leaking into the volume. The device 100 may further comprise an electric motor connected to the piston 130. The electric motor may be configured to move the piston 130 between the first position and the second position to expand and contract the volume.

Whilst the device 100 shown in Figs. 1A, IB, 1C and ID uses a piston 130 for the expansion mechanism, it will be appreciated that other expansion mechanisms may be used instead. As an example, the container 120 may comprise a folded concertina portion as the expansion mechanism, in which case, the volume may be expanded from the first size to the second size by manipulating the container 120 to unfold the concertina portion, thereby enlarging the volume defined by the container 120. Alternatively, as a further example, the container 120 may be formed as a telescopic cylinder arrangement, in which two or more concentric tubes are nested within one another to form an expansion mechanism comprising one or more sleeves around a main cylinder. The volume within such a container 120 may then be expanded from the first size to the second size by manipulating the one or more sleeves so that the container 120 expands telescopically, thereby enlarging the volume defined by the container 120. Yet further expansion mechanisms are envisaged in which the container 120 comprises a flexible, stretchable, balloon-like portion, which may be enlarged to increase the volume within the container 120. It will be appreciated that any expansion mechanism may be used which enables the volume to be expanded from a first size to a second size. The expansion mechanism may be a discrete component, such as the piston 130, which, at least partly, defines the volume together with the container 120, or may be a movable structure forming part of the container 120 itself (as in the above examples). In the latter case, the volume may (although not necessarily) be entirely defined by the container 120.

The inlet 140 enables gas to enter the volume when the volume is expanded to the second size (i.e. when the device 100 is in the second configuration as illustrated in Fig. 1C). The inlet 140 is configured to restrict the entry of gas into the volume during expansion of the volume from the first size to the second size. The inlet 140 may comprise a valve 180 configured to enable and restrict the entry of gas into the volume appropriately. For example, the valve 180 may be controlled electronically such that it is closed while volume is expanding from the first size to the second size, but is open when the volume reaches the second size. The valve 180 may be a non-return (or check) valve, such as a butterfly valve, which is configured to prevent gas from exiting the volume via the inlet 140. As an alternative or in addition to controlling the flow of air through the inlet 140 using a valve

180, the flow of air into the volume may further be controlled by the positioning of the inlet 140. In particular, the inlet 140 may be positioned such that the inlet 140 is in fluid communication with the volume only once the volume is substantially expanded to the second size. This may be achieved, for example, by locating the inlet 140 between the first and second positions of the piston 130 but in proximity to the second position of the piston 130, as illustrated in the device 100 shown in Figs. 1A, IB, 1C and ID. As can be seen, by locating the inlet 140 at such a position, the inlet 140 is not in fluid communication with the volume defined by the container 120 and the piston 130 when the piston 130 is in the first position, as shown in Fig. 1A, or while the piston 130 is in an intermediate position during expansion (or compression) of the volume, as shown in Fig. IB (or ID). This means that no air may enter the volume through the inlet 140 while the piston 130 is in the first position or the intermediate positions during expansion (or compression) of the volume. It is only when the volume is substantially expanded to the second size (i.e. when the piston 130 is substantially in the second position), as shown in Fig. 1C, that the inlet 140 is in fluid communication with the volume such that gas may enter the volume through the inlet 140. The gas entering the volume through the inlet 140 may be at atmospheric pressure (or the pressure of the gas within the environment being humidified) or may be pressurised to a higher pressure. In either case, the lower pressure within the volume when the volume is expanded to the second size results in gas entering the volume through the inlet 140. The proximity of the inlet 140 to the second position may be less than 20%, or less than 10%, of the distance between the second and first positions. In other words, the distance from the inlet 140 to the second position may be less than one fifth, or less than one tenth, of the distance from the inlet 140 to the first position. The inlet 140 may be aligned with the bottom of the piston 130 when the piston 130 is in the second position, as shown in Figs. 1A, IB, 1C, ID. Such an alignment of the top of the inlet 140 with the bottom of the piston 130 means that the inlet 140 is only fully in fluid communication with the volume once the piston 130 has reached the second position.

The outlet 150 enables gas comprising the vapor 105 to exit the volume. The outlet 150 is configured to restrict the entry of gas into the volume during expansion of the volume from the first size to the second size. The outlet 150 may comprise a valve 190 which is configured to enable and restrict the entry of gas into the volume appropriately. For example, the valve 190 may be controlled electronically such that it is closed while the volume is expanding from the first size to the second size, but is open when the volume reaches the second size once the pressure inside the volume has been equalised with the pressure (e.g. atmospheric pressure) of the gas entering the volume via the inlet 140 (and while the volume is being contracted back to the first size). The valve 190 may be a nonreturn (or check) valve, such as a butterfly valve, which is configured to prevent gas from entering the volume via the outlet 150. The gas comprising the vapor 105 may be expelled from the volume through outlet 150 as a result of displacement by gas entering the volume through the inlet 140 when the volume is the second size. Additionally or alternatively, the gas comprising the vapor 105 may be expelled from the volume through the outlet 150 due to the contraction of the volume from the second size back to the first size. Although the inlet 140 and the outlet 150 are shown as separate passages into the volume in Figs. 1A, IB, 1C and ID, the functions performed by the inlet 140 and the outlet 150 may be achieved by a single passage into the volume. For example, the container 120 might only contain a single inlet/outlet passage where the outlet 150 is provided in the device 100 shown in Figs. 1A, IB, 1C and ID. This single inlet/outlet passage may be provided with a valve which is configured to be closed while the volume is expanded from the first size to the second size, preventing any gas from entering or exiting the volume, and then opened once the volume is expanded to the second size, allowing gas to enter the volume due to the lower pressure inside the volume, and then kept open during a subsequent contraction of the volume back to the first size such that gas comprising the vapor 105 is expelled out of the volume through the passage.

Additionally, although the inlet 140 and the outlet 150 are shown as providing passages into the volume through the container 120, the inlet 140 and the outlet 150 may be provided in other locations. For example, either the inlet 140 or the outlet 150 or both may be provided through the piston 130 instead. Furthermore, whilst the inlet 140 is shown being higher than the outlet 150, which can make for a more simple and cost effective device, in other embodiments, the inlet 140 may be lower than the outlet 150. Similarly, the inlet 140 and the outlet 150 need not be provided on opposite sides of the container 120, as illustrated in Figs. 1A, IB, 1C and ID, and can be provided in any relative orientation including, for example, being on the same side of the container 120.

Furthermore, whilst generally the inlet 140 and the outlet 150 restrict the entry of gas into the volume during the expansion of the volume from the first size to the second size so as to cause the pressure of the gas within the volume to be reduced as a result of the expansion of the volume, this does not necessarily mean that no gas may enter the volume during expansion of the volume. Indeed, in some embodiments, either the inlet 140 or the outlet 150 or both may permit some gas to enter the volume during part or all of the expansion of the volume. However, in such embodiments, the rate of entry of gas into the volume is restricted to a sufficiently low rate that the pressure of the gas within the volume is reduced during part or all of the expansion thereby resulting in the production of the vapor 105.

The device 100 illustrated in Figs. 1A, IB, 1C and ID will now be discussed further with reference to Fig. 2 which schematically illustrates an exemplary method 200 of operating the device 100 according to an embodiment of the invention. At a step 210, the method 200 comprises expanding the volume from the first size to the second size. For example, the piston 130 may be moved from the first position to the second position transforming the device 100 from the first configuration shown in Fig. 1 A to the second configuration shown in Fig. 1C via one or more intermediate expansion configurations, such as that shown in Fig. IB. The entry of gas into the volume during this expansion is restricted by the inlet 140 and the outlet 150 thereby causing a reduction (or drop) in pressure of the gas inside the volume. This reduction in pressure results in an increased rate of evaporation of the liquid 1 10 inside the volume, thereby resulting in the production of vapor 105. Therefore, during the expansion of the volume to the second size, the proportion of vapor 105 in the gas inside the volume is increased.

At a step 220, the method 200 comprises allowing gas to enter the volume via the inlet 140 while the volume is expanded to the second size. For example, where the inlet 140 comprises a valve 180, the valve 180 may be opened (e.g. by sending an electronic control signal to an electronic valve). Alternatively, this step may be achieved as a result of the expansion of the volume to the second size, for example, when the inlet 140 is positioned so that it is only in fluid communication with the volume when the volume is substantially expanded to the second size, as described above. Gas will enter the volume via the inlet 140 due to the reduced pressure within the volume (compared to atmospheric pressure or the pressure of the environment being humidified) until equilibrium is reached (i.e. with atmospheric pressure or the pressure of the environment being humidified). In other words, the entry of the gas into the volume via the inlet 140 serves to gradually increase the pressure in the volume back to normal levels. The gas that enters the volume will mix with the vapor 105 and the gas that is already in the volume resulting in a mixture that has a higher relative humidity (i.e. proportion of vapor 105) than that of the gas that entered the volume.

At a step 230, the method 200 comprises contracting the volume from the second size to the first size. For example, the piston 130 may be moved from the second position to the first position thereby transforming the device 100 from the second

configuration shown in Fig. 1C back to the first configuration shown in Fig. 1 A via one or more intermediate contraction configurations, such as that shown in Fig. ID. During the contraction of the volume, the gas comprising the vapor 105 inside the volume is allowed to exit the volume via the outlet 150. For example, where the outlet 150 comprises a valve 190, the valve 190 may be opened (e.g. by sending an electronic control signal to an electronic valve). Alternatively, the valve 190 may comprise a non-return valve, such that the compression of the volume forces the air comprising the vapor 105 through the valve 190. In any case, the contraction of the volume expels the air through the outlet 150.

The method 200 may be performed continuously to provide on-going production of vapor 105. In particular, following the contraction of the volume from the second size to the first size at step 230, the device 100 is returned to the first configuration, as shown in Fig. 1 A, from which point step 210 may be performed again.

Whilst the operation of the device 100 has been described with reference to a first and second size of volume and a first and second size of piston 130, it will be appreciated that these positions and sizes need not be the same for each cycle of operation. So long as each cycle results in a drop of pressure due to an increase in size of the volume while the entry of gas into the volume is restricted, the device 100 will produce vapor 105 which can be expelled via the outlet 150 into the environment to be humidified. Similarly, the first and second sizes of the volume and the first and second positions of the piston 130 need not be at the limits of the expansion/contraction of the volume of the motion of the piston 130. That is to say, the piston 130 may move beyond the second position to expand the volume yet further, or indeed move beyond the first position to further contract the volume. In either case, the production of vapor 105 will still occur at the very least during the expansion of the volume from the first to the second size as the entry of gas into the volume during that part of the expansion is restricted, causing the pressure of the gas within the volume to drop.

The method 200 may be performed to maintain a target (or desired) level of humidity within an environment to be humidified. The method 200 may therefore comprise additional steps (shown connected using dashed lines in Fig. 2), as described below, to control the amount of vapor 105 produced by the device 100 to achieve the target humidity level in the environment to be humidified. The environment to be humidified is typically an enclosed space, such as the inside of a building or room, or the interior of a container of some sort.

At an additional step 240, the method 200 may comprise receiving a feedback signal 245. The feedback signal 245 indicates the relative humidity of the environment being humidified. The feedback signal 245 may, for example, be the electronic output of a humidity sensor located within the enclosed space.

At an additional step 250, the method 200 may comprise calculating a target position 255 for the piston 130 based on the feedback signal 245 and the target level of humidity that is desired. Because it is the movement of the piston 130 that produces and expels the vapor 105 from the device 100, the amount of vapor 105 that is provided by the device 100 into the environment being humidified can be controlled very accurately. At a high level, the amount of vapor 105 that is produced can be controlled based on limiting the number of humidifying cycles (i.e. repetitions of steps 210, 220 and 230) that are performed. At a more granular level, the amount of vapor 105 that is provided into the environment by the device 100 can be controlled by stopping the movement of the piston 130 at a desired point during a contraction of the volume (thereby halting the expulsion of the gas comprising the vapor 105 through the outlet 150). Therefore, the target position 255 of the piston 130 may comprise a number of expansion/contraction cycles by the piston 130, as well as a position for the piston 130 which is part way through a contraction (or expansion) cycle, such as the intermediate position of the piston 130 shown in Fig. ID.

At an additional step 260, the method 200 may comprise stopping the movement of the piston 130 when the piston 130 reaches the target position 255. This can be achieved, for example, at a high level by evaluating whether the target position 255 has been reached after each expansion/contraction cycle (i.e. between performing steps 230 and 210), as illustrated in Fig. 2. If the target position 255 has been reached, the method 200 may prevent the next cycle from being performed, otherwise the next cycle may be allowed to continue. Alternatively, the determination could be performed continuously with the cycle being interrupted at any point during the cycle, providing more granular control. As an example, in response to a determination that the target position 255 had been reached, the power to a motor driving the motion of the piston 130 may be cut. Alternatively, the target position 255 could be provided as an input into a control system for the motor which in turn moves the piston 130 until the target position 255 is reached. The calculation of the target position 255 may be performed periodically or in response to receiving an updated feedback signal 245. In this case, the target position 255 may be regularly updated, even before a previously calculated target position 255 has been reached by the piston 130. Other more simplistic control mechanisms are also contemplated. For example, the expansion/contraction cycle may be performed until the feedback signal 245 indicates that the relative humidity of the enclosed space matches the target humidity level at which point the operation of the device 100 (i.e. the expansion/contraction cycle) may be suspended until the feedback signal 245 indicates that the relative humidity of the enclosed space no longer matches the target humidity level. Such a simplistic control mechanism can eliminate the need to calculate a target position for the piston 130. Additionally, although the method 200 has been described in relation to the use of a piston 130 as an expansion mechanism, it will be appreciated that other expansion mechanisms, such as a container comprising folds in a concertina- type arrangement described above, will also allow control over the amount of vapor 105 that is provided from the device 100 and may be used with the method 200 to maintain a target (or desired) level of humidity within an environment to be humidified.

Fig. 3 schematically illustrates an exemplary food storage container 300 according to an embodiment of the invention. The food storage container 300 comprises a food storage chamber 310 and the device 100 as discussed above in relation to Figs. 1 A, IB, 1C, ID and 2. Although the device 100 is shown as being external to the food storage chamber 310 in Fig. 3, it will be appreciated that the device 100 could instead be internally situated within the food storage chamber 310 (in which case the food storage container 300 and the food storage chamber 310 may be considered to be the same thing). The inlet 140 and the outlet 150 are fluidly coupled to the food storage chamber 310. Therefore, when the device 100 is operated in accordance with the method 200, gas at a current level of relative humidity from the food storage chamber 310 enters the inlet 140 whilst gas comprising the generated vapor 105 at a higher level of relative humidity is expelled from the outlet 150 back into the food storage chamber 310. As a result, the relative humidity inside the food storage chamber 310 is increased. The device 100 may be operated according to the control loop discussed above in relation to Fig. 2 to maintain a target level of humidity within the food storage chamber 310.

The food storage container 300 may further comprise a refrigeration unit (not shown) for cooling the temperature of the gas within the food storage chamber 310. The food storage container 300 may therefore be considered to be a refrigerator (or refrigerating house or refrigerating container). It is noted that since the device 100 uses a decrease in pressure to evaporate the liquid 1 10, the temperature of the liquid 1 10, as well as the vapor 105 may be reduced to some extent due to adiabatic expansion. Therefore, not only does the device 100 not require heat to be removed from the gas comprising the vapor 105 that it produces (which would work contrary to the efforts of the refrigeration unit), but the device may actually cool the gas comprising the vapor 105 that it produces, working in synergy (or cooperation) with the refrigeration unit. Alternatively, the food storage container 300 may further comprise a heating element (not shown) for cooking food that is contained within the food storage chamber 310. The food storage container 300 may therefore be considered to be a cooker (or oven, or grill, or microwave, or air- frying cooker). Whilst Fig. 3 illustrates the use of the device 100 as part of a food storage container 300, it will be appreciated that the device 100 may be used in more general applications, such as, for example to humidify an enclosed room.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A device for producing a vapor from a liquid, the device comprising:

a container defining, at least in part, a volume for containing the liquid to be vaporized in fluid communication with gas inside the volume;

an expansion mechanism for expanding the volume from a first size to a second size;

an inlet for enabling gas to enter the volume when the volume is expanded to the second size; and

an outlet for enabling gas comprising the vapor produced from the liquid to exit the volume;

wherein the inlet and the outlet are configured to restrict the entry of gas into the volume during expansion of the volume from the first size to the second size.

2. The device of claim 1, wherein the expansion mechanism for expanding the volume from the first size to the second size comprises an expansion mechanism for expanding the volume from the first size to the second size and subsequently contracting the volume from the second size to the first size and wherein the outlet is further configured to enable the gas comprising the vapor to exit the volume during the contraction of the volume.

3. The device of either one of claims 1 or 2, wherein the expansion mechanism comprises a piston which at least partly defines the volume, the piston being movable between a first position, defining the first size of the volume, and a second position, defining the second size of the volume.

4. The device of claim 3, wherein the device further comprises a motor configured to move the piston between the first position and the second position to expand and contract the volume.

5. The device of claim 3, wherein the inlet is located between the first position of the piston and the second position of the piston in proximity to the second position.

6. The device of claim 1 wherein the outlet is lower than the inlet.

7. The device of claim 1, wherein the container comprises a detachable reservoir portion for containing the liquid.

8. The device of claim 1, wherein the inlet comprises a valve.

9. The device of claim 1, wherein the outlet comprises a valve.

10. The device of claim 1, wherein the liquid is water and/or the gas is air.

1 1. A food storage container comprising a device according to claim 1.

12. The food storage container of claim 1 1, wherein the food storage container further comprises a refrigeration unit.

13. The food storage container of claim 1 1, wherein the food storage container further comprises a heating element for cooking food contained in the food storage container.

14. A method of operating a device according to claim 2 to humidify an enclosed space, the method comprising:

expanding the volume from a first size to a second size while the entry of gas into the volume is restricted by the inlet and the outlet;

allowing gas to enter the volume via the inlet while the volume is expanded to the second size;

contracting the volume from the second size to the first size; and allowing gas comprising the vapor to exit the volume via the outlet during the contraction of the volume.

15. The method of claim 14 further comprising:

receiving a feedback signal indicating a relative humidity in the enclosed space;

calculating a target position for the piston based on the feedback signal and a target humidity level; and stopping the movement of the piston when the piston reaches the target position.