WO2020065693A1

WO2020065693A1 - Heating device with phase-change material

Info

Publication number: WO2020065693A1
Application number: PCT/IT2019/050214
Authority: WO
Inventors: Filippo BELLOMARE; Enrica Monticelli; Claudio PAVAN; Claudio ZILIO; Simone MANCIN
Original assignee: De' Longhi Appliances S.R.L. Con Unico Socio; Universita' Degli Studi Di Padova
Priority date: 2018-09-26
Filing date: 2019-09-26
Publication date: 2020-04-02

Abstract

Heating device, suitable to heat by contact or by irradiation parts of the body or objects which then transfer the heat to the body, such as blankets, clothing, towels or suchlike, or as a device for heating objects or rooms in general, which comprises at least one container (11) configured to contain a phase-change heat accumulation mean (13), and at least one heating element (12) configured to heat the heat accumulation mean (13).

Description

HEATING DEVICE WITH PHASE-CHANGE MATERIAL

* * * * *

FIELD OF THE INVENTION

The present invention concerns a heating device which uses a phase-change material, configured to exploit the latent heat released during a phase change of the material.

The heating device according to the present invention can be used as a household heating device, in particular as a personal heating device, to heat by contact, or by at least partial irradiation, parts of the body or objects which then transfer the heat to the body, such as blankets, clothing, towels or suchlike, or also as a heating device in general, personal or for rooms, in all cases where a constant and of medium-long duration source of heat is required, possibly, but not necessarily, in cordless mode.

The phase-change material used in the present invention is an organic, natural, non-toxic material and is therefore very suitable for the uses described above.

BACKGROUND OF THE INVENTION

In a household environment, but not only, there is often the need, at times a genuine necessity, to have a portable source of heat available, for example, to keep a part of the body warm, directly or indirectly, to heat rooms or heat a dish or a drink.

For this purpose, devices exist which use, as a heat accumulation mean, phase- change materials which, as known, are able to accumulate and release energy in a sensible manner, but above all in a latent manner when they reach the phase transition temperature.

In fact, phase-change materials are able to store a large amount of energy during the phase transition, typically solid-liquid and vice versa, maintaining their temperature constant even for a fairly long period of time, for example a few hours.

The amount of energy stored by the phase-change material essentially depends on its latent heat, which for the materials known for the uses of the present invention, is variable between about l OOJ/g and about 300J/g. Advantageously, given the same type of material and quantity considered, the greater the latent heat of the material, the greater the amount of energy accumulated. With regard to the type of application for which the heating device is used, the phase-change material of the heat accumulation mean is chosen based on the phase transition temperature, since the phase transition temperature remains constant during the phase transition.

The use of materials of this type for heating devices is known in the state of the art.

For example, document US20150012075 A1 describes a system for regulating body temperature which uses as a phase-change material wax or substances similar or comparable to wax, or wax emulsified with water, with a phase transition temperature of about 37°C.

Document EP2371324A1 describes a portable heating device which uses a phase-change material with a phase transition temperature comprised between about 55°C and about 60°C. In particular, document EP2371324A1 refers to a paraffin advantageously inserted inside a polymeric matrix in order to prevent its complete liquefaction during the heating phase.

Phase-change materials that are typically used as a heat accumulation mean in heating devices can be toxic, flammable and electrically conductive and, in the event of leaks in the device, can be hazardous to human and animal health.

From document US 2015/0148873 a container, such as a plastic bottle, is also known for containing a fluid suitable to provide heat for therapeutic purposes, comprising a saturated solution of water and erythritol in the form of crystals, in addition to one or more agents suitable to prevent the formation of crystals with large sizes, such as aluminum, silica, or nanoparticles of metal oxides. The container has no heating elements and is heated to a temperature comprised between about 120°F and about 140°F (48.88 - 60°C) by placing it in a microwave oven.

US 4,774,395 describes an apparatus to accumulate electric energy, such as an iron, a plate or a pan, comprising a metal body inside which is disposed a phase- change material comprising pentaerythritol. This apparatus is intended to provide high temperatures, greater than 180°C, suitable for ironing, or cooking foodstuffs, and is therefore not suitable to be used to heat a human body, or other objects, or to keep foodstuffs or drinks at a given temperature.

US 9,963,627 describes a phase-change material having a nanometric structure, suitable to achieve a thermoregulation coating on a substrate, and comprising a first agent having at least one of its dimensions in nanometric scale during the phase transition and a second agent which serves to maintain the nanometric structure of the material. The material described is suitable to undergo a solid-solid type phase transformation at temperatures comprised between about 25°C and about 40°C.

There is therefore the need to identify and select a phase-change material for a household heating device, for a personal heating device, for heating foodstuffs and drinks that can overcome at least one of the disadvantages of the state of the art.

One purpose of the present invention is to provide a heating device that uses as a heat accumulation mean a phase-change material that is particularly efficient in temperature bands typical of household heating devices.

Another purpose of the present invention is to provide a heating device that uses as a heat accumulation mean a phase-change material that is fully compatible with a household appliance and is totally safe for people’s health, for example in the event of leaks in the device.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

Embodiments described here concern a heating device which uses a phase- change material.

The present invention concerns in particular a personal heating device, or in any case a household heating device, to heat by contact or by at least partial irradiation parts of the body or objects which then transfer the heat to the body, such as blankets, clothing, towels or suchlike, or also as a device for heating objects in general, in all cases where a source of heat that is constant and of medium-long duration is required.

The device comprises at least one container configured to contain a heat accumulation mean, the heat accumulation mean being a phase-change material, and at least one heating element configured to heat the heat accumulation mean.

In accordance with one aspect of the present invention, the heat accumulation mean comprises a sugar. In particular, the heat accumulation mean wholly or partly comprises erythritol.

According to some embodiments, the heat accumulation mean can comprise erythritol added to other phase-change materials, suitable to undergo a solid- liquid phase transition during heating and a liquid-solid phase transition during cooling.

According to some embodiments, the solid-liquid phase transition temperature is comprised between 80 °C and 160 °C.

According to further embodiments, the solid-liquid phase transition temperature is comprised between 110 °C and 140 °C.

The present invention also concerns the use of erythritol, or of a phase-change material containing predominantly erythritol, or erythritol to which one or more different phase-change materials, or not, have been added as a heat accumulation mean in household heating devices, personal heating devices, devices for heating objects in general, devices for heating and cooking food and drinks.

The choice of erythritol for use in these devices derives from the fact that erythritol is an organic, natural, non-toxic material and is therefore very suitable for the uses described above, also possessing excellent thermophysical properties that mean it performs highly when storing and exchanging heat, in addition to making it a material that is very safe for human and animal health

The various aspects and characteristics described in the present description can be applied individually where possible. These individual aspects, for example aspects and characteristics present in the description or in the attached dependent claims, can be the object of divisional applications.

It is understood that any aspect or characteristic that is discovered, during the patenting process, to be already known, shall not be claimed and shall be the object of a disclaimer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a lateral view of a possible embodiment of the heating device according to the present invention; - fig. 2 is a section view of fig.1 ;

- fig. 3 is a lateral view of another possible embodiment of the heating device;

- fig. 4 is a section view of fig. 3;

- fig. 5 is a lateral view of another possible embodiment of the heating device; - fig. 6 is a section view of fig. 5;

- fig. 7 is a lateral view of another possible embodiment of the heating device;

- fig. 8 is a section view of fig. 7;

- fig. 9 is a section view of a possible embodiment of the heating device;

- fig. 10 is a qualitative graph of a possible thermal cycle of the heat accumulation mean used by the heating device.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

We will now refer in detail to the various embodiments of the present invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.

Before describing these embodiments, we must also clarify that the present description is not limited in its application to details of the construction and disposition of the components as described in the following description using the attached drawings. The present description can provide other embodiments and can be obtained or executed in various other ways. We must also clarify that the phraseology and terminology used here is for the purposes of description only, and cannot be considered as limitative.

Embodiments described using the attached drawings concern a heating device with phase-change material comprising erythritol, indicated with reference number 10 in the attached drawings. In accordance with some embodiments, the device 10 comprises at least one container 11, configured to contain a heat accumulation mean 13, and at least one heating element 12 configured to heat the heat accumulation mean 13.

According to some embodiments, the heating element 12 is positioned in contact with the container 11 , outside the latter.

According to other embodiments, the heating element 12 is positioned inside the container 11, in direct contact with the heat accumulation mean 13.

In accordance with one aspect of the present invention, the heat accumulation mean 13 consists of a phase-change material comprising erythritol.

In possible embodiments, the heat accumulation mean 13 can be 100% erythritol.

In other possible embodiments, the heat accumulation mean 13 can comprise erythritol to which a different material has been added. In this way it, is possible to modify, for example based on the specific application, some thermodynamic properties of the heat accumulation mean 13. For example, water can be added to the heat accumulation mean 13 comprising erythritol.

According to this embodiment, it is possible to provide that water can be added to the heat accumulation mean 13 maintaining a fluid form, configured to assume a solid or at least semi-solid form when it is cold or in the cooling phase.

According to some embodiments, the heat accumulation mean 13 comprises erythritol to which additional phase-change materials have been added, which are configured to also be subjected to a solid-liquid phase transition during heating and a liquid-solid phase transition during cooling.

It is understood that the present invention concerns a use of erythritol in a percentage higher than 50% in the phase-change material.

According to other embodiments, the phase-change material can comprise a percentage of erythritol greater than 60%, more in particular greater than 70%, and preferably greater than 80%.

Erythritol belongs to the sugar family and is therefore an organic and natural material. The device 10 which uses the heat accumulation mean 13 comprising erythritol can therefore be used in a household and personal environment. In fact, erythritol is a safe, non-toxic, cheap and easy to find phase-change material. Therefore, unfortunate leaks of the heat accumulation mean 13 from the container 1 1 do not entail a danger for human and animal health.

The Applicant has evaluated that for the applications of the device 10 in a household and personal environment, the heat accumulation mean 13 can be a phase-change material with a phase transition temperature comprised between about 80°C and about 160°C, preferably about 120°C.

These phase transition temperatures make the heating device according to the invention suitable to be used in various applications, from heating a part of a human body, to maintaining the temperature of or heating food, drinks or objects.

The Applicant, in particular, has experimented that erythritol has a phase transition temperature comprised between about 118°C and about 122°C, typically about 120°C.

With reference to fig. 10, the heat accumulation mean 13 comprising erythritol, when it is at a temperature lower than the phase transition temperature, that is, lower than about 120°C, is in a solid or semi-solid state, curve S, L2; when, instead, it is at a temperature at least equal to, or advantageously higher than, the phase transition temperature, it is in a liquid or semi-liquid state, curve LI .

During its useful life in the device 10, the heat accumulation mean 13 undergoes a certain number of thermal heating and cooling cycles, which essentially respond to the following equation:

where E_LAT is the latent energy exchanged during the phase change of the phase- change material, E_SENS is the sensible energy exchanged when the material is at a temperature lower than the phase transition temperature, E_LAT being proportional to the mass m of material and to the latent heat LH, E_SENS being proportional to the mass m, to the specific heat c_p and to the temperature difference AT between the material and the environment and the object with which the heat is exchanged.

With reference to fig. 10, a heating and cooling cycle of the heat accumulation mean 13 is described. The heat accumulation mean 13 can initially be at an ambient temperature, typically comprised between about 20°C and about 30°C, and undergo a sensible heating in order to reach a phase transition temperature of about 120°C following the curve S, which once reached all the heat accumulation mean 13 is liquefied. Once the phase transition temperature has been reached, the heat accumulation mean 13 maintains the phase transition temperature until the accumulated latent energy is exhausted, curve Ll . Subsequently, the heat accumulation mean 13 cools to below the phase transition temperature exchanging sensible energy, curve L2, until it is completely solidified.

The Applicant has experimented that erythritol has a latent heat comprised between about 330 J/g and about 350 J/g, very close to 340 J/g, thus being able to accumulate a large amount of energy for the same mass, and thus resulting in an excellent phase-change material to be used as a heat accumulation mean 13 for a device 10 with household and personal applications. In fact, thanks to this characteristic it is possible to produce devices 10 able to accumulate a large amount of energy, devices 10 which can however be very compact.

Advantageously, the heating device 10 comprising erythritol can be used for all household devices which require an operative temperature lower than the phase transition temperature of erythritol. This is because, although the phase transition temperature of the heat accumulation mean 13 comprising erythritol is about l20°C, this cannot be transferred completely to the application of use due, for example, to thermal dispersions.

The phase transition temperature as above allows the device 10, for example, to heat and, if necessary, cook food/drinks, or heat the air contained in a room or heat a person or part thereof.

In accordance with possible solutions, the device 10 can comprise an amount of heat accumulation mean 13 comprising erythritol variable between about 200 g and about 4000 g, preferably between 300 g and 1200 g.

In possible implementations, it is provided to use a quantity of heat accumulation mean 13 comprising erythritol greater than 4000 g, in applications, for example, in which the device 10 is used in devices for heating one or more, more or less large rooms of a building.

The device 10 can comprise a heating element 12 configured to heat the heat accumulation mean 13 at least to the phase transition temperature of the accumulation mean 13.

In accordance with possible solutions, the heating element 12 can be provided with heating plates, located directly in contact with the container 1 1 in order to transmit the heat, by conduction, to the heat accumulation mean 13 contained therein.

The heating element 12 can comprise, between the plates as above, an electric resistor circuit electrically powered by means of supply cables 18, and configured to heat the plates.

The heating element 12 can be electrically powered for a period of time typically comprised between about 5 minutes and about 15 minutes.

During this period of time, the heat accumulation mean 13, initially solid, is melted accumulating inside it a large amount of heat, directly proportional to the mass of the heat accumulation mean 13 present inside the container 11 and to its latent heat.

In possible conditions of use, it is provided to power the heating element 12 for the time required to heat the heat accumulation mean 13 contained in the device 10, at least to the phase transition temperature.

Once the phase transition temperature is reached, it is possible to interrupt the power supply to the device 10 and use it, for example, in cordless mode, that is, not connected to the electric power supply by cables or terminals.

Advantageously, once the phase transition temperature has been reached, the power supply to the device 10 is interrupted when the entire heat accumulation mean has completed the phase transition.

When the power supply is interrupted, the heat accumulated by the heat accumulation mean 13 is released over a period of time typically comprised between about 2 hours and about 5 hours, preferably between about 3 hours and about 4 hours.

In possible solutions, the device 10 can comprise a selectively openable and closable hole to replace the heat accumulation mean 13. In this way, the heat accumulation mean 13 is easily replaceable, for example due to a degradation of its thermophysical properties.

In the following description, by way of a non-limiting example, we describe possible solutions of a device 10 which uses a heat accumulation mean 13 comprising erythritol. The devices 10 shown in figs. 1-9 concern heating devices commonly used or usable in a household and personal environment, for which the characteristics of safety, non-flammability and non-toxicity of the heat accumulation mean 13 are essential features.

Example 1

In accordance with a possible embodiment, shown in figs. 1-2, an autonomous heating unit 30 is shown comprising the device 10 configured for use as a personal heating mean of the contact type, used not only to directly heat the user but also blankets, sheets, pillows and cushions, towels, clothes, and other similar or comparable items.

The device 10 comprises at least one container 11, configured to contain a heat accumulation mean (not shown in the drawings), and at least one heating element 12, positioned in contact with the container 11 and configured to heat the heat accumulation mean.

According to some embodiments, the device 10 comprises a pair of containers 1 1 , symmetrically coupled, between which the heating element 12 is positioned in contact.

The heating element 12 is electrically powered by means of cables 18, from which it is selectively removable, so as to make the device 10 cordless.

The container 11 comprises a compartment 16, suitable to contain the heat accumulation mean 13, and a top 17 which allows the selective opening/closing thereof in order to insert the heat accumulation mean 13.

The device 10 also comprises a temperature detection mean 29, for example a thermostat, able to detect the temperature of the heat accumulation mean contained in the device 10.

Example 2

In accordance with a possible embodiment, figs. 3-4 show a container for heating foodstuffs or drinks 31 , comprising a receptacle 14 and a heating device 10 located in contact with the receptacle 14 and configured to heat and maintain at temperature a drink 15 contained therein.

The drink 15 can be, by way of example only, a soup or a broth, coffee or tea, or any liquid, semi-liquid or gelatinous substance whatsoever which is intended to be heated or kept hot. The heating device 10 comprising the container 11 is advantageously positioned below the receptacle 14 inside which it is possible to insert the drink 15.

The receptacle 14 is provided with a compartment 16 for containing the drink 15 and a top 17.

In accordance with one aspect of the present invention, the container 11 contains within it the heat accumulation mean 13 which comprises a phase- change material comprising erythritol.

A heating element 12 is provided in contact with the container 1 1 configured to heat the heat accumulation mean 13 in order to bring it at least to a phase transition temperature for the period of time necessary to complete the transition phase from solid to liquid. The heating element 12 is electrically powered by means of cables 18, from which it is selectively removable, so as to make the device 10 cordless.

The container 11 and the receptacle 14 can be made in a single piece, or be made separately and suitably connected. Advantageously, the receptacle 14 is selectively separable from the container 11, for example by means of a threaded coupling with the latter.

Example 3

In accordance with a possible embodiment, shown in figs. 5-6, a heating apparatus 33 is provided comprising a receptacle 14 configured to receive a food item 19, and a heating device 10 configured to heat and maintain at temperature the food 19 positioned in the receptacle 14.

The heating apparatus 33 comprises, on an upper surface of the container 11, a base 20 on which to position the receptacle 14, for example a pan.

The receptacle 14 is provided with a compartment 16, inside which the food 19 can be disposed. The compartment 16 is closed by a top 17.

A heating element 12 is provided in contact with the container 1 1 configured to heat the heat accumulation mean 13 in order to bring it at least to a phase transition temperature for the period of time necessary to complete the transition phase from solid to liquid. The device 10 can, for example, be heated for a certain period of time between 5 minutes and 10 minutes, and positioned on a table in order to keep the food 19 hot, that is, it can be used in cordless mode to keep the food 19 served in a canteen or in any place used to serve meals hot. Example 4

In accordance with a possible embodiment, shown in figs. 7-8, a conditioning apparatus 33 is provided, suitable to generate a flow of air 21, and comprising a heating device 10 configured to heat the flow of air 21, for example to heat a room of a building.

The conditioning apparatus 33 is provided with a casing 22 inside which the container 11 is positioned.

A coil 25 is positioned inside the container 11, which is provided with an external surface in direct contact with the heat accumulation mean 13, which allows the passage of the flow of air 21 from an aperture 23 to an aperture 24 made on two opposite walls of the casing 22.

A heating element 12 is provided in contact with the container 11 configured to heat the heat accumulation mean 13 in order to bring it at least to a phase transition temperature for the period of time necessary to complete the transition phase from solid to liquid. In particular, the heat accumulation mean 13 exchanges heat with the flow of air 21 , which is heated as it passes inside the coil 25. The passage of the flow of air 21 from the aperture 23 to the aperture 24 is advantageously achieved by means of a fan 26.

Example 5

In accordance with a possible embodiment, shown in fig. 9, an iron 34 is provided comprising an ironing plate 27 and a heating device 10 provided with the heat accumulation mean 13 comprising erythritol configured to heat an ironing plate 27.

The iron 34 comprises a support structure 28 inside which the container 1 1 containing the heat accumulation mean 13 is positioned.

A heating element 12 is provided in contact with the container 11 configured to heat the heat accumulation mean 13 in order to bring it at least to a phase transition temperature for the period of time necessary to complete the transition phase from solid to liquid.

The power supply to the iron 34 is then interrupted and the device 10 can be used in cordless mode.

It is clear that modifications and/or additions of parts may be made to the heating device 10 with phase-change material as described heretofore, without departing from the field and scope of the present invention. It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of a heating device 10 with phase-change material, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

3. Heating device, suitable to heat by contact or by irradiation parts of the body or objects which then transfer the heat to the body, such as blankets, clothing, towels or suchlike, or as a device for heating objects, foodstuffs or drinks, or rooms in general, said device comprising at least one container (11) configured to contain a phase-change heat accumulation mean (13), and at least one heating element (12) configured to heat said heat accumulation mean (13), characterized in that said heat accumulation mean (13) comprises pure erythritol or erythritol to which other phase-change materials have been added, and is configured to undergo a solid-liquid phase transition during heating and a liquid-solid phase transition during cooling, wherein the solid-liquid phase transition temperature of said heat accumulation mean (13) is comprised between 80°C and 160°C.

2. Heating device as in claim 1 , characterized in that in the case of erythritol to which other phase-change materials have been added said heat accumulation mean (13) comprises erythritol in a percentage higher than 50%.

3. Heating device as in any claim hereinbefore, characterized in that said heat accumulation mean (13) has a phase transition temperature comprised between 110°C and l40°C.

4. Heating device as in any claim hereinbefore, characterized in that said heat accumulation mean (13) has a phase transition temperature comprised between 118°C and l22°C, in particular equal to 120°C.

5. Heating device as in any claim hereinbefore, characterized in that said heat accumulation mean (13) is configured so as to release heat in a time typically comprised between about 2 hours and about 5 hours, preferably between about 3 hours and about 4 hours.

6. Heating device as in any claim hereinbefore, characterized in that said heat accumulation mean (13) comprises a quantity of erythritol comprised between about 200g and about 4000g.

7. Heating device as in any claim hereinbefore, characterized in that said heat accumulation mean (13) comprises a quantity of erythritol comprised between about 300g and about l200g.

8. Heating device as in any claim hereinbefore, characterized in that said phase-change material is configured to deliver heat in cordless mode.

9. Personal heating device through contact, characterized in that it comprises a heating device (10) as in any claim from 1 to 7 configured to deliver heat in cordless mode.

10. Container to heat foodstuffs or drinks, characterized in that it comprises a receptacle (14) configured to contain a foodstuff or drink (15), and a heating device (10) as in any claim from 1 to 9 located in contact with said receptacle

(14) and configured to heat and maintain at temperature said foodstuff or drink

(15).

11. Iron, characterized in that it comprises an ironing plate (27) and a heating device (10) as in any claim from 1 to 9 located in proximity to or in contact with said ironing plate (27) and configured to heat the latter.

12. Conditioning apparatus for rooms, characterized in that it comprises a fan (26) suitable to generate a flow of air (21), and a heating device (10) as in any claim from 1 to 9, configured to heat said flow of air (21).

13. Use of erythritol or of a phase-change material containing erythritol or erythritol to which a different phase-change material has been added, or not, as a heat accumulation mean in household heating devices, personal heating devices, devices for heating objects or rooms in general, devices for heating and cooking food and drinks.